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  • richardmitnick 3:38 pm on July 30, 2021 Permalink | Reply
    Tags: "Why does the Milky Way have spiral arms? New Gaia data are helping solve the puzzle", , , , European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) GAIA Mission (EU), GAIA Early Data Release 3 (EDR3), New data from the star-mapping Gaia satellite are helping scientists unlock the mystery of our Milky Way galaxy's spiral arms., Our galaxy also possesses two less pronounced arms-or spurs-called the 'Sagittarius arm" and the "Local Arm" (which passes close to the sun)., Since the 1950s astronomers have known the Milky Waylooks like a spiral with several dense streams of stars and dust emanating from the galactic center winding through the galactic disc., , space.com, The European Gaia mission keeps uncovering the mysteries of the Milky Way., The Milky Way is known to have two main spiral arms: the "Perseus arm" and the "Scutum-Centaurus arm"., The short "Local arm" appeared much longer than the previous models expected., We derive the distance of the stars from a measure called the parallax-20% better with the latest release., When the researchers compared their galaxy map to previous models they found that the Perseus arm lies further away from the center of the galaxy in the studied region.   

    From European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) GAIA Mission (EU) via SPACE.com : “Why does the Milky Way have spiral arms? New Gaia data are helping solve the puzzle” 

    ESA/GAIA satellite

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

    via

    SPACE.com

    7.30.21
    Tereza Pultarova

    The European Gaia mission keeps uncovering the mysteries of the Milky Way.

    New data from the star-mapping Gaia satellite are helping scientists unlock the mystery of our Milky Way galaxy’s spiral arms.

    Recently published studies exploring the Early Data Release 3 (EDR3), a batch of observations made available to the scientific community last December, reveal the spiral structure of our galaxy with a greater precision and detail than was possible before.

    Since the 1950s astronomers have known that our galaxy-the Milky Way-looks like a spiral with several dense streams of stars and dust emanating from the galactic center winding through the galactic disc and dissolving around its edges. However, scientists have struggled to understand how many of these streams there are and what created them.

    “The problem with our galaxy is that we are inside its disc and therefore it’s very difficult to understand the structure as a whole,” Eleonora Zari, a scientist at the MPG Institute for Astronomy [MPG Institut für Astronomie](DE) in Heidelberg, Germany, and author of one of the new papers, told Space.com. “It’s like being in a forest and looking around. At some point, the trees are in front of each other. Plus the forest is a bit foggy, so you really can’t see what the whole forest looks like.”

    The European Space Agency’s (ESA) Gaia mission has been mapping the Milky Way since 2014, measuring the precise positions and distances from Earth of nearly two billion stars. The first two batches of data acquired by the spacecraft, which were released to the scientific community in 2016 and 2018, have revolutionized the study of our galaxy. In addition to the fixed positions, the spacecraft also measures how fast stars move in three-dimensional space, allowing astronomers to model the evolution of the Milky Way in the past as well as into the future.

    The latest data release, EDR3, improves the accuracy of the previous data sets. And it’s this precision that is enabling astronomers to disentangle the spiral arms from the rest of the stars in the galactic disc with better precision.

    Where are the arms?

    “We derive the distance of the stars from a measure called the parallax,” Zari said. “And this parallax measurement is 20% better with the latest release. That means that stars that previously we may have seen as part of the same structure now clearly belong to different structures.”

    Parallax is a star’s apparent movement against the background of more distant stars as Earth revolves around the sun. By measuring the change in the angle between the star and Earth from two opposite points in the planet’s orbit, astronomers can calculate the distance of the star using simple trigonometry.

    In one new paper [Astronomy & Astrophysics], Zari and her colleagues looked at concentrations of hot bright blue stars, called the OBA-type stars, in the Milky Way’s disc. In areas where they could see a higher-than-average concentration of these stars, they could assume the existence of a spiral arm. They then compared their analysis with previously developed models of the galaxy.

    “The position of the spiral arms is different and also the strength of the spiral arms, how bright they are, is different,” Zari said.

    The Milky Way is known to have two main spiral arms: the “Perseus arm” and the “Scutum-Centaurus arm”. Our galaxy also possesses two less pronounced arms-or spurs-called the ‘Sagittarius arm” and the “Local Arm” (which passes close to the sun).

    But in Zari’s study, the difference between the arms doesn’t seem so obvious.

    “The Perseus arm seems less bright, and instead the Local arm is more prominent,” she said. “Aso the other two arms — Sagittarius and Scutum Centaurus — at least in my study, they seem to have about the same brightness.”

    Zari’s colleague Eloisa Poggio looked at concentrations of 600,000 young stars to determine the precise position of the spiral arms. Young stars are especially valuable when studying the spiral arms, Poggio explained, because spiral arms, with their dense concentration of dust and gas, are believed to be where the majority of stars form.

    “We calculated, for each position in the disc, whether that region was more or less populated with respect to the average,” Poggio told Space.com. “Using that approach, we were able to construct a map of the spiral arms in the region that Gaia maps, that is about 16,000 light-years around the sun.”

    When the researchers compared their galaxy map to previous models they found that the Perseus arm lies further away from the center of the galaxy in the studied region. The short Local arm appeared much longer than the previous models expected.

    How do the arms form?

    Astronomers are also still speculating about the origin of those arms and their longevity. Some earlier theories proposed that the shape of the arms is somehow fixed and spins around the galactic center over a long period of time while individual stars, orbiting at their own velocities, move in and out of this shape.

    This so-called density wave theory, however, is being disputed by the latest findings enabled by the Gaia mission. Many scientists now think that the spiral arms might not be fixed at all. Instead, they might form temporarily, as a result of the rotation of the galactic disc, and later dissolve and reform again in a different configuration.

    To find which theory is correct, Alfred Castro, of the Leiden University [Universiteit Leiden] (NL), in the Netherlands, looked at so-called open clusters [On the Milky Way spiral arms from open clusters in Gaia EDR3], groups of thousands of young stars born from the same cloud of gas and dust. Due to their young age, these stars are still close to their birth place, that is within the spiral arms. If the newer theories were correct, the amount of younger open clusters in the spiral arms would be higher than the amount of older open clusters, Castro speculated. And that’s exactly what the data showed.

    “I saw in the data that the spiral structure appears to contain the younger population of stars but disappears if you look at the older stars,” Castro told Space.com. “We see that the rotation rate of the shape is more or less similar to the rotation rate of the stars and varies with the radius to the galactic center. The shape and the stars can’t be decoupled, and that means we don’t have a global shape, which would be the spiral arms, and then the stars moving in and out of them as the density wave theory suggests.”

    According to Castro’s analysis, the spiral arms may exist for about 80 to 100 million years, a small fraction of time in the 13-billion-year life of our galaxy.

    What gave the Milky Way the spiral arms?

    In the future, Poggio hopes, scientists might be able to find out why those spiral arms in the Milky Way exist in the first place. While some theories expect this swirl of stellar streams may have been born after another, smaller galaxy crashed into the Milky Way, others believe it came to existence naturally as a result of the rotation of the galactic disc.

    “We expect that we would see different signatures in the motion of the stars if the spiral arms were caused by an external impact,” Poggio said. “Future Gaia data releases will give us more information about the motion of stars in a greater portion of the galactic disc, and we hope we might be able to find something there.”

    The next batch of Gaia data, the full Data Release 3, is expected to be made available to scientists worldwide in about mid-2022. Gaia, one of the most productive missions in history (measured by the number of scientific papers it produces), will continue scanning the sky until 2025. The vast catalogues of stellar positions, motions and velocities it creates will keep astronomers busy for decades to come.

    The papers by Poggio, Castro and Zari were published in the journal Astronomy and Astrophysics in July.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Objective
    A global space astrometry mission, Gaia will make the largest, most precise three-dimensional map of our Galaxy by surveying more than a thousand million stars.

    Mission
    Gaia will monitor each of its target stars about 70 times over a five-year period. It will precisely chart their positions, distances, movements, and changes in brightness. It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and brown dwarfs, and observe hundreds of thousands of asteroids within our own Solar System. The mission will also study about 500 000 distant quasars and will provide stringent new tests of Albert Einstein’s General Theory of Relativity.

    Gaia will create an extraordinarily precise three-dimensional map of more than a thousand million stars throughout our Galaxy and beyond, mapping their motions, luminosity, temperature and composition. This huge stellar census will provide the data needed to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our Galaxy.

