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  • richardmitnick 9:51 pm on June 14, 2022 Permalink | Reply
    Tags: "There in a flash:: A weird star produced the fastest nova on record", , , , , , White dwarf stars   

    From The Arizona State University School of Earth and Space Exploration : “There in a flash:: A weird star produced the fastest nova on record” 

    From The Arizona State University School of Earth and Space Exploration

    June 14, 2022

    Mikala Kass
    Communications Specialist, ASU Knowledge Enterprise
    480-727-5616
    mkass@asu.edu

    Astronomers are buzzing after observing the fastest nova ever recorded. The unusual event drew scientists’ attention to an even more unusual star. As they study it, they may find answers to not only the nova’s many baffling traits, but to larger questions about the chemistry of our solar system, the death of stars and the evolution of the universe.

    The research team, led by Arizona State University Regents Professor Sumner Starrfield, Professor Charles Woodward from University of Minnesota and research scientist Mark Wagner from The Ohio State University, co-authored a report published today in the Research Notes of the American Astronomical Society [link is not available].

    1
    Illustration of an intermediate polar system, a type of two-star system that the research team thinks V1674 Hercules belongs to. A flow of gas from the large companion star impacts an accretion disk before flowing along magnetic field lines onto the white dwarf. Illustration by Mark Garlick.

    A nova is a sudden explosion of bright light from a two-star system. Every nova is created by a white dwarf — the very dense leftover core of a star — and a nearby companion star. Over time, the white dwarf draws matter from its companion, which falls onto the white dwarf. The white dwarf heats this material, causing an uncontrolled reaction that releases a burst of energy. The explosion shoots the matter away at high speeds, which we observe as visible light.

    The bright nova usually fades over a couple of weeks or longer. On June 12, 2021, the nova V1674 Hercules burst so bright that it was visible to the naked eye — but in just over one day, it was faint once more. It was like someone flicked a flashlight on and off.

    Nova events at this level of speed are rare, making this nova a precious study subject.

    “It was only about one day, and the previous fastest nova was one we studied back in 1991, V838 Herculis, which declined in about two or three days,” says Starrfield, an astrophysicist in ASU’s School of Earth and Space Exploration.

    As the astronomy world watched V1674 Hercules, other researchers found that its speed wasn’t its only unusual trait. The light and energy it sends out is also pulsing like the sound of a reverberating bell.

    Every 501 seconds, there’s a wobble that observers can see in both visible light waves and X-rays. A year after its explosion, the nova is still showing this wobble, and it seems it’s been going on for even longer. Starrfield and his colleagues have continued to study this quirk.

    “The most unusual thing is that this oscillation was seen before the outburst, but it was also evident when the nova was some 10 magnitudes brighter,” says Wagner, who is also the head of science at the Large Binocular Telescope Observatory being used to observe the nova.

    “A mystery that people are trying to wrestle with is what’s driving this periodicity that you would see it over that range of brightness in the system.”

    The team also noticed something strange as they monitored the matter ejected by the nova explosion — some kind of wind, which may be dependent on the positions of the white dwarf and its companion star, is shaping the flow of material into space surrounding the system.

    Though the fastest nova is (literally) flashy, the reason it’s worth further study is that novae can tell us important information about our solar system and even the universe as a whole.

    A white dwarf collects and alters matter, then seasons the surrounding space with new material during a nova explosion. It’s an important part of the cycle of matter in space. The materials ejected by novae will eventually form new stellar systems. Such events helped form our solar system as well, ensuring that Earth is more than a lump of carbon.

    “We’re always trying to figure out how the solar system formed, where the chemical elements in the solar system came from,” Starrfield says. “One of the things that we’re going to learn from this nova is, for example, how much lithium was produced by this explosion. We’re fairly sure now that a significant fraction of the lithium that we have on the Earth was produced by these kinds of explosions.”

    Sometimes a white dwarf star doesn’t lose all of its collected matter during a nova explosion, so with each cycle, it gains mass. This would eventually make it unstable, and the white dwarf could generate a type 1a supernova, which is one of the brightest events in the universe. Each type 1a supernova reaches the same level of brightness, so they are known as standard candles.

    “Standard candles are so bright that we can see them at great distances across the universe. By looking at how the brightness of light changes, we can ask questions about how the universe is accelerating or about the overall three-dimensional structure of the universe,” Woodward says. “This is one of the interesting reasons that we study some of these systems.”

    Additionally, novae can tell us more about how stars in binary systems evolve to their death, a process that is not well understood. They also act as living laboratories where scientists can see nuclear physics in action and test theoretical concepts.

    The nova took the astronomy world by surprise. It wasn’t on scientists’ radar until an amateur astronomer from Japan, Seidji Ueda, discovered and reported it.

    Citizen scientists play an increasingly important role in the field of astronomy, as does modern technology. Even though it is now too faint for other types of telescopes to see, the team is still able to monitor the nova, thanks to the Large Binocular Telescope’s wide aperture and its observatory’s other equipment, including its pair of multi-object double spectrographs and exceptional PEPSI high resolution spectrograph.

    They plan to investigate the cause of the outburst and the processes that led to it, the reason for its record-breaking decline, the forces behind the observed wind, and the cause of its pulsing brightness.

    See the full article here.

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    Science and engineering — essential for developing new instruments to explore Earth and space — are the foundation of our programs, which also emphasize the role of technology in advancing scientific knowledge.

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    ASU Tempe Campus

    ASU 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 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 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.

     
  • richardmitnick 10:56 am on October 13, 2021 Permalink | Reply
    Tags: "A Crystal Ball Into Our Solar System’s Future", , , , , , White dwarf stars   

    From W.M. Keck Observatory (US) : “A Crystal Ball Into Our Solar System’s Future” 

    From W.M. Keck Observatory (US)

    October 13, 2021

    Mari-Ela Chock, Communications Officer
    W. M. Keck Observatory
    (808) 554-0567
    mchock@keck.hawaii.edu

    Giant Gas Planet Orbiting a Dead Star Gives Glimpse Into the Predicted Aftermath of our Sun’s Demise.

    1
    Artist’s rendition of a newly-discovered jupiter-like exoplanet orbiting a white dwarf, or dead star. This system is evidence that planets can survive their host star’s explosive red giant phase and is the very first confirmed planetary system that serves as an analog to the fate of the sun and jupiter in our own solar system.
    Credit: Adam Makarenko/ W. M. Keck Observatory.

    Astronomers have discovered the very first confirmed planetary system that resembles the expected fate of our solar system, when the Sun reaches the end of its life in about five billion years.

    The researchers detected the system using W. M. Keck Observatory on Maunakea in Hawaiʻi; it consists of a Jupiter-like planet with a Jupiter-like orbit revolving around a white dwarf star located near the center of our Milky Way galaxy.

    “This evidence confirms that planets orbiting at a large enough distance can continue to exist after their star’s death,” says Joshua Blackman, an astronomy postdoctoral researcher at the The University of Tasmania (AU) and lead author of the study. “Given that this system is an analog to our own solar system, it suggests that Jupiter and Saturn might survive the Sun’s red giant phase, when it runs out of nuclear fuel and self-destructs.”

    The study is published in today’s issue of the journal Nature.

    “Earth’s future may not be so rosy because it is much closer to the Sun,” says co-author David Bennett, a senior research scientist at The University of Maryland (US) and The Goddard Space Flight Center | NASA (US). “If humankind wanted to move to a moon of Jupiter or Saturn before the Sun fried the Earth during its red supergiant phase, we’d still remain in orbit around the Sun, although we would not be able to rely on heat from the Sun as a white dwarf for very long.”

    A white dwarf is what main sequence stars like our Sun become when they die. In the last stages of the stellar life cycle, a star burns off all of the hydrogen in its core and balloons into a red giant star. It then collapses into itself, shrinking into a white dwarf, where all that’s left is a hot, dense core, typically Earth-sized and half as massive as the Sun. Because these compact stellar corpses are small and no longer have the nuclear fuel to radiate brightly, white dwarfs are very faint and difficult to detect.

    Animation showing an artist’s rendering of a main sequence star ballooning into a red giant as it burns the last of its hydrogen fuel, then collapses into a white dwarf. What remains is a hot, dense core roughly the size of Earth and about half the mass of the Sun. A gas giant similar to Jupiter orbits from a distance, surviving the explosive transformation. Credit: Adam Makarenko/W. M. Keck Observatory.

    See the full article here .


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    The W. M. Keck Observatory (US) operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.


    Keck UCal

    Instrumentation

    Keck 1

    HIRES – The largest and most mechanically complex of the Keck’s main instruments, the High Resolution Echelle Spectrometer breaks up incoming starlight into its component colors to measure the precise intensity of each of thousands of color channels. Its spectral capabilities have resulted in many breakthrough discoveries, such as the detection of planets outside our solar system and direct evidence for a model of the Big Bang theory.

    height=”375″ class=”size-full wp-image-32389″ /> Keck High-Resolution Echelle Spectrometer (HIRES), at the Keck I telescope.[/caption]

    LRIS – The Low Resolution Imaging Spectrograph is a faint-light instrument capable of taking spectra and images of the most distant known objects in the universe. The instrument is equipped with a red arm and a blue arm to explore stellar populations of distant galaxies, active galactic nuclei, galactic clusters, and quasars.

