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  • richardmitnick 11:04 am on October 16, 2021 Permalink | Reply
    Tags: "Parker Solar Probe has a Venus flyby today", EarthSky, , The Johns Hopkins University Applied Physics Lab (US)   

    From The Johns Hopkins University Applied Physics Lab (US) via EarthSky : “Parker Solar Probe has a Venus flyby today” 

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    This was the Parker Solar Probe’s location on September 30, 2021, when the spacecraft performed a short maneuver to set it on course for the October 16 Venus flyby. The green lines mark the spacecraft’s path since it launched on Aug. 12, 2018. The red loops show the probe’s future orbits, bringing it progressively closer to the sun. Image: Yanping Guo via The National Aeronautics and Space Agency (US)/ Johns Hopkins APL.

    Parker Solar Probe flyby and gravity assist

    Parker Solar Probe will perform its next Venus flyby on October 16, 2021. The spacecraft made a short preparatory maneuver on September 29. This maneuver changed the craft’s speed by 9.7 centimeters per second, or less than a third of a mile per hour. That slight change was critical for placing the craft on course for Saturday’s Venus gravity assist, when it will use the planet’s gravity to swing toward its 10th close approach to the sun.

    The September 29 maneuver was monitored from the mission operations center at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. APL also designed and built the Parker Solar Probe and said it is:

    “… healthy and its systems are operating normally. The spacecraft completed its 9th solar encounter on August 15, 2021, at closest approach coming within 6.5 million miles (10.4 million km) of the sun’s surface. The upcoming Venus gravity assist will send the spacecraft even closer to the sun’s blazing surface – about 5.6 million miles (9 million km) – on November 21.

    Assisted by two additional Venus flybys, Parker Solar Probe will eventually come within 4 million miles (6.4 million km) of the solar surface in late 2024.”

    Seven-year mission to touch the sun

    In all, the probe has 24 scheduled orbits around the sun during its seven-year mission. During this time, NASA likes to say, the probe will “touch” the sun, that is, fly within the sun’s atmosphere. During each of its sweeps past the sun, NASA said, the Parker Solar Probe will break its own nearness records to the sun.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Johns Hopkins University campus

    JHUAPL campus

    Founded on March 10, 1942—just three months after the United States entered World War II— The Johns Hopkins University Applied Physics Lab (US) -was created as part of a federal government effort to mobilize scientific resources to address wartime challenges.

    The Applied Physics Lab was assigned the task of finding a more effective way for ships to defend themselves against enemy air attacks. The Laboratory designed, built, and tested a radar proximity fuze (known as the VT fuze) that significantly increased the effectiveness of anti-aircraft shells in the Pacific—and, later, ground artillery during the invasion of Europe. The product of the Laboratory’s intense development effort was later judged to be, along with the atomic bomb and radar, one of the three most valuable technology developments of the war.

    On the basis of that successful collaboration, the government, The Johns Hopkins University, and APL made a commitment to continue their strategic relationship. The Laboratory rapidly became a major contributor to advances in guided missiles and submarine technologies. Today, more than seven decades later, the Laboratory’s numerous and diverse achievements continue to strengthen our nation.

    The Applied Physics Lab continues to relentlessly pursue the mission it has followed since its first day: to make critical contributions to critical challenges for our nation.

    Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

    The Johns Hopkins University (US) is a private research university in Baltimore, Maryland. Founded in 1876, the university was named for its first benefactor, the American entrepreneur and philanthropist Johns Hopkins. His $7 million bequest (approximately $147.5 million in today’s currency)—of which half financed the establishment of the Johns Hopkins Hospital—was the largest philanthropic gift in the history of the United States up to that time. Daniel Coit Gilman, who was inaugurated as the institution’s first president on February 22, 1876, led the university to revolutionize higher education in the U.S. by integrating teaching and research. Adopting the concept of a graduate school from Germany’s historic Ruprecht Karl University of Heidelberg, [Ruprecht-Karls-Universität Heidelberg] (DE), Johns Hopkins University is considered the first research university in the United States. Over the course of several decades, the university has led all U.S. universities in annual research and development expenditures. In fiscal year 2016, Johns Hopkins spent nearly $2.5 billion on research. The university has graduate campuses in Italy, China, and Washington, D.C., in addition to its main campus in Baltimore.

    Johns Hopkins is organized into 10 divisions on campuses in Maryland and Washington, D.C., with international centers in Italy and China. The two undergraduate divisions, the Zanvyl Krieger School of Arts and Sciences and the Whiting School of Engineering, are located on the Homewood campus in Baltimore’s Charles Village neighborhood. The medical school, nursing school, and Bloomberg School of Public Health, and Johns Hopkins Children’s Center are located on the Medical Institutions campus in East Baltimore. The university also consists of the Peabody Institute, Applied Physics Laboratory, Paul H. Nitze School of Advanced International Studies, School of Education, Carey Business School, and various other facilities.

    Johns Hopkins was a founding member of the American Association of Universities (US). As of October 2019, 39 Nobel laureates and 1 Fields Medalist have been affiliated with Johns Hopkins. Founded in 1883, the Blue Jays men’s lacrosse team has captured 44 national titles and plays in the Big Ten Conference as an affiliate member as of 2014.

    Research

    The opportunity to participate in important research is one of the distinguishing characteristics of Hopkins’ undergraduate education. About 80 percent of undergraduates perform independent research, often alongside top researchers. In FY 2013, Johns Hopkins received $2.2 billion in federal research grants—more than any other U.S. university for the 35th consecutive year. Johns Hopkins has had seventy-seven members of the Institute of Medicine, forty-three Howard Hughes Medical Institute Investigators, seventeen members of the National Academy of Engineering, and sixty-two members of the National Academy of Sciences. As of October 2019, 39 Nobel Prize winners have been affiliated with the university as alumni, faculty members or researchers, with the most recent winners being Gregg Semenza and William G. Kaelin.

    Between 1999 and 2009, Johns Hopkins was among the most cited institutions in the world. It attracted nearly 1,222,166 citations and produced 54,022 papers under its name, ranking No. 3 globally [after Harvard University (US) and the Max Planck Society (DE) in the number of total citations published in Thomson Reuters-indexed journals over 22 fields in America.

    In FY 2000, Johns Hopkins received $95.4 million in research grants from the National Aeronautics and Space Administration (US), making it the leading recipient of NASA research and development funding. In FY 2002, Hopkins became the first university to cross the $1 billion threshold on either list, recording $1.14 billion in total research and $1.023 billion in federally sponsored research. In FY 2008, Johns Hopkins University performed $1.68 billion in science, medical and engineering research, making it the leading U.S. academic institution in total R&D spending for the 30th year in a row, according to a National Science Foundation (US) ranking. These totals include grants and expenditures of JHU’s Applied Physics Laboratory in Laurel, Maryland.

    The Johns Hopkins University also offers the “Center for Talented Youth” program—a nonprofit organization dedicated to identifying and developing the talents of the most promising K-12 grade students worldwide. As part of the Johns Hopkins University, the “Center for Talented Youth” or CTY helps fulfill the university’s mission of preparing students to make significant future contributions to the world. The Johns Hopkins Digital Media Center (DMC) is a multimedia lab space as well as an equipment, technology and knowledge resource for students interested in exploring creative uses of emerging media and use of technology.

    In 2013, the Bloomberg Distinguished Professorships program was established by a $250 million gift from Michael Bloomberg. This program enables the university to recruit fifty researchers from around the world to joint appointments throughout the nine divisions and research centers. Each professor must be a leader in interdisciplinary research and be active in undergraduate education. Directed by Vice Provost for Research Denis Wirtz, there are currently thirty two Bloomberg Distinguished Professors at the university, including three Nobel Laureates, eight fellows of the American Association for the Advancement of Science (US), ten members of the American Academy of Arts and Sciences, and thirteen members of the National Academies.

     
  • richardmitnick 9:50 am on October 16, 2021 Permalink | Reply
    Tags: "Lucy spacecraft launched today October 16 2021 to Jupiter’s Trojans", , EarthSky,   

    From Southwest Research Institute (US) via EarthSky : “Lucy spacecraft launched today to Jupiter’s Trojans” 

    SwRI bloc

    From Southwest Research Institute (US)

    via

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    EarthSky

    October 16, 2021
    Kelly Kizer Whitt

    The Lucy spacecraft – named for a famous fossilized skeleton found in 1974 in Africa – launched from Cape Canaveral, Florida, on Saturday, October 16, 2021, beginning a 12-year journey. With the help of three gravity assists from Earth, Lucy will travel almost 4 billion miles (6 billion km) in 12 years, exploring one asteroid in the main asteroid belt and seven of Jupiter’s Trojan asteroids. The Trojans move in Jupiter’s orbit around the sun and have never been explored before. And scientists view them as fossils that are left over from the formation of the solar system.

    The inner Solar System, from the Sun to Jupiter. Also includes the asteroid belt (the white donut-shaped cloud), the Hildas (the orange “triangle” just inside the orbit of Jupiter), the Jupiter trojans (green), and the near-Earth asteroids. The group that leads Jupiter are called the “Greeks” and the trailing group are called the “Trojans” The image is looking down on the ecliptic plane as would have been seen on 1 September 2006 .

    Our fossilized ancestor called Lucy dates to some 3.2 million years ago. The skeleton of the fossil Lucy provided unique insight into human evolution. Likewise, the Lucy space mission will hopefully provide insight into our solar system’s evolution. Astronomer Hal Levison of the Southwest Research Institute (SwRI) in Boulder, Colorado, leads the Lucy mission. He spoke about Lucy’s journey to Jupiter’s Trojans and about how the mission got its name:

    “The Trojan asteroids are leftovers from the early days of our solar system, effectively fossils of the planet formation process. They hold vital clues to deciphering the history of our solar system. The Lucy spacecraft, like the human ancestor fossil for which it is named, will revolutionize the understanding of our origins.”

    Lucy’s 4-billion-mile journey will take it out to the orbit of Jupiter and the realm of Trojan asteroids, then back in toward Earth for gravity assists three times. This will be the first time a spacecraft has ever returned to Earth’s vicinity from the outer solar system.

    Target: Trojan asteroids

    Trojan asteroids are a unique group of rocky bodies. Left over from the formation of the solar system, they orbit the sun on either side of Jupiter. No spacecraft has previously explored this collection of solar system fossils. Jupiter’s gravity traps these asteroids in two swarms in its orbit, with some ahead of the planet and some trailing behind.

    Deputy principal investigator Cathy Olkin said:

    “Lucy’s ability to fly by so many targets means that we will not only get the first up-close look at this unexplored population, but we will also be able to study why these asteroids appear so different. The mission will provide an unparalleled glimpse into the formation of our solar system, helping us understand the evolution of the planetary system as a whole.”

    Launching the Lucy spacecraft

    Team members for the Lucy mission have spent weeks at NASA’s Kennedy Space Center prepping and practicing for the launch. Levison said the spacecraft is ready, elaborating:

    “Launching a spacecraft is almost like sending a child off to college. You’ve done what you can to get them ready for that next big step on their own. Lucy is ready to fly.”

    Lucy launched on an Atlas V rocket on its first attempt, at 5:34 a.m. EDT (09:34 UTC) on Saturday, October 16, 2021. The team checked in at 1 a.m. (05:00 UTC) to begin their run-through of the full launch countdown procedures.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    SwRI Campus

    Southwest Research Institute (SwRI) (US) is an independent, nonprofit applied research and development organization. The staff of nearly 2,800 specializes in the creation and transfer of technology in engineering and the physical sciences. SwRI’s technical divisions offer a wide range of technical expertise and services in such areas as engine design and development, emissions certification testing, fuels and lubricants evaluation, chemistry, space science, nondestructive evaluation, automation, mechanical engineering, electronics, and more.

    Southwest Research Institute (SwRI), headquartered in San Antonio, Texas, is one of the oldest and largest independent, nonprofit, applied research and development (R&D) organizations in the United States. Founded in 1947 by oil businessman Tom Slick, SwRI provides contract research and development services to government and industrial clients.

    The institute consists of nine technical divisions that offer multidisciplinary, problem-solving services in a variety of areas in engineering and the physical sciences. The Center for Nuclear Waste Regulatory Analyses, a federally funded research and development center sponsored by the U.S. Nuclear Regulatory Commission, also operates on the SwRI grounds. More than 4,000 projects are active at the institute at any given time. These projects are funded almost equally between the government and commercial sectors. At the close of fiscal year 2019, the staff numbered approximately 3,000 employees and research volume was almost $674 million. The institute provided more than $8.7 million to fund innovative research through its internally sponsored R&D program.

    A partial listing of research areas includes space science and engineering; automation; robotics and intelligent systems; avionics and support systems; bioengineering; chemistry and chemical engineering; corrosion and electrochemistry; earth and planetary sciences; emissions research; engineering mechanics; fire technology; fluid systems and machinery dynamics; and fuels and lubricants. Additional areas include geochemistry and mining engineering; hydrology and geohydrology; materials sciences and fracture mechanics; modeling and simulation; nondestructive evaluation; oil and gas exploration; pipeline technology; surface modification and coatings; and vehicle, engine, and powertrain design, research and development. In 2019, staff members published 673 papers in the technical literature; made 618 presentations at technical conferences, seminars and symposia around the world; submitted 48 invention disclosures; filed 33 patent applications; and received 41 U.S. patent awards.

    SwRI research scientists have led several National Aeronautics Space Agency(USA) missions, including the New Horizons mission to Pluto; the Juno mission to Jupiter; and the Magnetospheric Multiscale Mission(US) to study the Earth’s magnetosphere.

