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  • richardmitnick 5:42 pm on September 11, 2019 Permalink | Reply
    Tags: "Giant Bubbles Spotted Rushing Out from Milky Way’s Center", , , , , Discover Magazine   

    From Discover Magazine: “Giant Bubbles Spotted Rushing Out from Milky Way’s Center” 

    DiscoverMag

    From Discover Magazine

    September 11, 2019
    Mara Johnson-Groh

    1
    The MeerKAT telescope is superimposed on a radio image of the Milky Way’s center. Radio bubbles extend from between the two nearest antennas to the upper right corner, with filaments running parallel to the bubbles. (Credit: South African Radio Astronomy Observatory/MeerKAT)

    The Milky Way is blowing bubbles. Two giant radio bubbles, extending out from the galaxy for over 1,400 light years, were just discovered in X-ray data. Astronomers think the bubbles started forming a few million years ago due to some type of cataclysmic event near the galaxy’s central supermassive black hole.

    The bubbles’ location also closely matches the range of over 100 narrow, magnetized filaments of radio emissions that stretch for tens of light years in length. First discovered 35 years ago, these filaments’ origins have remained a mystery, but the bubbles’ discovery may now provide an answer.

    “The filaments have been a mystery for a long time,” said Ian Heywood, astronomer at the University of Oxford and lead author on the new discovery. He says their results hint that the event that created the bubbles could have also produced high-energy charged particles that created the filaments.

    The symmetry of the bubbles billowing above and below the galaxy suggests they were formed by an extremely energetic explosion near the supermassive black hole at the center of the Milky Way. The most likely explanation is a flare up in the black hole’s activity as it gobbled up extra nearby material and burped out other particles and radiation. The bubbles could also have been created by an extreme burst in star formation that sent a shock wave across the galactic center. Or possibly, it was a combination of both events.

    The discovery, published on September 11 in the journal Nature, used the MeerKAT telescope, a radio telescope with 64 antennas, at the South African Radio Astronomy Observatory (SARAO) in South Africa.

    SKA SARAO Meerkat telescope(s), 90 km outside the small Northern Cape town of Carnarvon, SA

    Astronomers there were taking some of the first science images with the new telescope, looking at the radio emissions of the central galactic region, when they made the surprising discovery.

    “These enormous bubbles have until now been hidden by the glare of extremely bright radio emission from the center of the galaxy,” said Fernando Camilo of SARAO in Cape Town, and a co-author on the paper, in a press release.

    The astronomers were specifically looking at a type of radio emission called synchrotron radiation. This type or radiation is created when relativistic electrons — those traveling at nearly the speed of light — encounter strong magnetic fields, which imparts a particular signature on the light. Astronomers often use this type of radiation to pinpoint highly energetic regions in space.

    The new discovery isn’t the first giant bubble seen escaping from the Milky Way. In 2010, astronomers discovered two similar giant bubbles of gamma ray radiation blossoming above and below the galaxy, extending a combined length of 50,000 light-years. Now known as the Fermi bubbles, the origin of these balloons of radiation is still unexplained, but likely linked to the galaxy’s central supermassive black hole. The astronomers on this latest research think that the new radio bubbles they’ve discovered may have been caused by a smaller but similar event.

    “These fascinating radio bubbles provide a new window into understanding recent activity at the galactic center,” Andrew Fox, astronomer at the Space Telescope Science Institute, in Baltimore, Maryland, who was not involved with the new research, said via email. “Other observations taken across the electromagnetic spectrum have revealed evidence for a burst of activity several million years ago, and these new observations provide another clue. Taken together, the results show that the Milky Way blows bubbles on different scales.”

    By connecting the origin location of the bubbles to the central black hole region of the galaxy, astronomers are starting to learn more about the processes in this dynamic region. It may also help them learn about events unfolding in other galaxies. Evidence for giant gamma ray bubbles, like the Fermi bubbles, have also been seen outside the Milky Way in its nearest neighbor, the Andromeda galaxy.

    See the full article here .