    VISIBLE BAND (0.3-1.0 Micron)

    MOSFIRE – The Multi-Object Spectrograph for Infrared Exploration gathers thousands of spectra from objects spanning a variety of distances, environments and physical conditions. What makes this huge, vacuum-cryogenic instrument unique is its ability to select up to 46 individual objects in the field of view and then record the infrared spectrum of all 46 objects simultaneously. When a new field is selected, a robotic mechanism inside the vacuum chamber reconfigures the distribution of tiny slits in the focal plane in under six minutes. Eight years in the making with First Light in 2012, MOSFIRE’s early performance results range from the discovery of ultra-cool, nearby substellar mass objects, to the detection of oxygen in young galaxies only 2 billion years after the Big Bang.

    OSIRIS – The OH-Suppressing Infrared Imaging Spectrograph is a near-infrared spectrograph for use with the Keck I adaptive optics system. OSIRIS takes spectra in a small field of view to provide a series of images at different wavelengths. The instrument allows astronomers to ignore wavelengths where the Earth’s atmosphere shines brightly due to emission from OH (hydroxl) molecules, thus allowing the detection of objects 10 times fainter than previously available.

    Keck 2

    DEIMOS – The Deep Extragalactic Imaging Multi-Object Spectrograph is the most advanced optical spectrograph in the world, capable of gathering spectra from 130 galaxies or more in a single exposure. In ‘Mega Mask’ mode, DEIMOS can take spectra of more than 1,200 objects at once, using a special narrow-band filter.

    NIRSPEC – The Near Infrared Spectrometer studies very high redshift radio galaxies, the motions and types of stars located near the Galactic Center, the nature of brown dwarfs, the nuclear regions of dusty starburst galaxies, active galactic nuclei, interstellar chemistry, stellar physics, and solar-system science.


    ESI – The Echellette Spectrograph and Imager captures high-resolution spectra of very faint galaxies and quasars ranging from the blue to the infrared in a single exposure. It is a multimode instrument that allows users to switch among three modes during a night. It has produced some of the best non-AO images at the Observatory.

    KCWI – The Keck Cosmic Web Imager is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution, various fields of view and image resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope enables studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters and lensed galaxies.

    NEAR-INFRARED (1-5 Micron)

    ADAPTIVE OPTICS – Adaptive optics senses and compensates for the atmospheric distortions of incoming starlight up to 1,000 times per second. This results in an improvement in image quality on fairly bright astronomical targets by a factor 10 to 20.

    LASER GUIDE STAR ADAPTIVE OPTICS [pictured above] – The Keck Laser Guide Star expands the range of available targets for study with both the Keck I and Keck II adaptive optics systems. They use sodium lasers to excite sodium atoms that naturally exist in the atmosphere 90 km (55 miles) above the Earth’s surface. The laser creates an “artificial star” that allows the Keck adaptive optics system to observe 70-80 percent of the targets in the sky, compared to the 1 percent accessible without the laser.

    NIRC-2/AO – The second generation Near Infrared Camera works with the Keck Adaptive Optics system to produce the highest-resolution ground-based images and spectroscopy in the 1-5 micron range. Typical programs include mapping surface features on solar system bodies, searching for planets around other stars, and analyzing the morphology of remote galaxies.


    ABOUT NIRES
    The Near Infrared Echellette Spectrograph (NIRES) is a prism cross-dispersed near-infrared spectrograph built at the California Institute of Technology by a team led by Chief Instrument Scientist Keith Matthews and Prof. Tom Soifer. Commissioned in 2018, NIRES covers a large wavelength range at moderate spectral resolution for use on the Keck II telescope and observes extremely faint red objects found with the Spitzer and WISE infrared space telescopes, as well as brown dwarfs, high-redshift galaxies, and quasars.

    Future Instrumentation

    KCRM – The Keck Cosmic Reionization Mapper will complete the Keck Cosmic Web Imager (KCWI), the world’s most capable spectroscopic imager. The design for KCWI includes two separate channels to detect light in the blue and the red portions of the visible wavelength spectrum. KCWI-Blue was commissioned and started routine science observations in September 2017. The red channel of KCWI is KCRM; a powerful addition that will open a window for new discoveries at high redshifts.

    KPF – The Keck Planet Finder (KPF) will be the most advanced spectrometer of its kind in the world. The instrument is a fiber-fed high-resolution, two-channel cross-dispersed echelle spectrometer for the visible wavelengths and is designed for the Keck II telescope. KPF allows precise measurements of the mass-density relationship in Earth-like exoplanets, which will help astronomers identify planets around other stars that are capable of supporting life.

     
  • richardmitnick 10:14 pm on July 21, 2021 Permalink | Reply
    Tags: "Planetary shields will buckle under stellar winds from their dying stars", All stars eventually run out of available hydrogen that fuels the nuclear fusion in their cores., Any life identified on planets orbiting white dwarf stars almost certainly evolved after the star’s death., , , , , In our solar system the habitable zone of the red giant sun would move from about 150 million km from the Sun-where Earth is currently positioned-up to 6 billion km or beyond Neptune., It is nearly impossible for life to survive cataclysmic stellar evolution unless the planet has an intensely strong magnetic field – or magnetosphere - that can shield it from the worst effects., Once the white dwarf star reaches this stage the danger to surviving planets has passed., , the loss of mass in the red giant star means it has a weaker gravitational pull so the remaining planets move further away., The process of stellar evolution also results in a shift in a star’s habitable zone which is the distance that would allow a planet to be the right temperature to support liquid water., The scientists found that the habitable zone moves outward more quickly than the planet posing additional challenges to any existing life hoping to survive the process., The Sun will then stretch to a diameter of tens of millions of kilometres as a red giant swallowing the inner planets possibly including the Earth., Two known gas giants are close enough to their white dwarf star’s habitable zone to suggest that life on such a planet could exist., , White dwarf stars   

    From University of Warwick (UK) : “Planetary shields will buckle under stellar winds from their dying stars” 

    From University of Warwick (UK)

    21 July 2021

    Peter Thorley
    Media Relations Manager (Warwick Medical School and Department of Physics) | Press & Media Relations | University of Warwick
    Email: peter.thorley@warwick.ac.uk
    Mob: +44 (0) 7824 540863

    1
    An illustration of material being ejected from the Sun (left) interacting with the magnetosphere of the Earth (right). When the Sun evolves to become a red giant star, the Earth may be swallowed by our star’s atmosphere, and with a much more unstable solar wind, even the resilient and protective magnetospheres of the giant outer planets may be stripped away.NASA Marshall Space Flight Center (US) / National Aeronautics Space Agency (US).

    Any life identified on planets orbiting white dwarf stars almost certainly evolved after the star’s death, says a new study led by the University of Warwick that reveals the consequences of the intense and furious stellar winds that will batter a planet as its star is dying.

    The research is published in MNRAS, and lead author Dr Dimitri Veras of the University of Warwick will present it today (21 July) at the online National Astronomy Meeting (NAM 2021).

    The research provides new insight for astronomers searching for signs of life around these dead stars by examining the impact that their winds will have on orbiting planets during the star’s transition to the white dwarf stage. The study concludes that it is nearly impossible for life to survive cataclysmic stellar evolution unless the planet has an intensely strong magnetic field – or magnetosphere – that can shield it from the worst effects.

    In the case of Earth, solar wind particles can erode the protective layers of the atmosphere that shield humans from harmful ultraviolet radiation. The terrestrial magnetosphere acts like a shield to divert those particles away through its magnetic field. Not all planets have a magnetosphere, but Earth’s is generated by its iron core, which rotates like a dynamo to create its magnetic field.

    All stars eventually run out of available hydrogen that fuels the nuclear fusion in their cores. In the Sun the core will then contract and heat up, driving an enormous expansion of the outer atmosphere of the star into a ‘red giant’. The Sun will then stretch to a diameter of tens of millions of kilometres, swallowing the inner planets, possibly including the Earth. At the same time the loss of mass in the star means it has a weaker gravitational pull so the remaining planets move further away.

    The Sun will then stretch to a diameter of tens of millions of kilometres, swallowing the inner planets, possibly including the Earth. At the same time the loss of mass in the star means it has a weaker gravitational pull, so the remaining planets move further away.

    During the red giant phase, the solar wind will be far stronger than today, and it will fluctuate dramatically. Veras and Vidotto modelled the winds from 11 different types of stars, with masses ranging from one to seven times the mass of our Sun.

    Their model demonstrated how the density and speed of the stellar wind, combined with an expanding planetary orbit, conspires to alternatively shrink and expand the magnetosphere of a planet over time. For any planet to maintain its magnetosphere throughout all stages of stellar evolution, its magnetic field needs to be at least one hundred times stronger than Jupiter’s current magnetic field.

    The process of stellar evolution also results in a shift in a star’s habitable zone which is the distance that would allow a planet to be the right temperature to support liquid water. In our solar system the habitable zone would move from about 150 million km from the Sun-where Earth is currently positioned-up to 6 billion km or beyond Neptune. Although an orbiting planet would also change position during the giant branch phases, the scientists found that the habitable zone moves outward more quickly than the planet posing additional challenges to any existing life hoping to survive the process.

    Eventually the red giant sheds its entire outer atmosphere, leaving behind the dense hot white dwarf remnant. These do not emit stellar winds, so once the star reaches this stage the danger to surviving planets has passed.

    Dr Dimitri Veras of the University of Warwick Department of Physics said: “This study demonstrates the difficulty of a planet maintaining its protective magnetosphere throughout the entirety of the giant branch phases of stellar evolution.”

    “One conclusion is that life on a planet in the habitable zone around a white dwarf would almost certainly develop during the white dwarf phase unless that life was able to withstand multiple extreme and sudden changes in its environment.”