    SwRI initiates contracts with clients based on consultations and prepares a formal proposal outlining the scope of work. Subject to client wishes, programs are kept confidential. As part of a long-held tradition, patent rights arising from sponsored research are often assigned to the client. SwRI generally retains the rights to institute-funded advancements.

    The institute’s headquarters occupy more than 2.3 million square feet of office and laboratory space on more than 1,200 acres in San Antonio. SwRI has technical offices and laboratories in Boulder, Colorado; Ann Arbor, Michigan; Warner-Robins, Georgia; Ogden, Utah; Oklahoma City, Oklahoma; Rockville, Maryland; Minneapolis, Minnesota; Beijing, China; and other locations.

    Technology Today, SwRI’s technical magazine, is published three times each year to spotlight the research and development projects currently underway. A complementary Technology Today podcast offers a new way to listen and learn about the technology, science, engineering, and research impacting lives and changing our world.

     
  • richardmitnick 9:25 am on October 10, 2021 Permalink | Reply
    Tags: "2 Old Open Star Clusters Merging in the Milky Way", 30 Doradus nebula [also known as the Tarantula Nebula], A composite of two clusters that differ in age by about one million years., , , , , EarthSky, Hubble Watches Star Clusters on a Collision Course.,   

    From Hubblesite (US)(EU) and NASA/ESA Hubble via EarthSky : “2 Old Open Star Clusters Merging in the Milky Way” 

    From Hubblesite (US)(EU) and NASA/ESA Hubble

    via

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    EarthSky

    October 7, 2021
    Deborah Byrd

    1
    08.16.12
    Hubble Watches Star Clusters on a Collision Course.
    This is a Hubble Space Telescope image of a pair of star clusters that are believed to be in the early stages of merging. The clusters lie in the gigantic 30 Doradus nebula, which is 170,000 light-years from Earth.

    Old open star clusters merging

    Open star clusters tend to be young collections of sibling stars, born together from a cloud or nebula in space. Open clusters are like families of stars. They’re still loosely bound by gravity and still move together through space. We know thousands of them in our Milky Way galaxy, and amateur astronomers love to gaze at them through small telescopes and binoculars, under dark skies. Most open star clusters don’t survive more than several orbits around our galaxy’s center before being disrupted and dispersed. But astronomer Denilso Camargo in Brazil reached out this week (early October 2021) about a new discovery of what he called:

    ” … the first old binary star cluster within our Milky Way galaxy.

    Close encounters between open star clusters are rare, he said. Obviously, the subsequent formation of binary clusters is even rarer. And the evolution to a merger event is extremely unlikely. Yet there it is. And that’s not all. Camargo said this system appears to be undergoing a merger during a close encounter. As the two star clusters merge, Camargo said, they’re leaving in their wake:

    … streams populated by bound substructures.”

    That’s the kind of news you’d expect to hear from ESA’s Gaia space observatory.

    European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) GAIA satellite

    And indeed Camargo used Gaia data, along with images from NASA’s WISE infrared space telescope.

    National Aeronautics and Space Administration(US) Wise/NEOWISE Telescope.

    The study is accepted for publication in The Astrophysical Journal.

    One cluster becomes 2

    Camargo is at The Federal University of Rio Grande do Sul [Universidade Federal do Rio Grande do Sul](BR). Via data from the two space observatories, he closely examined a single known open cluster called NGC 1605 and found it was really two clusters. NGC 1605 one of the open star clusters amateur astronomers like to see. As deep-sky objects go, it’s relatively bright (about 11th magnitude) and can be seen with a 6-inch or larger telescope (in a dark sky). One known cluster has become two, so, Camargo said:

    “I called the two clusters as NGC 1605a and NGC 1605b.”

    Camargo said his study reveals one cluster is 2 billion years old, and the other only 600 million years old. And those ages give a clue to the clusters’ histories. Writing for IFLScience on October 4, 2021, Stephen Luntz explained:

    “It’s clear NGC 1605a and b are unlike anything else we have seen. Most binary clusters are young, which probably indicates they formed together from a single cloud that broke apart. That can’t be the case for a pair of such different ages.

    Instead, these two must have been drifting past each other, and come close enough their gravitational fields caused them to interact. The two have now come so close their star populations overlap.”

    2
    The Goddard Space Flight Center | NASA

    The Hubble observations, made with the Wide Field Camera 3, were taken Oct. 20-27, 2009.

    National Aeronautics Space Agency(USA) European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ Hubble Wide Field Camera 3

    The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen. Image Credit: R. O’Connell (University of Virginia (US))NASA, ESA, and the Wide Field Camera 3 Science Oversight Committee.

    Astronomers using data from NASA’s Hubble Space Telescope have caught two clusters full of massive stars that may be in the early stages of merging. The clusters are 170,000 light-years away in the Large Magellanic Cloud, a small satellite galaxy to our Milky Way.

    lmc Large Magellanic Cloud. ESO’s VISTA telescope reveals a remarkable image of the Large Magellanic Cloud.

    Part of ESO’s Paranal Observatory the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

    What at first was thought to be only one cluster in the core of the massive star-forming region 30 Doradus (also known as the Tarantula Nebula) has been found to be a composite of two clusters that differ in age by about one million years.

    The entire 30 Doradus complex has been an active star-forming region for 25 million years, and it is currently unknown how much longer this region can continue creating new stars. Smaller systems that merge into larger ones could help to explain the origin of some of the largest known star clusters.

    Lead scientist Elena Sabbi of the Space Telescope Science Institute in Baltimore, Md., and her team began looking at the area while searching for runaway stars, fast-moving stars that have been kicked out of their stellar nurseries where they first formed. “Stars are supposed to form in clusters, but there are many young stars outside 30 Doradus that could not have formed where they are; they may have been ejected at very high velocity from 30 Doradus itself,” Sabbi said.

    She then noticed something unusual about the cluster when looking at the distribution of the low-mass stars detected by Hubble. It is not spherical, as was expected, but has features somewhat similar to the shape of two merging galaxies where their shapes are elongated by the tidal pull of gravity. Hubble’s circumstantial evidence for the impending merger comes from seeing an elongated structure in one of the clusters, and from measuring a different age between the two clusters.

    According to some models, the giant gas clouds out of which star clusters form may fragment into smaller pieces. Once these small pieces precipitate stars, they might then interact and merge to become a bigger system. This interaction is what Sabbi and her team think they are observing in 30 Doradus.

    Also, there are an unusually large number of high-velocity stars around 30 Doradus. Astronomers believe that these stars, often called “runaway stars” were expelled from the core of 30 Doradus as the result of dynamical interactions. These interactions are very common during a process called core collapse, in which more-massive stars sink to the center of a cluster by dynamical interactions with lower-mass stars. When many massive stars have reached the core, the core becomes unstable and these massive stars start ejecting each other from the cluster.

    The big cluster R136 in the center of the 30 Doradus region is too young to have already experienced a core collapse. However, since in smaller systems the core collapse is much faster, the large number of runaway stars that has been found in the 30 Doradus region can be better explained if a small cluster has merged into R136.

    Follow-up studies will look at the area in more detail and on a larger scale to see if any more clusters might be interacting with the ones observed. In particular, the infrared sensitivity of NASA’s planned James Webb Space Telescope (JWST) will allow astronomers to look deep into the regions of the Tarantula Nebula that are obscured in visible-light photographs.

    National Aeronautics Space Agency(USA)/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ Canadian Space Agency [Agence Spatiale Canadienne](CA) Webb Infrared Space Telescope(US) James Webb Space Telescope annotated. Scheduled for launch in October 2021.

    In these areas cooler and dimmer stars are hidden from view inside cocoons of dust. Webb will better reveal the underlying population of stars in the nebula.

    The 30 Doradus Nebula is particularly interesting to astronomers because it is a good example of how star-forming regions in the young universe may have looked. This discovery could help scientists understand the details of cluster formation and how stars formed in the early universe.

    The members of Sabbi’s team are D.J. Lennon (ESA/STScI), M. Gieles (University of Cambridge (UK)), S.E. de Mink (STScI/Johns Hopkins University (US)), N.R. Walborn, J. Anderson, A. Bellini, N. Panagia, and R. van der Marel (STScI), and J. Maiz Appelaniz (Institute of Astrophysics of Andalusia [Instituto de Astrofísica de Andalucía] CSIC (ES)).

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition
    The NASA/ESA Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA’s Great Observatories, along with the NASA Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the NASA Spitzer Infared Space Telescope.

    National Aeronautics Space Agency(USA) Compton Gamma Ray Observatory



    Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope(US). Credit: Emilio Segre Visual Archives/AIP/SPL).

    Hubble features a 2.4-meter (7.9 ft) mirror, and its four main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble’s orbit outside the distortion of Earth’s atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of the most detailed visible light images, allowing a deep view into space. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe.

    The Hubble telescope was built by the United States space agency National Aeronautics Space Agency(US) with contributions from the European Space Agency [Agence spatiale européenne](EU). The Space Telescope Science Institute (STScI) selects Hubble’s targets and processes the resulting data, while the NASA Goddard Space Flight Center(US) controls the spacecraft. Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the 1986 Challenger disaster. It was finally launched by Space Shuttle Discovery in 1990, but its main mirror had been ground incorrectly, resulting in spherical aberration that compromised the telescope’s capabilities. The optics were corrected to their intended quality by a servicing mission in 1993.

    Hubble is the only telescope designed to be maintained in space by astronauts. Five Space Shuttle missions have repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments. The fifth mission was initially canceled on safety grounds following the Columbia disaster (2003), but NASA administrator Michael D. Griffin approved the fifth servicing mission which was completed in 2009. The telescope was still operating as of April 24, 2020, its 30th anniversary, and could last until 2030–2040. One successor to the Hubble telescope is the National Aeronautics Space Agency(USA)/European Space Agency [Agence spatiale européenne](EU)/Canadian Space Agency(CA) Webb Infrared Space Telescope scheduled for launch in October 2021.

    Proposals and precursors

    In 1923, Hermann Oberth—considered a father of modern rocketry, along with Robert H. Goddard and Konstantin Tsiolkovsky—published Die Rakete zu den Planetenräumen (“The Rocket into Planetary Space“), which mentioned how a telescope could be propelled into Earth orbit by a rocket.

    The history of the Hubble Space Telescope can be traced back as far as 1946, to astronomer Lyman Spitzer’s paper entitled Astronomical advantages of an extraterrestrial observatory. In it, he discussed the two main advantages that a space-based observatory would have over ground-based telescopes. First, the angular resolution (the smallest separation at which objects can be clearly distinguished) would be limited only by diffraction, rather than by the turbulence in the atmosphere, which causes stars to twinkle, known to astronomers as seeing. At that time ground-based telescopes were limited to resolutions of 0.5–1.0 arcseconds, compared to a theoretical diffraction-limited resolution of about 0.05 arcsec for an optical telescope with a mirror 2.5 m (8.2 ft) in diameter. Second, a space-based telescope could observe infrared and ultraviolet light, which are strongly absorbed by the atmosphere.

    Spitzer devoted much of his career to pushing for the development of a space telescope. In 1962, a report by the U.S. National Academy of Sciences recommended development of a space telescope as part of the space program, and in 1965 Spitzer was appointed as head of a committee given the task of defining scientific objectives for a large space telescope.

    Space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. The first ultraviolet spectrum of the Sun was obtained in 1946, and the National Aeronautics and Space Administration (US) launched the Orbiting Solar Observatory (OSO) to obtain UV, X-ray, and gamma-ray spectra in 1962.

    An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel space program, and in 1966 NASA launched the first Orbiting Astronomical Observatory (OAO) mission. OAO-1’s battery failed after three days, terminating the mission. It was followed by OAO-2, which carried out ultraviolet observations of stars and galaxies from its launch in 1968 until 1972, well beyond its original planned lifetime of one year.

    The OSO and OAO missions demonstrated the important role space-based observations could play in astronomy. In 1968, NASA developed firm plans for a space-based reflecting telescope with a mirror 3 m (9.8 ft) in diameter, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979. These plans emphasized the need for crewed maintenance missions to the telescope to ensure such a costly program had a lengthy working life, and the concurrent development of plans for the reusable Space Shuttle indicated that the technology to allow this was soon to become available.

    Quest for funding

    The continuing success of the OAO program encouraged increasingly strong consensus within the astronomical community that the LST should be a major goal. In 1970, NASA established two committees, one to plan the engineering side of the space telescope project, and the other to determine the scientific goals of the mission. Once these had been established, the next hurdle for NASA was to obtain funding for the instrument, which would be far more costly than any Earth-based telescope. The U.S. Congress questioned many aspects of the proposed budget for the telescope and forced cuts in the budget for the planning stages, which at the time consisted of very detailed studies of potential instruments and hardware for the telescope. In 1974, public spending cuts led to Congress deleting all funding for the telescope project.
    In response a nationwide lobbying effort was coordinated among astronomers. Many astronomers met congressmen and senators in person, and large scale letter-writing campaigns were organized. The National Academy of Sciences published a report emphasizing the need for a space telescope, and eventually the Senate agreed to half the budget that had originally been approved by Congress.

    The funding issues led to something of a reduction in the scale of the project, with the proposed mirror diameter reduced from 3 m to 2.4 m, both to cut costs and to allow a more compact and effective configuration for the telescope hardware. A proposed precursor 1.5 m (4.9 ft) space telescope to test the systems to be used on the main satellite was dropped, and budgetary concerns also prompted collaboration with the European Space Agency. ESA agreed to provide funding and supply one of the first generation instruments for the telescope, as well as the solar cells that would power it, and staff to work on the telescope in the United States, in return for European astronomers being guaranteed at least 15% of the observing time on the telescope. Congress eventually approved funding of US$36 million for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983. In 1983 the telescope was named after Edwin Hubble, who confirmed one of the greatest scientific discoveries of the 20th century, made by Georges Lemaître, that the universe is expanding.