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  • richardmitnick 2:45 pm on September 5, 2019 Permalink | Reply
    Tags: , Astronomers have witnessed a rare event: the birth of massive stars 2.73 million light-years away in the Triangulum Galaxy (Messier 33)., , , , , Discover Magazine   

    From Discover Magazine: “Massive Clouds Colliding in Space Could be Birthing Huge Stars” 

    DiscoverMag

    From Discover Magazine

    September 4, 2019
    Mara Johnson-Groh

    1
    This star-forming region is one of many in M33 that’s birthing new stars from massive clouds of dust and gas. (Credit: ESA/Hubble and NASA)

    Astronomers have witnessed a rare event: the birth of massive stars 2.73 million light-years away in the Triangulum Galaxy (Messier 33). At the center of two giant colliding gas clouds are some 10 young stars with masses tens of times that of the Sun. Their discovery indicates that such cloud-cloud collisions are a main pathway to creating giant stars in the nearby universe, which could help answer the long-standing question of how big stars form.

    Cosmic Collision

    High-mass stars — those at least eight times the mass of the Sun — are the celebrities of galaxies. Although they’re relatively rare, they produce most of a galaxy’s visible light. They also strongly influence the environment around them through the radiation they release during their lifetimes and the heavy elements they scatter upon their explosive deaths. Their formation, however, remains debated.

    New research submitted to the Publications of the Astronomical Society of Japan uses the Atacama Large Millimeter/submillimeter Array to study two giant clouds in Messier 33.

    The Triangulum Galaxy, Messier 33, via The VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile. This beautifully detailed image of the galaxy Messier 33. This nearby spiral, the second closest large galaxy to our own galaxy, the Milky Way, is packed with bright star clusters, and clouds of gas and dust. This picture is amongst the most detailed wide-field views of this object ever taken and shows the many glowing red gas clouds in the spiral arms with particular clarity.

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

    The clouds are 190,000 and 240,000 times more massive than the Sun, respectively, and contain molecules such as molecular hydrogen and carbon dioxide. The two clouds collided at supersonic speeds around 500,000 years ago. (Here, “supersonic” means faster than the speed of sound in the clouds’ environment. In dense regions of space, the speed of sound can be a few miles per second or more; on Earth at sea level, the speed of sound is just over 1,100 feet [340 meters] per second).

    The researchers looked specifically for signatures of carbon monoxide, which can be easily seen in radio observations, to chart the denser filamentary structures in the clouds. They also looked for a specific signature of hydrogen that indicates the presence of massive stars. At the center of the collision, they found 10 objects that appear to be young, massive stars. That makes it highly likely that the collision caused changes in the clouds’ gas that made it collapse to form the stars.

    Go Big

    Massive stars, which are harder to form than smaller stars, aren’t seen everywhere low-mass star formation occurs. So, the question is: Why not?

    Astronomers think massive star formation must require some sort of additional triggering mechanism, such as cloud-cloud collisions, strong winds blown off active stars, expanding gas heated by other massive stars or shockwaves sent out by exploding supernovae. But until recently, there was scant observational evidence supporting cloud-cloud collisions. This study, however, now bolsters that option as a way to form massive stars.

    “We have a number of different ideas of how massive star formation is initiated,” says Harold Yorke, an astronomer at the NASA Ames Research Center in Mountain View, California. “We know that molecular clouds are turbulent, so you would suspect massive stars could form in those conditions.”

    “Recently, there has been a lot of observational, theoretical evidence of the cloud-to-cloud collision as the formation mechanism of massive stars,” says Toshikazu Onishi at the Osaka Prefecture University in Osaka, Japan, and co-author on the new study. “This paper provides the first observational evidence of [cloud-to-cloud collision] for massive star formation in the [Triangulum Galaxy].”

    See the full article here .

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  • richardmitnick 9:07 am on August 29, 2019 Permalink | Reply
    Tags: "How Galaxies Live Breathe and Die", , , , , Discover Magazine, Gas called the intergalactic medium fills the space between galaxies   

    From Discover Magazine: “How Galaxies Live, Breathe and Die” 

    DiscoverMag

    From Discover Magazine

    August 28, 2019
    Ann Finkbeiner

    1
    Gas glows white, lit by a stellar nursery, in this view of a region within the Large Magellanic Cloud, the Milky Way’s largest satellite galaxy. Most cosmic gas is not so visible and lies outside of galaxies — in halos surrounding galaxies and in the vast spaces in between. Yet the gas determines galactic life cycles. (Credit: ESA/Hubble & NASA)

    NASA/ESA Hubble Telescope

    Most of what astronomers know about the universe comes from what they can see. So their ideas have been prejudiced toward stars and galaxies, which are bright. But most of the regular matter in the universe is in the form of gas, which is dim. Gas called the intergalactic medium fills the space between galaxies; the gas of the circumgalactic medium surrounds galaxies more closely. The gas in both places regulates the birth, life and death of the galaxies, and holds a detailed history of the universe. Only lately have astronomers been able to detect it.