    “We know that the solar wind in the past eroded the Martian atmosphere, which, unlike Earth, does not have a large-scale magnetosphere. What we were not expecting to find is that the solar wind in the future could be as damaging even to those planets that are protected by a magnetic field”, says Dr Aline Vidotto of Trinity College Dublin, the University of Dublin(IE), the co-author of the study.

    Future missions like the James Webb Space Telescope due to be launched later this year should reveal more about planets that orbit white dwarf stars, including whether planets within their habitable zones show biomarkers that indicate the presence of life, so the study provides valuable context to any potential discoveries.

    So far no terrestrial planet that could support life around a white dwarf has been found, but two known gas giants are close enough to their star’s habitable zone to suggest that such a planet could exist. These planets likely moved in closer to the white dwarf as a result of interactions with other planets further out.

    Dr Veras adds: “These examples show that giant planets can approach very close to the habitable zone. The habitable zone for a white dwarf is very close to the star because they emit much less light than a Sun-like star. However, white dwarfs are also very steady stars as they have no winds. A planet that’s parked in the white dwarf habitable zone could remain there for billions of years, allowing time for life to develop provided that the conditions are suitable.”

    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 establishment of the The University of Warwick (UK) was given approval by the government in 1961 and received its Royal Charter of Incorporation in 1965.

    The idea for a university in Coventry was mooted shortly after the conclusion of the Second World War but it was a bold and imaginative partnership of the City and the County which brought the University into being on a 400-acre site jointly granted by the two authorities. Since then, the University has incorporated the former Coventry College of Education in 1978 and has extended its land holdings by the purchase of adjoining farm land.

    The University initially admitted a small intake of graduate students in 1964 and took its first 450 undergraduates in October 1965. In October 2013, the student population was over 23,000 of which 9,775 are postgraduates. Around a third of the student body comes from overseas and over 120 countries are represented on the campus.

    The University of Warwick is a public research university on the outskirts of Coventry between the West Midlands and Warwickshire, England. The University was founded in 1965 as part of a government initiative to expand higher education. The Warwick Business School was established in 1967, the Warwick Law School in 1968, Warwick Manufacturing Group (WMG) in 1980, and Warwick Medical School in 2000. Warwick incorporated Coventry College of Education in 1979 and Horticulture Research International in 2004.

    Warwick is primarily based on a 290 hectares (720 acres) campus on the outskirts of Coventry, with a satellite campus in Wellesbourne and a central London base at the Shard. It is organised into three faculties — Arts, Science Engineering and Medicine, and Social Sciences — within which there are 32 departments. As of 2019, Warwick has around 26,531 full-time students and 2,492 academic and research staff. It had a consolidated income of £679.9 million in 2019/20, of which £131.7 million was from research grants and contracts. Warwick Arts Centre is a multi-venue arts complex in the university’s main campus and is the largest venue of its kind in the UK, which is not in London.

    Warwick has an average intake of 4,950 undergraduates out of 38,071 applicants (7.7 applicants per place).

    Warwick is a member of Association of Commonwealth Universities (UK), the Association of MBAs, EQUIS, the European University Association (EU), the Midlands Innovation group, the Russell Group (UK), Sutton 13. It is the only European member of the Center for Urban Science and Progress, a collaboration with New York University (US). The university has extensive commercial activities, including the University of Warwick Science Park and Warwick Manufacturing Group.

    Warwick’s alumni and staff include winners of the Nobel Prize, Turing Award, Fields Medal, Richard W. Hamming Medal, Emmy Award, Grammy, and the Padma Vibhushan, and are fellows to the British Academy, the Royal Society of Literature, the Royal Academy of Engineering, and the Royal Society. Alumni also include heads of state, government officials, leaders in intergovernmental organisations, and the current chief economist at the Bank of England. Researchers at Warwick have also made significant contributions such as the development of penicillin, music therapy, Washington Consensus, Second-wave feminism, computing standards, including ISO and ECMA, complexity theory, contract theory, and the International Political Economy as a field of study.

    Twentieth century

    The idea for a university in Warwickshire was first mooted shortly after World War II, although it was not founded for a further two decades. A partnership of the city and county councils ultimately provided the impetus for the university to be established on a 400-acre (1.6 km^2) site jointly granted by the two authorities. There was some discussion between local sponsors from both the city and county over whether it should be named after Coventry or Warwickshire. The name “University of Warwick” was adopted, even though Warwick, the county town, lies some 8 miles (13 km) to its southwest and Coventry’s city centre is only 3.5 miles (5.6 km) northeast of the campus. The establishment of the University of Warwick was given approval by the government in 1961 and it received its Royal Charter of Incorporation in 1965. Since then, the university has incorporated the former Coventry College of Education in 1979 and has extended its land holdings by the continuing purchase of adjoining farm land. The university also benefited from a substantial donation from the family of John ‘Jack’ Martin, a Coventry businessman who had made a fortune from investment in Smirnoff vodka, and which enabled the construction of the Warwick Arts Centre.

    The university initially admitted a small intake of graduate students in 1964 and took its first 450 undergraduates in October 1965. Since its establishment Warwick has expanded its grounds to 721 acres (2.9 km^2), with many modern buildings and academic facilities, lakes, and woodlands. In the 1960s and 1970s, Warwick had a reputation as a politically radical institution.

    Under Vice-Chancellor Lord Butterworth, Warwick was the first UK university to adopt a business approach to higher education, develop close links with the business community and exploit the commercial value of its research. These tendencies were discussed by British historian and then-Warwick lecturer, E. P. Thompson, in his 1970 edited book Warwick University Ltd.

    The Leicester Warwick Medical School, a new medical school based jointly at Warwick and University of Leicester (UK), opened in September 2000.

    On the recommendation of Tony Blair, Bill Clinton chose Warwick as the venue for his last major foreign policy address as US President in December 2000. Sandy Berger, Clinton’s National Security Advisor, explaining the decision in a press briefing on 7 December 2000, said that: “Warwick is one of Britain’s newest and finest research universities, singled out by Prime Minister Blair as a model both of academic excellence and independence from the government.”

    Twenty-first century
    The university was seen as a favoured institution of the Labour government during the New Labour years (1997 to 2010). It was academic partner for a number of flagship Government schemes including the National Academy for Gifted and Talented Youth and the NHS University (now defunct). Tony Blair described Warwick as “a beacon among British universities for its dynamism, quality and entrepreneurial zeal”. In a 2012 study by Virgin Media Business, Warwick was described as the most “digitally-savvy” UK university.

    In February 2001, IBM donated a new S/390 computer and software worth £2 million to Warwick, to form part of a “Grid” enabling users to remotely share computing power. In April 2004 Warwick merged with the Wellesbourne and Kirton sites of Horticulture Research International. In July 2004 Warwick was the location for an important agreement between the Labour Party and the trade unions on Labour policy and trade union law, which has subsequently become known as the “Warwick Agreement”.

    In June 2006 the new University Hospital Coventry opened, including a 102,000 sq ft (9,500 m^2) university clinical sciences building. Warwick Medical School was granted independent degree-awarding status in 2007, and the School’s partnership with the University of Leicester was dissolved in the same year. In February 2010, Lord Bhattacharyya, director and founder of the WMG unit at Warwick, made a £1 million donation to the university to support science grants and awards.

    In February 2012 Warwick and Melbourne-based Monash University (AU) announced the formation of a strategic partnership, including the creation of 10 joint senior academic posts, new dual master’s and joint doctoral degrees, and co-ordination of research programmes. In March 2012 Warwick and Queen Mary, University of London announced the creation of a strategic partnership, including research collaboration, some joint teaching of English, history and computer science undergraduates, and the creation of eight joint post-doctoral research fellowships.

    In April 2012 it was announced that Warwick would be the only European university participating in the Center for Urban Science and Progress, an applied science research institute to be based in New York consisting of an international consortium of universities and technology companies led by New York University and NYU Tandon School of Engineering (US). In August 2012, Warwick and five other Midlands-based universities — Aston University (UK), the University of Birmingham (UK), the University of Leicester (UK), Loughborough University (UK) and the University of Nottingham — formed the M5 Group, a regional bloc intended to maximise the member institutions’ research income and enable closer collaboration.

    In September 2013 it was announced that a new National Automotive Innovation Centre would be built by WMG at Warwick’s main campus at a cost of £100 million, with £50 million to be contributed by Jaguar Land Rover and £30 million by Tata Motors.

    In July 2014, the government announced that Warwick would be the host for the £1 billion Advanced Propulsion Centre, a joint venture between the Automotive Council and industry. The ten-year programme intends to position the university and the UK as leaders in the field of research into the next generation of automotive technology.

    In September 2015, Warwick celebrated its 50th anniversary (1965–2015) and was designated “University of the Year” by The Times and The Sunday Times.

    Research

    In 2013/14 Warwick had a total research income of £90.1 million, of which £33.9 million was from Research Councils; £25.9 million was from central government, local authorities and public corporations; £12.7 million was from the European Union; £7.9 million was from UK industry and commerce; £5.2 million was from UK charitable bodies; £4.0 million was from overseas sources; and £0.5 million was from other sources.

    In the 2014 UK Research Excellence Framework (REF), Warwick was again ranked 7th overall (as 2008) amongst multi-faculty institutions and was the top-ranked university in the Midlands. Some 87% of the University’s academic staff were rated as being in “world-leading” or “internationally excellent” departments with top research ratings of 4* or 3*.

    Warwick is particularly strong in the areas of decision sciences research (economics, finance, management, mathematics and statistics). For instance, researchers of the Warwick Business School have won the highest prize of the prestigious European Case Clearing House (ECCH: the equivalent of the Oscars in terms of management research).