    Construction and engineering

    Once the Space Telescope project had been given the go-ahead, work on the program was divided among many institutions. NASA Marshall Space Flight Center (MSFC) was given responsibility for the design, development, and construction of the telescope, while Goddard Space Flight Center was given overall control of the scientific instruments and ground-control center for the mission. MSFC commissioned the optics company Perkin-Elmer to design and build the Optical Telescope Assembly (OTA) and Fine Guidance Sensors for the space telescope. Lockheed was commissioned to construct and integrate the spacecraft in which the telescope would be housed.

    Optical Telescope Assembly

    Optically, the HST is a Cassegrain reflector of Ritchey–Chrétien design, as are most large professional telescopes. This design, with two hyperbolic mirrors, is known for good imaging performance over a wide field of view, with the disadvantage that the mirrors have shapes that are hard to fabricate and test. The mirror and optical systems of the telescope determine the final performance, and they were designed to exacting specifications. Optical telescopes typically have mirrors polished to an accuracy of about a tenth of the wavelength of visible light, but the Space Telescope was to be used for observations from the visible through the ultraviolet (shorter wavelengths) and was specified to be diffraction limited to take full advantage of the space environment. Therefore, its mirror needed to be polished to an accuracy of 10 nanometers, or about 1/65 of the wavelength of red light. On the long wavelength end, the OTA was not designed with optimum IR performance in mind—for example, the mirrors are kept at stable (and warm, about 15 °C) temperatures by heaters. This limits Hubble’s performance as an infrared telescope.

    Perkin-Elmer intended to use custom-built and extremely sophisticated computer-controlled polishing machines to grind the mirror to the required shape. However, in case their cutting-edge technology ran into difficulties, NASA demanded that PE sub-contract to Kodak to construct a back-up mirror using traditional mirror-polishing techniques. (The team of Kodak and Itek also bid on the original mirror polishing work. Their bid called for the two companies to double-check each other’s work, which would have almost certainly caught the polishing error that later caused such problems.) The Kodak mirror is now on permanent display at the National Air and Space Museum. An Itek mirror built as part of the effort is now used in the 2.4 m telescope at the Magdalena Ridge Observatory.

    Construction of the Perkin-Elmer mirror began in 1979, starting with a blank manufactured by Corning from their ultra-low expansion glass. To keep the mirror’s weight to a minimum it consisted of top and bottom plates, each one inch (25 mm) thick, sandwiching a honeycomb lattice. Perkin-Elmer simulated microgravity by supporting the mirror from the back with 130 rods that exerted varying amounts of force. This ensured the mirror’s final shape would be correct and to specification when finally deployed. Mirror polishing continued until May 1981. NASA reports at the time questioned Perkin-Elmer’s managerial structure, and the polishing began to slip behind schedule and over budget. To save money, NASA halted work on the back-up mirror and put the launch date of the telescope back to October 1984. The mirror was completed by the end of 1981; it was washed using 2,400 US gallons (9,100 L) of hot, deionized water and then received a reflective coating of 65 nm-thick aluminum and a protective coating of 25 nm-thick magnesium fluoride.

    Doubts continued to be expressed about Perkin-Elmer’s competence on a project of this importance, as their budget and timescale for producing the rest of the OTA continued to inflate. In response to a schedule described as “unsettled and changing daily”, NASA postponed the launch date of the telescope until April 1985. Perkin-Elmer’s schedules continued to slip at a rate of about one month per quarter, and at times delays reached one day for each day of work. NASA was forced to postpone the launch date until March and then September 1986. By this time, the total project budget had risen to US$1.175 billion.

    Spacecraft systems

    The spacecraft in which the telescope and instruments were to be housed was another major engineering challenge. It would have to withstand frequent passages from direct sunlight into the darkness of Earth’s shadow, which would cause major changes in temperature, while being stable enough to allow extremely accurate pointing of the telescope. A shroud of multi-layer insulation keeps the temperature within the telescope stable and surrounds a light aluminum shell in which the telescope and instruments sit. Within the shell, a graphite-epoxy frame keeps the working parts of the telescope firmly aligned. Because graphite composites are hygroscopic, there was a risk that water vapor absorbed by the truss while in Lockheed’s clean room would later be expressed in the vacuum of space; resulting in the telescope’s instruments being covered by ice. To reduce that risk, a nitrogen gas purge was performed before launching the telescope into space.

    While construction of the spacecraft in which the telescope and instruments would be housed proceeded somewhat more smoothly than the construction of the OTA, Lockheed still experienced some budget and schedule slippage, and by the summer of 1985, construction of the spacecraft was 30% over budget and three months behind schedule. An MSFC report said Lockheed tended to rely on NASA directions rather than take their own initiative in the construction.

    Computer systems and data processing

    The two initial, primary computers on the HST were the 1.25 MHz DF-224 system, built by Rockwell Autonetics, which contained three redundant CPUs, and two redundant NSSC-1 (NASA Standard Spacecraft Computer, Model 1) systems, developed by Westinghouse and GSFC using diode–transistor logic (DTL). A co-processor for the DF-224 was added during Servicing Mission 1 in 1993, which consisted of two redundant strings of an Intel-based 80386 processor with an 80387 math co-processor. The DF-224 and its 386 co-processor were replaced by a 25 MHz Intel-based 80486 processor system during Servicing Mission 3A in 1999. The new computer is 20 times faster, with six times more memory, than the DF-224 it replaced. It increases throughput by moving some computing tasks from the ground to the spacecraft and saves money by allowing the use of modern programming languages.

    Additionally, some of the science instruments and components had their own embedded microprocessor-based control systems. The MATs (Multiple Access Transponder) components, MAT-1 and MAT-2, utilize Hughes Aircraft CDP1802CD microprocessors. The Wide Field and Planetary Camera (WFPC) also utilized an RCA 1802 microprocessor (or possibly the older 1801 version). The WFPC-1 was replaced by the WFPC-2 [below] during Servicing Mission 1 in 1993, which was then replaced by the Wide Field Camera 3 (WFC3) [below] during Servicing Mission 4 in 2009.

    Initial instruments

    When launched, the HST carried five scientific instruments: the Wide Field and Planetary Camera (WF/PC), Goddard High Resolution Spectrograph (GHRS), High Speed Photometer (HSP), Faint Object Camera (FOC) and the Faint Object Spectrograph (FOS). WF/PC was a high-resolution imaging device primarily intended for optical observations. It was built by NASA JPL-Caltech(US), and incorporated a set of 48 filters isolating spectral lines of particular astrophysical interest. The instrument contained eight charge-coupled device (CCD) chips divided between two cameras, each using four CCDs. Each CCD has a resolution of 0.64 megapixels. The wide field camera (WFC) covered a large angular field at the expense of resolution, while the planetary camera (PC) took images at a longer effective focal length than the WF chips, giving it a greater magnification.

    The GHRS was a spectrograph designed to operate in the ultraviolet. It was built by the Goddard Space Flight Center and could achieve a spectral resolution of 90,000. Also optimized for ultraviolet observations were the FOC and FOS, which were capable of the highest spatial resolution of any instruments on Hubble. Rather than CCDs these three instruments used photon-counting digicons as their detectors. The FOC was constructed by ESA, while the University of California, San Diego(US), and Martin Marietta Corporation built the FOS.

    The final instrument was the HSP, designed and built at the University of Wisconsin–Madison(US). It was optimized for visible and ultraviolet light observations of variable stars and other astronomical objects varying in brightness. It could take up to 100,000 measurements per second with a photometric accuracy of about 2% or better.

    HST’s guidance system can also be used as a scientific instrument. Its three Fine Guidance Sensors (FGS) are primarily used to keep the telescope accurately pointed during an observation, but can also be used to carry out extremely accurate astrometry; measurements accurate to within 0.0003 arcseconds have been achieved.

    Ground support

    The Space Telescope Science Institute (STScI) is responsible for the scientific operation of the telescope and the delivery of data products to astronomers. STScI is operated by the Association of Universities for Research in Astronomy(US) (AURA) and is physically located in Baltimore, Maryland on the Homewood campus of Johns Hopkins University(US), one of the 39 U.S. universities and seven international affiliates that make up the AURA consortium. STScI was established in 1981 after something of a power struggle between NASA and the scientific community at large. NASA had wanted to keep this function in-house, but scientists wanted it to be based in an academic establishment. The Space Telescope European Coordinating Facility (ST-ECF), established at Garching bei München near Munich in 1984, provided similar support for European astronomers until 2011, when these activities were moved to the European Space Astronomy Centre.

    One rather complex task that falls to STScI is scheduling observations for the telescope. Hubble is in a low-Earth orbit to enable servicing missions, but this means most astronomical targets are occulted by the Earth for slightly less than half of each orbit. Observations cannot take place when the telescope passes through the South Atlantic Anomaly due to elevated radiation levels, and there are also sizable exclusion zones around the Sun (precluding observations of Mercury), Moon and Earth. The solar avoidance angle is about 50°, to keep sunlight from illuminating any part of the OTA. Earth and Moon avoidance keeps bright light out of the FGSs, and keeps scattered light from entering the instruments. If the FGSs are turned off, the Moon and Earth can be observed. Earth observations were used very early in the program to generate flat-fields for the WFPC1 instrument. There is a so-called continuous viewing zone (CVZ), at roughly 90° to the plane of Hubble’s orbit, in which targets are not occulted for long periods.

    Challenger disaster, delays, and eventual launch

    By January 1986, the planned launch date of October looked feasible, but the Challenger explosion brought the U.S. space program to a halt, grounding the Shuttle fleet and forcing the launch of Hubble to be postponed for several years. The telescope had to be kept in a clean room, powered up and purged with nitrogen, until a launch could be rescheduled. This costly situation (about US$6 million per month) pushed the overall costs of the project even higher. This delay did allow time for engineers to perform extensive tests, swap out a possibly failure-prone battery, and make other improvements. Furthermore, the ground software needed to control Hubble was not ready in 1986, and was barely ready by the 1990 launch.

    Eventually, following the resumption of shuttle flights in 1988, the launch of the telescope was scheduled for 1990. On April 24, 1990, Space Shuttle Discovery successfully launched it during the STS-31 mission.

    From its original total cost estimate of about US$400 million, the telescope cost about US$4.7 billion by the time of its launch. Hubble’s cumulative costs were estimated to be about US$10 billion in 2010, twenty years after launch.

    List of Hubble instruments

    Hubble accommodates five science instruments at a given time, plus the Fine Guidance Sensors, which are mainly used for aiming the telescope but are occasionally used for scientific astrometry measurements. Early instruments were replaced with more advanced ones during the Shuttle servicing missions. COSTAR was a corrective optics device rather than a science instrument, but occupied one of the five instrument bays.
    Since the final servicing mission in 2009, the four active instruments have been ACS, COS, STIS and WFC3. NICMOS is kept in hibernation, but may be revived if WFC3 were to fail in the future.

    Advanced Camera for Surveys (ACS; 2002–present)
    Cosmic Origins Spectrograph (COS; 2009–present)
    Corrective Optics Space Telescope Axial Replacement (COSTAR; 1993–2009)
    Faint Object Camera (FOC; 1990–2002)
    Faint Object Spectrograph (FOS; 1990–1997)
    Fine Guidance Sensor (FGS; 1990–present)
    Goddard High Resolution Spectrograph (GHRS/HRS; 1990–1997)
    High Speed Photometer (HSP; 1990–1993)
    Near Infrared Camera and Multi-Object Spectrometer (NICMOS; 1997–present, hibernating since 2008)
    Space Telescope Imaging Spectrograph (STIS; 1997–present (non-operative 2004–2009))
    Wide Field and Planetary Camera (WFPC; 1990–1993)
    Wide Field and Planetary Camera 2 (WFPC2; 1993–2009)
    Wide Field Camera 3 (WFC3; 2009–present)

    Of the former instruments, three (COSTAR, FOS and WFPC2) are displayed in the Smithsonian National Air and Space Museum. The FOC is in the Dornier museum, Germany. The HSP is in the Space Place at the University of Wisconsin–Madison. The first WFPC was dismantled, and some components were then re-used in WFC3.

    Flawed mirror

    Within weeks of the launch of the telescope, the returned images indicated a serious problem with the optical system. Although the first images appeared to be sharper than those of ground-based telescopes, Hubble failed to achieve a final sharp focus and the best image quality obtained was drastically lower than expected. Images of point sources spread out over a radius of more than one arcsecond, instead of having a point spread function (PSF) concentrated within a circle 0.1 arcseconds (485 nrad) in diameter, as had been specified in the design criteria.

    Analysis of the flawed images revealed that the primary mirror had been polished to the wrong shape. Although it was believed to be one of the most precisely figured optical mirrors ever made, smooth to about 10 nanometers, the outer perimeter was too flat by about 2200 nanometers (about 1⁄450 mm or 1⁄11000 inch). This difference was catastrophic, introducing severe spherical aberration, a flaw in which light reflecting off the edge of a mirror focuses on a different point from the light reflecting off its center.