    For example, Gaia will identify which stars are relics from smaller galaxies long ago ‘swallowed’ by the Milky Way. By watching for the large-scale motion of stars in our Galaxy, it will also probe the distribution of dark matter, the invisible substance thought to hold our Galaxy together.

    Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye).

    For all objects brighter than magnitude 15 (4000 times fainter than the naked eye limit), Gaia will measure their positions to an accuracy of 24 microarcseconds. This is comparable to measuring the diameter of a human hair at a distance of 1000 km.

    It will allow the nearest stars to have their distances measured to the extraordinary accuracy of 0.001%. Even stars near the Galactic centre, some 30 000 light-years away, will have their distances measured to within an accuracy of 20%.

    The vast catalogue of celestial objects expected from Gaia’s scientific haul will not only benefit studies of our own Solar System and Galaxy, but also the fundamental physics that underpins our entire Universe.

     
  • richardmitnick 6:44 pm on January 31, 2021 Permalink | Reply
    Tags: "We may have found the most powerful particle accelerator in the galaxy", A source of gamma rays exceeding 200 TeV called HAWC J1825-134., , , , Charged particles traveling through interstellar space respond to our galaxy's magnetic field., , , Gamma rays shoot straight-line through the galaxy allowing us to directly pinpoint their origins., , space.com, When cosmic rays accidentally strike a cloud of interstellar gas they can emit gamma rays.   

    From SPACE.com: “We may have found the most powerful particle accelerator in the galaxy” 

    From SPACE.com

    1.29.21
    Paul Sutter

    And it’s quite a surprising source.

    1
    This image, created using data from the European Space Agency’s Herschel and Planck space telescopes, shows a piece of the Taurus Molecular Cloud.© ESA/Herschel/Planck; J. D. Soler, MPIA.

    ESA/Herschel spacecraft active from 2009 to 2013.

    ESA/Planck 2009 to 2013

    Astronomers have long wondered where high-energy cosmic rays come from within our galaxy.

    And now, new observations with the High Altitude Water Cherenkov Experiment (HAWC) observatory reveal an unlikely candidate: an otherwise mundane giant molecular cloud.

    HAWC High Altitude Čerenkov Experiment, a US Mexico Europe collaboration located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters(13,500ft), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays.

    Taking the knee

    Cosmic rays are not rays at all but rather tiny particles cruising through the universe at nearly the speed of light. They can be made of electrons, protons or even ions of heavier elements. They are created in all sorts of high-energy processes throughout the cosmos, from supernova explosions to the mergers of stars to the final insane moments when gas gets sucked up by a black hole.

    Cosmic rays come in all sorts of energies, and generally speaking the higher-energy cosmic rays are rarer than their low-energy relatives. This relationship changes in a very slight way at a particular energy — 10^15 electron-volts — which is called the “knee.” The electron-volt, or eV, is just the way that particle physicists enjoy measuring energy levels. For comparison, the most powerful particle collider on Earth, the Large Hadron Collider, can achieve 13 X 10^12 eV, which is often denoted as 13 tera electron-volts, or 13 TeV.

    CERN (CH) LHC Map

    Above an energy of 10^15 eV, cosmic rays are much rarer than you would expect. This has led astronomers to believe that any cosmic rays at this energy level and higher come from outside the galaxy, while processes within the Milky Way are capable of producing cosmic rays up to and including 10^15 eV.

    For those of you keeping score at home, whatever is creating these cosmic rays would be in the “peta” range of Greek prefixes, and therefore over 1,000 times more powerful than our best particle accelerators — natural “PeVatrons” roaming the galaxy.

    A hawkeyed sleuth

    The mission is simple: find the source of PeV-scale cosmic rays in the Milky Way. But despite their energies, it’s hard to pinpoint their origins. That’s because cosmic rays are made of charged particles, and charged particles traveling through interstellar space respond to our galaxy’s magnetic field. Thus when you see a high-energy cosmic ray coming from a particular direction in the sky, you actually have no idea where it truly came from — its path has bent and curved over the course of its journey to Earth.

    But instead of hunting for cosmic rays directly, we can search for some of their relatives. When cosmic rays accidentally strike a cloud of interstellar gas, they can emit gamma rays, a high-energy form of radiation. These gamma rays shoot straight-line through the galaxy, allowing us to directly pinpoint their origins.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet).

    So if we see a source of strong gamma-ray emission, we can look for nearby sources of PeV cosmic rays.

    This was the method employed by a team of researchers using HAWC, which is located on the Sierra Negra Volcano of south-central Mexico. HAWC “stares” up at the sky with a series of tanks filled with ultra-pure water. When high-energy particles or radiation enter the tanks, they emit a flash of blue light, allowing astronomers to trace back the source onto the sky.

    Detailed in a paper recently appearing in The Astrophysical Journal Letters, the astronomers found a source of gamma rays exceeding 200 TeV, which could only be created by even more powerful cosmic rays — the kinds of cosmic rays that reach up into the PeV scale. The source, called HAWC J1825-134, lies roughly in the direction of the galactic center. HAWC J1825-134 appears to us as a bright blotch of gamma rays, illuminated by some unknown fount of cosmic rays — perhaps the most powerful known source of cosmic rays in the Milky Way.

    An unlikely heavyweight

    A few of the usual suspect sources of high-energy cosmic rays sit within a few thousand light-years of HAWC J1825-134, but none of them can easily explain the signal.

    For example, the galactic center itself is a known generator of intense cosmic ray action, but it’s way too far away from HAWC J1825-134, so it has no bearing on this measurement.

    There are some supernova remnants, and supernovae sure are powerful. But all the supernovae in the region of HAWC J1825-134 went off ages ago — far too long in the past to be creating these high-energy cosmic rays now.

    Pulsars — the rapidly spinning dense remnant cores of massive stars — also produce copious amounts of cosmic rays. But those too sit too far away from the source of gamma rays — the energies of the electrons and protons coming off the pulsar just aren’t punchy enough to travel the thousands of light-years to the location of the gamma ray emission.

    Surprisingly, the source of these record-breaking cosmic rays appears to be none other than a giant molecular cloud. These clouds are giant, lumbering brutes, filled with dust and gas, that roam the galaxy. They occasionally contract in on themselves and turn into stars, but otherwise they can remain cool and loose for billions of years. Not causing anyone any serious threat — and barely even noticeable unless you have good infrared telescopes — they are the last place you would expect to find such insanely high energies.

    Located within the cloud complex is a cluster of newborn stars, but even the crankiest and loudest of baby stars aren’t thought to be powerful enough to launch cosmic rays like this. The researchers themselves admit that they don’t know how this cloud is doing it, but somehow, when nobody was paying attention, it generated some of the most powerful particles in the entire galaxy.

    See the full article here .

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    Please help promote STEM in your local schools.

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  • richardmitnick 11:15 am on January 3, 2021 Permalink | Reply
    Tags: "The Milky Way is probably full of dead civilizations", , , , Carl Sagan's "Cosmos" miniseries, , , space.com, We are likely a frontier civilization in terms of galactic geography and relative latecomers to the self-aware Milky Way inhabitant scene.   

    From SPACE.com: “The Milky Way is probably full of dead civilizations” 

    From SPACE.com

    1.2.21
    Rafi Letzter

    1
    © European Southern Observatory.

    That’s the takeaway of a new study, published Dec. 14 to the arXiv database [A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy], which used modern astronomy and statistical modeling to map the emergence and death of intelligent life in time and space across the Milky Way. Their results amount to a more precise 2020 update of a famous equation that Search for Extraterrestrial Intelligence founder Frank Drake wrote in 1961.

    Frank Drake with his Drake Equation. Credit Frank Drake.

    The Drake equation, popularized by physicist Carl Sagan in his Cosmos miniseries, relied on a number of mystery variables — like the prevalence of planets in the universe, then an open question.

    This new paper, authored by three Caltech physicists and one high school student, is much more practical. It says where and when life is most likely to occur in the Milky Way, and identifies the most important factor affecting its prevalence: intelligent creatures’ tendency toward self-annihilation.

    “Since Carl Sagan’s time, there’s been lots of research,” said study co-author Jonathan H. Jiang, an astrophysicist at NASA’s Jet Propulsion Laboratory at Caltech. “Especially since the Hubble Space Telescope and Kepler Space Telescope, we have lots of knowledge about the densities [of gas and stars] in the Milky Way galaxy and star formation rates and exoplanet formation … and the occurrence rate of supernova explosions. We actually know some of the numbers [that were mysteries at the time of the famous Cosmos episode].”

