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  • richardmitnick 3:54 pm on July 25, 2016 Permalink | Reply
    Tags: , Astronomy, ,   

    From Goddard: “NASA to Map the Surface of an Asteroid” 

    NASA Goddard Banner

    NASA Goddard Space Flight Center

    July 25, 2016
    Sarah Schlieder
    sarah.schlieder@nasa.gov
    NASA’s Goddard Space Flight Center in Greenbelt, Md.

    NASA’s OSIRIS-REx spacecraft will launch September 2016 and travel to a near-Earth asteroid known as Bennu to harvest a sample of surface material and return it to Earth for study. The science team will be looking for something special. Ideally, the sample will come from a region in which the building blocks of life may be found.

    NASA OSIRIS-Rex Spacecraft
    NASA OSIRIS-Rex Spacecraft

    To identify these regions on Bennu, the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) team equipped the spacecraft with an instrument that will measure the spectral signatures of Bennu’s mineralogical and molecular components.

    NASA OSIRIS-REX OVIRS
    NASA OSIRIS-REX OVIRS


    The OSIRIS-REx Visible and Infrared Spectrometer, or OVIRS, will look at the asteroid’s spectral signature to detect organics and other minerals.

    Known as OVIRS (short for the OSIRIS-REx Visible and Infrared Spectrometer), the instrument will measure visible and near-infrared light reflected and emitted from the asteroid and split the light into its component wavelengths, much like a prism that splits sunlight into a rainbow.

    “OVIRS is key to our search for organics on Bennu,” said Dante Lauretta, principal investigator for the OSIRIS-REx mission at the University of Arizona in Tucson. “In particular, we will rely on it to find the areas of Bennu rich in organic molecules to identify possible sample sites of high science value, as well as the asteroid’s general composition.”

    OVIRS will work in tandem with another OSIRIS-REx instrument — the Thermal Emission Spectrometer, or OTES. While OVIRS maps the asteroid in the visible and near infrared, OTES picks up in the thermal infrared. This allows the science team to map the entire asteroid over a range of wavelengths that are most interesting to scientists searching for organics and water, and help them to select the best site for retrieving a sample.

    In the visible and infrared spectrum, minerals and other materials have unique signatures like fingerprints. These fingerprints allow scientists to identify various organic materials, as well as carbonates, silicates and absorbed water, on the surface of the asteroid. The data returned by OVIRS and OTES will actually allow scientists to make a map of the relative abundance of various materials across Bennu’s surface.

    “I can’t think of a spectral payload that has been quite this comprehensive before,” said Dennis Reuter, OVIRS instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

    OVIRS will be active during key phases throughout the mission. As the OSIRIS-REx spacecraft approaches Bennu, OVIRS will view one entire hemisphere at a time to measure how the spectrum changes as the asteroid rotates, allowing scientists to compare ground-based observations to those from the spacecraft. Once at the asteroid, OVIRS will gather spectral data and create detailed maps of the surface and help in the selection of a sample site.

    Using information gathered by OVIRS and OTES from the visible to the thermal infrared, the science team will also study the Yarkovsky Effect, or how Bennu’s orbit is affected by surface heating and cooling throughout its day. The asteroid is warmed by sunlight and re-emits thermal radiation in different directions as it rotates. This asymmetric thermal emission gives Bennu a small but steady push, thus changing its orbit over time. Understanding this effect will help scientists study Bennu’s orbital path, improve our understanding of the Yarkovsky effect, and improve our predictions of its influence on the orbits of other asteroids.

    But despite its capabilities to perform complex science, OVIRS is surprisingly inexpensive and compact in its design. The entire spectrometer operates at 10 watts, requiring less power than a standard household light bulb.

    “When you put it into that perspective, you can see just how efficient this instrument is, even though it is taking extremely complicated science measurements,” said Amy Simon, deputy instrument scientist for OVIRS at Goddard. “We’ve put a big job in a compact instrument.”

    Unlike most spectrometers, OVIRS has no moving parts, reducing the risk of a malfunction.

    “We designed OVIRS to be robust and capable of lasting a long time in space,” Reuter said. “Think of how many times you turn on your computer and something doesn’t work right or it just won’t start up. We can’t have that type of thing happen during the mission.”

    Drastic temperature changes in space will put the instrument’s robust design to the test. OVIRS is a cryogenic instrument, meaning that it must be at very low temperatures to produce the best data. Generally, it doesn’t take much for something to stay cool in space. That is, until it comes in contact with direct sunlight.

    Heat inside OVIRS would increase the amount of thermal radiation and scattered light, interfering with the infrared data. To avoid this risk, the scientists anodized the spectrometer’s interior coating. Anodizing increases a metal’s resistance to corrosion and wear. Anodized coatings can also help reduce scattered light, lowering the risk of compromising OVIRS’ observations.

    The team also had to plan for another major threat: water. The scientists will search for traces of water when they scout the surface for a sample site. Because the team will be searching for tiny water levels on Bennu’s surface, any water inside OVIRS would skew the results. And while the scientists don’t have to worry about a torrential downpour in space, the OSIRIS-REx spacecraft may accumulate moisture while resting on its launch pad in Florida’s humid environment.

    Immediately after launch, the team will turn on heaters on the instrument to bake off any water. The heat will not be intense enough to cause any damage to OVIRS, and the team will turn the heaters off once all of the water has evaporated.

    “There are always challenges that we don’t know about until we get there, but we try to plan for the ones that we know about ahead of time,” said Simon.

    OVIRS will be essential for helping the team choose the best sample site. Its data and maps will give the scientists a picture of what is present on Bennu’s surface.