    Shortly after its birth, the universe was filled with gas, mostly hydrogen. Over time, here and there, gravity pulled the gas into clouds which turned into galaxies and in which stars ignited. Stars shine by thermonuclear burning of the gas; of those that die in explosions, some blow the gas back out of the galaxies. Out in intergalactic space, the gas cools and gets denser, until gravity pulls it back into the galaxy where new stars form. The process repeats: Gravity condenses gas into galaxies and stars, stars blow up and kick the gas out, gravity cycles the gas back in and makes new stars.

    In time, any given galaxy begins to run out of recyclable gas. Without gas, it can’t form new stars; the old stars live out their lives and die, and eventually the galaxy dies too. Galaxies sit in a bath of gas, the medium from which they were born and which fuels them. The galaxies breathe gas in and out, and their stars burn until their gas is gone.

    3
    Within a galaxy, relatively dense gases fuel star birth. Just outside, the gases thin in the circumgalactic medium, and become even less dense farther out into the intergalactic medium. Astronomers were unable to study the gases between galaxies until the 1960s, when they began to gather light from distant quasars, filtered through the gas, for spectral analysis. In the last decade they have turned their focus to the circumgalactic medium. (Credit: J Tumlinson et al./AR Astronomy and Astrophysics 2017;ESO/M. Kornmesser)

    This is theory. The problem with verifying it has been that astronomers’ instruments could barely detect signs of gas, let alone map its comings and goings. With more sensitive instruments and dogged surveys, astronomers now know more. Convincing evidence suggests that the intergalactic medium is rich in gas, which fills the universe and seeds galaxies. Less-convincing and sometimes puzzling evidence in the circumgalactic medium shows that galaxies live by recycling gas into and out of stars. And astronomers have only preliminary evidence supporting arguments for how galaxies might run out of gas, stop forming stars and die.

    Connecting Gas and Galaxies

    Part of the problem has been that, though galaxies and gas are intrinsically related, the astronomers studying one didn’t talk to those looking at the other. Historically, astronomers studying galaxies, which were easier to see, were in a separate community from those studying gas, which was harder. The arrangers of scientific meetings, says Charles Steidel of the California Institute of Technology, who studied gas, would “put us on the last day when the galaxy people went home, before we could tell them about the rest of the universe.”

    In 1989, Steidel used a technique (pioneered by his mentor at Caltech, Wallace Sargent) that allowed gas to be observed at distances at which galaxies couldn’t be seen. He collected enough evidence to argue that he’d found, as had others, gas between galaxies, out in the intergalactic medium. He also found evidence that clouds of gas in the vicinity of those otherwise invisible galaxies showed signs of having once been inside the galaxies, further linking the gas between galaxies with the galaxies themselves. When he wrote his doctoral thesis, he carefully put both “intergalactic medium” and “galaxies” in the title. “Once I finished my degree,” he says, “my goal has been to connect galaxies with gas.”

    By 2013 when Steidel’s student Gwen Rudie, now at the Carnegie Observatories in Pasadena, California, wrote her own doctoral thesis, observational techniques had improved enough that at the same distances as Steidel’s gas clouds, she could find the previously invisible galaxies.

    The galaxies were young, forming stars furiously and using gas fast. She found that the gas immediately around these galaxies, in the circumgalactic medium, was a thousand times denser than the average of gas in the intergalactic medium; like others, she also found signs of gas flowing out of galaxies.

    By now, gas and galaxies were inextricably connected, and the study of galaxies now commonly includes the study of the gas around and between them, out of which they’re created and by which they live.