    The authors looked at a range of factors presumed to influence the development of intelligent life, such as the prevalence of sun like stars harboring Earth-like planets; the frequency of deadly, radiation-blasting supernovas; the probability of and time necessary for intelligent life to evolve if conditions are right; and the possible tendency of advanced civilizations to destroy themselves.

    Modeling the evolution of the Milky Way over time with those factors in mind, they found that the probability of life emerging based on known factors peaked about 13,000 light-years from the galactic center and 8 billion years after the galaxy formed. Earth, by comparison, is about 25,000 light-years from the galactic center, and human civilization arose on the planet’s surface about 13.5 billion years after the Milky Way formed (though simple life emerged soon after the planet formed.)

    In other words, we’re likely a frontier civilization in terms of galactic geography and relative latecomers to the self-aware Milky Way inhabitant scene. But, assuming life does arise reasonably often and eventually becomes intelligent, there are probably other civilizations out there — mostly clustered around that 13,000-light-year band, mostly due to the prevalence of sunlike stars there.

    2
    A figure from the paper plots the age of the Milky Way in billions of years (y axis) against distance from the galactic center (x axis), finding a hotspot for civilization 8 billion years after the galaxy formed and 13,000 light years from the galactic center. Credit: Cai et al.

    Most of these other civilizations that still exist in the galaxy today are likely young, due to the probability that intelligent life is fairly likely to eradicate itself over long timescales. Even if the galaxy reached its civilizational peak more than 5 billion years ago, most of the civilizations that were around then have likely self-annihilated, the researchers found .

    This last bit is the most uncertain variable in the paper; how often do civilizations kill themselves? But it’s also the most important in determining how widespread civilization is, the researchers found. Even an extraordinarily low chance of a given civilization wiping itself out in any given century — say, via nuclear holocaust or runaway climate change — would mean that the overwhelming majority of peak Milky Way civilizations are already gone.

    The above paper has been submitted to a journal for publication and is awaiting peer review.

    See the full article here .

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    Please help promote STEM in your local schools.

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  • richardmitnick 11:54 am on December 18, 2019 Permalink | Reply
    Tags: "The Asteroids Might Remember a Forgotten Giant Planet", , , , , , , space.com   

    From Ohio State University via SPACE.com: “The Asteroids Might Remember a Forgotten Giant Planet” 

    OSU

    From Ohio State University

    space-dot-com logo

    SPACE.com

    12.18.19
    Paul Sutter-
    Paul M. Sutter is an astrophysicist at The Ohio State University

    We have much to learn from the rocks of the asteroid belt.

    1
    An artist’s illustration of the asteroid belt.(Image: © ESA/ATG medialab)

    The formation of the solar system is a deeply perplexing puzzle. We’re left with clues all over the place: the positions and sizes of the planets, the members of the asteroid belt, Kuiper Belt, and Oort Cloud and the populations of moons around the planets.

    The inner Solar System, from the Sun to Jupiter. Also includes the asteroid belt (the white donut-shaped cloud), the Hildas (the orange “triangle” just inside the orbit of Jupiter), the Jupiter trojans (green), and the near-Earth asteroids. The group that leads Jupiter are called the “Greeks” and the trailing group are called the “Trojans” (Murray and Dermott, Solar System Dynamics, pg. 107)
    This image is based on data found in the en:JPL DE-405 ephemeris, and the en:Minor Planet Center database of asteroids (etc) published 2006 Jul 6. The image is looking down on the en:ecliptic plane as would have been seen on 2006 August 14. It was rendered by custom software written for Wikipedia. The same image without labels is also available at File:InnerSolarSystem.png. Mdf at English Wikipedia

    Kuiper Belt. Minor Planet Center

    Oort Cloud, The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA, Universe Today


    Oort Cloud NASA

    But how did we get to this from a vague disk of gas and dust billions of years ago?

    Simulations and models lead the way, and recently researchers have turned to the asteroid belt for more help: the asteroids living closest to the sun actually preserve a memory from when the solar system was still evolving, and might even offer clues to the hypothesis that we once had five giant planets.

    Billions of years ago, our solar system was just a bunch of random gas and dust floating around as a nebula. As it collapsed, it formed a rapidly spinning merry-go-round of a flat disk around the young and hungry proto-sun. Over the course of 100 million years, that disk somehow became the planets and other smaller denizens of our home system.

    Computer simulations of the disk-to-planet process are fantastically difficult, due to all the rich and complex physics involved, but they have a few general features. The innermost worlds tend to be small and rocky, while the outermost planets tend to be big and gassy and/or icy. Plus the process of formation leads to a bunch of random junk floating around.

    Another general feature is that newborn planets tend to move quickly into resonant motion, meaning that orbits become integer multiples of each other. For example, Mars might orbit four times for every Jupiter orbit, and Jupiter might orbit twice for every turn around the sun that Saturn gets.

    And when it comes to our solar system in particular, in simulations the giant planets tend to form much closer together, and much closer to the sun, than they are today.

    So then the question becomes: Once we’ve got a batch of baby planets formed from our protostellar disk, how do we get those planets in their modern-day positions?

    It’s Nice out there

    Enter the Nice Model, named after the city in southern France where a few sun-baked researchers cooked up the idea in 2005. In the bare-bones version of the model, the too-close-for-comfort giant planets are surrounded by a disk of leftovers: tiny planetesimals that never got to play the planet game and had to hang out in the outskirts of the solar system.

    But not for long. Ever so slowly, over the course of 100 million years, the outermost giant planet (usually thought to be Neptune, but in some versions of the model it’s Uranus) drifts close to one of those leftovers. Close enough to interact gravitationally, doing a little orbital dance where the planet pulls the bit of rock inward to a smaller orbit, and in exchange sends itself farther out.

    And then that little scattered rock encounters the next planet in and does the same thing. And then it approaches Saturn and repeats the process again, going ever sunward and spreading out three of the giant planets.

    And then that plucky little planetesimal finds Jupiter, who is generally in no mood for games and doesn’t like to be told what to do. Instead of nudging the rock inward, the massive bulk of our system’s largest planet just sends that unlucky bit of debris out of the solar system altogether. That doesn’t come without a price, however; the energy needed to eject the planetesimal reduces Jupiter’s own orbit, sending it slightly closer to the sun.

    This model is able to explain in large part the modern-day positions of the planets, and how they were able to get there from their birthplaces. And since 2005, more sophisticated versions of the Nice Model have appeared, trying to explain finer details of our system’s makeup, including the possibility that we once were home to a fifth giant planet that got lost in all the gravitational reshuffling.

    Look to the asteroids

    But all versions of the Nice Model have a particular problem with the asteroid belt. All that orbital dancing in the outer system can have big impacts on the inner worlds and their own population of planetary leftovers. The on-again-off-again gravitational resonances that the outer planets experience as they migrate to and fro in the outer reaches destabilize members of the nascent asteroid belt, scattering them into all sorts of crazy orbits.

    In particular, the various versions of the Nice Model tend to send the innermost belt members (the chunks of rock within 2.5 astronomical units) into orbits with high inclination, meaning that they’re angled with respect to the rest of the solar system. (One astronomical unit, or AU, is the average Earth-sun distance — about 93 million miles, or 150 million kilometers.) And yet, we find most asteroids are on an even keel with the major planets, so we must be getting something wrong in our models.

    Recently, a team of researchers took a more refined approach to the simulations [MNRAS], looking especially at the interactions of Jupiter and Saturn as they waltzed together in the early days of the solar system. The scientists found that during the process of planetary migration, Jupiter and Saturn approach a 5:2 resonance, meaning that Jupiter orbits five times for every two orbits of Saturn.

    Baby solar systems

    Billions of years ago, our solar system was just a bunch of random gas and dust floating around as a nebula. As it collapsed, it formed a rapidly spinning merry-go-round of a flat disk around the young and hungry proto-sun. Over the course of 100 million years, that disk somehow became the planets and other smaller denizens of our home system.

    Computer simulations of the disk-to-planet process are fantastically difficult, due to all the rich and complex physics involved, but they have a few general features. The innermost worlds tend to be small and rocky, while the outermost planets tend to be big and gassy and/or icy. Plus the process of formation leads to a bunch of random junk floating around.

    Another general feature is that newborn planets tend to move quickly into resonant motion, meaning that orbits become integer multiples of each other. For example, Mars might orbit four times for every Jupiter orbit, and Jupiter might orbit twice for every turn around the sun that Saturn gets.

    And when it comes to our solar system in particular, in simulations the giant planets tend to form much closer together, and much closer to the sun, than they are today.