    The effect of the mirror flaw on scientific observations depended on the particular observation—the core of the aberrated PSF was sharp enough to permit high-resolution observations of bright objects, and spectroscopy of point sources was affected only through a sensitivity loss. However, the loss of light to the large, out-of-focus halo severely reduced the usefulness of the telescope for faint objects or high-contrast imaging. This meant nearly all the cosmological programs were essentially impossible, since they required observation of exceptionally faint objects. This led politicians to question NASA’s competence, scientists to rue the cost which could have gone to more productive endeavors, and comedians to make jokes about NASA and the telescope − in the 1991 comedy The Naked Gun 2½: The Smell of Fear, in a scene where historical disasters are displayed, Hubble is pictured with RMS Titanic and LZ 129 Hindenburg. Nonetheless, during the first three years of the Hubble mission, before the optical corrections, the telescope still carried out a large number of productive observations of less demanding targets. The error was well characterized and stable, enabling astronomers to partially compensate for the defective mirror by using sophisticated image processing techniques such as deconvolution.

    Origin of the problem

    A commission headed by Lew Allen, director of the Jet Propulsion Laboratory, was established to determine how the error could have arisen. The Allen Commission found that a reflective null corrector, a testing device used to achieve a properly shaped non-spherical mirror, had been incorrectly assembled—one lens was out of position by 1.3 mm (0.051 in). During the initial grinding and polishing of the mirror, Perkin-Elmer analyzed its surface with two conventional refractive null correctors. However, for the final manufacturing step (figuring), they switched to the custom-built reflective null corrector, designed explicitly to meet very strict tolerances. The incorrect assembly of this device resulted in the mirror being ground very precisely but to the wrong shape. A few final tests, using the conventional null correctors, correctly reported spherical aberration. But these results were dismissed, thus missing the opportunity to catch the error, because the reflective null corrector was considered more accurate.

    The commission blamed the failings primarily on Perkin-Elmer. Relations between NASA and the optics company had been severely strained during the telescope construction, due to frequent schedule slippage and cost overruns. NASA found that Perkin-Elmer did not review or supervise the mirror construction adequately, did not assign its best optical scientists to the project (as it had for the prototype), and in particular did not involve the optical designers in the construction and verification of the mirror. While the commission heavily criticized Perkin-Elmer for these managerial failings, NASA was also criticized for not picking up on the quality control shortcomings, such as relying totally on test results from a single instrument.

    Design of a solution

    Many feared that Hubble would be abandoned. The design of the telescope had always incorporated servicing missions, and astronomers immediately began to seek potential solutions to the problem that could be applied at the first servicing mission, scheduled for 1993. While Kodak had ground a back-up mirror for Hubble, it would have been impossible to replace the mirror in orbit, and too expensive and time-consuming to bring the telescope back to Earth for a refit. Instead, the fact that the mirror had been ground so precisely to the wrong shape led to the design of new optical components with exactly the same error but in the opposite sense, to be added to the telescope at the servicing mission, effectively acting as “spectacles” to correct the spherical aberration.

    The first step was a precise characterization of the error in the main mirror. Working backwards from images of point sources, astronomers determined that the conic constant of the mirror as built was −1.01390±0.0002, instead of the intended −1.00230. The same number was also derived by analyzing the null corrector used by Perkin-Elmer to figure the mirror, as well as by analyzing interferograms obtained during ground testing of the mirror.

    Because of the way the HST’s instruments were designed, two different sets of correctors were required. The design of the Wide Field and Planetary Camera 2, already planned to replace the existing WF/PC, included relay mirrors to direct light onto the four separate charge-coupled device (CCD) chips making up its two cameras. An inverse error built into their surfaces could completely cancel the aberration of the primary. However, the other instruments lacked any intermediate surfaces that could be figured in this way, and so required an external correction device.

    The Corrective Optics Space Telescope Axial Replacement (COSTAR) system was designed to correct the spherical aberration for light focused at the FOC, FOS, and GHRS. It consists of two mirrors in the light path with one ground to correct the aberration. To fit the COSTAR system onto the telescope, one of the other instruments had to be removed, and astronomers selected the High Speed Photometer to be sacrificed. By 2002, all the original instruments requiring COSTAR had been replaced by instruments with their own corrective optics. COSTAR was removed and returned to Earth in 2009 where it is exhibited at the National Air and Space Museum. The area previously used by COSTAR is now occupied by the Cosmic Origins Spectrograph.

    Servicing missions and new instruments

    Servicing Mission 1

    The first Hubble serving mission was scheduled for 1993 before the mirror problem was discovered. It assumed greater importance, as the astronauts would need to do extensive work to install corrective optics; failure would have resulted in either abandoning Hubble or accepting its permanent disability. Other components failed before the mission, causing the repair cost to rise to $500 million (not including the cost of the shuttle flight). A successful repair would help demonstrate the viability of building Space Station Alpha, however.

    STS-49 in 1992 demonstrated the difficulty of space work. While its rescue of Intelsat 603 received praise, the astronauts had taken possibly reckless risks in doing so. Neither the rescue nor the unrelated assembly of prototype space station components occurred as the astronauts had trained, causing NASA to reassess planning and training, including for the Hubble repair. The agency assigned to the mission Story Musgrave—who had worked on satellite repair procedures since 1976—and six other experienced astronauts, including two from STS-49. The first mission director since Project Apollo would coordinate a crew with 16 previous shuttle flights. The astronauts were trained to use about a hundred specialized tools.

    Heat had been the problem on prior spacewalks, which occurred in sunlight. Hubble needed to be repaired out of sunlight. Musgrave discovered during vacuum training, seven months before the mission, that spacesuit gloves did not sufficiently protect against the cold of space. After STS-57 confirmed the issue in orbit, NASA quickly changed equipment, procedures, and flight plan. Seven total mission simulations occurred before launch, the most thorough preparation in shuttle history. No complete Hubble mockup existed, so the astronauts studied many separate models (including one at the Smithsonian) and mentally combined their varying and contradictory details. Service Mission 1 flew aboard Endeavour in December 1993, and involved installation of several instruments and other equipment over ten days.

    Most importantly, the High Speed Photometer was replaced with the COSTAR corrective optics package, and WFPC was replaced with the Wide Field and Planetary Camera 2 (WFPC2) with an internal optical correction system. The solar arrays and their drive electronics were also replaced, as well as four gyroscopes in the telescope pointing system, two electrical control units and other electrical components, and two magnetometers. The onboard computers were upgraded with added coprocessors, and Hubble’s orbit was boosted.

    On January 13, 1994, NASA declared the mission a complete success and showed the first sharper images. The mission was one of the most complex performed up until that date, involving five long extra-vehicular activity periods. Its success was a boon for NASA, as well as for the astronomers who now had a more capable space telescope.

    Servicing Mission 2

    Servicing Mission 2, flown by Discovery in February 1997, replaced the GHRS and the FOS with the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), replaced an Engineering and Science Tape Recorder with a new Solid State Recorder, and repaired thermal insulation. NICMOS contained a heat sink of solid nitrogen to reduce the thermal noise from the instrument, but shortly after it was installed, an unexpected thermal expansion resulted in part of the heat sink coming into contact with an optical baffle. This led to an increased warming rate for the instrument and reduced its original expected lifetime of 4.5 years to about two years.

    Servicing Mission 3A

    Servicing Mission 3A, flown by Discovery, took place in December 1999, and was a split-off from Servicing Mission 3 after three of the six onboard gyroscopes had failed. The fourth failed a few weeks before the mission, rendering the telescope incapable of performing scientific observations. The mission replaced all six gyroscopes, replaced a Fine Guidance Sensor and the computer, installed a Voltage/temperature Improvement Kit (VIK) to prevent battery overcharging, and replaced thermal insulation blankets.

    Servicing Mission 3B

    Servicing Mission 3B flown by Columbia in March 2002 saw the installation of a new instrument, with the FOC (which, except for the Fine Guidance Sensors when used for astrometry, was the last of the original instruments) being replaced by the Advanced Camera for Surveys (ACS). This meant COSTAR was no longer required, since all new instruments had built-in correction for the main mirror aberration. The mission also revived NICMOS by installing a closed-cycle cooler and replaced the solar arrays for the second time, providing 30 percent more power.

    Servicing Mission 4

    Plans called for Hubble to be serviced in February 2005, but the Columbia disaster in 2003, in which the orbiter disintegrated on re-entry into the atmosphere, had wide-ranging effects on the Hubble program. NASA Administrator Sean O’Keefe decided all future shuttle missions had to be able to reach the safe haven of the International Space Station should in-flight problems develop. As no shuttles were capable of reaching both HST and the space station during the same mission, future crewed service missions were canceled. This decision was criticised by numerous astronomers who felt Hubble was valuable enough to merit the human risk. HST’s planned successor, the James Webb Telescope (JWST), as of 2004 was not expected to launch until at least 2011. A gap in space-observing capabilities between a decommissioning of Hubble and the commissioning of a successor was of major concern to many astronomers, given the significant scientific impact of HST. The consideration that JWST will not be located in low Earth orbit, and therefore cannot be easily upgraded or repaired in the event of an early failure, only made concerns more acute. On the other hand, many astronomers felt strongly that servicing Hubble should not take place if the expense were to come from the JWST budget.

    In January 2004, O’Keefe said he would review his decision to cancel the final servicing mission to HST, due to public outcry and requests from Congress for NASA to look for a way to save it. The National Academy of Sciences convened an official panel, which recommended in July 2004 that the HST should be preserved despite the apparent risks. Their report urged “NASA should take no actions that would preclude a space shuttle servicing mission to the Hubble Space Telescope”. In August 2004, O’Keefe asked Goddard Space Flight Center to prepare a detailed proposal for a robotic service mission. These plans were later canceled, the robotic mission being described as “not feasible”. In late 2004, several Congressional members, led by Senator Barbara Mikulski, held public hearings and carried on a fight with much public support (including thousands of letters from school children across the U.S.) to get the Bush Administration and NASA to reconsider the decision to drop plans for a Hubble rescue mission.

    The nomination in April 2005 of a new NASA Administrator, Michael D. Griffin, changed the situation, as Griffin stated he would consider a crewed servicing mission. Soon after his appointment Griffin authorized Goddard to proceed with preparations for a crewed Hubble maintenance flight, saying he would make the final decision after the next two shuttle missions. In October 2006 Griffin gave the final go-ahead, and the 11-day mission by Atlantis was scheduled for October 2008. Hubble’s main data-handling unit failed in September 2008, halting all reporting of scientific data until its back-up was brought online on October 25, 2008. Since a failure of the backup unit would leave the HST helpless, the service mission was postponed to incorporate a replacement for the primary unit.

    Servicing Mission 4 (SM4), flown by Atlantis in May 2009, was the last scheduled shuttle mission for HST. SM4 installed the replacement data-handling unit, repaired the ACS and STIS systems, installed improved nickel hydrogen batteries, and replaced other components including all six gyroscopes. SM4 also installed two new observation instruments—Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS)—and the Soft Capture and Rendezvous System, which will enable the future rendezvous, capture, and safe disposal of Hubble by either a crewed or robotic mission. Except for the ACS’s High Resolution Channel, which could not be repaired and was disabled, the work accomplished during SM4 rendered the telescope fully functional.

    Major projects

    Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey [CANDELS]

    The survey “aims to explore galactic evolution in the early Universe, and the very first seeds of cosmic structure at less than one billion years after the Big Bang.” The CANDELS project site describes the survey’s goals as the following:

    The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey is designed to document the first third of galactic evolution from z = 8 to 1.5 via deep imaging of more than 250,000 galaxies with WFC3/IR and ACS. It will also find the first Type Ia SNe beyond z > 1.5 and establish their accuracy as standard candles for cosmology. Five premier multi-wavelength sky regions are selected; each has multi-wavelength data from Spitzer and other facilities, and has extensive spectroscopy of the brighter galaxies. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to 109 solar masses out to z ~ 8.

    Frontier Fields program

    The program, officially named Hubble Deep Fields Initiative 2012, is aimed to advance the knowledge of early galaxy formation by studying high-redshift galaxies in blank fields with the help of gravitational lensing to see the “faintest galaxies in the distant universe”. The Frontier Fields web page describes the goals of the program being:

    To reveal hitherto inaccessible populations of z = 5–10 galaxies that are ten to fifty times fainter intrinsically than any presently known
    To solidify our understanding of the stellar masses and star formation histories of sub-L* galaxies at the earliest times
    To provide the first statistically meaningful morphological characterization of star forming galaxies at z > 5
    To find z > 8 galaxies stretched out enough by cluster lensing to discern internal structure and/or magnified enough by cluster lensing for spectroscopic follow-up.

    Cosmic Evolution Survey (COSMOS)

    The Cosmic Evolution Survey (COSMOS) is an astronomical survey designed to probe the formation and evolution of galaxies as a function of both cosmic time (redshift) and the local galaxy environment. The survey covers a two square degree equatorial field with spectroscopy and X-ray to radio imaging by most of the major space-based telescopes and a number of large ground based telescopes, making it a key focus region of extragalactic astrophysics. COSMOS was launched in 2006 as the largest project pursued by the Hubble Space Telescope at the time, and still is the largest continuous area of sky covered for the purposes of mapping deep space in blank fields, 2.5 times the area of the moon on the sky and 17 times larger than the largest of the CANDELS regions. The COSMOS scientific collaboration that was forged from the initial COSMOS survey is the largest and longest-running extragalactic collaboration, known for its collegiality and openness. The study of galaxies in their environment can be done only with large areas of the sky, larger than a half square degree. More than two million galaxies are detected, spanning 90% of the age of the Universe. The COSMOS collaboration is led by Caitlin Casey, Jeyhan Kartaltepe, and Vernesa Smolcic and involves more than 200 scientists in a dozen countries.

    Important discoveries

    Hubble has helped resolve some long-standing problems in astronomy, while also raising new questions. Some results have required new theories to explain them.