    The Intergalactic Medium: Making Galaxies Out of Gas

    Galaxies shine, gas barely glows. Gas becomes visible when it sits in front of something bright — most notably quasars, the cores of extremely distant and extraordinarily brilliant galaxies — and absorbs its light. To astronomers analyzing the light that reaches Earth, the gas shows up as dark lines in the spectra of the quasars’ light. The pattern of the dark absorption lines held a surprising amount of information, including the distance (and so the age) of the gas: It was visible at distances vastly greater, and therefore at times vastly earlier, than normal galaxies then were. Because spectra also reveal the gas’s chemical components, density, temperature, and motion toward or away from Earth, for the last 50 years quasar absorption line studies have remained one of the best ways to study cosmic gas.

    Most noticeable in the quasars’ spectra were crowds of dark absorption lines at distances reaching back to the early universe and packed so closely together that they looked, says Charles Danforth, then at the University of Colorado, Boulder, “like tree trunks, boom, boom, boom.”

    The trees were called the Lyman alpha forest — the gas absorbing the light was hydrogen in a specific transition between states called Lyman alpha — and showed a young universe full of airy hydrogen clouds.

    By the mid-1990s, writes Matthew McQuinn of the University of Washington in the 2016 Annual Review of Astronomy and Astrophysics, astronomers had come to understand the Lyman alpha forest as gas between the earliest galaxies — the intergalactic medium.

    The intergalactic medium has been around from early on: The Lyman alpha forest begins when the universe is around a billion years old. “Run the Lyman alpha forest forward” in simulations, says McQuinn, “and it looks like today’s intergalactic medium.”

    5
    Gas clouds show up as dark absorption lines in the spectrum of a quasar’s light, which can be analyzed to better understand the distance and nature of the gas. At high resolutions, the absorption lines show up at a range of wavelengths as distinct “trees” in what was termed the Lyman alpha forest. (Credit: M. Rauch/AR Astronomy and Astrophysics 1998)

    The intergalactic medium of the young universe accounted for 98 percent of its regular matter: “People usually think of the universe as the stuff that lights up,” says Molly Peeples of the Space Telescope Science Institute (STScI) in Baltimore, but the quasar absorption line studies show that in the gas outside the stars and galaxies are “most of the atoms of the universe.”

    Even in the young universe, however, the gas is not uniform. Mostly it’s cold, between 100 and 1,000 kelvins. But scattered patches of the intergalactic medium are hot, reaching 20,000 kelvins or more — evidence of stars turning on and galaxies forming.

    The intergalactic medium is also not pure hydrogen: It is salted sparingly with elements heavier than hydrogen, created when stars blow up and die. The intergalactic medium is “clumpy,” says Michael Shull of the University of Colorado, Boulder, in places where gravity has pulled slightly denser gas into even denser clumps.

    Despite the pockets of hot gas, the intergalactic medium is generally cooling, says Anson D’Aloisio at the University of California, Riverside, “because the universe is expanding.” With time, on average, the gas has also thinned out: “As you go toward today,” says Jason Prochaska at the University of California, Santa Cruz, “you can see by eyeball in the spectra, you can see the forest thins.”

    This ancient, clumpy, cooling, rarefied intergalactic medium, says Prochaska, “is a pretty well understood entity” that holds a convincing picture of when and from what galaxies emerged.

    The Circumgalactic Medium: Regulating Galaxies’ Lives

    In the quasar spectra data, the Lyman alpha forest’s hydrogen clouds were just the most rarefied and chemically the purest. Scientists found other clouds, too, that were denser and sprinkled with heavier elements that astronomers call metals — such as carbon, oxygen, silicon, iron and magnesium. Astronomers reasoned that because these metals are made only by stars, and because all stars are in galaxies, then these metal-rich, denser clouds must be somehow associated with galaxies. They classified the types of clouds into a little zoo: Denser, more metallic clouds were called Lyman limit systems, and the densest clouds with higher metallicities were called damped Lyman alpha systems. The systems looked like a progression — the Lyman alpha forest through the Lyman limit to the damped Lyman alpha systems — of gas closer to and more intimately associated with galaxies.