    In addition to OVIRS, Goddard will provide overall mission management, systems engineering and safety and mission assurance for OSIRIS-REx. Dante Lauretta is the mission’s principal investigator at the University of Arizona. Lockheed Martin Space Systems in Denver built the spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages New Frontiers for the agency’s Science Mission Directorate in Washington.

    For more information about OSIRIS-REx, visit:

    http://www.nasa.gov/osiris-rex

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA Goddard Campus
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  • richardmitnick 2:55 pm on July 25, 2016 Permalink | Reply
    Tags: , Astronomy, ,   

    From Ethan Siegel: “The Stars Of Andromeda, Inside And Out, As Revealed By Hubble” 

    From Ethan Siegel

    Andromeda Galaxy Adam Evans
    Andromeda Galaxy Adam Evans

    The Milky Way’s plane obscures our view of most stars in our own galaxy, but an even grander spiral — Andromeda — lies 2.5 million light years away.

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    A Mosaic of the 117 million resolved stars — plus many more unresolved ones — in the disk of the Andromeda galaxy. Image credit: NASA, ESA, J. Dalcanton, B.F. Williams, L.C. Johnson (University of Washington), the PHAT team, and R. Gendler.

    Even at this modest distance, incredible telescope and camera technology is needed to resolve individual stars in a galaxy beyond our own.

    The Hubble Space Telescope recently completed the Panchromatic Hubble Andromeda Treasury, mapping a third of Andromeda’s disk and resolving over 117 million individual stars.

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    Closeup of a large region of the Andromeda galaxy’s disk, containing hundreds of open star clusters (identifiable as bright blue sparkles). Image credit: NASA, ESA, J. Dalcanton, B.F. Williams, L.C. Johnson (University of Washington), the PHAT team, and R. Gendler.

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    Six of the most spectacular star clusters in Andromeda. The brilliant red star in the fifth image is actually a foreground star in the Milky Way. Over a thousand new clusters were found in this survey. Image Credit: NASA, ESA, and Z. Levay (STScI); Science Credit: NASA, ESA, J. Dalcanton, B.F. Williams, L.C. Johnson (University of Washington), and the PHAT team.

    Far outside of the center, in the outer disk and the faint galactic halo, a different set of populations thrive.

    5
    Image credit: NASA, ESA and T.M. Brown (STScI), of the stars in Andromeda’s outer disc.

    The outer disc of Andromeda (above) shows a wide variety of stars, including many Sun-like ones and older variables.

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    Image credit: NASA, ESA and T.M. Brown (STScI), of the stars in Andromeda’s giant stellar stream. The Milky Way’s foreground stars are clearly identified by their diffraction spikes.

    The stars from the giant stellar stream are also densely packed, obscuring the Universe beyond.

    While the diffuse halo’s low-density regions contain many of the oldest, least evolved stars.

    They’re lower in heavy elements than any stars found in the disk, with galaxies up to billions of light years away visible through the gaps in the halo stars.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 2:32 pm on July 25, 2016 Permalink | Reply
    Tags: Astronomy, , Milky Way Galaxy’s 'Halo',   

    From NASA: “Astronomers Discover Dizzying Spin of the Milky Way Galaxy’s ‘Halo’ “ 

    NASA image

    NASA

    July 25, 2016
    Felicia Chou
    felicia.chou@nasa.gov
    NASA Headquarters, Washington, D.C.

    Astronomers at the University of Michigan’s College of Literature, Science, and the Arts (LSA) discovered for the first time that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at comparable speed as the galaxy’s disk, which contains our stars, planets, gas, and dust. This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies like our own, and what the future holds for these galaxies.

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    Our Milky Way galaxy and its small companions are surrounded by a giant halo of million-degree gas (seen in blue in this artists’ rendition) that is only visible to X-ray telescopes in space. University of Michigan astronomers discovered that this massive hot halo spins in the same direction as the Milky Way disk and at a comparable speed. Credits: NASA/CXC/M.Weiss/Ohio State/A Gupta et al, 2012

    “This flies in the face of expectations,” says Edmund Hodges-Kluck, assistant research scientist. “People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary – but that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk.”

    The new NASA-funded research using the archival data obtained by XMM-Newton, a European Space Agency telescope, was recently published [Published 2016 April 27] in the Astrophysical Journal. The study focuses on our galaxy’s hot gaseous halo, which is several times larger than the Milky Way disk and composed of ionized plasma.

    Because motion produces a shift in the wavelength of light, the U-M researchers measured such shifts around the sky using lines of very hot oxygen. What they found was groundbreaking: The line shifts measured by the researchers show that the galaxy’s halo spins in the same direction as the disk of the Milky Way and at a similar speed—about 400,000 mph for the halo versus 540,000 mph for the disk.

    “The rotation of the hot halo is an incredible clue to how the Milky Way formed,” said Hodges Kluck. “It tells us that this hot atmosphere is the original source of a lot of the matter in the disk.”

    Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80% of the matter in the universe is the mysterious “dark matter” that, so far, can only be detected by its gravitational pull. But even most of the remaining 20% of “normal” matter is missing from galaxy disks. More recently, some of the “missing” matter has been discovered in the halo. The U-M researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.

    “Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed – and its eventual destiny,” says Joel Bregman, a U-M LSA professor of astronomy.

    “We can use this discovery to learn so much more – the rotation of this hot halo will be a big topic of future X-ray spectrographs,” Bregman says.

    For more information, please visit:

    http://heasarc.gsfc.nasa.gov/docs/xmm/xmmgof.html

    See the full article here .