    Age of the universe

    Among its primary mission targets was to measure distances to Cepheid variable stars more accurately than ever before, and thus constrain the value of the Hubble constant, the measure of the rate at which the universe is expanding, which is also related to its age. Before the launch of HST, estimates of the Hubble constant typically had errors of up to 50%, but Hubble measurements of Cepheid variables in the Virgo Cluster and other distant galaxy clusters provided a measured value with an accuracy of ±10%, which is consistent with other more accurate measurements made since Hubble’s launch using other techniques. The estimated age is now about 13.7 billion years, but before the Hubble Telescope, scientists predicted an age ranging from 10 to 20 billion years.

    Expansion of the universe

    While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. Astronomers from the High-z Supernova Search Team and the Supernova Cosmology Project used ground-based telescopes and HST to observe distant supernovae and uncovered evidence that, far from decelerating under the influence of gravity, the expansion of the universe may in fact be accelerating. Three members of these two groups have subsequently been awarded Nobel Prizes for their discovery.

    Saul Perlmutter [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt and Adam Riess [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

    The cause of this acceleration remains poorly understood; the most common cause attributed is Dark Energy.

    Black holes

    The high-resolution spectra and images provided by the HST have been especially well-suited to establishing the prevalence of black holes in the center of nearby galaxies. While it had been hypothesized in the early 1960s that black holes would be found at the centers of some galaxies, and astronomers in the 1980s identified a number of good black hole candidates, work conducted with Hubble shows that black holes are probably common to the centers of all galaxies. The Hubble programs further established that the masses of the nuclear black holes and properties of the galaxies are closely related. The legacy of the Hubble programs on black holes in galaxies is thus to demonstrate a deep connection between galaxies and their central black holes.

    Extending visible wavelength images

    A unique window on the Universe enabled by Hubble are the Hubble Deep Field, Hubble Ultra-Deep Field, and Hubble Extreme Deep Field images, which used Hubble’s unmatched sensitivity at visible wavelengths to create images of small patches of sky that are the deepest ever obtained at optical wavelengths. The images reveal galaxies billions of light years away, and have generated a wealth of scientific papers, providing a new window on the early Universe. The Wide Field Camera 3 improved the view of these fields in the infrared and ultraviolet, supporting the discovery of some of the most distant objects yet discovered, such as MACS0647-JD.

    The non-standard object SCP 06F6 was discovered by the Hubble Space Telescope in February 2006.

    On March 3, 2016, researchers using Hubble data announced the discovery of the farthest known galaxy to date: GN-z11. The Hubble observations occurred on February 11, 2015, and April 3, 2015, as part of the CANDELS/GOODS-North surveys.

    Solar System discoveries

    HST has also been used to study objects in the outer reaches of the Solar System, including the dwarf planets Pluto and Eris.

    The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 was fortuitously timed for astronomers, coming just a few months after Servicing Mission 1 had restored Hubble’s optical performance. Hubble images of the planet were sharper than any taken since the passage of Voyager 2 in 1979, and were crucial in studying the dynamics of the collision of a comet with Jupiter, an event believed to occur once every few centuries.

    During June and July 2012, U.S. astronomers using Hubble discovered Styx, a tiny fifth moon orbiting Pluto.

    In March 2015, researchers announced that measurements of aurorae around Ganymede, one of Jupiter’s moons, revealed that it has a subsurface ocean. Using Hubble to study the motion of its aurorae, the researchers determined that a large saltwater ocean was helping to suppress the interaction between Jupiter’s magnetic field and that of Ganymede. The ocean is estimated to be 100 km (60 mi) deep, trapped beneath a 150 km (90 mi) ice crust.

    From June to August 2015, Hubble was used to search for a Kuiper belt object (KBO) target for the New Horizons Kuiper Belt Extended Mission (KEM) when similar searches with ground telescopes failed to find a suitable target.

    This resulted in the discovery of at least five new KBOs, including the eventual KEM target, 486958 Arrokoth, that New Horizons performed a close fly-by of on January 1, 2019.

    In August 2020, taking advantage of a total lunar eclipse, astronomers using NASA’s Hubble Space Telescope have detected Earth’s own brand of sunscreen – ozone – in our atmosphere. This method simulates how astronomers and astrobiology researchers will search for evidence of life beyond Earth by observing potential “biosignatures” on exoplanets (planets around other stars).
    Hubble and ALMA image of MACS J1149.5+2223.

    Supernova reappearance

    On December 11, 2015, Hubble captured an image of the first-ever predicted reappearance of a supernova, dubbed “Refsdal”, which was calculated using different mass models of a galaxy cluster whose gravity is warping the supernova’s light. The supernova was previously seen in November 2014 behind galaxy cluster MACS J1149.5+2223 as part of Hubble’s Frontier Fields program. Astronomers spotted four separate images of the supernova in an arrangement known as an “Einstein Cross”.

    The light from the cluster has taken about five billion years to reach Earth, though the supernova exploded some 10 billion years ago. Based on early lens models, a fifth image was predicted to reappear by the end of 2015. The detection of Refsdal’s reappearance in December 2015 served as a unique opportunity for astronomers to test their models of how mass, especially dark matter, is distributed within this galaxy cluster.

    Impact on astronomy

    Many objective measures show the positive impact of Hubble data on astronomy. Over 15,000 papers based on Hubble data have been published in peer-reviewed journals, and countless more have appeared in conference proceedings. Looking at papers several years after their publication, about one-third of all astronomy papers have no citations, while only two percent of papers based on Hubble data have no citations. On average, a paper based on Hubble data receives about twice as many citations as papers based on non-Hubble data. Of the 200 papers published each year that receive the most citations, about 10% are based on Hubble data.

    Although the HST has clearly helped astronomical research, its financial cost has been large. A study on the relative astronomical benefits of different sizes of telescopes found that while papers based on HST data generate 15 times as many citations as a 4 m (13 ft) ground-based telescope such as the William Herschel Telescope, the HST costs about 100 times as much to build and maintain.

    Deciding between building ground- versus space-based telescopes is complex. Even before Hubble was launched, specialized ground-based techniques such as aperture masking interferometry had obtained higher-resolution optical and infrared images than Hubble would achieve, though restricted to targets about 108 times brighter than the faintest targets observed by Hubble. Since then, advances in “adaptive optics” have extended the high-resolution imaging capabilities of ground-based telescopes to the infrared imaging of faint objects.

    The usefulness of adaptive optics versus HST observations depends strongly on the particular details of the research questions being asked. In the visible bands, adaptive optics can correct only a relatively small field of view, whereas HST can conduct high-resolution optical imaging over a wide field. Only a small fraction of astronomical objects are accessible to high-resolution ground-based imaging; in contrast Hubble can perform high-resolution observations of any part of the night sky, and on objects that are extremely faint.

    Impact on aerospace engineering

    In addition to its scientific results, Hubble has also made significant contributions to aerospace engineering, in particular the performance of systems in low Earth orbit. These insights result from Hubble’s long lifetime on orbit, extensive instrumentation, and return of assemblies to the Earth where they can be studied in detail. In particular, Hubble has contributed to studies of the behavior of graphite composite structures in vacuum, optical contamination from residual gas and human servicing, radiation damage to electronics and sensors, and the long term behavior of multi-layer insulation. One lesson learned was that gyroscopes assembled using pressurized oxygen to deliver suspension fluid were prone to failure due to electric wire corrosion. Gyroscopes are now assembled using pressurized nitrogen. Another is that optical surfaces in LEO can have surprisingly long lifetimes; Hubble was only expected to last 15 years before the mirror became unusable, but after 14 years there was no measureable degradation. Finally, Hubble servicing missions, particularly those that serviced components not designed for in-space maintenance, have contributed towards the development of new tools and techniques for on-orbit repair.

    Archives

    All Hubble data is eventually made available via the Mikulski Archive for Space Telescopes at STScI, CADC and ESA/ESAC. Data is usually proprietary—available only to the principal investigator (PI) and astronomers designated by the PI—for twelve months after being taken. The PI can apply to the director of the STScI to extend or reduce the proprietary period in some circumstances.

    Observations made on Director’s Discretionary Time are exempt from the proprietary period, and are released to the public immediately. Calibration data such as flat fields and dark frames are also publicly available straight away. All data in the archive is in the FITS format, which is suitable for astronomical analysis but not for public use. The Hubble Heritage Project processes and releases to the public a small selection of the most striking images in JPEG and TIFF formats.

    Outreach activities

    It has always been important for the Space Telescope to capture the public’s imagination, given the considerable contribution of taxpayers to its construction and operational costs. After the difficult early years when the faulty mirror severely dented Hubble’s reputation with the public, the first servicing mission allowed its rehabilitation as the corrected optics produced numerous remarkable images.

    Several initiatives have helped to keep the public informed about Hubble activities. In the United States, outreach efforts are coordinated by the Space Telescope Science Institute (STScI) Office for Public Outreach, which was established in 2000 to ensure that U.S. taxpayers saw the benefits of their investment in the space telescope program. To that end, STScI operates the HubbleSite.org website. The Hubble Heritage Project, operating out of the STScI, provides the public with high-quality images of the most interesting and striking objects observed. The Heritage team is composed of amateur and professional astronomers, as well as people with backgrounds outside astronomy, and emphasizes the aesthetic nature of Hubble images. The Heritage Project is granted a small amount of time to observe objects which, for scientific reasons, may not have images taken at enough wavelengths to construct a full-color image.

    Since 1999, the leading Hubble outreach group in Europe has been the Hubble European Space Agency Information Centre (HEIC). This office was established at the Space Telescope European Coordinating Facility in Munich, Germany. HEIC’s mission is to fulfill HST outreach and education tasks for the European Space Agency. The work is centered on the production of news and photo releases that highlight interesting Hubble results and images. These are often European in origin, and so increase awareness of both ESA’s Hubble share (15%) and the contribution of European scientists to the observatory. ESA produces educational material, including a videocast series called Hubblecast designed to share world-class scientific news with the public.

    The Hubble Space Telescope has won two Space Achievement Awards from the Space Foundation, for its outreach activities, in 2001 and 2010.

    A replica of the Hubble Space Telescope is on the courthouse lawn in Marshfield, Missouri, the hometown of namesake Edwin P. Hubble.

    Major Instrumentation

    Hubble WFPC2 no longer in service.

    Wide Field Camera 3 [WFC3]

    Advanced Camera for Surveys [ACS]

    Cosmic Origins Spectrograph [COS]

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    ESA50 Logo large

     
  • richardmitnick 10:01 am on September 29, 2021 Permalink | Reply
    Tags: "Solar superflares hit Earth multiple times", EarthSky, Finding a carbon-14 spike on a tree ring provides an incredibly precise date for when the event occurred., Tree rings from Switzerland; Germany; Ireland; Russia and the U.S. were analyzed., Trees around the world bear evidence of the carbon-14 spike showing that the event was global in scale., When energetic particles from a solar flare interact with Earth’s atmosphere they can produce carbon-14.   

    From EarthSky : “Solar superflares hit Earth multiple times” 

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    From EarthSky

    September 29, 2021

    Kelly Kizer Whitt

    1
    A solar flare erupted from the sun on September 10, 2017. This flare would pale in comparison to any solar superflares. Image via NASA/ SDO/ NASA Goddard Space Flight Center (US).

    Scientists discover ancient solar superflares

    A solar superstorm rocked Earth in 774-775 CE. Scientists uncovered this event in 2012 when analyzing a spike in carbon-14 found in tree rings. Trees around the world bear evidence of the carbon-14 spike showing that the event was global in scale. Last month, scientists announced that after searching just 1/6 of the available tree ring data, they found evidence of two more events, in 5259 BCE and 7176 BCE.

    The scientists submitted their paper for peer review to Research Square on August 10, 2021. Their research shows that more solar superflares from the past might exist. So these events may not be all that “rare,” which serves as a warning to future Earth.

    For the new discoveries, scientists once again analyzed tree rings. They analyzed trees from Switzerland, Germany, Ireland, Russia and the U.S. When energetic particles from a solar flare interact with Earth’s atmosphere they can produce carbon-14, which eventually becomes incorporated into the tree as a chemical imprint. One tree ring equals one year in the life of that tree. Therefore, finding a carbon-14 spike on a tree ring provides an incredibly precise date for when the event occurred.

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    Scientists used data from tree rings to find and date the carbon-14 spike. Image via Gabriel Jimenez/ Unsplash.

    Carbon-14 in tree rings

    The Holocene epoch, which began 12,000 years ago and which we are currently in, provides plenty of tree ring data. But it takes weeks of analyzing just to go through one year of data. So having found two more events might change the meaning of “rare” for these events. As the scientists said in their paper:

    “The increasing number of discovered strong SEP [solar energetic particle] events hitting Earth over the past 10,000 years indicates that they cannot be considered as extremely rare. So far, only 16.5% of the past 12,400 years have been analyzed.”

    The scientists didn’t stumble onto the dates 7176 and 5259 BCE. Other data led them to deduce these years. Scientists already suspected the 7176 BCE. date through data from ice cores. In ice cores, the scientists look for beryllium 10 and chlorine 36 as signatures of solar flares. Previous analysis showed a beryllium 10 spike around the 7176 date. For the 5259 BCE date, Alexandra Bayliss of The University of Stirling (SCT), one of the authors on the paper, noticed a gap in archaeological data around this time.

    So, out of the last 10,000-plus years, scientists know of three major solar superflare events that left behind evidence in the way of carbon-14 spikes. With some 85% of tree ring data left to search, we might discover that these strong solar energetic particle events are more frequent than we believed.

    What would happen if a solar superflare hit today?