    Warwick has established a number of stand-alone units to manage and extract commercial value from its research activities. The four most prominent examples of these units are University of Warwick Science Park; Warwick HRI; Warwick Ventures (the technology transfer arm of the University); and WMG.

     
  • richardmitnick 1:04 pm on July 12, 2021 Permalink | Reply
    Tags: , About 2000 light years away from Earth there is a star catapulting toward the edge of the Milky Way., , It’s a piece of shrapnel from a past explosion—a cosmic event known as a supernova—that’s still being propelled forward., Supernovas occur when a white dwarf gets too massive to support itself eventually triggering a cosmic detonation of energy., This particular star known as LP 40−365., This star is moving so fast that it’s almost certainly leaving the galaxy., To have gone through partial detonation and still survive is very cool and unique., White dwarf stars   

    From Boston University (US) : “Why Is This Weird Metallic Star Hurtling Out of the Milky Way?” 

    From Boston University (US)

    July 8, 2021
    Jessica Colarossi

    Supernova Shrapnel

    BU astronomers analyzed light data from a piece of supernova shrapnel—a star called LP 40−365—to gain clues about where it came from.

    1
    A close pair of white dwarf stars set up to explode in what is called a supernova.Photo courtesy of California Institute of Technology (US)/Caltech Palomar Zwicky Transient Factory.

    About 2,000 light years away from Earth there is a star catapulting toward the edge of the Milky Way. This particular star, known as LP 40−365, is one of a unique breed of fast-moving stars—remnant pieces of massive white dwarf stars—that have survived in chunks after a gigantic stellar explosion.

    “This star is moving so fast that it’s almost certainly leaving the galaxy…[it’s] moving almost two million miles an hour,” says JJ Hermes, Boston University College of Arts & Sciences assistant professor of astronomy. But why is this flying object speeding out of the Milky Way? Because it’s a piece of shrapnel from a past explosion—a cosmic event known as a supernova—that’s still being propelled forward.

    “To have gone through partial detonation and still survive is very cool and unique, and it’s only in the last few years that we’ve started to think this kind of star could exist,” says Odelia Putterman, a former BU student who has worked in Hermes’ lab.

    In a new paper published in The Astrophysical Journal Letters, Hermes and Putterman uncover new observations about this leftover “star shrapnel” that gives insight to other stars with similar catastrophic pasts.

    Putterman and Hermes analyzed data from NASA’s Hubble Space Telescope and Transiting Exoplanet Survey Satellite (TESS), which surveys the sky and collects light information on stars near and far. By looking at various kinds of light data from both telescopes, the researchers and their collaborators found that LP 40−365 is not only being hurled out of the galaxy but, based on the brightness patterns in the data, is also rotating on its way out.

    “The star is basically being slingshotted from the explosion, and we’re [observing] its rotation on its way out,” says Putterman, who previously studied astronomy at BU and is second author on the paper.

    “We dug a little deeper to figure out why that star [was repeatedly] getting brighter and fainter, and the simplest explanation is that we’re seeing something at [its] surface rotate in and out of view every nine hours,” suggesting its rotation rate, Hermes says. All stars rotate—even our sun slowly rotates on its axis every 27 days. But for a star fragment that’s survived a supernova, nine hours is considered relatively slow.

    Supernovas occur when a white dwarf gets too massive to support itself eventually triggering a cosmic detonation of energy. Finding the rotation rate of a star like LP 40−365 after a supernova can lend clues into the original two-star system it came from. It’s common in the universe for stars to come in close pairs, including white dwarfs, which are highly dense stars that form toward the end of a star’s life.

    If one white dwarf gives too much mass to the other, the star being dumped on can self-destruct, resulting in a supernova. Supernovas are commonplace in the galaxy and can happen in many different ways, according to the researchers, but they are usually very hard to see. This makes it hard to know which star did the imploding and which star dumped too much mass onto its star partner.

    Based on LP 40−365’s relatively slow rotation rate, Hermes and Putterman feel more confident that it is shrapnel from the star that self-destructed after being fed too much mass by its partner, when they were once orbiting each other at high speed. Because the stars were orbiting each other so quickly and closely, the explosion slingshotted both stars, and now we only see LP 40–365.

    “This [paper] adds one more layer of knowledge into what role these stars played when the supernova occurred,” and what can happen after the explosion, Putterman says. “By understanding what’s happening with this particular star, we can start to understand what’s happening with many other similar stars that came from a similar situation.”

    “These are very weird stars,” Hermes says. Stars like LP 40–365 are not only some of the fastest stars known to astronomers, but also the most metal-rich stars ever detected. Stars like our sun are composed of helium and hydrogen, but a star that has survived a supernova is primarily composed of metal material, because “what we’re seeing are the byproducts of violent nuclear reactions that happen when a star blows itself up,” Hermes says, making star shrapnel like this especially fascinating to study.

    This research was supported by a NASA TESS Cycle 2 grant; the European Research Council; a UK Science and Technology Facilities Council grant; the postdoctoral fellowship program Beatriu de Pinós, funded by the Secretary of Universities and Research (Government of Catalonia); the Horizon 2020 program of research and innovation of the European Union under a Maria Skłodowska-Curie grant; NASA’s Astrophysics Theory Program; and by a Leverhulme Research Fellowship.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Boston University is a private research university in Boston, Massachusetts. The university is nonsectarian but has a historical affiliation with the United Methodist Church. It was founded in 1839 by Methodists with its original campus in Newbury, Vermont, before moving to Boston in 1867.

    The university now has more than 4,000 faculty members and nearly 34,000 students, and is one of Boston’s largest employers. It offers bachelor’s degrees, master’s degrees, doctorates, and medical, dental, business, and law degrees through 17 schools and colleges on three urban campuses. The main campus is situated along the Charles River in Boston’s Fenway-Kenmore and Allston neighborhoods, while the Boston University Medical Campus is located in Boston’s South End neighborhood. The Fenway campus houses the Wheelock College of Education and Human Development, formerly Wheelock College, which merged with BU in 2018.

    BU is a member of the Boston Consortium for Higher Education (US) and the Association of American Universities (US). It is classified among “R1: Doctoral Universities – Very High Research Activity”.

    Among its alumni and current or past faculty, the university counts eight Nobel Laureates, 23 Pulitzer Prize winners, 10 Rhodes Scholars, six Marshall Scholars, nine Academy Award winners, and several Emmy and Tony Award winners. BU also has MacArthur, Fulbright, and Truman Scholars, as well as American Academy of Arts and Sciences (US) and National Academy of Sciences (US) members, among its past and present graduates and faculty. In 1876, BU professor Alexander Graham Bell invented the telephone in a BU lab.

    The Boston University Terriers compete in the NCAA Division I. BU athletic teams compete in the Patriot League, and Hockey East conferences, and their mascot is Rhett the Boston Terrier. Boston University is well known for men’s hockey, in which it has won five national championships, most recently in 2009.

    Research

    In FY2016, the University reported in $368.9 million in sponsored research, comprising 1,896 awards to 722 faculty investigators. Funding sources included the National Science Foundation (US), the National Institutes of Health (US), the Department of Defense (US), the European Commission of the European Union, the Susan G. Komen Foundation (US), and the federal Health Resources and Services Administration (US). The University’s research enterprise encompasses dozens of fields, but its primary focus currently lies in seven areas: Data Science, Engineering Biology, Global Health, Infectious Diseases, Neuroscience, Photonics, and Urban Health.

    The University’s strategic plan calls for the removal of barriers between previously siloed departments, schools, and fields. The result has been an increasing emphasis by the University on interdisciplinary work and the creation of multidisciplinary centers such as the Rajen Kilachand Center for Integrated Life Sciences & Engineering, a $140 million, nine-story research facility that has brought together life scientists, engineers, and physicians from the Medical and Charles River Campuses; the Institute for Health Systems Innovation & Policy, a cross-campus initiative combining business, health law, medicine, and public policy; a neurophotonics center that combines photonics and neuroscience to study the brain; and the Software and Application Innovation Lab, where technologists work with colleagues in the arts and humanities and together develop digital research tools. The University also made a large investment in an emerging field, when it created a new university-wide academic unit called the Faculty of Computing & Data Sciences in 2019 and began construction of the nineteen-story Center for Computing & Data Sciences, slated to open in 2022.

    In 2003, the National Institute of Allergy and Infectious Diseases awarded Boston University a grant to build one of two National Biocontainment Laboratories. The National Emerging Infectious Diseases Laboratories (NEIDL) was created to study emerging infectious diseases that pose a significant threat to public health. NEIDL has biosafety level 2, 3, and 4 (BSL-2, BSL-3, and BSL-4, respectively) labs that enable researchers to work safely with the pathogens. BSL-4 labs are the highest level of biosafety labs and work with diseases with a high risk of aerosol transmission.

    The strategic plan also encouraged research collaborations with industry and government partners. In 2016, as part of a broadbased effort to solve the critical problem of antibiotic resistance, the US Department of Health & Human Services selected the Boston University School of Law (LAW)—and Kevin Outterson, a BU professor of law—to lead a $350 million trans-Atlantic public-private partnership called CARB-X to foster the preclinical development of new antibiotics and antimicrobial rapid diagnostics and vaccines.

    That same year, BU researcher Avrum Spira joined forces with Janssen Research & Development and its Disease Interception Accelerator group. Spira—a professor of medicine, pathology and laboratory medicine, and bioinformatics—has spent his career at BU pursuing a better, and earlier, way to diagnose pulmonary disorders and cancers, primarily using biomarkers and genomic testing. In 2015, under a $13.7 million Defense Department grant, Spira’s efforts to identify which members of the military will develop lung cancer and COPD caught the attention of Janssen, part Johnson & Johnson. They are investing $10.1 million to collaborate with Spira’s lab with the hope that his discoveries—and potential therapies—could then apply to the population at large.