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    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 12:21 pm on July 25, 2016 Permalink | Reply
    Tags: A Pulsar and a Disk, , Astronomy,   

    From AAS NOVA: “A Pulsar and a Disk” 

    AASNOVA

    American Astronomical Society

    25 July 2016
    Susanna Kohler

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    Artist’s illustration of a Be star and its circumstellar disk, orbited by an accreting compact object. Recent observations of a similar system, SXP 214, suggest that the pulsar periodically passes through the circumstellar disk of its companion. [SMM (IAC)/Gabriel Pérez]

    Recent, unusual X-ray observations from our galactic neighbor, the Small Magellanic Cloud, have led to an interesting model for SXP 214, a pulsar in a binary star system.

    An Intriguing Binary

    An X-ray pulsar is a magnetized, rotating neutron star in a binary system with a stellar companion. Material is fed from the companion onto the neutron star, channeled by the object’s magnetic fields onto a “hotspot” that’s millions of degrees. This hotspot rotating past our line of sight is what produces the pulsations that we observe from X-ray pulsars.

    Located in the Small Magellanic Cloud, SXP 214 is a transient X-ray pulsar in a binary with a Be-type star. This star is spinning so quickly that material is thrown off of it to form a circumstellar disk.

    Recently, a team of authors led by JaeSub Hong (Harvard-Smithsonian Center for Astrophysics) have presented new Chandra X-ray observations of SXP 214, tracking it for 50 ks (~14 hours) in January 2013. These observations reveal some very unexpected behavior for this pulsar.

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    The energy distribution of the X-ray emission from SXP 214 over time. Dark shades or blue colors indicate high counts, and light shades or yellow colors indicate low counts. Lower-energy X-ray emission appeared only later, after about 20 ks. [Hong et al. 2016]

    X-ray Puzzle

    Three interesting pieces of information came from the Chandra observations:

    SXP 214’s rotation period was measured to be 211.5 s — an increase in the spin rate since the discovery measurement of a 214-second period. Pulsars usually spin down as they lose angular momentum over time … so what caused this one to spin up?
    Its overall X-ray luminosity steadily increased over the 50 ks of observations.
    Its spectrum became gradually softer (lower energy) over time; in the first 20 ks, the spectrum only consisted of hard X-ray photons above 3 keV, but after 20 ks, softer X-ray photons below 2 keV appeared.

    Hong and collaborators were then left with the task of piecing together this strange behavior into a picture of what was happening with this binary system.

    4
    The authors’ proposed model for SXP 214. Here the binary has a ~30-day orbit tilted at 15° to the circumstellar disk. The pulsar passes through the circumstellar disk of its companion once per orbit. The interval marked “A” (orange line) is suggested as the period of time corresponding to the Chandra observations in this study: just as the neutron star is emerging from the disk after passing through it. [Hong et al. 2016]

    Passing Through a Disk

    In the model the authors propose, the pulsar is on a ~30-day eccentric orbit that takes it through the circumstellar disk of its companion once per orbit.

    In this picture, the authors’ Chandra detections must have been made just as the pulsar was emerging from the circumstellar disk. The disk had initially hidden the soft X-ray emission from the pulsar, but as the pulsar emerged, that component became brighter, causing both the overall rise in X-ray counts and the shift in the spectrum to lower energies.

    Since the pulsar’s accretion is fueled by material picked up as it passes through the circumstellar disk, the accretion from a recent passage through the disk likely also caused the observed spin-up to the shorter period.

    If the authors’ model is correct, this series of observations of the pulsar as it emerges from the disk provides a rare opportunity to examine what happens to X-ray emission during this passage. More observations of this intriguing system can help us learn about the properties of the disk and the emission geometry of the neutron star surface.

    Citation

    JaeSub Hong et al 2016 ApJ 826 4. doi:10.3847/0004-637X/826/1/4

    See the full article here .

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  • richardmitnick 10:45 am on July 25, 2016 Permalink | Reply
    Tags: Astronomy, , Long dead stars,   

    From Hubble: “A long-dead star” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    1

    This NASA/ESA Hubble Space Telescope image captures the remnants of a long-dead star. These rippling wisps of ionised gas, named DEM L316A, are located some 160 000 light-years away within one of the Milky Way’s closest galactic neighbours — the Large Magellanic Cloud (LMC).

    The explosion that formed DEM L316A was an example of an especially energetic and bright variety of supernova, known as a Type Ia. Such supernova events are thought to occur when a white dwarf star steals more material than it can handle from a nearby companion, and becomes unbalanced. The result is a spectacular release of energy in the form of a bright, violent explosion, which ejects the star’s outer layers into the surrounding space at immense speeds. As this expelled gas travels through the interstellar material, it heats it up and ionise it, producing the faint glow that Hubble’s Wide Field Camera 3 has captured here.

    The LMC orbits the Milky Way as a satellite galaxy and is the fourth largest in our group of galaxies, the Local Group. DEM L316A is not alone in the LMC; Hubble came across another one in 2010 with SNR 0509 (heic1018),

    3
    SNR 0509

    and in 2013 it snapped SNR 0519 (potw1317a).

    4
    SNR 0519

    See the full article here .

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

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  • richardmitnick 9:18 am on July 25, 2016 Permalink | Reply
    Tags: Astronomy, , Seven new embedded clusters detected in the Galactic halo   

    From phys.org: “Seven new embedded clusters detected in the Galactic halo” 

    physdotorg
    phys.org

    July 25, 2016
    Tomasz Nowakowski

    1
    WISE (15′ ×15′) multicolour images centered on the central coordinates of the embedded clusters C 1074, C 939, C 1099, and C 934. North is to the top and east to the left. Circles encompass more probable cluster stars. Credit: Camargo et al., 2016.