    So then the question becomes: Once we’ve got a batch of baby planets formed from our protostellar disk, how do we get those planets in their modern-day positions?

    But all versions of the Nice Model have a particular problem with the asteroid belt. All that orbital dancing in the outer system can have big impacts on the inner worlds and their own population of planetary leftovers. The on-again-off-again gravitational resonances that the outer planets experience as they migrate to and fro in the outer reaches destabilize members of the nascent asteroid belt, scattering them into all sorts of crazy orbits.

    In particular, the various versions of the Nice Model tend to send the innermost belt members (the chunks of rock within 2.5 astronomical units) into orbits with high inclination, meaning that they’re angled with respect to the rest of the solar system. (One astronomical unit, or AU, is the average Earth-sun distance — about 93 million miles, or 150 million kilometers.) And yet, we find most asteroids are on an even keel with the major planets, so we must be getting something wrong in our models.

    Recently, a team of researchers took a more refined approach to the simulations, looking especially at the interactions of Jupiter and Saturn as they waltzed together in the early days of the solar system. The scientists found that during the process of planetary migration, Jupiter and Saturn approach a 5:2 resonance, meaning that Jupiter orbits five times for every two orbits of Saturn.

    They don’t stay in that resonance for long. But the details of Saturn’s orbit while near the resonance give it just the right gravitational effect on the inner system to clear away any high-inclination wannabes in the asteroid belt.

    And what about the more exotic models, like early solar systems including a fifth giant planet? It too has an effect on all the resonances, which means that the modern-day asteroid belt may actually be a fossil record, remembering what the young system was like. And the more we study those little leftover asteroids, the more we can learn about our own origins.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Ohio State University (OSU, commonly referred to as Ohio State) is a public research university in Columbus, Ohio. Founded in 1870 as a land-grant university and the ninth university in Ohio with the Morrill Act of 1862,[4] the university was originally known as the Ohio Agricultural and Mechanical College. The college originally focused on various agricultural and mechanical disciplines but it developed into a comprehensive university under the direction of then-Governor (later, U.S. President) Rutherford B. Hayes, and in 1878 the Ohio General Assembly passed a law changing the name to “The Ohio State University”.[5] The main campus in Columbus, Ohio, has since grown into the third-largest university campus in the United States.[6] The university also operates regional campuses in Lima, Mansfield, Marion, Newark, and Wooster.

    The university has an extensive student life program, with over 1,000 student organizations; intercollegiate, club and recreational sports programs; student media organizations and publications, fraternities and sororities; and three student governments. Ohio State athletic teams compete in Division I of the NCAA and are known as the Ohio State Buckeyes. As of the 2016 Summer Olympics, athletes from Ohio State have won 104 Olympic medals (46 gold, 35 silver, and 23 bronze). The university is a member of the Big Ten Conference for the majority of sports.

     
  • richardmitnick 8:57 am on November 18, 2019 Permalink | Reply
    Tags: , , , , McDonald Observatory: Searching for Dark Energy, space.com,   

    From SPACE.com: “McDonald Observatory: Searching for Dark Energy” 

    space-dot-com logo

    From SPACE.com

    McDonald Observatory is a Texas-based astronomical site that has made significant contributions in research and education for more than 80 years.

    Administered by the University of Texas at Austin, the McDonald Observatory has several telescopes perched at an altitude of 6791 feet (2070 meters) above sea level on Mount Locke and Mount Fowlkes, part of the Davis Mountains in western Texas, about 450 miles (724 kilometers) west of Austin. McDonald “enjoys the darkest night skies of any professional observatory in the continental United States,” according to a news release issued for the observatory’s 80th anniversary.

    McDonald is home to the Hobby-Eberly Telescope, one of the world’s largest optical telescopes, with a 36-foot-wide (11 meter) mirror.

    A visitor center offers daytime tours of the grounds and big telescopes, daytime solar viewing, a twilight program in an outdoor amphitheater, and nighttime star parties with telescope viewing.

    The observatory is also known for its daily StarDate program, which runs on more than 300 radio stations across the country.

    The gift of an observatory

    The regents of the University of Texas were surprised when they opened the will of William Johnson McDonald, a banker from Paris, Texas, who died in 1926. He had left the bulk of his fortune to the university for the purpose of building an astronomical observatory. After court proceedings were done, about $850,000 (the equivalent of $11 million today) was available, according to the Texas State Historical Association.

    “McDonald is said to have thought that an observatory would improve weather forecasting and therefore help farmers to plan their work,” the association said.

    But there were two major challenges to overcome before McDonald’s wish could become reality. First, the money was enough to build an observatory but not enough to run it, so the university would need to acquire more funds. Second, at that time, the University of Texas had no astronomers on its faculty, so it needed to recruit a team of space experts.

    Fortunately, the University of Chicago had astronomers who were looking for another telescope to use in addition to their university’s refracting telescope at Yerkes Observatory. So, the presidents of the two universities made a deal: The University of Texas would build the new observatory, and the University of Chicago would provide experts to operate it.

    McDonald’s first major telescope — later named the Otto Struve Telescope after the observatory’s first director — was finished in 1939 and is still in use today.

    McDonald Observatory Otto Struve telescope
    Altitude 2,026 m (6,647 ft)

    Its main mirror is 82 inches (2.08 meters) across. One of the main purposes of the Struve Telescope was to analyze the exact colors of light coming from stars and other celestial bodies, to determine their chemical composition, temperature, and other properties. To do this, the telescope was designed to send light through a series of mirrors into a spectrograph — an instrument that separates light into its component colors — in another room. This required the telescope to be mounted on a strange-looking arrangement of axes and counterweights, designed and built by the Warner & Swasey company. “With its heavy steel mounting and black, half-open framework, the Struve is not just a scientific instrument, but it is a work of art,” the Observatory’s website says.

    The Struve Telescope helped astronomers gather the first evidence of an atmosphere on Saturn’s moon Titan. Gerard Kuiper, assisted by Struve himself, found the clues while examining our solar system’s largest moons in 1944. Kuiper published his spectroscopic study in The Astrophysical Journal.

    In 1956, a reflecting telescope with a 36-inch (0.9 m) mirror was added to the McDonald site at the request of the University of Chicago.

    McDonald Observatory .9 meter telescope, Altitude 2,026 m (6,647 ft)

    Housed in a dome made from locally quarried rock and leftover metal from the Struve Telescope dome, this instrument was designed primarily to measure changes in the brightness of stars. It is now obsolete for professional research, but is regularly used for special public-viewing nights.

    The Harlan J. Smith Telescope, with a main mirror 107 inches (2.7 m) across, was built by NASA to examine other planets in preparation for spacecraft missions. It was the world’s third-largest telescope when it saw first light in 1968.

    U Texas at Austin McDonald Observatory Harlan J Smith 2.7-meter Telescope , Altitude 2,026 m (6,647 ft)

    From 1969 to 1985, the Smith telescope was also used to aim laser light at special reflecting mirrors left on the moon by Apollo astronauts. Measuring the time required for the reflected light to return to Earth enables astronomers to measure the moon’s distance to an accuracy of 1.2 inches (3 centimeters). These measurements, in turn, contribute to our understanding of Earth’s rotation rate, the moon’s composition, long-term changes in the moon’s orbit, and the behavior of gravity itself, including small effects predicted by Albert Einstein’s General Theory of Relativity.

    When the Smith telescope was being built, a circular hole was cut in the center of its main quartz mirror to allow light to pass to instruments at the back of the telescope. The cutout quartz disk was made into a new mirror 30 inches (0.8 m) across for another telescope. This instrument, built nearby in 1970 and known simply as the 0.8 meter telescope, has the advantage of an unusually wide field of view.

    McDonald’s biggest telescope

    Today, the giant at McDonald is the Hobby-Eberly Telescope (HET), on neighboring Mount Fowlkes, almost a mile (1.3 km) from the cluster of original domes on Mount Locke.

    U Texas Austin McDonald Observatory Hobby-Eberly Telescope, Altitude 2,026 m (6,647 ft)

    The HET is a joint project of the University of Texas at Austin, Pennsylvania State University, and two German universities: Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

    Dedicated in 1997, the HET makes a striking technological contrast with the classic Struve instrument. HET’s main mirror is not one piece of glass or quartz, but an array of 91 individually controlled hexagonal segments making a honeycomb-like reflecting area that’s 36 feet (11 m) wide. A mushroom-shaped tower next to the main dome contains lasers that are aimed at the mirror segments to test and adjust their alignment.