    In its effort to increase diversity and inclusion, Boston University appointed Ibram X. Kendi in July 2020 as a history professor and the director and founder of its newly established Center for Antiracist Research. The university also appointed alumna Andrea Taylor as its first senior diversity officer.

     
  • richardmitnick 9:02 am on September 1, 2020 Permalink | Reply
    Tags: "Record EOS measurement pressures shed light on stellar evolution", , , , Measuring the basic properties of matter such as the equation of state (EOS)., The EOS research is an outgrowth of the NIF Discovery Science “Gbar (gigabar or one billion atmospheres) Campaign.", White dwarf stars   

    From Lawrence Livermore National Laboratory: “Record EOS measurement pressures shed light on stellar evolution” 

    From Lawrence Livermore National Laboratory

    8.5.20

    Breanna Bishop
    bishop33@llnl.gov
    925-423-9802

    Charlie Osolin

    1
    Composite image of a white dwarf star inside a NIF hohlraum. A white dwarf with the mass of the sun would be about the size of planet Earth, making it one of densest objects in space after neutron stars and black holes. Credit: Mark Meamber and Clayton Dahlen/LLNL.

    2
    White dwarfs are among the most ancient stellar objects, so their temperatures and predictable lifecycles enable them to work as “cosmic clocks” that can help determine the age of the universe and nearby stars and galaxies. (Greg Stewart/SLAC National Accelerator Laboratory).

    Using the power of the National Ignition Facility (NIF) [below], the world’s highest-energy laser system, researchers at Lawrence Livermore National Laboratory (LLNL) and an international team of collaborators have developed an experimental capability for measuring the basic properties of matter, such as the equation of state (EOS), at the highest pressures thus far achieved in a controlled laboratory experiment.

    The results are relevant to the conditions at the cores of giant planets, the interiors of brown dwarfs (failed stars), the carbon envelopes of white dwarf stars and many applied science programs at LLNL.

    The studies were published today in Nature.

    According to the authors, the overlap with white dwarf envelopes is particularly significant — this new research enables experimental benchmarks of the basic properties of matter in this regime. The results should ultimately lead to improved models of white dwarfs, which represent the final stage of evolution for most stars in the universe.

    After billions of years, the sun and other medium- and low-mass stars will undergo a sequence of expansions and contractions that results in the formation of white dwarfs — the fate of stars that have exhausted their nuclear fuel and collapsed into hot, super-dense mixtures of carbon and oxygen.

    In an effort to resolve disagreements in EOS models at extreme pressures that are relevant to white dwarf stars and various laboratory research projects, scientists conducted the first laboratory studies of matter at the conditions in the outer carbon layer of an unusual class of white dwarf called a “hot DQ.”

    The research subjected solid hydrocarbon samples to pressures ranging from 100 to 450 megabars (100 to 450 million times Earth’s atmospheric pressure) to determine the EOS — the relationship between pressure and compression — in the convection layer of a hot DQ. These were the highest pressures ever achieved in laboratory EOS measurements.

    “White dwarf stars provide important tests of stellar physics models, but EOS models at these extreme conditions are largely untested,” said LLNL physicist Annie Kritcher, the paper’s lead author.

    “NIF can duplicate conditions ranging from the cores of planets and brown dwarfs to those in the center of the sun,” Kritcher added. “We’re also able in NIF experiments to deduce the opacity along the shock Hugoniot (the Hugoniot curve is a plot of the increase in a material’s pressure and density under strong shock compression). This is a necessary component in studies of stellar structure and evolution.”

    Hot DQs have atmospheres primarily composed of carbon — instead of hydrogen and helium as in most white dwarfs — and are unusually hot and bright. Some also pulsate as they rotate because of magnetic spots on their surface, providing observable variations in brightness. Analyzing these variations “provides stringent tests of white dwarf models and a detailed picture of the outcome of the late stages of stellar evolution,” the researchers said.

    They added, however, that current EOS models relevant to white dwarf envelopes at pressures in the hundreds of millions of atmospheres can vary by nearly 10 percent, “a significant uncertainty for stellar evolution models.” Previous researchers have called this the “weakest link in the constitutive physics” that inform white dwarf modeling, Kritcher said.

    The NIF research could help resolve the differences by providing the first EOS data that reach conditions deep in the convection zone of a hot DQ — the region where models show the greatest variability. Results of the experiments agree with EOS models that recognize the extent to which extreme pressures can strip inner-shell electrons from their carbon atoms, decreasing the opacity and increasing the compressibility of the resulting ionized plasma.

    The EOS research is an outgrowth of the NIF Discovery Science “Gbar (gigabar, or one billion atmospheres) Campaign,” initiated by Roger Falcone and his students and postdocs at University of California, Berkeley and other NIF academic users and early career scientists from LLNL. It was supported by the LLNL Laboratory Directed Research and Development Program, the University of California Office of the President, the National Nuclear Security Administration and the Department of Energy Office of Science.

    “The NIF Discovery Science Program enabled our diverse team of researchers — from universities, national labs and industry — to work together on a long-term effort to fundamentally understand the behavior of matter under the most extreme pressures and temperatures,” Falcone said. “NIF is the only facility in the world capable of creating and probing those conditions, and its expert support teams were key to our success. This paper highlights the strength of that collaboration and is evidence for how basic research can find applications in many fields, including astrophysics.”

    In the EOS experiments, NIF’s lasers delivered 1.1 million joules of ultraviolet light to the inside of a pencil-eraser-size hollow gold cylinder called a hohlraum, creating a uniform X-ray “bath” with a peak radiation temperature of nearly 3.5 million degrees. The X-rays were absorbed by a solid plastic sphere mounted in the center of the hohlraum.

    The plastic was heated and ablated, or blown off like rocket exhaust, by the X-rays, creating ablation pressure that launched converging shock waves at 150 to 220 kilometers a second toward the center of the target capsule. The shocks coalesced into a single stronger shock that reached pressures approaching a billion times Earth’s atmosphere.

    Researchers determined the Hugoniot — the density and pressure at the shock front — using temporally and spatially resolved streaked X-ray radiography. The studies showed consistent results for experiments fielded at both cryogenic and ambient temperatures – which produced different initial starting densities – and with varying laser pulse shapes. They also measured the bulk shocked material’s electron temperature and degree of ionization with X-ray Thomson scattering.

    “We measured a reduction in opacity at high pressures, which is associated with a significant ionization of the carbon inner shell,” Kritcher said. “This pressure range along the Hugoniot corresponds to the conditions in the carbon envelope of white dwarf stars. Our data agree with equation-of-state models that include the detailed electronic shell structure.”

    Those models “show a sharper bend in the Hugoniot and higher maximum compression than models that lack electronic shells,” she said, suggesting a “softening” of the EOS. This leads to increased compression resulting from this “pressure ionization.”

    The experimental data can contribute to better models of pulsating hot DQ stars and a more accurate determination of their internal structures, pulsation properties, spectral evolution and complex origin, the researchers concluded.

    Kritcher and Falcone were joined on the paper by LLNL researchers Damian Swift, Tilo Döppner, Benjamin Bachmann, Lorin Benedict, Jonathan DuBois, Jim Gaffney, Sebastien Hamel, Amy Jenei, Natalie Kostinski, Mike MacDonald, Brian Maddox, Madison Martin, Abbas Nikroo, Joe Nilsen, Bruce Remington, Phillip Sterne, Alfredo Correa Tedesco and Heather Whitley; Rip Collins, Laboratory for Laser Energetics at the University of Rochester; Wendi Sweet and Fred Elsner, General Atomics; Gilles Fontaine, University of Montreal; Walter Johnson, University of Notre Dame; Dominik Kraus, Helmholtz-Zentrum Dresden-Rossendorf and Institute of Solid State and Materials Physics at the Technische Universität Dresden in Dresden, Germany; Paul Neumayer, GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany; Didier Saumon, Los Alamos National Laboratory; and Siegfried Glenzer, SLAC National Accelerator Laboratory.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition


    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security Administration
    Lawrence Livermore National Laboratory (LLNL) is an American federal research facility in Livermore, California, United States, founded by the University of California, Berkeley in 1952. A Federally Funded Research and Development Center (FFRDC), it is primarily funded by the U.S. Department of Energy (DOE) and managed and operated by Lawrence Livermore National Security, LLC (LLNS), a partnership of the University of California, Bechtel, BWX Technologies, AECOM, and Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium named after it.
    LLNL is self-described as “a premier research and development institution for science and technology applied to national security.” Its principal responsibility is ensuring the safety, security and reliability of the nation’s nuclear weapons through the application of advanced science, engineering and technology. The Laboratory also applies its special expertise and multidisciplinary capabilities to preventing the proliferation and use of weapons of mass destruction, bolstering homeland security and solving other nationally important problems, including energy and environmental security, basic science and economic competitiveness.

    The Laboratory is located on a one-square-mile (2.6 km2) site at the eastern edge of Livermore. It also operates a 7,000 acres (28 km2) remote experimental test site, called Site 300, situated about 15 miles (24 km) southeast of the main lab site. LLNL has an annual budget of about $1.5 billion and a staff of roughly 5,800 employees.

    LLNL was established in 1952 as the University of California Radiation Laboratory at Livermore, an offshoot of the existing UC Radiation Laboratory at Berkeley. It was intended to spur innovation and provide competition to the nuclear weapon design laboratory at Los Alamos in New Mexico, home of the Manhattan Project that developed the first atomic weapons. Edward Teller and Ernest Lawrence,[2] director of the Radiation Laboratory at Berkeley, are regarded as the co-founders of the Livermore facility.