    A team of Brazilian astronomers, led by Denilso Camargo of the Federal University of Rio Grande do Sul in Porto Alegre, has discovered seven new embedded clusters located unusually far away from the Milky Way’s disc. The findings, presented in a paper published July 3 on arXiv.org, could provide new insights on star cluster formation.

    Embedded clusters are stellar clusters encased in an interstellar dust or gas, consisting of extremely young stars. They are crucial for astronomers to better understand star formation and early stellar evolution. Studying these clusters could reveal the origin of stellar masses as well as the origin and evolution of protoplanetary disks, where planet formation processes take place.

    In the Milky Way galaxy, most of embedded clusters lie within the thin disc less than 1,000 light years from the galactic midplane, especially in the spiral arms. However, Camargo and his team detected two young stellar clusters earlier this year, and now, after spotting seven more, suggest that they could be more common on the outskirts of the galaxy than previously thought.

    “Now, we discovered seven star clusters far away from the Milky Way disc. Thus, this work points to a new paradigm in the star and star cluster formation, in the sense that the formation of such objects occurs in the halo and it seems to be frequent,” Camargo told Phys.org.

    The scientists found the new clusters by analyzing the data provided by NASA’s Wide-field Infrared Survey Explorer (WISE).

    NASA/WISE Telescope
    NASA/WISE Telescope

    This space telescope is monitoring the entire galaxy in infrared light, snapping pictures of mainly remote galaxies, stars and asteroids. WISE was chosen for this job as it captures embedded clusters that are invisible at optical wavelengths, due to the fact that they are engulfed in significant amounts of interstellar dust.

    “WISE provided infrared images of the entire sky, allowing us to penetrate the gas and dust within giant molecular clouds, in which the star formation can take place. Recently, we discovered more than 1,000 embedded clusters using WISE,” Camargo said.

    According to the research paper, three newly found objects, designated C 932, C 934, and C 939, are high-latitude embedded clusters, projected within the newly identified cloud complex. These clusters are located at a vertical distance of about 16,300 light years below the galactic disc. Other new clusters, named C 1074, C 1099, C 1100, and C 1101, are in the range from 5,500 to 10,400 light years above the disc. All these clusters are younger than five million years.

    The team noted that the new findings indicate that a sterile galactic halo could host ongoing star formation. The newly detected embedded clusters provide evidence of widespread star cluster forming processes far away from the Milky Way’s disc.

    “The discovery of stellar clusters far away from the disc suggests that the Galactic halo is more actively forming stars than previously thought. Moreover, since most young clusters do not survive for more than five million years, the halo may be raining stars into the disc. The halo harbors generations of stars formed in clusters like those hereby detected,” Camargo said.

    Before the team’s paper was published, it was thought that star formation processes in the Milky Way occur in the disk, but not in the halo. Thus, as Camargo concluded, this new study represents a paradigm shift, in the sense that a sterile halo becomes now a host of ongoing star formation.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 8:31 pm on July 24, 2016 Permalink | Reply
    Tags: Astronomy, , , , Will The 'Great Attractor' Defeat Dark Energy?   

    From Ethan Siegel: “Will The ‘Great Attractor’ Defeat Dark Energy?” 

    From Ethan Siegel

    Jul 23, 2016

    Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.
    The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    On the largest scales in the Universe, dark energy causes the Universe’s expansion to accelerate. It not only drives distant galaxies farther and farther apart over time, it causes them to speed up relative to one another’s perspective. But on the other hand, gravitation causes matter to clump together, like our own galaxy and local group have, and can defeat this expansion if you get a large enough amount of matter together in one location. But galaxies and groups aren’t the biggest structures we know of. The Universe also has clusters and superclusters of galaxies, and we have some right in our own backyard! Will one of those defeat dark energy in the end? Bob Simone wants to know:

    “If we are only ultimately bound to [Andromeda], and everything else will eventually slip out of our visible universe, how can all the we all be heading to the great attractor (or whatever we’re all heading towards at the gravitational center of Laniakea)?”

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    Milky Way Andromeda collision in 4 billion years. Credit: NASA/ESA/Z. Levay and R. van der Marel (STScI)/A. Mellinger

    There are thousands of galaxies not all that far away, cosmically, that are tugging on us.

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    Markarian’s chain with the name of the galaxies, located at/near the center of the Virgo Cluster. Image credit: Wikimedia Commons user Bilbo-le-hobbit, based on the work by By Packbj, under a c.c.-by-s.a. 3.0 license.

    Will they pull us in in the end, despite dark energy? Or will dark energy cause us to expand fast enough, and soon enough, to prevent that from ever happening? To answer this question, we’ll need to look at three things: the Universe’s expansion, local imperfections to that motion, and what the Universe looks like near us.

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    Hubble’s discovery of a Cepheid variable in Andromeda galaxy, M31, opened up the Universe to us. Image credit: E. Hubble, NASA, ESA, R. Gendler, Z. Levay and the Hubble Heritage Team.

    1.) The Universe’s expansion. Back in the 1920s, Edwin Hubble was able to identify a known class of star — Cepheid variables — in the spiral-shaped objects seen in the sky. Over time, they appeared to brighten and dim periodically, with a specific amount of time inherent to each star. There’s a brightness/time period relationship that these stars all obey, meaning that if you can measure that time period and their apparent brightness, you can figure out how distant each star, and therefore the galaxy it’s in, actually is from you.