    Another remarkable feature of the HET is that the telescope can rotate to point toward any compass direction, but it cannot tilt up or down to point at different heights in the sky. Instead, the main mirror is supported at a fixed angle pointing 55 degrees above the horizon. A precisely controlled tracking support moves light-gathering instruments to various locations above the main mirror, which has the effect of aiming at slightly different parts of the sky. This unique, simplified design allowed the HET to be built for a fraction of the cost of a conventional telescope of its size, while still allowing access to 70% of the sky visible from its location.

    The HET was designed primarily for spectroscopy, which is a key method in current research areas such as measuring motions of space objects, determining distances to galaxies and discovering the history of the universe since the Big Bang.

    Habitable planets and dark energy

    In 2017, the HET was rededicated after a $40 million upgrade. The tracking system was replaced with a new unit that uses more of the main mirror and has a wider field of view. And, new sensing instruments were created.

    One of the new instruments is the Habitable Zone Planet Finder (HPF), built in conjunction with the National Institute of Standards and Technology.

    3
    Habitable Zone Planet Finder

    The HPF is optimized to study infrared light from nearby, cool red dwarf stars, according to an announcement from the observatory. These stars have long lifetimes and could provide steady energy for planets orbiting close to them. The HPF allows precise measurements of a star’s radial velocity, measured by the subtle change in the color of the star’s spectra as it is tugged by an orbiting planet, which is critical information in the discovery and confirmation of new planets.

    Advancing another frontier is the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).Billed as the first major experiment searching for the mysterious force pushing the universe’s expansion, the HETDEX “will tell us what makes up almost three-quarters of all the matter and energy in the universe. It will tell us if the laws of gravity are correct, and reveal new details about the Big Bang in which the universe was born,” the HETDEX project website says.

    4
    VIRUS-P undergoes testing at the Harlan J. Smith Telescope at McDonald Observatory. HETDEX will consist of 145 identical VIRUS units attached to the Hobby-Eberly Telescope. [Martin Harris/McDonald Observatory]

    A key piece of technology for the dark-energy search is the Visible Integral-Field Replicable Unit Spectrographs, or VIRUS, a set of 156 spectrographs mounted alongside the telescope and receiving light via 35,000 optical fibers coming from the telescope. With this package of identical instruments sharing the telescope, the HET can observe several hundred galaxies at once, measuring how their light is affected by their own motions and the expansion of the universe.

    The HETDEX will spend about three years observing a minimum of 1 million galaxies to produce a large map showing the universe’s expansion rate during different time periods. Any changes in how quickly the universe grows could yield differences in dark energy.

    Keeping the skies dark

    In 2019, the McDonald Observatory received a grant from the Apache Corp., an oil and gas exploration and production company, to promote awareness of the value of dark skies as a natural resource and as an aid to astronomical research. The gift will fund education programs, outreach events, and a new exhibit at the observatory’s visitors center. According to the observatory’s announcement, Apache has served as a model for other businesses in west Texas by adjusting and shielding the lights at its drilling sites and related facilities.

    See the full article here .

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  • richardmitnick 10:20 am on June 9, 2019 Permalink | Reply
    Tags: "Einstein's Quest to 'Know God's Thoughts' Could Take Millennia" Don Lincoln of FNAL, , , , , space.com   

    From SPACE.com: “Einstein’s Quest to ‘Know God’s Thoughts’ Could Take Millennia” Don Lincoln of FNAL 

    space-dot-com logo

    From SPACE.com

    6.9.19

    1
    (Image: © Shutterstock)

    In 1925, Einstein went on a walk with a young student named Esther Salaman. As they wandered, he shared his core guiding intellectual principle: “I want to know how God created this world. I’m not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; the rest are just details.”

    The phrase “God’s thoughts” is a delightfully apt metaphor for the ultimate goal of modern physics, which is to develop a perfect understanding of the laws of nature — what physicists call “a theory of everything,” or TOE. Ideally, a TOE would answer all questions, leaving nothing unanswered. Why is the sky blue? Covered. Why does gravity exist? That’s covered, too. Stated in a more scientific way, a TOE would ideally explain all phenomena with a single theory, a single building block and a single force. In my opinion, finding a TOE could take hundreds, or even thousands, of years. To understand why, let’s take stock.

    We know of two theories that, when taken together, give a good description of the world around us, but both are light-years from being a TOE.

    The first is Einstein’s theory of general relativity, which describes gravity and the behavior of stars, galaxies and the universe on the largest scales. Einstein described gravity as the literal bending of space and time. This idea has been validated many times, most notably with the discovery of gravitational waves in 2016.

    The second theory is called the Standard Model, which describes the subatomic world. It is in this domain that scientists have made the most obvious progress toward a theory of everything.

    Standard Model of Particle Physics

    If we look at the world around us — the world of stars and galaxies, poodles and pizza, we can ask why things have the properties they do. We know everything is made up of atoms, and those atoms are made up of protons, neutrons and electrons.

    And, in the 1960s, researchers discovered that the protons and neutrons were made of even smaller particles called quarks and the electron was a member of the class of particles called leptons.

    Finding the smallest building blocks is only the first step in devising a theory of everything. The next step is understanding the forces that govern how the building blocks interact. Scientists know of four fundamental forces, three of which — electromagnetism, and the strong and weak nuclear forces — are understood at the subatomic level. Electromagnetism holds atoms together and is responsible for chemistry. The strong force holds together the nucleus of atoms and keeps quarks inside protons and neutrons. The weak force is responsible for some types of nuclear decay.

    Each of the known subatomic forces has an associated particle or particles that carry that force: The gluon carries the strong force, the photon governs electromagnetism, and the W and Z bosons control the weak force. There is also a ghostly energy field, called the Higgs field, that permeates the universe and gives mass to quarks, leptons and some of the force-carrying particles. Taken together, these building blocks and forces make up the Standard Model.

    2
    A theory of everything will explain all known phenomena. We aren’t there yet, but we have unified the behavior of the quantum world in the standard model (yellow) and we understand gravity (pink). In the future, we imagine a series of additional unifications (green). However, the problem is that there are phenomena we don’t understand (blue) that need to fit in somewhere. And we are not certain that we won’t find other phenomena as we go to higher energy (red circles). (Image: © Don Lincoln)

    Using quarks and leptons and the known force-carrying particles, one can build atoms, molecules, people, planets and, indeed, all of the known matter of the universe. This is undoubtedly a tremendous achievement and a good approximation of a theory of everything.

    And yet it really isn’t. The goal is to find a single building block and a single force that could explain the matter and motion of the universe. The Standard Model has 12 particles (six quarks and six leptons) and four forces (electromagnetism, gravity, and the strong and weak nuclear forces). Furthermore, there is no known quantum theory of gravity (meaning our current definition covers just gravity involving things larger than, for example, common dust), so gravity isn’t even part of the Standard Model at all. So, physicists continue to look for an even more fundamental and underlying theory. To do that they need to reduce the number of both building blocks and forces.

    Finding a smaller building block will be difficult, because that requires a more powerful particle accelerator than humans have ever built. The time horizon for a new accelerator facility coming on line is several decades and that facility will provide only a relatively modest incremental improvement over existing capabilities. So, scientists must instead speculate on what a smaller building block might look like. A popular idea is called superstring theory, which postulates that the smallest building block isn’t a particle, but rather a small and vibrating “string.” In the same way a cello string can play more than one note, the different patterns of vibrations are the different quarks and leptons. In this way, a single type of string could be the ultimate building block.

    The problem is that there is no empirical evidence that superstrings actually exist. Further, the expected energy required to see them is called the Planck energy, which is a quadrillion (10 raised to the 15th power) times higher than we can currently generate. The very large Planck energy is intimately connected to what’s known as the Planck length, an unfathomably tiny length beyond which quantum effects become so large that it is literally impossible to measure anything smaller. Meanwhile, go smaller than the Planck length (or bigger than the Planck energy), and the quantum effects of gravity between photons, or light particles, become important and relativity no longer works. That makes it likely this is the scale at which quantum gravity will be understood. This is, of course, all very speculative, but it reflects our current best prediction. And, if true, superstrings will have to remain speculative for the foreseeable future.

    The plethora of forces is also a problem. Scientists hope to “unify” the forces, showing that they are just different manifestations of a single force. (Sir Isaac Newton did just that when he showed the force that made things fall on Earth and the force that governed the motion of the heavens were one and the same; James Clerk Maxwell showed that electricity and magnetism were really different behaviors of a unified force called electromagnetism.)