    The new laboratory was sited at a former naval air station of World War II. It was already home to several UC Radiation Laboratory projects that were too large for its location in the Berkeley Hills above the UC campus, including one of the first experiments in the magnetic approach to confined thermonuclear reactions (i.e. fusion). About half an hour southeast of Berkeley, the Livermore site provided much greater security for classified projects than an urban university campus.

    Lawrence tapped 32-year-old Herbert York, a former graduate student of his, to run Livermore. Under York, the Lab had four main programs: Project Sherwood (the magnetic-fusion program), Project Whitney (the weapons-design program), diagnostic weapon experiments (both for the Los Alamos and Livermore laboratories), and a basic physics program. York and the new lab embraced the Lawrence “big science” approach, tackling challenging projects with physicists, chemists, engineers, and computational scientists working together in multidisciplinary teams. Lawrence died in August 1958 and shortly after, the university’s board of regents named both laboratories for him, as the Lawrence Radiation Laboratory.

    Historically, the Berkeley and Livermore laboratories have had very close relationships on research projects, business operations, and staff. The Livermore Lab was established initially as a branch of the Berkeley laboratory. The Livermore lab was not officially severed administratively from the Berkeley lab until 1971. To this day, in official planning documents and records, Lawrence Berkeley National Laboratory is designated as Site 100, Lawrence Livermore National Lab as Site 200, and LLNL’s remote test location as Site 300.[3]

    The laboratory was renamed Lawrence Livermore Laboratory (LLL) in 1971. On October 1, 2007 LLNS assumed management of LLNL from the University of California, which had exclusively managed and operated the Laboratory since its inception 55 years before. The laboratory was honored in 2012 by having the synthetic chemical element livermorium named after it. The LLNS takeover of the laboratory has been controversial. In May 2013, an Alameda County jury awarded over $2.7 million to five former laboratory employees who were among 430 employees LLNS laid off during 2008.[4] The jury found that LLNS breached a contractual obligation to terminate the employees only for “reasonable cause.”[5] The five plaintiffs also have pending age discrimination claims against LLNS, which will be heard by a different jury in a separate trial.[6] There are 125 co-plaintiffs awaiting trial on similar claims against LLNS.[7] The May 2008 layoff was the first layoff at the laboratory in nearly 40 years.[6]

    On March 14, 2011, the City of Livermore officially expanded the city’s boundaries to annex LLNL and move it within the city limits. The unanimous vote by the Livermore city council expanded Livermore’s southeastern boundaries to cover 15 land parcels covering 1,057 acres (4.28 km2) that comprise the LLNL site. The site was formerly an unincorporated area of Alameda County. The LLNL campus continues to be owned by the federal government.

    LLNL/NIF


    DOE Seal
    NNSA

     
  • richardmitnick 8:34 am on August 18, 2020 Permalink | Reply
    Tags: "Experiments replicate high densities in ‘white dwarf’ star remnants", , , , Simulating the crushing pressure created as stars cease to produce their own fuel leaving only an extremely dense core., , White dwarf stars   

    From University of Rochester: “Experiments replicate high densities in ‘white dwarf’ star remnants” 

    From University of Rochester

    August 16, 2020
    Bob Marcotte
    bmarcotte@ur.rochester.edu

    1
    To study the pressures created by white dwarf stars, researchers fired nanometer laser light into a hohlraum—a tiny gold cylinder—bathing a 1 mm sample of a carbon-based compound in radiation heated to nearly 3.5 million degrees, at pressures ranging from 100 to 450 million atmospheres. (Illustration courtesy of Lawrence Livermore National Laboratory.)

    Work to understand astrophysical processes may offer ideas for creating new materials on Earth.

    For the first time, researchers have found a way to describe conditions deep in the convection zone of “white dwarf” stars, which are home to some of the densest collections of matter in the Universe.

    In a project conducted at the National Ignition Facility at Lawrence Livermore National Laboratory, the research team, including University of Rochester engineering professor Gilbert (Rip) Collins, simulated the crushing pressure created as stars cease to produce their own fuel, leaving only an extremely dense core.

    National Ignition Facility at LLNL


    “This is the first time we have been able to lock down an equation of state, describing the behavior of matter that is intrinsic to white dwarf stars, in particular the regime in a part of white dwarfs where oscillations occur that have been particularly difficult to model,” says Collins, who was a coauthor on the team’s paper published in Nature Research.

    Collins is the director of science, technology, and academics at the Laboratory for Laser Energetics and is the Tracy Hyde Harris Professor of Mechanical Engineering and is a professor in the Department of Physics and Astronomy.

    University of Rochester Laboratory for Laser Energetics

    The results are important because they add to the growing body of evidence being collected by high-energy-density researchers about the formation and evolution of planets, stars, and other astrophysical bodies, which in turn can suggest possible approaches to creating novel materials in laboratories on Earth.

    “Decades ago, underground nuclear tests made a couple of measurements in a similar regime, but now we’re able to do this with a much higher level of accuracy and precision,” says Collins.

    Inwardly converging shock waves

    White dwarf stars, sometimes called “star corpses” in popular literature, are what stars like our sun become after they have exhausted their nuclear fuel and expelled most their outer material. The process leaves behind a hot core that cools down over the next billion years or so, according to information from NASA’s Goddard Space Flight Center. A white dwarf star the size of the Earth is 200,000 times as dense.

    The density is achieved when the star is no longer able to create internal, outwardly directed pressure, because fusion has ceased. As that happens, gravity compacts the star’s matter inward until even the electrons that compose the dwarf star’s atoms are smashed together. One recent analysis has suggested that white dwarf stars are an important source of carbon found in galaxies.

    To study the process, researchers fired nanometer laser light into a hohlraum—a tiny gold cylinder—bathing a spherical 1 mm sample of a carbon-based compound known as CH (methylidyne) in x-ray radiation heated to nearly 3.5 million degrees, at pressures ranging from 100 to 450 million atmospheres.

    The experiments described in the paper simulate what happens in hot DQ white dwarf stars, first discovered in 2007, which contain a carbon and oxygen core surrounded by an envelope, or atmosphere, of mostly carbon. The researchers focused specifically on replicating the high pressure regimes that occur in an area of oscillating pulsations where previous attempts to model the behavior of matter have produced inconsistent results.

    The paper describes how the x-ray radiation bath in the hohlraum is absorbed by an outer region (ablator) of the spherical fuel sample, which heats and expands, launching inwardly converging shock waves toward the center of sphere. The shocks coalesce into a single strong shock, traveling at a speed of 150 to 220 kilometers per second and traversing the sample in about 9 nanoseconds.

    The 29 researchers who collaborated on the paper represent an array of North American and German research centers and institutions, including Lawrence Livermore, Los Alamos National Laboratory, the SLAC National Accelerator, the University of Montreal, the University of Notre Dame, University of California Berkeley, and the Dresden University of Technology.

    The project was supported with funding from various offices of the US Department of Energy and from the University of California.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Rochester

    The University of Rochester is one of the country’s top-tier research universities. Our 158 buildings house more than 200 academic majors, more than 2,000 faculty and instructional staff, and some 10,500 students—approximately half of whom are women.

    Learning at the University of Rochester is also on a very personal scale. Rochester remains one of the smallest and most collegiate among top research universities, with smaller classes, a low 10:1 student to teacher ratio, and increased interactions with faculty.

     
  • richardmitnick 2:28 pm on January 12, 2019 Permalink | Reply
    Tags: Astronomers find signatures of a ‘messy’ star that made its companion go supernova, , , , , , It takes many astronomers and a wide variety of types of telescopes working together to understand transient cosmic phenomena, , SN 2015cp, , , White dwarf stars   

    From University of Washington: “Astronomers find signatures of a ‘messy’ star that made its companion go supernova” 

    U Washington

    From University of Washington

    January 10, 2019
    James Urton

    1
    An X-ray/infrared composite image of G299, a Type Ia supernova remnant in the Milky Way Galaxy approximately 16,000 light years away.NASA/Chandra X-ray Observatory/University of Texas/2MASS/University of Massachusetts/Caltech/NSF

    NASA/Chandra X-ray Telescope


    Caltech 2MASS Telescopes, a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center (IPAC) at Caltech, at the Whipple Observatory on Mt. Hopkins south of Tucson, AZ, Altitude 2,606 m (8,550 ft) and at the Cerro Tololo Inter-American Observatory at an altitude of 2200 meters near La Serena, Chile.

    Many stars explode as luminous supernovae when, swollen with age, they run out of fuel for nuclear fusion. But some stars can go supernova simply because they have a close and pesky companion star that, one day, perturbs its partner so much that it explodes.

    These latter events can happen in binary star systems, where two stars attempt to share dominion. While the exploding star gives off lots of evidence about its identity, astronomers must engage in detective work to learn about the errant companion that triggered the explosion.

    On Jan. 10 at the 2019 American Astronomical Society meeting in Seattle, an international team of astronomers announced that they have identified the type of companion star that made its partner in a binary system, a carbon-oxygen white dwarf star, explode. Through repeated observations of SN 2015cp, a supernova 545 million light years away, the team detected hydrogen-rich debris that the companion star had shed prior to the explosion.

    “The presence of debris means that the companion was either a red giant star or similar star that, prior to making its companion go supernova, had shed large amounts of material,” said University of Washington astronomer Melissa Graham, who presented the discovery and is lead author on the accompanying paper accepted for publication in The Astrophysical Journal.