    Confirmation of these ideas had to wait for more sensitive instruments and for the beginning, at least 10 years ago, of painstaking and systematic surveys still using quasar absorption lines. Researchers showed (to no one’s surprise) that, in the maturing universe, if the Lyman alpha forest gas was the intergalactic medium, the Lyman limit and damped Lyman alpha systems were the circumgalactic.

    One survey, the Keck Baryonic Structure Survey (KBSS), grew out of Steidel and company’s mission of connecting gas with galaxies. The KBSS team chose the 15 brightest quasars and found in their absorption lines evidence of 5,000 galaxies. Within those, the team looked for gas around galaxies from 10 billion to 11 billion years ago. A few billion years after the universe began, this was a time when stars were forming furiously — “cosmic noon,” astronomers call it.

    Another large survey, using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, was called COS-Halos. COS-Halos was essentially KBSS for nearby galaxies; it began with 44 local galaxies — both active ones still forming stars and quiescent ones — whose surrounding gas was pierced by the sight lines to quasars.

    Together the surveys characterized wholesale the density, temperature, and metallicity of galaxies’ circumgalactic media. The circumgalactic gas was up to 1,000 times denser than gas in the intergalactic medium, and ranged in temperature from cooler than the intergalactic medium to much, much hotter, from 10,000 to 1 million kelvins. And the closer to the host galaxy, the more metallic the gas.

    There’s no agreement on where the intergalactic medium ends and the circumgalactic medium begins. “It’s nomenclature,” Peeples says.

    Her colleague Jason Tumlinson, also of STScI, concurs: “The arguments about the boundary are all human. Nature has stuff crossing any boundary you can set. What was once in the intergalactic medium will be in the circumgalactic medium, and what’s in the circumgalactic medium will make it back out into the intergalactic medium.”

    That is, though the gas in the intergalactic and circumgalactic media changes with time and proximity to a galaxy, it’s still all the same gas. And in flowing between the two, somehow or other, it keeps galaxies alive. “What’s not understood,” Prochaska says, “is the astrophysics of how the intergalactic medium fuels the circumgalactic medium and the galaxies.”

    One possible scenario of this fueling flow, called galactic recycling, is simple: Gas falls into galaxies and fuels stars, then is blown back out, then falls back in to fuel more stars. Gathering evidence to back the scenario is painstaking and so far inconclusive. Infalling streams of gas are hard to see — they come into galaxies as narrow rivers — though some observers think they’ve seen them.

    But, says Crystal Martin of the University of California, Santa Barbara, “the inflow signal often overlaps with the signal from the galaxy itself,” that is, the infall can be hard to see against the galaxy.

    On the other hand, observers commonly detect outflows, gas heavy in metals flowing in wide swaths out of the galaxies. “Essentially every spectrum we take of a star-forming galaxy has evidence of winds being driven out of the galaxy,” says Rudie.

    No one knows for sure what could be driving the outflows — maybe supernova explosions, or the massive jets shot out of the chaos around black holes, or the winds from hot stars. Nor does anyone know whether the gas is recycling locally between the galaxy and the circumgalactic medium, or whether it circulates more widely with the intergalactic medium; evidence exists for both scenarios.

    What is not a scenario but shown by hard evidence is that at some point, a galaxy runs out of fuel and dies — a process called “quenching.” Astronomers have known for nearly two decades, when the Sloan Digital Sky Survey classified galaxies into two general categories, that galaxies with lots of gas and actively forming stars are blue, and those with little gas and dying stars are red. Most galaxies are either blue or red, with almost nothing in between.

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    If galaxies are either living or dying, and if they die by running out of gas to make new stars, it means that however galaxies die, they run out of gas fast. How that happens remains unclear. Finding evidence for recycling has proved difficult, and finding evidence for a quenching mechanism is so far impossible. The circumgalactic medium should hold that evidence, but in fact observations have only made the problem more intractable.

    COS-Halos found gas around red, dead galaxies that is bound gravitationally to the galaxies and at 10,000 to 100,000 kelvins — which should be cool enough to fall into them. But it doesn’t. Scientists have proposed that something somehow shuts off the infalling gas, or something else heats it up so it’s too feisty to fall in.