    In the 1960s, scientists were able to show that the weak nuclear force and electromagnetism were actually two different facets of a combined force called the electroweak force. Now, researchers hope that the electroweak force and the strong force can be unified into what is called a grand unified force. Then, they hope that the grand unified force can be unified with gravity to make a theory of everything.

    3
    Historically, scientists have shown how seemingly unrelated phenomena originate from a single underlying force. We imagine that this process will continue, resulting in a theory of everything. (Image: © Don Lincoln)

    However, physicists suspect this final unification would also take place at the Planck energy, again because this is the energy and size at which quantum effects can no longer be ignored in relativity theory. And, as we’ve seen, this is a much higher energy than we can hope to achieve inside a particle accelerator any time soon. To give a sense of the chasm between current theories and a theory of everything, if we represented the energies of particles we can detect as the width of a cell membrane, the Planck energy is the size of Earth. While it is conceivable that someone with a thorough understanding of cell membranes might predict other structures within a cell — things like DNA and mitochondria — it is inconceivable that they could accurately predict the Earth. How likely is it that they could predict volcanoes, oceans or Earth’s magnetic field?

    The simple fact is that with such a large gap between currently achievable energy in particle accelerators and the Planck energy, correctly devising a theory of everything seems improbable.

    That doesn’t mean physicists should all retire and take up landscape painting — there is still meaningful work to be done. We still need to understand unexplained phenomena such as dark matter and dark energy, which make up 95% of the known universe, and use that understanding to create a newer, more comprehensive theory of physics. This newer theory will not be a TOE, but will be incrementally better than the current theoretical framework. We will have to repeat that process over and over again.

    Disappointed? So am I. After all, I’ve devoted my life to trying to uncover some of the secrets of the cosmos, but perhaps some perspective is in order. The first unification of forces was accomplished in the 1670s with Newton’s theory of universal gravity. The second was in the 1870s with Maxwell’s theory of electromagnetism. The electroweak unification was relatively recent, only half a century ago.

    Given that 350 years has elapsed since our first big successful step in this journey, perhaps it’s less surprising that the path ahead of us is longer still. The notion that a genius will have an insight that results in a fully developed theory of everything in the next few years is a myth. We’re in for a long slog — and even the grandchildren of today’s scientists won’t see the end of it.

    But what a journey it will be.

    See the full article here .

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  • richardmitnick 2:38 pm on May 1, 2019 Permalink | Reply
    Tags: , Charged particles travel faster than light through the quantum vacuum of space that surrounds pulsars., , Dame Susan Jocelyn Bell Burnell (1943 – ) still working, , , space.com   

    From SPACE.com: “Faster-Than-Light Particles Emit Superbright Gamma Rays that Circle Pulsars” 

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    From SPACE.com

    5.1.19
    Yasemin Saplakoglu

    1
    The Vela pulsar that lives 1,000 light years from our planet. (Image: © NASA/CXC/Univ of Toronto/M.Durant et al)

    Charged particles travel faster than light through the quantum vacuum of space that surrounds pulsars. As these electrons and protons fly by pulsars, they create the ultrabright gamma-ray flashes emitted by the rapidly twirling neutron stars, new research reveals.

    These gamma-rays, called Cherenkov emissions, are also found in powerful particle accelerators on Earth, such as the Large Hadron Collider near Geneva, Switzerland. The rays are also the source of the bluish-white glow in the waters of a nuclear reactor.

    LHC

    CERN map


    CERN LHC Tunnel

    CERN LHC particles

    Daya Bay, nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

    But until now, no one thought that pulsar emissions consisted of Cherenkov radiation.

    That’s in part because of Albert Einstein’s famous theory of relativity, which holds that nothing can travel faster than light in a vacuum. Because of those propositions, scientists previously thought that Cherenkov emissions couldn’t happen in the quantum vacuum of space surrounding pulsars. That area is mostly devoid of matter but home to ghostly quantum particles that flicker in and out of existence.

    So, does this new research mean Einstein’s landmark theory was just violated? Not at all, said study co-author Dino Jaroszynski, a professor of physics at the University of Strathclyde in Scotland.

    Pulsars create crushingly strong electromagnetic fields in the quantum vacuum surrounding the stars. These fields warp, or polarize, the vacuum, essentially creating speed bumps that slow down light particles, Jaroszynski told Live Science. Meanwhile, charged particles such as protons and electrons zoom through these fields, racing past light.

    As charged particles fly through this field, they displace electrons along their path and emit radiation, which gathers into an electromagnetic wave. This wave, like an optical version of a sonic boom, is what we see as the gamma-ray flash, according to a statement.

    The team still doesn’t know exactly how bright these gamma-ray flashes are, Jaroszynski said.

    “What we do know is that, under the right conditions, vacuum Cherenkov radiation outshines synchrotron radiation,” he added, referring to another type of radiation that is emitted from pulsars by charged particles moving along a curved path.

    But the new findings could have implications beyond pulsars, the researchers said.

    “This is a very exciting new prediction because it could provide answers to basic questions such as what is the origin of the gamma-ray glow at the centre of galaxies?” Jaroszynski said in the statement. “It provides a new way of testing some of the most fundamental theories of science by pushing them to their limits.”

    The researchers reported their findings April 25 in the journal Physical Review Letters.

    See the full article here .

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

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  • richardmitnick 12:05 pm on May 1, 2018 Permalink | Reply
    Tags: , , , , , space.com   

    From SPACE.com: “Dawn Mission: Shedding Light on Asteroids” 

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    SPACE.com

    May 1, 2018
    Nola Taylor Redd

    NASA Dawn Spacescraft

    When NASA’s Dawn mission launched in 2007, it was on its way to breaking several records. When it entered orbit around the Vesta, it became the first to orbit a main-belt asteroid. After leaving Vesta, it journeyed on to Ceres, becoming the first spacecraft to visit and then orbit a dwarf planet and the first spacecraft to orbit two extraterrestrial targets.

    The journey hasn’t been smooth. Along the way, the spacecraft lost threeof its four reaction wheels that keep it oriented. It successfully concluded its primary mission to study both targets in 2016. Once it runs out of fuel near the end of 2018, it will continue to orbit Ceres for another 50 years.

    “To me, the real story here is how cool it is that we’re exploring what, in my view, are some of the last uncharted worlds in the inner solar system,” chief engineer and Dawn mission director Marc Rayman told Space.com. “Most people think of asteroids as chips of rock, but these are whole new worlds.”

    1

    This map from NASA’s Dawn mission shows locations of bright material on the dwarf planet Ceres. There are more than 300 bright areas, called “faculae,” on Ceres.
    Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/Caltech

    Out of this world

    Dawn launched from Cape Canaveral, Florida, on Sept. 27, 2007. Its arrived at the asteroid Vesta on July 16, 2011. The spacecraft spent almost a year in orbit around the second-largest object in the asteroid belt, departing on Sept. 5, 2012.

    On March 6, 2015, Dawn entered orbit around Ceres. Ceres is by far the most massive object in the asteroid belt between Mars and Jupiter, weighing in at nearly two-thirds the total mass of the belt. Its massive size and roundness means it qualifies as a dwarf planet. Unlike a full-size planet, a dwarf planet is a round object that fails to clear out its orbit. Dawn was just barely the first mission to arrive at a dwarf planet; NASA’s New Horizons mission zipped by Pluto only a few months later (though, in fairness, New Horizons launched first but had much farther to travel).

    Dawn traveled 1.7 billion miles (2.8 billion kilometers) to reach Vesta, then another 3.1 billion miles (4.9 billion km) to Ceres. Boosted by an ion propulsion system, the spacecraft took four days to accelerate from 0 to 60 mph (0 to 97 km/h) at maximum throttle. Each engine produces about the same amount of force as a single piece of paper notebook paper presses against your hand.

    Over time, however, that small force adds up. In 2010, it surpassed the previous record for velocity change held by NASA’s Deep Space 1 when its accumulated acceleration over the mission exceeded 9,600 MPH (4.3 km per second).

    “I am delighted that it will be Dawn that surpasses DS1’s record,” Rayman, who was a previous project manager for Deep Space 1, said in a statement. “It is a tribute to all those involved in the design and operations of this remarkable spacecraft.