    The scientists said in the paper that a solar superflare, such as the ones they found in ancient history through tree rings, would be devastating to our modern world:

    “The impact of the newly discovered events would have been catastrophic for aircraft, satellites, modern telecommunication and computer systems, if they occurred today.”

    One of the most famous solar storms in recorded history is the Carrington Event of 1859. This event, which fried telegraph systems – the peak technology of the time – isn’t even detectable in the carbon-14 data in tree rings. So it would be but a whisper compared to the thundering onslaught of a solar superflare. One of the most recent solar events in history is the March 1989 solar storm. With only a minuscule amount of energy that a super solarflare would produce, it nonetheless caused an hours-long blackout in Quebec. A solar superflare striking Earth could take the “worldwide” out of the worldwide web, knocking out undersea cables, and possibly destroying electronic data including banking and health information.

    But before you worry too much about a coming technological dark age, take comfort in a fact noted in the paper:

    “Statistics of sun-like stars suggest that superflares are extremely rare.”

    While the sun has perhaps undergone more superflares than we once expected, they still seem to be an infrequent event, fortunately.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 9:01 am on September 24, 2021 Permalink | Reply
    Tags: "Delta Cephei helps measure cosmic distances", , , , EarthSky,   

    From EarthSky : “Delta Cephei helps measure cosmic distances” 

    1

    From EarthSky

    September 24, 2021

    Bruce McClure
    Shireen Gonzaga

    1
    Like lights in a dark tunnel, stars in the distant universe are fainter as they’re located farther away. But stars like Delta Cephei pulsate at a rate always correlated to their intrinsic brightnesses. So they reveal their own true distances. Image via The Last Word on Nothing.

    Delta Cephei is a pulsating star

    Delta Cephei, in the constellation Cepheus the King, is a variable star that changes in brightness with clocklike precision. It doubles in brightness and fades back to minimum brightness every 5.366 days. With careful observation under a dark sky, you can see this star change in brightness over several days. This star, and others like it, are important players in establishing the distance scale of our galaxy … and our universe.

    Delta Cephei itself looms large in the history of astronomy. An entire class of supergiant stars – called Cepheid variables – is named in this star’s honor.

    Cepheid variable stars, also called Cepheids, dependably change their brightnesses over regular intervals ranging from a few days to a few weeks. In 1912, astronomer Henrietta Leavitt discovered that the star’s periodic change in brightness was directly related to its intrinsic brightness (or actual luminosity). She found that the longer the brightness pulsation cycle, the greater the intrinsic brightness of the star. This Cepheid period-luminosity relationship is now sometimes called the Leavitt law.

    Why are these stars varying in brightness? It’s thought that these stars vary because they expand (get brighter) and then contract (get fainter) in a regular way.

    Cepheids help measure cosmic distances

    The regularity of Cepheids’ brightening and dimming is a powerful tool in astronomy. It lets astronomers probe distances across vast space. You might know that the surest way to measure star distances is via stellar parallax. But, for the parallax method to work, the stars have to be relatively nearby (within about 1000 light-years). Luckily, in recent years, astronomers have been able to make direct parallax measurements of more distant stars, thanks to space-based telescopes such as Gaia.

    Still, the problem remains. How can we find the distance to stars that are too faraway to give us a reliable distance measurement via parallax? Suppose you measured the distance to a nearby Cepheid star using the parallax method. Then suppose you watched its pulsations, which you know are correlated with the star’s intrinsic – real – brightness. Then you know both its distance and how bright the star looks at that distance. Armed with this information, you can then look farther out in the universe, toward more distant Cepheids, those too far for parallax measurements. You can measure the apparent brightness – which is fainter – and pulsation rate of such a star. With a few simple steps of math, you can then find the distance to it.

    The Cepheid variable stars are used to measure distances across space. For this reason, they’re known as standard candles by astronomers.

    In 1923, the astronomer Edwin Hubble used Cepheids to determine that the then-called Andromeda nebula is actually not a nebula but a giant galaxy lying beyond our Milky Way. It released us from the confines of a single galaxy and gave us the vast universe we know today. This work in understanding the size of the universe is sometimes called the cosmic distance ladder.

    The work continues today, not just with Cepheids but also with other astronomical objects and phenomena.

    Cepheids in other galaxies

    Distance determinations using Cepheids in other galaxies, as well as other techniques, is an active area of research in astronomy. Astronomers are constantly improving distance accuracies to further constrain the value of the Hubble Constant that indicates the expansion rate of the universe.

    Cepheids have been observed as far away as 100 million light-years in the galaxy NGC 4603, by the Hubble Space Telescope. However, measuring them at distances of 30 million light-years and farther is difficult because it’s hard to isolate Cepheids from their neighboring stars. At such distances, astronomers transition to other methods to determine distances, such as observing type 1a supernovae.

    How to spot Delta Cephei in the night sky

    The original Cepheid, Delta Cephei, is circumpolar – always above the horizon – in the northern half of the United States.

    Even so, Delta Cephei is much easier to see when it’s high in the northern sky on autumn and winter evenings. If you’re far enough north, you can find the constellation Cepheus by way of the Big Dipper. First, use the Big Dipper “pointer stars” to locate Polaris, the North Star. Then jump beyond Polaris by a fist-width to land on Cepheus.

    You’ll see the constellation Cepheus the King close to his wife, Cassiopeia the Queen, her signature W or M-shaped figure of stars making her the flashier of the two constellations. They’re high in your northern sky on November and December evenings.

    2
    A larger view of Cepheus, showing the Cepheid variable Delta Cepheid (in crosshairs) near two other stars, Zeta and Epsilon Cephei. Delta Cephei displays about a two-fold change in brightness (0.23 visual magnitudes) every 5.366 days, ranging from a visual magnitude of 3.48 at its brightest to 4.37 at its faintest. Zeta and Epsilon Cephei are useful comparison stars for noting changes in brightness of Delta Cephei from one night to the next. Zeta Cephei has a visual magnitude of 3.35, which is close to the maximum brightness of Delta Cephei. Epsilon Cephei has a visual magnitude of 4.15, which is close to the minimum brightness of Delta Cephei. Image via Stellarium.

    How to watch Delta Cephei vary in brightness

    The real answer to that question is: time and patience. But two stars lodging near Delta Cephei on the sky’s dome – Epsilon Cephei and Zeta Cephei – match the low and high ends of Delta Cephei’s brightness scale. That fact should help you watch Delta Cephei change.

    So look at the charts above, and locate the stars Epsilon and Zeta Cephei. At its faintest, Delta Cephei is as dim as the fainter star, Epsilon Cephei. At its brightest, Delta Cephei matches the brightness of the brighter star, Zeta Cephei.

    Have fun!

    3
    Astrophotographer Alan Dyer captured this image of Delta Cephei (center), with the Wizard Nebula on its left, and the nebula Sharpless 2-135 on its right. The orangish star on the far right is Zeta Cephei. Image via Alan Dyer / AmazingSky.com /Flickr. Used with permission.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 9:21 am on September 21, 2021 Permalink | Reply
    Tags: "Asteroid 2021 SG came from the sun’s direction", , , , , EarthSky   

    From EarthSky : “Asteroid 2021 SG came from the sun’s direction” 

    1

    From EarthSky

    September 20, 2021

    Eddie Irizarry
    Deborah Byrd

    1
    This illustration shows asteroid 2021 SG’s location just 24 hours before its closest approach to Earth on September 16, 2021. It was close to the sun’s direction in our sky. So astronomers didn’t spot it until September 17, the day after its closest approach. Illustration by Eddie Irizarry /Stellarium.

    Asteroid 2021 SG: Bigger than Chelyabinsk

    New-found asteroid 2021 SG is some four times larger than the 17-meter (18-yard) space rock that disintegrated over Chelyabinsk, Russia, on February 15, 2013. The Chelyabinsk meteor created a shock wave that broke windows in six Russian cities. It caused some 1,500 people to seek medical attention, mostly from flying glass. But newly found asteroid 2021 SG didn’t hit. It just passed close, at only about half the distance from Earth to the moon, last week. Astronomers finally picked up the asteroid – discovering it for the first time – a day later on September 17, 2021. They were using a large telescope, the 48-inch (1.2 meter) telescope at Mount Palomar in California. Why didn’t they spot it sooner? Because it came from the direction of the sun.

    An analysis of its orbit indicates that asteroid 2021 SG was closest to Earth on September 16 at 20:28 UTC (4:28 p.m. ET).

    Asteroid 2021 SG has an estimated diameter of between 42 – 94 meters (138-308 feet). Its average diameter is 68 meters (223 feet). That’s in contrast to 17 meters for the Chelyabinsk meteor before it entered Earth’s atmosphere.

    It came from the direction of the sun. Those words might sound chilling to you. And they do, too – perhaps more so – to scientists who work to detect near-Earth asteroids, in an effort to keep our planet safe. The Chelyabinsk meteor that did so much damage and caused so much consternation in 2013 also came, unexpectedly, from the sun’s direction. The fact is that astronomers have become very good at detecting near-Earth asteroids. And there are programs in place to watch for them. Some observatories constantly take images of the night skies in search for new asteroids. And astronomers feel they have a good handle on all the potentially damaging asteroids out there … except those that might come to us from the sun’s direction.

    If it entered our atmosphere, an asteroid as big as 2021 SG would produce a huge, very impressive meteor. Asteroid 2021 SG isn’t just big. It’s also a fast-moving asteroid, traveling through space at the amazing speed of 53,281 miles per hour (85,748 km/h or 23.8 km per second), relative to Earth. At closest approach on September 16, 2021, asteroid 2021 SG came closest to Canada and Greenland.

    The orbit of 2021 SG shows it’s an Apollo type asteroid that completes a revolution or orbit around the sun every 27 months (2.24 years). This time, it passed Earth just after just passing Mercury’s orbit.

    2
    The orbit of asteroid 2021 SG shows it comes as close to the sun as Mercury, our sun’s innermost planet. And then it goes as far out as between the orbits of Mars and Jupiter. In 2021, it swept past Earth not long after passing close to Mercury’s orbit. Image via NASA JPL-Caltech (US).

    Asteroids from the sun’s direction

    Can astronomers detect asteroids coming from the sun’s direction?

    Right now, no, they can’t. But astronomers will soon have a new tool to detect many space rocks, including those hiding in the sun’s glare. NASA is developing a new Infrared Space Telescope called the Near-Earth Object Surveyor space telescope, or NEO Surveyor.

    NASA expects this telescope to find 90% of near-Earth objects with diameters of at least 140 meters. An impact from an object that large could level a city. This telescope – expected to launch in 2026 – would have spotted both the Chelyabinsk space rock and 2021 SG. It should improve our planetary defense.

    Meanwhile, scientists now think that a Chelyabinsk-type event might occur more frequently than previously thought. For example, another good-sized space rock passed by Earth in 2015. 2015 TB45 was about the same size as 2021 SG. Its diameter was about 2,000 feet (610 meters). It passed a bit farther, just outside the moon’s orbit. Still, in the vastness of our solar system … that’s pretty close. Astronomers spotted it three weeks before the closest approach on October 31, 2015. Some radar images coincidently showed a skull-shaped space rock. And so some dubbed it the Halloween Asteroid.

    What does it all mean? Perhaps that – even with astronomers watching – an impressive asteroid event is currently possible without previous warning, at any time. That would be true if the object came from the sun’s direction. But in a few years we should all have extra protection from the new NEO Surveyor. And that fact ought to help all of us – astronomers included – feel safer!


    Halloween Asteroid is a Radar Science Treat.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 11:54 am on September 17, 2021 Permalink | Reply
    Tags: "What are red giants?", A red giant is a star in its death stages. It has slowly swollen up to many times its original size. Once at the red giant stage a star might stay that way for up to a billion years., EarthSky, Hydrogen: A star’s 1st fuel, It’s our sun’s destiny to become a red giant star (and afterwards a white dwarf and then a black dwarf), Our sun as an average star of its type was born with enough hydrogen to last for around 10 billion years., Stars radiate energy by converting hydrogen to helium via nuclear fusion., Stars that mostly burn hydrogen are in what’s known as the main-sequence phase., Stellar equilibrium: the outward radiation pressure from the sun’s internal fusion reactions exactly balances the inward push of the sun’s own gravity., We call the current stage of our star’s life the hydrogen-burning phase because its energy source is the fusion of hydrogen atoms. But burning is a bit of a misnomer. It’s nuclear fusion not chemi   

    From EarthSky : “What are red giants?” 

    1

    From EarthSky

    September 17, 2021
    Andy Briggs

    1
    Artist’s concept of the evolved stars known as red giants, at different distances in this illustration. Image credit: Chris Smith (KBRwyle) via NASA Goddard Space Flight Center (US).

    A red giant is a star in its death stages. It has slowly swollen up to many times its original size. Once at the red giant stage a star might stay that way for up to a billion years. Then the star will slowly contract and cool to become a white dwarf: Earth-sized, ultra-dense star corpses radiating a tiny fraction of their original energy. Eventually, after billions of years, these stars will become totally cold and radiate no energy. They’ll end their lives as a so-called black dwarf: a tiny, burned-out, virtually-invisible cinder.

    To become a red giant, a particular star must have between half our sun’s mass, and eight times our times our sun’s mass. Astronomers call such stars low- or intermediate-mass stars. So you can see that our sun is one of the stars that will inevitably, someday, become a red giant.

    So it’s our sun’s destiny to become a red giant star (and afterwards a white dwarf and then a black dwarf). But what processes will drive the sun’s evolution to the red giant stage? And what will happen exactly, inside the star, as it changes? Let’s examine the fate of low- or intermediate-mass stars such as our sun, as they evolve to the red giant phase.