    Whatever the answer is, it’s going to be found in the circumgalactic medium. Jessica Werk, at the University of Washington and on the COS-Halos team, is putting together a survey that will increase the number of red galaxies observed by a factor of 10. “A lot of the questions,” she says, “come down to what happens to galaxies that stop star formation and how that plays out in the circumgalactic medium.”

    Re-creating Galactic Birth

    So far, what observers have found doesn’t add up to a coherent story of how galaxies are born, live and die. Stories are theory’s job, and in astronomy, theory often comes in the form of computer simulations. Theorists put together gravity, hydrodynamics, regular matter that shines and dark matter that doesn’t, and let the simulation re-create the evolution of galaxies. Then they compare the simulated galaxies with real ones: shape, rates of star formation, assumed method of quenching, rates of outflows, evidence of infalls, temperatures, density and metallicity. At present, the simulations run on two scales, the large intergalactic and smaller circumgalactic; no one simulation can cover both.

    6
    Galaxies are not distributed evenly throughout the universe, but their distribution can’t be understood without also understanding the role of gas. Here, a still from a simulation shows one of the largest structures identified in the universe, a supercluster of galaxies, voids and galactic filaments called the BOSS Great Wall. (Credit: Max Planck Institute for Astrophysics/Wikimedia Commons)

    Max Planck Institute for Astrophysics

    The simulations help astronomers interpret their current observations, or suggest new ones. For instance, in theorist Molly Peeples’ simulation, metals show up unexpectedly, far outside the circumgalactic medium, so observer Charles Danforth can be a little more confident of his observations of metals out in the intergalactic medium.

    In simulations, “infalling cold gas is unambiguous,” says Crystal Martin, but it’s not obvious to observers like her. So her group looks specifically for cold, low-pressure gas in the circumgalactic medium that moves slowly enough and with enough drag that it should spiral in to the galaxy. Most simulations show the intergalactic medium containing pockets of gas at warm-to-hot temperatures, called WHIM, that no observer has yet convincingly seen. “I love simulators, they’re the best,” says Werk, “but I’m not sure their universe is the real one.”

    Real or not, the simulations (several of them, done by separate groups) are the clearest visualizations of how gas might have made galaxies, and they’re gorgeous. Here’s what they look like: Begin in a 200 million-year-old universe, before galaxies and stars. The gas has been cooling but is still very hot, around 100,000 kelvins; it looks like an uneven fog, clearing in places, thickening in others. Eventually, in the thickest places, stars form.

    When the universe reaches an age of 500 million years, the cooling, condensing gas gravitationally falls in on itself into sheets; then the sheets narrow into splotchy filaments. The clearings in the spaces between grow larger and blanker. At around a billion years, the filaments intersect with other filaments and a network grows. At 1.5 billion years, gas runs down the filaments and at some nodes puddles up and forms into galaxies, huge and white-hot, heated to between 10 million and 100 million kelvins by shock waves and explosions from dying stars.

    By 2 billion years, supermassive black holes at the galaxies’ centers and more exploding stars send shocks flooding into the intergalactic medium. At 3.5 billion years, within the spreading shock fronts are little knots of galaxies. The galaxies collect the intergalactic gas into their own circumgalactic media, and enrich it with metals splashed into it by exploding supernovae.

    By 7 billion years, the intergalactic medium has noticeably thinned: Its fraction of all matter has fallen from 95 percent to 80 percent. At 10 billion years, the galaxies and circumgalactic media are more metallic, the filaments are ropier and still hot, the clearings are larger, blacker and cold.

    And now, at present, 13.8 billion years after the universe began, only 60 percent of the gas remains in the intergalactic medium; the rest is in the circumgalactic media and in galaxies. The galaxies are strung around voids, looking like the lit-up interstates and cities of a dark fly-over country.

    Stars have shot metals all over the place, both out into the circumgalactic medium and within the galaxy, ready to be reprocessed into other stars. New stars coalesce out of the metallic gas along with dust. Around them form protoplanetary disks, which here and there condense into planets, on one of which is us. “Every atom in your body,” says Werk, “cycled through the intergalactic medium and the circumgalactic medium.” So this history is a story, she says, not only about galaxies but also “about our cosmic origins.”

    See the full article here .