    NASA Deep Space 1

    Ion engines are extremely fuel-efficient — Dawn only carried 937 lbs. (425 kilograms) of xenon propellant at launch — but the fuel won’t last forever. The spacecraft also carried 100.5 lbs. (45.6 kg) of hydrazine propellant used to change the spacecraft’s orientation, and that tank is quickly running dry. Dawn is expected to run out of hydrazine fuel in the second half of 2018.

    “When the last of the hydrazine is exhausted, the spacecraft will no longer be able to control its orientation, so it won’t be able to point its solar arrays at the sun, its sensors at Ceres, nor its antenna at Earth,” Rayman told Space.com in 2017. “That will be the end of Dawn’s operational life.”

    Dawn will continue to orbit Ceres for decades. Planetary protection rules insisted on at least 20 years before the spacecraft crashed into the dwarf planet, to reduce the chances of contamination. The Dawn team opted to set the spacecraft on an orbit that would keep it aloft for at least 50 years.

    2
    The dwarf planet Ceres spins in this series of photos captured by NASA’s Dawn spacecraft on April 29, 2017, when the probe was between Ceres and the sun.
    Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

    Exploring Vesta

    Dawn’s first stop was Vesta, a rocky asteroid and the second largest inhabitant of the asteroid belt, where it made several significant findings at Vesta. It discovered a geologic landscape that scientists called “exotic and diverse,” and compiled the first map of the 330-mile (530 km) wide body.

    The Dawn team reasoned that reaching those temperatures would have caused the heavy elements to melt and sink down to the core in a process known as differentiation. In fact, joked JPL’s Carol Raymond, Dawn’s deputy principal investigator, “We like to call Vesta ‘the smallest terrestrial planet.'”

    Dawn also confirmed that Vesta is the source of the howardite-eucrite-diogenite (HED) meteorites found on Earth and Mars. The Dawn team thinks that the HEDs came from an impact basin the team named Rheasilvia. The basin itself has an age of about 1 billion years, and formed from a massive collision that stripped the away the bulk of the asteroid’s southern hemisphere. With a diameter of 310 miles (500 km), Rheasilvia is nearly as large as Vesta itself.

    “Vesta likely came close to shattering,” said Raymond.

    A second basin showcases another dangerous impact beneath Rheasilvia. Named Veneneia, the basin is nearly as big and nearly a billion years younger than Rheasilvia and may be another potential source for HED meteorites.

    Research from Dawn also suggests that Vesta may hide ice beneath its surface. Originally, the scientists suspected that roughness on the asteroid’s surface came from impacts, but Dawn’s data suggests that some of the features are caused by ice buried beneath the surface.

    “We suggest that modifications of the surface by melting of buried ice could be responsible for smoothing those areas,” Essam Heggy, a planetary scientist at the University of Southern California in Los Angeles, told Space.com. “Buried ice could have been brought to the surface after an impact, which caused heated ice to melt and travel up through the fractures to the surface.”

    “We went to Vesta to fill in the blanks of our knowledge about the early history of our solar system,” said Dawn principal investigator Christopher Russell, of UCLA, said in a statement.

    “Dawn has filled in those pages, and more, revealing to us how special Vesta is as a survivor from the earliest days of the solar system. We can now say with certainty that Vesta resembles a small planet more closely than a typical asteroid.”

    4

    215 years after its discovery, we know so much more about the dwarf planet Ceres. NASA’s Dawn spacecraft captured this amazing view of Ceres in the asteroid belt, showing the dwarf planet’s Occator Crater in false color, after it arrived in orbit around Ceres in 2015. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

    Ceres science

    While Vesta is rocky, Ceres is surprisingly icy. Before Dawn arrived, scientists estimated that water could make up as much as a quarter of the dwarf planet, though that water would be tucked beneath the surface. Observations made by the Hubble Space Telescope revealed a cloud of vapor that suggested the dwarf planet might be degassing, though no strong signs of such activity has been spotted by Dawn.

    On the surface, Ceres appears relatively bland. Aside from a few craters — though less than scientists anticipated — the only outstanding feature is a single mountain, Ahuna Mons. Researchers suspected the mountain was a cryovolcano, oozing ice instead of hot lava. Further studies revealed that, while it may be thought of as a “lonely mountain” today, it could have had companions in the past. Made of ice, these mountains may have slowly flowed back onto the surface.

    “We think we have a very good case that there have been lots of cryovolcanoes on Ceres but they have deformed,” Dawn researcher Michael Sori of the University of Arizona in Tucson said in a statement.

    The same fate may await the lonely volcano.

    “Ahuna Mons is at most 200 million years old. It just hasn’t had time to deform,” Sori said.

    From a distance, Dawn caught sight of bright spots from a distance that soon resolved into more than 130 bright patches, most of them tied to craters. Initially thought to be Epsom salt, the patches turned out to be a version of salts that require water to form. Since water skips to gas almost immediately on the dwarf planet’s surface, that suggests that the liquid must lie beneath the crust.

    “That was something we had not expected,” Russell told Space.com. “The carbonates are a very strong indication of the processes now that we believe took place in the interior, that makes it more Earthlike, when it can alter the chemistry inside.”

    “It’s not something that’s just lying around out there in space,” he added.

    The flowing ice that formed Ahuna Mons and the presence of salts suggest that an ancient ocean once lie beneath the crust of Ceres.

    “We believe these bright spots are a sign that Ceres once had a global ocean,” planetary geologist Lynnae Quick, of the Smithsonian Institute in Washington, D.C., told Space.com.

    “It’s possible there is still brine coming up to the surface,” Nathan Stein, a planetary scientist at the California Institute of Technology in Pasadena, told Space.com. “It’s certainly intriguing.”

    Researchers also spotted ammonia-rich clays on the dwarf planet. Ammonia is more commonly found in the outer solar system. The material could have been delivered to Ceres by comets, or its presence could be a sign that the dwarf planet formed in the outer solar system.

    These and other discoveries by Dawn have revealed that Ceres is a rich, evolving world.

    “The IAU [International Astronomical Union] has defined what a planet is in a particular way,” Russell said, “but I think of a planet more as a body which, when it’s big enough and has enough activity … is now making things, producing things in its interior that are not just sitting there for the eons but in fact that the body evolves with time inside.”

    Additional resources

    NASA Dawn mission
    Dawn mission home page (JPL)

    See the full article here .

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  • richardmitnick 12:15 pm on April 2, 2018 Permalink | Reply
    Tags: , , , , , space.com, Target is asteroid 162173 Ryugu   

    From SPACE.com: “Hayabusa2: Japan’s 2nd Asteroid Sample Mission” 

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    SPACE.com

    March 30, 2018
    Elizabeth Howell

    JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

    Hayabusa2 is a Japanese asteroid-sampling spacecraft that launched in December 2014. It is currently on the way to asteroid 162173 Ryugu and will arrive there between June and July 2018, according to the Japanese Aerospace Exploration Agency (JAXA). The mission is a follow-up of Hayabusa, which returned samples of asteroid 25143 Itokawa to Earth in 2010 despite numerous technical difficulties.

    JAXA’s original Hayabusa spacecraft

    Mission development

    Hayabusa2 was first selected by Japan’s Space Activities Commission in 2006, and received funding in August 2010 (shortly after Hayabusa’s return). The cost is estimated at 16.4 billion yen ($150 million).

    A year after launch, Hayabusa2 briefly returned to Earth. The spacecraft made a planned flyby to get a speed boost by using the Earth’s gravitational field. Meanwhile, astronomers are doing periodic observations of Ryugu to gather information ahead of the spacecraft’s arrival. The 600-kg spacecraft is expected to remain at the asteroid for 18 months, and return to Earth in 2020 with samples on board.

    The basic configuration of Hayabusa2 is very similar to Hayabusa, except for some improved technology, according to JAXA. Here are some of the improvements on Hayabusa2.

    Ion engine: Improving the lifespan of the neutralizers (which failed on Hayabusa) by strengthening the internal magnetic field. Also, more careful checks of the ion engine will be performed to improve its propulsion generation and ignition stability.
    Sampler mechanism: Better seal performance, more compartments and an improved mechanism for picking up material from the surface. On Hayabusa, it was unclear at the time of sample collection if it had actually picked up something from the surface.
    Re-entry capsule: JAXA has added an instrument to measure acceleration, movement and interior temperatures during flight. (The Hayabusa capsule broke up during re-entry.)
    Flat antennas: Instead of Hayabusa’s parabolic antenna, Hayabusa2 will have flat antennas. This will allow it to have the same communications capacity as Hayabusa, while saving on weight (and launch fuel). “A flat antenna can perform to the same capacity as a parabolic antenna due to technological improvements … Thanks to the flat design, the weight of the antenna is reduced to one-fourth, compared to a parabolic antenna whose performance is the same.” JAXA said.