    This concept is known as a standard candle, and we’ve progressed from Cepheids to other properties of galaxies to type Ia supernovae as the brightest, most easily identifiable standard candles out there. What we’ve been able to determine through these methods is that there’s a relationship known as Hubble’s law in all directions that we look: that the speed at which an object appears to move away from us is proportional to the Hubble parameter multiplied by the distance to that object. You might have heard it called the “Hubble constant” before, and that was a good way to think about it in the years and decades before the Hubble Space Telescope, since we had only looked about halfway across the Universe at that point. But the farther we looked, the better we were able to realize that the Universe’s expansion was not only changing over time, it was speeding up in a way that told us there was more to the Universe than matter, radiation and curved space alone.

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    The distance/redshift relation, including the most distant objects of all, seen with type Ia supernovae. All of Hubble’s original data would fit within the first pixel on the graph. Image credit: Ned Wright, based on the latest data from Betoule et al.

    Instead, the Universe today was made up of approximately 70% dark energy, which becomes more and more important as time goes on. Half the Universe’s age ago, dark energy was not yet noticeable, as it was only a tiny percentage of the total energy density. But as the matter and radiation dilutes and drops in density, dark energy comes to dominate the Universe’s expansion, causing the acceleration we see today. It means that any structures that weren’t already gravitationally bound — that hadn’t become denser-than-average by a large enough amount — would never wind up bound together in this Universe. Instead, they would accelerate away as the expansion of the Universe dictated.

    2.) Local imperfections to that motion. But even on distance scales millions of light years in size, gravitation had plenty of time to bring the Universe together. Trillions of star clusters and hundreds of billions of galaxies formed in the Universe over the first few billion years since the Big Bang, as the large-scale structure of the Universe became rich and complex. The largest overdense regions grew into not only galaxies but into groups and clusters of tens, hundreds or thousands of galaxies, all bound together in one giant region.

    The gravitational pull of these imperfections matters a great deal. When we look out at a galaxy like Andromeda, our closest neighbor, we see it some 2.5 million light years away. Based on the expansion of the Universe, it ought to be moving away from us. But the gravitational pull of the Milky Way on Andromeda — and of Andromeda back on us in the Milky Way — can defeat the expansion if these two galaxies are massive enough. If the attractive force between them is large enough, and was large enough early enough on, we’ll become gravitationally bound together. although dark energy might push the distant galaxies away from us, we’ll eventually fall into one another, and merge into a single giant structure over time.

    5
    Illustration sequence depicting the collision of the Milky Way (right) and Andromeda galaxies, as seen from our vantage point. Image credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas, and A. Mellinger.

    This will happen! This is the actual fate of our local group. The big question, then, to get to Bob’s point, is what’s going on with the great attractor, and the nearest clusters and superclusters to our location? For that, we need to map out the nearby, local Universe.

    Local Group. Andrew Z. Colvin 3 March 2011
    Local Group. Andrew Z. Colvin 3 March 2011

    3.) What the Universe looks like near us. With over 80% precision, we’ve done exactly that! (The parts we’ve missed are the galaxies located behind the galactic plane, which are very hard to see from our perspective.) We can take a look at three things all at once:

    All the individual galaxies around us, and measure their motions relative to us.
    Hubble’s expansion of the Universe, and combined with the galactic distances, infer how much these galactic motions depart from Hubble’s law.
    The measured and inferred masses of what we see around us, and determine what masses need to be present at what locations in the Universe to cause the motions we see.

    So we map out the local Universe, in terms of position and motion, and we map out the local mass, and we see how things are moving and why.

    The cosmic flows project recently put all this information together, and determined that the Milky Way is bound as part of the local group, that our group is one of many groups nearby but outside of the Virgo Cluster, and that all of these groups and clusters, combined with a few others, form a larger superstructure known as the Laniakea supercluster. The mass has to be there in order to explain the motions of these local structures, where the missing mass was previously simply referred to as the “Great Attractor” because the motions we saw didn’t match up with the masses we had found.

    The very large structure — the collection of galaxies in Laniakea which is responsible for this great, attractive force — causes the local group and many other galaxies in our local supercluster to move towards this mass. They depart from the Hubble flow significantly: by many hundreds of kilometers per second. It’s a real force, a substantial effect, and it works to fight against the Hubble expansion and dark energy.

    But it loses.

    6
    The various galaxies of the Virgo Supercluster, grouped and clustered together. Each individual group/cluster is unbound from all the others. Image credit: Andrew Z. Colvin, via Wikimedia Commons.

    Dark energy and the present expansion of the Universe is not only stronger than the attractive pull of the local supercluster, it’s not even a contest. The peculiar velocity, or the departure from the Hubble expansion, is only about 20% of what it would need to be to bind us to this large structure. In fact, the structure itself isn’t even bound; this supercluster is only an apparent structure, and as the Universe evolves, Laniakea itself will dissociate.

    So the full answer to your question, Bob, is that we are being pulled towards Laniakea, towards the “Great Attractor,” but the force we’re being pulled with is woefully insufficient to cause us to fall in. All it can cause is for the supercluster to accelerate away from us at a somewhat lower rate than average, and to remain within our reach for a few billion years longer than an equidistant galaxy on the opposite side of the sky. Laniakea is real and massive, but it’s also temporary, and it’s not massive enough to hold itself together or to eventually pull us in. The fate of our local group is a lonely one after all.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 9:55 am on July 24, 2016 Permalink | Reply
    Tags: Astronomy, , , Time and Space   

    From Ethan Siegel: “Are there different types of space and time?” 