    The supernova material smacked into this stellar litter at 10 percent the speed of light, causing it to glow with ultraviolet light that was detected by the Hubble Space Telescope and other observatories nearly two years after the initial explosion. By looking for evidence of debris impacts months or years after a supernova in a binary star system, the team believes that astronomers could determine whether the companion had been a messy red giant or a relatively neat and tidy star.

    The team made this discovery as part of a wider study of a particular type of supernova known as a Type Ia supernova. These occur when a carbon-oxygen white dwarf star explodes suddenly due to activity of a binary companion. Carbon-oxygen white dwarfs are small, dense and — for stars — quite stable. They form from the collapsed cores of larger stars and, if left undisturbed, can persist for billions of years.

    Type Ia supernovae have been used for cosmological studies because their consistent luminosity makes them ideal “cosmic lighthouses,” according to Graham. They’ve been used to estimate the expansion rate of the universe and served as indirect evidence for the existence of dark energy.

    2
    An image of SN 1994D (lower left), a Type Ia supernova detected in 1994 at the edge of galaxy NGC 4526 (center).NASA/ESA/The Hubble Key Project Team/The High-Z Supernova Search Team.

    NASA/ESA Hubble Telescope

    Yet scientists are not certain what kinds of companion stars could trigger a Type Ia event. Plenty of evidence indicates that, for most Type Ia supernovae, the companion was likely another carbon-oxygen white dwarf, which would leave no hydrogen-rich debris in the aftermath. Yet theoretical models have shown that stars like red giants could also trigger a Type Ia supernova, which could leave hydrogen-rich debris that would be hit by the explosion. Out of the thousands of Type Ia supernovae studied to date, only a small fraction were later observed impacting hydrogen-rich material shed by a companion star. Prior observations of at least two Type Ia supernovae detected glowing debris months after the explosion. But scientists weren’t sure if those events were isolated occurrences, or signs that Type Ia supernovae could have many different kinds of companion stars.

    “All of the science to date that has been done using Type Ia supernovae, including research on dark energy and the expansion of the universe, rests on the assumption that we know reasonably well what these ‘cosmic lighthouses’ are and how they work,” said Graham. “It is very important to understand how these events are triggered, and whether only a subset of Type Ia events should be used for certain cosmology studies.”

    The team used Hubble Space Telescope observations to look for ultraviolet emissions from 70 Type Ia supernovae approximately one to three years following the initial explosion.

    “By looking years after the initial event, we were searching for signs of shocked material that contained hydrogen, which would indicate that the companion was something other than another carbon-oxygen white dwarf,” said Graham.

    In the case of SN 2015cp, a supernova first detected in 2015, the scientists found what they were searching for. In 2017, 686 days after the supernova exploded, Hubble picked up an ultraviolet glow of debris. This debris was far from the supernova source — at least 100 billion kilometers, or 62 billion miles, away. For reference, Pluto’s orbit takes it a maximum of 7.4 billion kilometers from our sun.

    3
    In 2017, 686 days after the initial explosion, the Hubble Space Telescope recorded an ultraviolet emission (blue circle) from SN 2015cp, which was caused by supernova material impacting hydrogen-rich material previously shed by a companion star. Yellow circles indicate cosmic ray strikes, which are unrelated to the supernova. NASA/Hubble Space Telescope/Graham et al. 2019.

    By comparing SN 2015cp to the other Type Ia supernovae in their survey, the researchers estimate that no more than 6 percent of Type Ia supernovae have such a litterbug companion. Repeated, detailed observations of other Type Ia events would help cement these estimates, Graham said.

    The Hubble Space Telescope was essential for detecting the ultraviolet signature of the companion star’s debris for SN 2015cp. In the fall of 2017, the researchers arranged for additional observations of SN 2015cp by the W.M. Keck Observatory in Hawaii, the Karl G. Jansky Very Large Array in New Mexico, the European Southern Observatory’s Very Large Telescope and NASA’s Neil Gehrels Swift Observatory, among others. These data proved crucial in confirming the presence of hydrogen and are presented in a companion paper lead by Chelsea Harris, a research associate at Michigan State University.

    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level,

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo, with an elevation of 2,635 metres (8,645 ft) above sea level,

    NASA Neil Gehrels Swift Observatory

    “The discovery and follow-up of SN 2015cp’s emission really demonstrates how it takes many astronomers, and a wide variety of types of telescopes, working together to understand transient cosmic phenomena,” said Graham. “It is also a perfect example of the role of serendipity in astronomical studies: If Hubble had looked at SN 2015cp just a month or two later, we wouldn’t have seen anything.”

    Graham is also a senior fellow with the UW’s DIRAC Institute and a science analyst with the Large Synoptic Survey Telescope, or LSST.

    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes, altitude 2,663 m (8,737 ft),

    “In the future, as a part of its regularly scheduled observations, the LSST will automatically detect optical emissions similar to SN 2015cp — from hydrogen impacted by material from Type Ia supernovae,” said Graham said. “It’s going to make my job so much easier!”

    Co-authors are Harris; Peter Nugent at the University of California, Berkeley and the Lawrence Berkeley National Laboratory; Kate Maguire at Queen’s University Belfast; Mark Sullivan and Mathew Smith at the University of Southampton; Stefano Valenti at the University of California, Davis; Ariel Goobar at Stockholm University; Ori Fox at the Space Telescope Science Institute; Ken Shen, Tom Brink and Alex Filippenko at the University of California, Berkeley; Patrick Kelly at the University of Minnesota; and Curtis McCully at the University of California, Santa Barbara and the Las Cumbres Observatory. The research was funded by the National Science Foundation, NASA, the European Research Council and the U.K.’s Science and Technology Facilities Council.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    u-washington-campus
    The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.
    So what defines us —the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 12:16 pm on October 20, 2017 Permalink | Reply
    Tags: , , , , , , White dwarf stars   

    From astrobites: “Energy transport in white dwarfs: what about magnetic fields?” 

    Astrobites bloc

    astrobites

    Oct 20, 2017
    Ingrid Pelisoli

    Title: Can magnetic fields suppress convection in the atmosphere of cool white dwarfs? A case study on WD2105-820
    Authors: N. P. Gentile Fusillo, P.-E. Tremblay, S. Jordan, B. T. Gänsicke, J. S. Kalirai, J. Cummings
    First Author’s Institution: University of Warwick, UK

    Status: Submitted to MNRAS, open access

    Did you know that the bright yellow ball that shines in the sky, which we call the Sun, is also a huge magnet? However, it is huge only in terms of spatial dimensions – the strength of the magnetic field is only about 1 Gauss (G), or 10-4 Tesla (T). This is 10,000 weaker than the strongest magnet you can buy. The strongest magnet ever built on Earth produces a magnetic field of at least 45 T. Meanwhile, there are some other tiny dots in the sky with fields as strong as 108G, or 104T!

    Tiny giant magnets

    These tiny dots are white dwarf stars, which are about the size of the Earth, but with a mass comparable to the Sun. They maintain their hydrostatic equilibrium thanks to the Pauli exclusion principle: gravity can not further compress the object without pushing electrons into the same energy states, so the electrons push back, causing what is known as degeneracy pressure. The high field observed in some white dwarf stars is probably related to the fact that they are tiny: their progenitors had much smaller fields, but when they are compressed into a planetary size, the field is strengthened due to the magnetic flux being conserved. However, the process of evolution involves lots of mass being lost, and we don’t know exactly what happens to the magnetic field during these stages. As a result, we cannot fully understand the origin of such high magnetic fields.

    1
    Figure 1: The author’s spectral fit to the hydrogen Balmer lines, from H8 to Hß. The top panel shows the best fit using a convective model, and the bottom panel shows the best radiative model. The obtained values of effective temperature and logarithm of the surface gravity are indicated. Figure 1 in the paper

    With the data release 2 of Gaia, which has made many astronomers draw a big circle around April 2018 on their calendars, we should identify hundreds of thousands of new white dwarfs. Something between 5 and 30% of them should be magnetic, based on the fraction of known magnetic white dwarfs. So it’s about time we start learning more about these objects! One particular problem we currently have is that it is very hard to estimate the mass of magnetic white dwarfs. We usually cannot apply spectroscopic analysis, our main method of estimating masses, because the spectral lines of magnetic white dwarfs are affected by the Zeeman effect. This effect causes an extra broadening which we have not (yet) been able to model together with the other important effects. In summary, no complete model exists! Gaia will give us a hand with that by allowing us to estimate the radius of white dwarfs – which is related to their mass (more about it in this bite). But we still have to know the temperature of the white dwarf to be able to do further cool science, such as estimating the age of stellar populations (like here and here).

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 2:46 pm on August 17, 2017 Permalink | Reply
    Tags: , , , , , , White dwarf stars   

    From Many Worlds: “Of White Dwarfs, “Zombie” Stars and Supernovae Explosions” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2017-08-17
    Marc Kaufman

    1
    Artistic view of the aftermath of a supernova explosion, with an unexpected white dwarf remnant. These super-dense but no longer active stars are thought to play a key role in many supernovae explosion. (Copyright Russell Kightley)

    White dwarf stars, the remnant cores of low-mass stars that have exhausted all their nuclear fuel, are among the most dense objects in the sky.

    Their mass is comparable to that of the sun, while their volume is comparable to that of Earth. Very roughly, this means the average density of matter in a white dwarf would be on the order of 1,000,000 times greater than the average density of the sun.

    Thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star — a category that includes the sun and over 97% of the other stars in the Milky Way — they are dim objects first identified a century ago but only in the last decade the subject of broad study.