    Here are the major instruments of the mission:

    Small Carry-on Impactor (SCI): This will create an artificial crater on the surface of the asteroid. Hayabusa2 will look at the changes on the surface before and after the impact takes place. They will also sample the crater to get “fresh” materials from underground.
    Near InfraRed Spectrometer (NIRS3) and Thermal Infrared Imager (TIR): The spectrometer will look at mineral composition of the asteroid, and the properties of water there. The imager will study the temperature and thermal inertia (resistance to changing temperature) of the asteroid.
    The small rovers MINERVA-II: Three small rovers will bounce along the surface and collect data from close-up. They are successors to the MINERVA rover aboard Hayabusa, which failed to meet its target after launch.
    A small lander (MASCOT): This is a lander that will jump only once after it arrives on the surface. It will also perform close-up observations of the surface. This instrument is built by DLR (Germany’s space agency) and the CNES (France’s space agency).

    Science goals

    Japan chose a different type of asteroid to study for Hayabusa2. The goal is to collect information about a wide variety of asteroids across the solar system. Ryugu is a C-type asteroid, meaning that it is carbonaceous; with a high percentage of carbon, this is the most common type of asteroid in the solar system. (The target for Hayabusa was Itokawa, an S-type asteroid — meaning that it is made up more of stony materials and nickel iron.)

    Ryugu is an older type of body than Itokawa, and likely contains more organic or hydrated minerals, JAXA stated. Organics and water are key elements for life on Earth, although their presence on other bodies doesn’t necessarily mean life itself. “We expect to clarify the origin of life by analyzing samples acquired from a primordial celestial body such as a C-type asteroid to study organic matter and water in the solar system, and how they co-exist while affecting each other,” JAXA said.

    See the full article here .

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  • richardmitnick 12:49 pm on January 25, 2018 Permalink | Reply
    Tags: , , , , , space.com,   

    From SETI Institute via SPACE.com: “‘Search for Extraterrestrial Intelligence’ Needs a New Name, SETI Pioneer Says” 

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    SETI Institute

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    SPACE.com

    January 25, 2018
    Calla Cofield

    2
    Jill Tarter at the Arecibo radio telescope in Puerto Rico, which was used to search for communications signals from alien civilizations.
    Credit: Acey Harper/The LIFE Images Collection/Getty

    NAIC/Arecibo Observatory, Puerto Rico, USA, at 497 m (1,631 ft)

    Astrophysicist Jill Tarter is one of the world’s best-known leaders in the search for extraterrestrial intelligence, or SETI. For 35 years, she served as the director of the Center for SETI Research (part of the SETI institute) and was also the project scientist for NASA’s SETI program, before its cancellation in 1993.

    Despite her longtime association with that four-letter acronym, Tarter says it’s time for “SETI” to be rebranded.

    At a recent meeting of the National Academy of Sciences’ Committee on Astrobiology Science Strategy for the Search for Life in the Universe, held here at the University of California, Irvine, Tarter explained that the phrase “search for extraterrestrial intelligence” generates an incorrect perception of what scientists in this field are actually doing. A more appropriate title for the field, she said, would be “the search for technosignatures,” or signs of technology created by intelligent alien civilizations.

    “We need to be very careful about our language,” Tarter said during a presentation at the committee meeting on Jan. 18. “SETI is not the search for extraterrestrial intelligence. We can’t define intelligence, and we sure as hell don’t know how to detect it remotely. [SETI] … is searching for evidence of someone else’s technology. We use technology as a proxy for intelligence.

    “[The acronym] ‘SETI’ has been problematic in history, and we should just drop [it] and just continue to talk about a search for technosignatures,” she said.

    Signs of life

    What constitutes a “technosignature”? Tarter reviewed some of the possibilities that she and other SETI scientists have proposed.

    “We have a pragmatic definition for technology, which is the ability to deliberately modify an environment in ways that can be sensed over interstellar or interplanetary distances, including the unintended consequences of that modification,” Tarter said. “Life does this, but it doesn’t do it deliberately.”

    One technosignature that scientists have been actively seeking for decades is communication signals. These could include signals used by members of an alien civilization to communicate with each other or attempts to communicate with other civilizations. The SETI Institute continues to search for alien communications in radio waves, using the Allen Telescope Array.

    SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA, Altitude 986 m (3,235 ft)

    (Tarter was the inspiration for the main character in Carl Sagan’s novel Contact, which was adapted into a movie; in that story, aliens make contact with Earth via radio waves.) But recent SETI efforts have expanded to look for other mediums of alien communication, and SETI scientists have theorized that an interstellar civilization might use laser light to communicate.

    Laser SETI, the future of SETI Institute research

    Science-fiction writer Arthur C. Clarke wrote that “any sufficiently advanced technology is indistinguishable from magic,” which would mean that alien technology could be as mysterious and unexplainable to humans as technologies that appear in science-fiction TV shows and movies. That opens up a dauntingly large range of possibilities for what technosignatures might look like. What if an alien civilization were communicating via a mechanism that Earth-based scientists haven’t discovered yet? Would humans immediately recognize these “magical” technosignatures, or would we not see them as unnatural?

    Tarter said she prefers to focus on a slight alteration of Clarke’s prediction written by the futurist Karl Schroeder: “Any sufficiently advanced technology is indistinguishable from nature.”

    “[The system] will be so efficient that there will be no wastage, and [it] will appear to be natural,” Tarter said. If this prediction is correct, it might also be impossible for humans to identify technosignatures from very advanced civilizations. But Tarter uses it as a jumping-off point to brainstorm how scientists might identify technologies that have not yet reached that level of sophistication.

    In the field of exoplanet science, new techniques and new instruments are increasing scientists’ ability to study exoplanets and gather information about their atmospheres and surface conditions. The central focus in that field is to find habitable planets, or planets with “unintelligent” life-forms (like plants). Tarter said those tools could also provide the opportunity to look for signs of technology that artificially alters a planet’s climate or conditions.

    “As we begin to look for exoplanets and image them, you might get an unexpected glint, [because] maybe mirrors re cooling their planet, reflecting light away from the planet,” Tarter said.

    But a technosignature wouldn’t necessarily have to be the detection of the technology itself. The artificial alteration of a planet’s climate could be revealed simply because the planet in question is too close or too far away from its parent star to have the observed climate. A star system with multiple planets that all have similarly moderate, habitable climates, despite their particular proximity to the parent star, could indicate large-scale bioengineering by an intelligent civilization, Tartar said.

    “[An alien civilization] also might want to decrease latitudinal variation in temperature; maybe they want more of their planet to be nice and cozy,” Tarter said. “It’s going to take a lot of energy to do that, but I don’t know the physics that says you can’t.”

    Into the future

    The search for technosignatures is daunting, but Tarter says now is “a really opportunistic time” for it. The field is benefiting from new instruments and a wider array of instruments. SETI scientists are often searching through large volumes of data, seeking the proverbial needle in the haystack. Artificial intelligence and artificial “neural networks” can help aid this effort by combing through this vast data to search for signals that the scientists program machines to find and also allowing “the data to tell us what kind of signals are there,” Tarter said, which increases the odds of finding an unanticipated technosignature.

    Tarter listed multiple SETI projects and initiatives that are underway around the world. The most high-profile is Breakthrough Listen, a private initiative that has funded a group of researchers at the University of California, Berkeley to utilize various telescopes to search for signs of alien communication or other possible technosignatures.

    Breakthrough Listen Project

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    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA



    GBO radio telescope, Green Bank, West Virginia, USA


    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

    The Berkeley group has led an effort to crack the mystery of Boyajian’s star, which has exhibited a very strange pattern of dimming and brightening. A few years ago, some researchers proposed that perhaps the strange light patterns were created by an alien megastructure orbiting the star — a fantastic example of a technosignature. Though that possibility has largely been ruled out, the Breakthrough Listen researchers are still working to understand this phenomenon.

    The challenge of searching for alien technosignatures may be daunting, but Tarter remains unwavering in her optimism for the search for life beyond Earth.

    “In 2004, Craig Venter and Daniel Cohen made a really bold statement: They said the 20th century had been the century of physics, but the 21st century would be the century of biology,” Tarter said. “I think they were right, but I don’t think they were bold enough. Because I think the 21st century is going to be the century of biology on Earth and beyond.”

    See the full article here .

    Please help promote STEM in your local schools.

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