    From Ethan Siegel

    7.23.16

    If everything is relative, as Einstein says, then how do cosmologists measure these quantities in ways everyone can agree

    “A human being is part of a whole, called by us the Universe, a part limited in time and space. He experiences himself, his thoughts and feelings, as something separated from the rest a kind of optical delusion of his consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest us. Our task must be to free ourselves from this prison by widening our circles of compassion to embrace all living creatures and the whole of nature in its beauty.” -Albert Einstein

    One of the most counterintuitive lessons of Einstein’s relativity is that there’s no such thing as absolute space or absolute time. If I ask you when and where you are, you can tell me; but if you and I go to distant locations and I ask you when and where you perceive me to be, what you answer and what I answer won’t necessarily match up. As it turns out, there’s no universally good way to define time and space (or distances) for any location other than your own in general relativity. As a result, we have multiple ways of defining these things, and that’s what Patreon supporter Thomas Sola wants to know about:

    “I’d love to see your explanation of conformal time and comoving distance… what they are and when and how they’re used as compared to colloquial time and distance.”

    When we use concepts like “time” and “distance” in our everyday language, there are a host of assumptions we rarely think about.

    1
    Galaxy cluster SDSS J1004+4112. Defining a distance to this object is not so simple. Image credit: ESA, NASA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech).

    If you think you can tell me that it’s 10:05 AM where I am and that I’m located 2,400 feet away from you, you may not realize why you think you can tell me that. You assume that your clock and my clock run at the same speed, that they originated at a common point where we agreed upon what time means, and that when we bring those two clocks back together again, they’ll be in agreement once again. Simple enough, right?

    Except this only happens if two important things are true:

    1. Nothing is moving relative to anything else. If any two things obtain a relative velocity with respect to one another, they experience the passage of time (and their perception of distance) differently from one another. Unstable particles moving close to the speed of light appear to live longer because of time dilation, and astronauts aboard the ISS, in rapid motion around the Earth, age at a slightly (but perceptibly) different rate from stationary humans on Earth. And…
    2. Space is completely flat, which it never is. In our Universe, we’re governed by general relativity, which tells us that the existence of matter and energy mean that space is curved, and that clocks run at different rates depending on how deep of a gravitational field they’re in. A clock at the top of the Empire State building will run a few microseconds slower every year than one at the bottom.

    2
    The curvature of space means that clocks that are deeper into a gravitational well — and hence, in more severely curved space — run at a different rate than ones in a shallower, less-curved portion of space. Image credit: NASA.

    For distances, those same constraints are true: motion and the curvature of space both make it inherently impossible for observers at different locations to necessarily agree on a universal standard of distance. But there’s something extra that comes into play if we start looking at really large distances: the fact that the fabric of the Universe itself — space — is expanding on a cosmic scale. No longer can we talk about the distance between galaxies as things that we can measure with an agreed-upon ruler, because the space between those galaxies expands over time. This gets us into trouble when we talk about, for example, measuring the most distant galaxy in the Universe.

    3
    Hubble spectroscopically confirms farthest galaxy to date, at a redshift of 11.1. Image credits: NASA, ESA, and A. Feild (STScI).

    The current cosmic record-holder is located at a redshift of 11.1, which means that — in our 13.8 billion years since the Big Bang — its light is only reaching us now after journeying for 13.4 billion of those years. But how far away is that galaxy? You might think, based on light-travel-time, that it’s 13.4 billion light years away, but that’s hardly fair. At the time the light reaching us right now was emitted, that galaxy was less than two billion light years from us. Thanks to the expansion of the Universe, using our conventional standards of measurement, that galaxy is around 32 billion light years away. A universal standard of distance is hard to define in an expanding Universe, where distances change over time.

    4
    Standard candles and standard rulers are two complementary — yet fundamentally different — ways to measure distances in the Universe. Image credit: NASA / JPL-Caltech.

    So one of the things we introduce, to address Thomas’ question, is the concept of different types of distances. The one he asks about in particular — comoving distance — is one of my favorites: it simply recognizes that distances in the Universe are changing due to the Hubble expansion, and so it scales the expansion out. This is incredibly useful when we’re doing simulations of how structures like stars, galaxies and clusters-and-filaments form in the Universe. Sure, gravitation is at work, but the Universe is expanding the whole time as well. By knowing how to scale the distances to the expansion (i.e., by using comoving distances), we can see how the large-scale structure of the Universe evolves. Visually, this gives us a much more interesting way to look at things than to watch the Universe expand and try to pick out structure formation amidst an expanding Universe.

    And because space and time are inextricably linked into a unified concept — spacetime — it’s necessarily true that we need a new concept of time to correspond to each individual concept of distance we come up with. The time counterpart of comoving distance is, in fact, conformal time. If you were to magically (and it would be an act of magic) “freeze” the expansion of the Universe, everywhere, instantaneously, conformal time corresponds to how long it would take a light ray to travel from one location directly to you.

    For the most distant galaxy in the Universe, that corresponds to a conformal time of 32 billion years. For the perceived location of the hot Big Bang, that corresponds to a conformal time of 46 billion years. This is true, even though only 400 million years passed between the Big Bang and the emission of light from that distant galaxy; the expansion of space was so rapid early on — and those differences propagate to today — so that a 14 billion year difference in conformal time corresponds to a “proper time” (which is what we typically assign the meaning of “time” to) difference of just 400 million years.

    5
    The history of the expanding Universe, including what it’s composed of at present. Image credit: ESA and the Planck collaboration (main), with modifications by E. Siegel; NASA / wikimedia commons user 老陳 (inset).

    If you’re talking about things here on Earth and nothing’s moving close to the speed of light or changing in its gravitational field very much, all of the different types of “distance” and “time” you can use are pretty much the same. But if you’re talking about the expanding Universe on a large, cosmic scale, proper distance and proper time might not be as useful (or interesting) to think about as comoving distance and conformal time. The next time you see a simulation of the Universe, and you note that it doesn’t appear to be expanding, be aware that’s because the simulation is using comoving distance, even though it may also be using proper time.