    In recent years the white dwarfs have become more and more closely associated with supernovae explosions, though the processes involved remained hotly debated. A team using the Hubble Space Telescope even captured before and after images of what is hypothesized to be an incomplete white dwarf supernova. What was left behind has been described by some as a “zombie star.”

    Now a team of astronomers led by Stephane Vennes of the Czech Academy of Sciences has detected another zombie white dwarf, LP-40-365 , that they put forward as a far-flung remnant of a long-ago supernova explosion. This is considered important and unusual because it would represent a first detection of such a remnant long after the supernova conflagration.

    This dynamic is well captured in an animation accompanying the Science paper that describes the possible remnant.

    A supernova — among the most powerful forces in the universe — occurs when there is a change in the core of a star. A change can occur in two different ways, with both resulting in a thermonuclear explosion.

    Type Ia supernova occurs at the end of a single star’s lifetime. As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force. The core collapses, which results in the giant explosion of a supernova. The sun is a single star, but it does not have enough mass to become a supernova.

    The second type takes place only in binary star systems. Binary stars are two stars that orbit the same point. One of the stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter. Having too much matter causes the star to explode, resulting in a supernova.

    Type Ia supernovae, which are the result of the complete destruction of the star in a thermonuclear explosion, have a fairly uniform brightness that makes them useful for cosmology. The light emitted by the supernova explosion can be, for a short while at least, as bright as the whole of the Milky Way.

    Recently, astronomers have discovered a related form of supernova, called Type Iax, which look like Type Ia, but are much fainter. Type Iax supernovae may be caused by the partial destruction of a white dwarf star in such an explosion. If that interpretation is correct, part of the white dwarf should survive as a leftover object.

    And that leftover object is precisely what Vennes et al claim to have found.

    They have identified LP 40-365 as an unusual white dwarf with a low mass, high velocity and strange composition of oxygen, sodium and magnesium – exactly as might be expected for the leftover star from a Type Iax event. Vennes describes the white dwarf remnant his team has detected as a “compact star,” and perhaps the first of its kind in terms of the elements it contains.

    The team calculate that the explosion must have occurred between five and 50 million years ago.

    2
    The two inset images show before-and-after images captured by NASA’s Hubble Space Telescope of Supernova 2012Z in the spiral galaxy NGC 1309, what some call a “zombie star.”. The white X at the top of the main image marks the location of the supernova in the galaxy. A supernova typically obliterates the exploding white dwarf, or dying star. In 2014, scientists found that this faint supernova may have left behind a surviving portion of the white dwarf star.(NASA,ESA)

    In an email exchange, Vennes told me that he has been studying the local white dwarf population for thirty years.

    “These compact, dead stars tell us a lot about the “old” Milky Way, how stars were born and how they died,” he wrote.

    “Tens of thousands of these white dwarfs have been catalogued over this past century, most of them in the last decade, but we keep an eye on outliers, objects that are out of the norm. We look for exceedingly large velocity, peculiar chemical composition or abnormal mass or radii.

    “The strange case of LP40-365 came unexpectedly, but this was a classic case of serendipity in astronomy. Out of hundreds of targets we observed at the telescope, this one was uniquely peculiar. Fortunately, theorists are very imaginative and the model we adopted to interpret the observed properties of this object were only recently published. Our research on this object was certainly inspired and directed by their theory.”

    Vennes says the team was surprised to learn that the white dwarf LP40-365 is relatively bright among its peers and that similar objects did not show up in large-scale surveys such as the Sloan Digital Sky Survey.

    “This fact has convinced us that many more similarly peculiar white dwarfs await discovery. We should search among fainter, more distant samples of white dwarfs,” he wrote.

    And that search can be done by the European Space Agency’s Gaia astrometric space telescope, with follow-up observations at large telescopes such as the European Southern Observatory’s Very Large Telescope and the Gemini observatory in Chile.

    ESA/GAIA satellite

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level


    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    “It is also likely that our adopted model involving a subluminous {faint} Type Ia supernova will be modified or even superseded by teams of theorists coming up with new ideas. But we remain confident that these new ideas would still involve a cataclysmic event on the scale of a supernova.”

    A supernova burns for only a short period of time, but it can tell scientists a lot about the universe.

    One kind of supernova has shown scientists that we live in an expanding universe, one that is growing at an ever increasing rate.

    Scientists also have determined that supernovas play a key role in distributing elements throughout the universe. When the star explodes, it shoots elements and debris into space. Many of the elements we find here on Earth are made in the core of stars.

    These elements travel on to form new stars, planets and everything else in the universe — making white dwarfs and supernovae essential to the process that ultimately led to life.

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 3:28 pm on February 10, 2017 Permalink | Reply
    Tags: , , , Dwarf star 200 light-years away contains life’s building blocks, The constellation Boötes, , WD 1425+540, White dwarf stars   

    From UCLA: “Dwarf star 200 light-years away contains life’s building blocks” 

    UCLA bloc

    UCLA

    February 09, 2017
    Stuart Wolpert

    UCLA-led team discovers object in the constellation Boötes with carbon, nitrogen, oxygen and hydrogen.

    rendering
    Rendering of a white dwarf star (bright white spot), with rocky debris from former asteroids or a minor planet that has been broken apart by gravity (red rings). University of Warwick

    Many scientists believe the Earth was dry when it first formed, and that the building blocks for life on our planet — carbon, nitrogen and water — appeared only later as a result of collisions with other objects in our solar system that had those elements.

    Today, a UCLA-led team of scientists reports that it has discovered the existence of a white dwarf star whose atmosphere is rich in carbon and nitrogen, as well as in oxygen and hydrogen, the components of water. The white dwarf is approximately 200 light-years from Earth and is located in the constellation Boötes.

    Benjamin Zuckerman, a co-author of the research and a UCLA professor of astronomy, said the study presents evidence that the planetary system associated with the white dwarf contains materials that are the basic building blocks for life. And although the study focused on this particular star — known as WD 1425+540 — the fact that its planetary system shares characteristics with our solar system strongly suggests that other planetary systems would also.

    “The findings indicate that some of life’s important preconditions are common in the universe,” Zuckerman said.

    The scientists report that a minor planet in the planetary system was orbiting around the white dwarf, and its trajectory was somehow altered, perhaps by the gravitational pull of a planet in the same system. That change caused the minor planet to travel very close to the white dwarf, where the star’s strong gravitational field ripped the minor planet apart into gas and dust. Those remnants went into orbit around the white dwarf — much like the rings around Saturn, Zuckerman said — before eventually spiraling onto the star itself, bringing with them the building blocks for life.

    The researchers think these events occurred relatively recently, perhaps in the past 100,000 years or so, said Edward Young, another co-author of the study and a UCLA professor of geochemistry and cosmochemistry. They estimate that approximately 30 percent of the minor planet’s mass was water and other ices, and approximately 70 percent was rocky material.

    The research suggests that the minor planet is the first of what are likely many such analogs to objects in our solar system’s Kuiper belt. The Kuiper belt is an enormous cluster of small bodies like comets and minor planets located in the outer reaches of our solar system, beyond Neptune.

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Astronomers have long wondered whether other planetary systems have bodies with properties similar to those in the Kuiper belt, and the new study appears to confirm for the first time that one such body exists.

    White dwarf stars are dense, burned-out remnants of normal stars. Their strong gravitational pull causes elements like carbon, oxygen and nitrogen to sink out of their atmospheres and into their interiors, where they cannot be detected by telescopes.

    The research, published in the Astrophysical Journal Letters, describes how WD 1425+540 came to obtain carbon, nitrogen, oxygen and hydrogen. This is the first time a white dwarf with nitrogen has been discovered, and one of only a few known examples of white dwarfs that have been impacted by a rocky body that was rich in water ice.

    “If there is water in Kuiper belt-like objects around other stars, as there now appears to be, then when rocky planets form they need not contain life’s ingredients,” said Siyi Xu, the study’s lead author, a postdoctoral scholar at the European Southern Observatory in Germany who earned her doctorate at UCLA.

    “Now we’re seeing in a planetary system outside our solar system that there are minor planets where water, nitrogen and carbon are present in abundance, as in our solar system’s Kuiper belt,” Xu said. “If Earth obtained its water, nitrogen and carbon from the impact of such objects, then rocky planets in other planetary systems could also obtain their water, nitrogen and carbon this way.”

    A rocky planet that forms relatively close to its star would likely be dry, Young said.

    “We would like to know whether in other planetary systems Kuiper belts exist with large quantities of water that could be added to otherwise dry planets,” he said. “Our research suggests this is likely.”

    According to Zuckerman, the study doesn’t settle the question of whether life in the universe is common.

    “First you need an Earth-like world in its size, mass and at the proper distance from a star like our sun,” he said, adding that astronomers still haven’t found a planet that matches those criteria.

    The researchers observed WD 1425+540 with the Keck Telescope in 2008 and 2014, and with the Hubble Space Telescope in 2014.

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory, Mauna Kea, Hawaii, USA

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    They analyzed the chemical composition of its atmosphere using an instrument called a spectrometer, which breaks light into wavelengths. Spectrometers can be tuned to the wavelengths at which scientists know a given element emits and absorbs light; scientists can then determine the element’s presence by whether it emits or absorbs light of certain characteristic wavelengths. In the new study, the researchers saw the elements in the white dwarf’s atmosphere because they absorbed some of the background light from the white dwarf.

    In addition to Xu, Young and Zuckerman, co-authors of the research are Michael Jura, a UCLA professor of astronomy who died in 2016; Beth Klein, a former graduate student of Jura’s; and Patrick Dufour, an assistant professor of physics at the University of Montreal.

    See the full article here .

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