    Betelgeuse-a superluminous red giant star 650 light-years away in the infrared from the European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)Herschel Space Observatory (EU) Stars like Betelgeuse, end their lives as supernovae. Credit: Decin et al.

    Hydrogen: A star’s 1st fuel

    Stars radiate energy by converting hydrogen to helium via nuclear fusion. It’s this process that causes our sun to radiate light, heat and other forms of energy as a byproduct. But nuclear fusion in stars at first requires hydrogen. And stars don’t have an infinite supply of hydrogen. Our sun converts around 600 million tons of hydrogen into helium every second. If that sounds as if the supply should therefore soon exhaust itself, just remember that the sun is a star nearly a million miles across. And if you have trouble visualizing that, imagine boarding a jet airliner for a flight that is going to last 226 days. That is how long it would take you to fly around our local star.

    In truth, our sun as an average star of its type was born with enough hydrogen to last for around 10 billion years. Astronomers estimate our star is now around 4.5 billion years old. So the sun is leaving the halcyon days of its youth behind it. It’s entering into middle age. And like people, it won’t be too long until its processes start to change and falter.

    Hydrogen burning and the main sequence

    We call the current stage of our star’s life the hydrogen-burning phase because its energy source is the fusion of hydrogen atoms. But burning is a bit of a misnomer. It’s nuclear fusion not chemical burning. Stars do not burn in the conventional sense of the word. Still, astronomers do use the term burning to describe the type of fusion going on inside a star. Hence, you might hear of carbon burning or helium burning. Both are stages of nuclear fusion, consuming different elements, when a star nears the end of its life.

    Stars that mostly burn hydrogen are in what’s known as the main-sequence phase. As a main sequence star, our sun is in what’s called stellar equilibrium. That means the outward radiation pressure from the sun’s internal fusion reactions exactly balances the inward push of the sun’s own gravity.

    It’s important to realize that, when the sun’s on the main sequence, even the consumption of hundreds of millions of tons of hydrogen per second does not immediately deplete the sun’s hydrogen. Only 0.7% of our sun’s hydrogen consumed in the fusion process will ultimately be radiated as energy. The rest is used up converting the hydrogen atomic nuclei into helium atoms. That tiny percentage of energy has been giving us all the light and heat we get from the sun for the last 4.5 billion years!

    The star begins to die

    Eventually, as its nuclear fires falter, a star starts to contract under its own gravity. At the same time the star is shrinking, its temperature is increasing. So the star becomes brighter.

    In an aging star, this phase of shrinking and brightening can last for several million years. The shrinking core, which is heating up as it shrinks under gravity, brings more hydrogen towards the center of the star, into the place previously occupied by the now-shrunken core. Eventually, temperatures and pressures are sufficient to ignite this shell of hydrogen around the core: radiation from this new hydrogen-shell burning pushes outward through the star, causing its outer layers to expand. There are complex physical processes at work here, but the laws of the conservation of energy, in conjunction with the way gravity behaves, mean that if the core of the star shrinks, the rest of the star must expand. The star has started evolving into what is known as a subgiant star, representing an intermediate phase between the main sequence and the red giant stage.

    It becomes a red giant

    The hydrogen-shell burning occurs through fusion processes that are far more intense than they were when the star was on the main sequence. The result is that the star brightens by a modest amount. But the outer layers of the expanding star, now being further away from the hydrogen shell around the core, cool at the same time, dropping from a maximum of between 6,000 and 30,000 degrees down to 5,000. This also means that the star’s light reddens, in the same way that a cooling poker removed from a fire will cool from white through yellow to red over time.

    The hydrogen-burning phase can last for between a few hundred million to a billion years, depending on the initial mass of the star. For stars between 0.8 and 2 times the mass of our sun, this results in a subgiant which is 10 times the diameter of our sun. Stars of mass outside this range may then follow different evolutionary paths, but for a star like the sun the next phase will be a massive increase in size, a huge rise in brightness and more cooling. The driving energy for this will arise from the helium core, collapsing, getting denser until, at the end of the subgiant phase, it becomes hot enough to burn its helium. This causes a large increase of energy output which forces the expansion of the star. Eventually, after perhaps hundreds of millions of years, the star will be a hundred times the diameter of the sun and distinctly red in color.

    And so a red giant is born.

    A star will be in the red giant phase for typically around a billion years. What happens next will depend on the star’s mass. High-mass stars will explode as supernovae. Low- to intermediate-mass stars like our sun will slowly shrink and cool into white dwarf stars.

    2
    Comparison of the size of our sun to the smallest and largest red giant for which oscillations (starquakes) have been detected with the Kepler Space Telescope. Image via Daniel Huber/ The University of Sydney (AU).

    NASA Kepler Space Telescope (US).

    In the night sky

    We can look up and see several red giants with our unaided eyes. Aldebaran and Antares are just two examples. But perhaps the most famous is Betelgeuse, in the constellation of Orion. It’s famous because it hit the headlines a little while ago when it suddenly started getting dimmer, over a period which lasted for several months in 2019. Its brightness dropped by more than 60%, meaning it was noticeably dimmer in the night sky. Read more about Betelgeuse’s extraordinary dimming.

    So what of our sun? Over the next few hundred million years, it will slowly increase in brightness and start to radiate more energy across the electromagnetic spectrum, as it heads towards its subgiant phase. That’s bad news for the Earth. In about a billion years, increasing radiation from our star will have sterilized our planet, extinguishing all life.

    Eventually, as our sun completes its changes from a modest G-type star into a red giant, it will expand to swallow Mercury, Venus and perhaps Earth too. And that will be the end of our world.

    The study of red giants is complex, as there are many variables and exceptions. It can throw out the unexpected, like the dimming of Betelgeuse. But these giant stars are just going through a natural phase of life, getting old and dying. By the time our sun, for example, ends its life as a white dwarf, it will have lived for ten billion years. And perhaps, when our star swells up to enormous size, it will be studied by alien civilizations looking from afar, as we study Betelgeuse and the other giants in our skies. They will have little idea that, once, a tiny blue dot orbited that star, whose inhabitants looked to the stars and wondered, too.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 9:05 am on September 15, 2021 Permalink | Reply
    Tags: "SpaceX lasers define next era of Starlink technology", 2018., EarthSky, On Monday September 13 2021 SpaceX launched its first whole batch of laser-equipped Starlinks., SpaceX is concentrating on providing Starlink service to a small market unreachable with conventional fiber connections., The 51 Starlink satellites launched this week took a step forward toward the goal of providing global broadband coverage for high-speed internet access., The first-ever test satellites – known as TinTin A and TinTin B – took flight from the base on February 22, The first-stage booster launched and landed for the 10th time continuing the company’s custom of booster recycling., The launch Monday night brings the total number of Starlink spacecraft SpaceX has launched to 1791 satellites., They have the potential to interfere with the professional astronomical observations that have brought us our modern-day view of the cosmos., Unfortunately what the laser-equipped satellites did not do is address the ever-concerning controversy that Starlinks are problematically bright.   

    From EarthSky : “SpaceX lasers define next era of Starlink technology” 

    1

    From EarthSky

    September 15, 2021
    Lia De La Cruz


    Starlink Mission

    Love ’em or hate ’em, the 51 Starlink satellites launched this week took a step forward toward the goal of providing global broadband coverage for high-speed internet access, particularly for people across the world in rural and remote areas. On Monday September 13 2021 SpaceX launched its first whole batch of laser-equipped Starlinks. These SpaceX lasers are expected to improve how the satellite network relays broadband signals around the world. Ground stations are costly and not without geographical and political constraints on where they can be positioned on Earth.

    These new inter-satellite SpaceX lasers will enable the network to operate with fewer ground stations. They’ll route data around the constellation (between satellites), rather than between Earth and space. Fewer “hops” between the ground and orbit reduces the time it takes for a signal to travel between destinations. The goal is to provide Starlink patrons with improved latency. That improvement should translate to faster internet speeds.

    Kate Tice, Starlink’s senior reliability engineer, said in 2020 – and as the Starlink team confirmed in a letter to Beta users as recently as summer 2021:

    “Once the space lasers are fully deployed, Starlink will be one of the fastest options available to transfer data around the world.”

    Spaceflight Now said:

    “The launch Monday night brings the total number of Starlink spacecraft SpaceX has launched to 1,791 satellites, including failed and decommissioned spacecraft, adding to the largest fleet ever put into orbit.

    A tabulation by Jonathan McDowell (@planet4589 on Twitter), an astronomer and respected tracker of spaceflight activity, shows SpaceX currently has 1,420 operational Starlink satellites, with more than 100 additional craft moving into their operational positions in orbit.”

    Over the next few decades, SpaceX hopes to put something like 42,000 Starlinks into orbit.

    SpaceX lasers take to the skies

    Monday’s launch was the first time an entire batch of 51 laser links made it into orbit. But several were already tested in a handful of prior launches, beginning with a set of 10 that debuted in January 2021. According to CNET, the lasers are something SpaceX has long touted as part of its overall Starlink plan.

    SpaceX president Gwynne Shotwell said during a panel discussion at the Space Symposium last month that the company has been rushing to develop the laser system since May. It hasn’t launched any routers to orbit since June 30. Two months is an exceptionally long pause for a program that has, at times, managed near-weekly launches to build up its satellite network. But Shotwell said the pause allowed the satellites launched on September 13 to be completely fitted with laser links. And, SpaceX hopes, the small batch will mark a transition to all Starlink satellites carrying laser crosslinks in the future. Shotwell commented:

    “We were hoping to do so a little bit sooner, but we’re working on our laser communication terminals …”

    A “huge leap forward” in tech

    Echoing previous comments from CEO Elon Musk, Shotwell said at last month’s symposium that SpaceX is concentrating on providing Starlink service to a small market unreachable with conventional fiber connections. She said:

    “We’re looking forward to continuing to enhance the network by putting more capacity in space, and really looking forward to truly connect those that are very difficult to connect … Customers are great at selecting great service and great value, so we will find out over the next five or so years what is too much, and what’s not too much. I do believe that there is insatiable demand for data.”

    Youmei Zhou, a SpaceX engineer, hosted the company’s launch webcast. She called it a “huge leap forward” in tech.

    The mission also marked a homecoming of sorts. It was the first Starlink launch from the Vandenberg Space Force Base in Northern California, a memorable setting for the private spaceflight company. Its first-ever test satellites – known as TinTin A and TinTin B – took flight from the base on February 22, 2018.

    The first-stage booster launched and landed for the 10th time continuing the company’s custom of booster recycling. It touched down on the drone ship Of Course I Still Love You in the Pacific Ocean and will be returned to port to see if it has an 11th flight in it at some point in the future.

    Meanwhile …

    Unfortunately what the laser-equipped satellites did not do is address the ever-concerning controversy that Starlinks are problematically bright. They have the potential to interfere with the professional astronomical observations that have brought us our modern-day view of the cosmos. Although SpaceX has tried to address the issue, the satellites’ brightness still has the potential to disrupt observations of the night sky. At this rate, there’s little in the way of a future where people can look up and see the sky crawling with satellite lights.

    1
    SpaceX’s payload stack, onboarded with Starlink satellites and laser links at the bottom. Image via SpaceX.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 8:39 am on September 15, 2021 Permalink | Reply
    Tags: "Impact on Jupiter surprises skywatchers", EarthSky,   

    From EarthSky : “Impact on Jupiter surprises skywatchers” 

    1

    From EarthSky

    September 14, 2021
    Kelly Kizer Whitt

    1
    Harald Paleske in Langendorf, Germany, captured this image of a bright flash of light as something impacted Jupiter on September 13, 2021. Io and its shadow are on the left side of Jupiter, while the flash is to the right of center. Image via https://spaceweathergallery.com .

    Photographers capture an impact on Jupiter

    Observers around the globe were surprised on September 13, 2021, when they witnessed an apparent impact on the giant planet Jupiter. A bright flash of light distracted them from their observing target: an ongoing transit of the shadow of the Jovian moon Io across the face of Jupiter. A couple of lucky astrophotographers managed to snap images of the flash.

    The image at top comes from Germany. Harald Paleske told SpaceWeather.com he was watching the dark shadow of Io cross onto Jupiter’s surface when the burst of light startled him. He said:

    “A bright flash of light surprised me. It could only be an impact.”

    Paleske had been taking a video of the transit of Io’s shadow when the event occurred. He looked over his video frames, searching for a satellite or plane that might have shown up as the bright patch. But he found no evidence that the event happened close to Earth or that’s he’d witnessed an earthly event with Jupiter as mere backdrop. He timed the event as happening at 22:39:27 UTC on September 13 and lasting for two seconds.

    Another astronomer, José Luis Pereira of Brazil, also captured the flash from the impact. ESA Operations tweeted his photo via Flickr.

    Light on at Jupiter! Anyone home? This bright impact flash was spotted yesterday on the giant planet by astronomer José Luis Pereira.

    Not a lot of info on the impacting object yet but its likely to be large and/or fast!

    Thanks Jupiter for taking the hit??#PlanetaryDefence pic.twitter.com/XLFzXjW4KQ2

    — ESA Operations (@esaoperations) September 14, 2021

    A French astrophotographer, J.P. Arnould, also captured the surprising event.

    Impact Flash on Jupiter confirmed by at least 2 amateur astronomers: H. Paleske in Germany & by J.P. Arnould in France. See attached images & for more info about past Jupiter impact events: https://t.co/VIpSt2TQfn #astronomy #jupiter #impact pic.twitter.com/0kMP7iRMao

    — Ernesto Guido (@comets77) September 14, 2021

    What hit Jupiter?