    Published on May 6, 2014
    The Illustris simulation is the most ambitious computer simulation of our Universe yet performed. The calculation tracks the expansion of the universe, the gravitational pull of matter onto itself, the motion of cosmic gas, as well as the formation of stars and black holes. These physical components and processes are all modeled starting from initial conditions resembling the very young universe 300,000 years after the Big Bang and until the present day, spanning over 13.8 billion years of cosmic evolution. The simulated volume contains tens of thousands of galaxies captured in high-detail, covering a wide range of masses, rates of star formation, shapes, sizes, and with properties that agree well with the galaxy population observed in the real universe. The simulations were run on supercomputers in France, Germany, and the US. The largest was run on 8,192 compute cores, and took 19 million CPU hours. A single state-of-the-art desktop computer would require more than 2000 years to perform this calculation.

    And when you hear talk of a super-distant object that’s assigned a distance of less than 14 billion light years, keep in mind that’s likely also a use of comoving distance. According to our conventional, proper rulers, it’s likely to be much farther than that!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 9:16 am on July 24, 2016 Permalink | Reply
    Tags: Astronomy, , The search for E.T., Xinhua News   

    From Xinhua News: “Feature: ET, when will we see you?” 

    1

    Xinhua News

    2016-07-19
    Lu Hui

    FIRST CONTACT

    However, with no clues of extraterrestrial life over the past five decades, questions are constantly asked as whether the search methods are appropriate.

    Even on Earth, land and sea host completely different forms of life. “It is highly possible that life on other planets is entirely different from that on Earth, and it might not be carbon-based,” says Jin Hairong, deputy curator of Beijing Planetarium.

    Liu Cixin, a Chinese science fiction writer and winner of the Hugo Award for his novel The Three Body Problem, points out the current method assumes that aliens also communicate in radio waves. “But if it’s a truly advanced civilization, it is possible to use other more advanced forms of communication, such as gravitational waves.”

    But Mao Shude believes many methods deserve a try: “Who knows what they are and how they think?

    “When we study the origin of life, we risk going down a blind alley if we only have one sample from Earth,” Mao says. “If we could find more samples in the universe, we could look at the puzzle more comprehensively and solve it more easily.”

    He gives an example in astronomy to explain the limitations of a single sample. “When scientists started to look for planets around Sun-like stars, they thought it must be difficult as their period might be as long as a year. However, the first such planet discovered outside our solar system takes only four days to orbit its host star – much faster than astronomers expected. At that time, some people doubted it, showing how the example of our solar system narrowed their thinking.”

    “If we really discover extraterrestrial life, I’d like to know how life spreads in the universe. Is it distributed uniformly in space, or clustered?” Mao wonders.

    However, the idea communicating with aliens comes with concerns.

    British astrophysicist Stephen Hawking has warned that communicating with aliens could be a threat to Earth: “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans.”

    The Three Body Problem by Liu Cixin depicted the universe as a jungle with every civilization as a hidden hunter. Those who are exposed will be eliminated.

    But Han Song, another leading Chinese science fiction writer, believes humans naturally want to connect, citing the Internet as proof.

    “I think aliens might think similarly. It is a biological instinct to connect with each other. Everyone wants to prove that they are not alone in the universe. Loneliness is intolerable to humans,” he says.

    He also points out that the contact will be driven by curiosity and real requirements. “Humans will ultimately go to space to find resources and expand their living area, so it will be hard to avoid aliens. Contact with them, especially those with more advanced intelligence, may help us leap forward in civilization.”

    Regardless of the theoretical debate, scientists have never wavered in the search.

    “I think we shall call out. As a matter of fact, we have been yelling for years, and our radios and televisions are broadcasting in space all the time,” Mao says, “Aren’t you curious what our counterparts would look like?

    “If they are inferior or equal to us in terms of civilization, we won’t be easily destroyed. If they are much more intelligent than us, they wouldn’t be so narrow-minded as to compete with us. Some worry they will come to rob us of our natural resources, but they likely have the power to transform the entire globe already. What’s the point of eliminating a much lower civilization?”

    Mao believes the result will be significant however it turns out. “If we find other life, it will undoubtedly be the most important scientific discovery in our history; if not, it shows that life on Earth is unique and we should respect life and cherish each other.

    “No matter the outcome, we shall never stop searching, and I hope to hear more voices and contributions from Chinese scientists.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 3:31 pm on July 22, 2016 Permalink | Reply
    Tags: Astronomy, , ,   

    From Spitzer: “Seeing the Milky Way’s Giant Black Hole with New Eyes” 

    NASA Spitzer Telescope

    Spitzer

    07.21.16

    1

    At the center of our Milky Way galaxy lies a cosmic beast called Sagittarius A*. This supermassive black hole packs about four million sun-masses into a volume roughly the size of our solar system.

    Sag A*  NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way
    Sag A* NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

    Recently, NASA’s Spitzer Space Telescope began exploring this exotic object. The telescope has observed a great many cosmic phenomena, from galaxy clusters to stellar nurseries during its 13-year career, but the black hole at the center of the Milky Way was never a part of the spacecraft designers’ plans.

    “A decade ago, no one would have taken you seriously if you had mentioned doing science like this with Spitzer,” said Varoujan Gorjian, a research astronomer at NASA’s Jet Propulsion Laboratory in Pasadena, California, who studies supermassive black holes. “We are very pleased that, because of its recent sensitivity boost, Spitzer can now serve as another arrow in our quiver when targeting the black hole at the heart of the Milky Way.”

    The sensitivity boost involves an observing mode originally intended to study exoplanets. It has given Spitzer the unexpected capability to monitor infrared flares emitted by this monster black hole, known as Sagittarius A* (pronounced “Sagittarius-A-star”). In a trial run in December 2013, Spitzer took an unprecedented 23-hour exposure. Though other telescopes have observed variability in the Sagittarius A* region, Spitzer was the first to observe it at the wavelength of 4.5 microns.

    Building on that success, a fresh round of observations has just been completed, with Spitzer observing Sagittarius A* simultaneously with NASA’s Chandra X-ray Observatory and the ground-based ALMA and SMA microwave observatories .

    NASA/Chandra Telescope
    NASA/Chandra Telescope

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at  Chajnantor plateau, at 5,000 metres
    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    SMA Submillimeter Array
    CfA SMA Submillimeter Array 8-element radio interferometer, Maunakea, Hawaii, USA

    Spitzer’s contributions will aid ongoing efforts in understanding why the Milky Way’s big black hole accretes, or gobbles up, material so calmly, compared to black holes in similar galaxies.

    “We can now use Spitzer to study the emission from the innermost regions of the accretion flow onto the black hole, near the event horizon,” said Joseph Hora, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, and the lead author of a 2014 study in The Astrophysical Journal reporting Spitzer’s Sagittarius A* observations. The observing project was led by Giovanni Fazio, also of CfA, with collaborators including the University of California, Los Angeles (UCLA) Galactic Center group led by Andrea Ghez.

    Eyeing a monster

    Located 26,000 light years away, Sagittarius A* is completely obscured by dust. Radio telescopes on Earth were the first to hone in on Sagittarius A* because radio waves freely pass through this dust, as well as our planet’s atmosphere. Other critical insights into Sagittarius A* have since come from the Chandra telescope, which scoops up dust-penetrating X-rays in space.

    The study of Sagittarius A* in infrared light has been knottier, but hugely successful. Although infrared light can also penetrate dust, only certain infrared wavelengths transmit through Earth’s atmosphere. Plus, these sorts of observations must contend with infrared light emitted by both the atmosphere and telescopic equipment itself.

    Despite these obstacles, starting in the mid-1990s, the 10-meter Keck Telescope in Hawaii tracked the orbits of stars (in infrared) whipping about an unseen, colossal mass emitting radio waves and X-rays at the center of our galaxy.

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

    Ground-based observations more recently captured an outburst of infrared light from Sagittarius A* itself, presumably as it wolfed down some matter that had strayed too close. Researchers desperately want more of these sorts of observations of Sagittarius A*’s variability. Comparing these data in additional wavelengths to radio waves and X-rays will help them construct a thorough model for just how Sagittarius A* interacts with its cosmic environment.

    Encouraged by the Keck results, Fazio and colleagues began considering using Spitzer’s infrared camera to investigate Sagittarius A*. The odds did not look good, though. Because Spitzer’s resolution cannot match that of the Keck telescope, the light from Sagittarius A* would be blended with the light of the many bright stars in the black hole’s central galactic vicinity. Tracking its variability therefore seemed out of Spitzer’s reach.

    Unleashing Spitzer’s full power

    Fortunately, NASA engineers in the early 2010s were already seeking to increase Spitzer’s stability and targeting — essentially, its ability to pick one spot in the universe and stare at it with minimal wobbling. The intended purpose of this upgrade was to let Spitzer point fixedly at a star and watch for miniscule dimming as an exoplanet crossed, or transited. Such transits reveal an exoplanet’s size, as well as clues about its atmospheric composition.

    Planet transit. NASA/Ames
    Planet transit. NASA/Ames

    To achieve the necessary stability for exoplanet studies, Spitzer’s engineers took three steps. First, in October 2010, they figured out an intermittent wobble within Spitzer stemmed from an internal heater switching on for an hour to warm a battery. The engineers managed to cut the wobble in half while preserving the battery by reducing the heater to 30-minute cycles. Next, in September 2011, the engineers repurposed a “Peak-Up” camera, used during Spitzer’s early, cryogenic mission. The Peak-Up Camera can precisely place infrared light onto an exact part of a pixel in Spitzer’s infrared camera. Engineers also mapped an individual pixel for its “sweet spot” that returns the most stable observations.

    With these refinements in place, Spitzer could theoretically look for tiny brightness changes due to Sagittarius A* without having to isolate the object from its nearby stars. Because those neighboring stars do not vary much in brightness, any variations seen in the combined light from that region can be chalked up to activity by Sagittarius A*. Remarkably, Spitzer can detect a change of a few tenths of a percent in infrared light emanating from the Milky Way’s core.

    “When Sagittarius A* flares, it produces an increase in light in the infrared range. If the flare is bright enough, then Spitzer sees that as light poured on top of what’s coming at the telescope already,” said Gorjian.

    With a view undisturbed by Earth’s atmosphere and the ability to monitor Sagittarius A* for more than 20 hours straight, Spitzer is an important extension of ground-based infrared observations of the black hole.

    “With Spitzer, you can monitor longer, and that’s critical in determining what is causing the variability in Sagittarius A*,” said Hora.

    Spitzer’s upcoming observations this summer in tandem with Chandra will gather infrared and X-ray emission to probe material very close to the Sagittarius A* black hole itself, helping test models of what causes the flare. It’s a whole new science objective for Spitzer, which continues to surprise and delight so many years after its launch in the summer of 2003.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory located on the campus of the California Institute of Technology and part of NASA’s Infrared Processing and Analysis Center.

    NASA image

    NASA JPL Icon

     
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