    It’s too soon to know, but a comet or asteroid would be the most likely culprit. As Spaceweather.com said:

    An asteroid in the 100-meter size range (about 300 feet) would do the trick.

    Skywatchers with telescopes from all parts of Earth are poised to view Jupiter following the impact. They’re hoping to spot a dark mark or temporary scar resulting from the impact. That’s what happened during the best-known impacts on Jupiter, which happened in July of 1994. Comet Shoemaker-Levy 9 blazed a path directly toward Jupiter. Professional observatories were ready to catch the resulting collision. Shoemaker-Levy 9 left an entire trail of debris across the gas giant planet, as Jupiter’s intense tidal forces tore it to pieces.

    3
    Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter’s atmosphere in July 1994. Image via Wikimedia Commons.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 8:42 am on September 14, 2021 Permalink | Reply
    Tags: "Missing impact debris mystery solved?", , , , , EarthSky,   

    From The Arizona State University (US) via EarthSky : “Missing impact debris mystery solved?” 

    From The Arizona State University (US)

    via

    1

    EarthSky

    September 14, 2021
    Paul Scott Anderson

    1
    Artist’s concept of planet-forming collisions in the early solar system. Where is this debris today? Hint: It’s not in the asteroid belt. Image via NASA/ JPL-Caltech (US)/ ASU.

    The case of the missing impact debris

    Billions of years ago, the early solar system was a chaotic and violent place. Solid objects called planetesimals had condensed from the primordial cloud that gave birth to our solar system. And the planetesimals frequently collided, and at times stuck together. The process formed larger and larger objects, leading to bigger and bigger collisions. Over eons of time, this process built the major planets, like Earth. So, today, we’d expect to glimpse some of the debris from these early planet-forming collisions. We’d expect to find it orbiting our sun, in the asteroid belt in particular. But why don’t we? New computer simulations by Arizona astronomers offer a solution to the missing impact debris problem. They suggest that, instead of creating rocky debris, large collisions in the early solar system caused solid rocky bodies to vaporize into gas. And, the astronomers said:

    “Unlike solid and molten debris, this gas more easily escapes the solar system, leaving little trace of these planet-smashing events.”

    The researchers published their peer-reviewed results in The Astrophysical Journal Letters on July 13, 2021.

    2
    Artist’s concept of small planetesimals colliding in the early solar system to form a larger planet. Image via Alan Brandon/ Nature/ Planet Hunters.

    Simulating the early solar system

    Travis Gabriel and Harrison Allen-Sutter, both at Arizona State University, led the new research. While previous studies by other scientists mostly focused on the effects of these early impacts, these scientists took a different approach. As Allen-Sutter explained:

    “Most researchers focus on the direct effects of impacts, but the nature of the debris has been underexplored.”

    And Gabriel added:

    “It has long since been understood that numerous large collisions are required to form Mercury, Venus, Earth, the moon and perhaps Mars. But the tremendous amount of impact debris expected from this process is not observed in the asteroid belt, so it has always been a paradoxical situation.”

    Scientists refer to the mystery of the apparently missing impact debris as the “Missing Mantle Paradox” (mantle, in this case, doesn’t refer to Earth’s mantle). Or they call it the “Great Dunite Shortage”. Dunite is a kind of rock, consisting largely of olivine, and it’s olivine that’s at the heart of this mystery.

    Formation of the moon

    The results also have implications for the formation of Earth’s own moon. According to current understanding, the moon was formed from a collision between a Mars-sized body and the early Earth. That collision also released debris into the solar system. According to Gabriel:

    “After forming from debris bound to the Earth, the moon would have also been bombarded by the ejected material that orbits the sun over the first hundred million years or so of the moon’s existence. If this debris was solid, it could compromise or strongly influence the moon’s early formation, especially if the collision was violent.

    If the material was in gas form, however, the debris may not have influenced the early moon at all.”

    3
    Scientists think that our own moon formed from a collision between the early Earth and another rocky body about the size of Mars. Image via Hagai Perets/ Smithsonian Magazine.

    Impact debris around other stars

    Also, since our solar system is thought to have formed in a similar way to planetary systems around other stars, the study results could provide clues about impact debris elsewhere. Gabriel commented on this, saying:

    “There is growing evidence that certain telescope observations may have directly imaged giant impact debris around other stars. Since we cannot go back in time to observe the collisions in our solar system, these astrophysical observations of other worlds are a natural laboratory for us to test and explore our theory.”

    In 2019, astronomers also found evidence of a planetary collision in a solar system 300 light-years away. That impact is estimated to have occurred sometime within only the past 1,000 years, showing that such events still happen, even between planets.

    It would seem then that the mystery of the missing impact debris may have been solved. As science marches on – and if the new simulations hold solid – they will provide valuable clues about how our solar system formed billions of years ago. And they’ll also offer a glimpse into planet-forming processes in other solar systems.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Arizona State University (US) is a public research university in the Phoenix metropolitan area. Founded in 1885 by the 13th Arizona Territorial Legislature, ASU is one of the largest public universities by enrollment in the U.S.

    One of three universities governed by the Arizona Board of Regents, ASU is a member of the Universities Research Association (US) and classified among “R1: Doctoral Universities – Very High Research Activity.” ASU has nearly 150,000 students attending classes, with more than 38,000 students attending online, and 90,000 undergraduates and more nearly 20,000 postgraduates across its five campuses and four regional learning centers throughout Arizona. ASU offers 350 degree options from its 17 colleges and more than 170 cross-discipline centers and institutes for undergraduates students, as well as more than 400 graduate degree and certificate programs. The Arizona State Sun Devils compete in 26 varsity-level sports in the NCAA Division I Pac-12 Conference and is home to over 1,100 registered student organizations.

    ASU’s charter, approved by the board of regents in 2014, is based on the New American University model created by ASU President Michael M. Crow upon his appointment as the institution’s 16th president in 2002. It defines ASU as “a comprehensive public research university, measured not by whom it excludes, but rather by whom it includes and how they succeed; advancing research and discovery of public value; and assuming fundamental responsibility for the economic, social, cultural and overall health of the communities it serves.” The model is widely credited with boosting ASU’s acceptance rate and increasing class size.

    The university’s faculty of more than 4,700 scholars has included 5 Nobel laureates, 6 Pulitzer Prize winners, 4 MacArthur Fellows, and 19 National Academy of Sciences members. Additionally, among the faculty are 180 Fulbright Program American Scholars, 72 National Endowment for the Humanities fellows, 38 American Council of Learned Societies fellows, 36 members of the Guggenheim Fellowship, 21 members of the American Academy of Arts and Sciences, 3 members of National Academy of Inventors, 9 National Academy of Engineering members and 3 National Academy of Medicine members. The National Academies has bestowed “highly prestigious” recognition on 227 ASU faculty members.

    History

    Arizona State University was established as the Territorial Normal School at Tempe on March 12, 1885, when the 13th Arizona Territorial Legislature passed an act to create a normal school to train teachers for the Arizona Territory. The campus consisted of a single, four-room schoolhouse on a 20-acre plot largely donated by Tempe residents George and Martha Wilson. Classes began with 33 students on February 8, 1886. The curriculum evolved over the years and the name was changed several times; the institution was also known as Tempe Normal School of Arizona (1889–1903), Tempe Normal School (1903–1925), Tempe State Teachers College (1925–1929), Arizona State Teachers College (1929–1945), Arizona State College (1945–1958) and, by a 2–1 margin of the state’s voters, Arizona State University in 1958.

    In 1923, the school stopped offering high school courses and added a high school diploma to the admissions requirements. In 1925, the school became the Tempe State Teachers College and offered four-year Bachelor of Education degrees as well as two-year teaching certificates. In 1929, the 9th Arizona State Legislature authorized Bachelor of Arts in Education degrees as well, and the school was renamed the Arizona State Teachers College. Under the 30-year tenure of president Arthur John Matthews (1900–1930), the school was given all-college student status. The first dormitories built in the state were constructed under his supervision in 1902. Of the 18 buildings constructed while Matthews was president, six are still in use. Matthews envisioned an “evergreen campus,” with many shrubs brought to the campus, and implemented the planting of 110 Mexican Fan Palms on what is now known as Palm Walk, a century-old landmark of the Tempe campus.

    During the Great Depression, Ralph Waldo Swetman was hired to succeed President Matthews, coming to Arizona State Teachers College in 1930 from Humboldt State Teachers College where he had served as president. He served a three-year term, during which he focused on improving teacher-training programs. During his tenure, enrollment at the college doubled, topping the 1,000 mark for the first time. Matthews also conceived of a self-supported summer session at the school at Arizona State Teachers College, a first for the school.

    1930–1989

    In 1933, Grady Gammage, then president of Arizona State Teachers College at Flagstaff, became president of Arizona State Teachers College at Tempe, beginning a tenure that would last for nearly 28 years, second only to Swetman’s 30 years at the college’s helm. Like President Arthur John Matthews before him, Gammage oversaw the construction of several buildings on the Tempe campus. He also guided the development of the university’s graduate programs; the first Master of Arts in Education was awarded in 1938, the first Doctor of Education degree in 1954 and 10 non-teaching master’s degrees were approved by the Arizona Board of Regents in 1956. During his presidency, the school’s name was changed to Arizona State College in 1945, and finally to Arizona State University in 1958. At the time, two other names were considered: Tempe University and State University at Tempe. Among Gammage’s greatest achievements in Tempe was the Frank Lloyd Wright-designed construction of what is Grady Gammage Memorial Auditorium/ASU Gammage. One of the university’s hallmark buildings, ASU Gammage was completed in 1964, five years after the president’s (and Wright’s) death.

    Gammage was succeeded by Harold D. Richardson, who had served the school earlier in a variety of roles beginning in 1939, including director of graduate studies, college registrar, dean of instruction, dean of the College of Education and academic vice president. Although filling the role of acting president of the university for just nine months (Dec. 1959 to Sept. 1960), Richardson laid the groundwork for the future recruitment and appointment of well-credentialed research science faculty.

    By the 1960s, under G. Homer Durham, the university’s 11th president, ASU began to expand its curriculum by establishing several new colleges and, in 1961, the Arizona Board of Regents authorized doctoral degree programs in six fields, including Doctor of Philosophy. By the end of his nine-year tenure, ASU had more than doubled enrollment, reporting 23,000 in 1969.

    The next three presidents—Harry K. Newburn (1969–71), John W. Schwada (1971–81) and J. Russell Nelson (1981–89), including and Interim President Richard Peck (1989), led the university to increased academic stature, the establishment of the ASU West campus in 1984 and its subsequent construction in 1986, a focus on computer-assisted learning and research, and rising enrollment.

    1990–present

    Under the leadership of Lattie F. Coor, president from 1990 to 2002, ASU grew through the creation of the Polytechnic campus and extended education sites. Increased commitment to diversity, quality in undergraduate education, research, and economic development occurred over his 12-year tenure. Part of Coor’s legacy to the university was a successful fundraising campaign: through private donations, more than $500 million was invested in areas that would significantly impact the future of ASU. Among the campaign’s achievements were the naming and endowing of Barrett, The Honors College, and the Herberger Institute for Design and the Arts; the creation of many new endowed faculty positions; and hundreds of new scholarships and fellowships.

    In 2002, Michael M. Crow became the university’s 16th president. At his inauguration, he outlined his vision for transforming ASU into a “New American University”—one that would be open and inclusive, and set a goal for the university to meet Association of American Universities (US) criteria and to become a member. Crow initiated the idea of transforming ASU into “One university in many places”—a single institution comprising several campuses, sharing students, faculty, staff and accreditation. Subsequent reorganizations combined academic departments, consolidated colleges and schools, and reduced staff and administration as the university expanded its West and Polytechnic campuses. ASU’s Downtown Phoenix campus was also expanded, with several colleges and schools relocating there. The university established learning centers throughout the state, including the ASU Colleges at Lake Havasu City and programs in Thatcher, Yuma, and Tucson. Students at these centers can choose from several ASU degree and certificate programs.

    During Crow’s tenure, and aided by hundreds of millions of dollars in donations, ASU began a years-long research facility capital building effort that led to the establishment of the Biodesign Institute at Arizona State University, the Julie Ann Wrigley Global Institute of Sustainability, and several large interdisciplinary research buildings. Along with the research facilities, the university faculty was expanded, including the addition of five Nobel Laureates. Since 2002, the university’s research expenditures have tripled and more than 1.5 million square feet of space has been added to the university’s research facilities.

    The economic downturn that began in 2008 took a particularly hard toll on Arizona, resulting in large cuts to ASU’s budget. In response to these cuts, ASU capped enrollment, closed some four dozen academic programs, combined academic departments, consolidated colleges and schools, and reduced university faculty, staff and administrators; however, with an economic recovery underway in 2011, the university continued its campaign to expand the West and Polytechnic Campuses, and establish a low-cost, teaching-focused extension campus in Lake Havasu City.

    As of 2011, an article in Slate reported that, “the bottom line looks good,” noting that:

    “Since Crow’s arrival, ASU’s research funding has almost tripled to nearly $350 million. Degree production has increased by 45 percent. And thanks to an ambitious aid program, enrollment of students from Arizona families below poverty is up 647 percent.”

    In 2015, the Thunderbird School of Global Management became the fifth ASU campus, as the Thunderbird School of Global Management at ASU. Partnerships for education and research with Mayo Clinic established collaborative degree programs in health care and law, and shared administrator positions, laboratories and classes at the Mayo Clinic Arizona campus.

    The Beus Center for Law and Society, the new home of ASU’s Sandra Day O’Connor College of Law, opened in fall 2016 on the Downtown Phoenix campus, relocating faculty and students from the Tempe campus to the state capital.

     
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