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  • richardmitnick 12:23 pm on July 31, 2019 Permalink | Reply
    Tags: "The Hidden Volcanoes of Central Oregon", , Discover Magazine, , , Mystery volcano: the Tumalo Volcanic Center,   

    From Discover Magazine: “The Hidden Volcanoes of Central Oregon” 

    DiscoverMag

    From Discover Magazine

    July 31, 2019
    Erik Klemetti

    1
    A river channel filled with cliff swallow holes carved into the Desert Spring Tuff. Image by Erik Klemetti

    Earlier this month, I spent a little over a week exploring one of the biggest mysteries in then Cascade Range. These volcanoes span from Northern California into British Columbia and host such well-known peaks as Mount St. Helens, Hood and Shasta. Yet, some of the largest eruptions over the past million years in the Cascades may have come from volcanoes that are totally hidden from view today. One of those mystery volcanoes is the Tumalo Volcanic Center.

    I’ve been fascinated by the TVC since I was in graduate school. We would take field trips from Oregon State University to visit the area around Bend in central Oregon. Now, if you’ve never been to Bend, you’re missing a true volcanic wonderland. The city is built on layer after layer of volcanic rock that go back millions of years.

    Some of the volcanic features are very young (geologically-speaking), having formed in the past few thousand years. This includes basaltic and rhyolite lava from from Newberry, steep cinder cones like Mt. Bachelor, sticky rhyolite domes like the Devil’s Hills along with the ash and pumice from the TVC.

    This project in the TVC is part a National Science Foundation grant that was awarded to me and Adam Kent (Oregon State University) to pick apart, date and unravel the processes that formed the massive explosive eruptions (and smaller stuff). We looked at a lot of volcanic material over our field work, but right now, I’m going to focus on some cool stuff we saw in the Oregon State University Cascades campus pumice quarry.

    2
    An annotated image of one of the walls in the OSU-C quarry. The three main TVC units seen are the Desert Spring Tuff, Bend Pumice and Tumalo Tuff. The only one missing is the Shevlin Park Tuff. Image and annotation: Erik Klemetti

    The wall pictured above captures three of the “big 4” eruption deposits from the TVC. The oldest we know of is the Desert Spring Tuff (at the bottom). It is pretty tough because it has become partially welded, when the volcanic glass remelts after the ash and debris lands on the ground.

    Above that (thus younger) are the Bend Pumice and Tumalo Tuff. These two might be consecutive eruptions — a one-two punch of a big pumice fall followed by pyroclastic flows. Image a tall ash plume from a massive explosive eruption that rained pumice across the landscape and then collapse, sending searing hot flows of pumice, ash and debris away from the volcano.

    Both units are pretty loose unlike the Desert Spring Tuff. You can walk up to the Bend Pumice and pluck individual pumice chunks right out. You can see a close up of some of the pumice from a smaller pumice fall below the Bend Pumice (also seen on the image above). These might be little blasts that preceded the Bend Pumice by days, weeks or more. In the Bend Pumice, the pumice changes sizes as well and this recorded how the force of the eruption might have changed over the duration of the eruption.

    3
    Layers of pumice in the Bend Pumice, each potentially marking a pulse of the main eruption or blasts that happened before the main event. Image by Erik Klemetti.

    A few details to note: You might notice the top of the Tumalo Tuff (above) looks less like a pile of rubble. That’s because it may have been altered by vapor percolating through the ash and pumice, “gluing” it together into a wall. Also, at the bottom of the Tumalo Tuff is a lag deposit made of larger chunks of pumice that may have been deposited as a pyroclastic flow slowed down.

    The pumice erupted from the TVC actually did have some real monetary value. Pumice was and is mined from various locations around Bend for decades as an abrasive and some of the rocks that might be part of the TVC were also used a good, local building stone. One of these quarries is now part of the OSU-C campus, but as the school grows, they need more land, so the quarry is going to be mostly filled to make way for new structures.

    This is just a taste of the Tumalo Volcano Center and over the next few years, we hope to find out a lot more about this hidden volcano in Central Oregon. Although the likelihood of it reawakening is very small, it is never a bad idea to understand the volcanic history of a region growing as fast as Deschutes County and Bend.

    See the full article here .

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  • richardmitnick 10:45 am on July 13, 2019 Permalink | Reply
    Tags: "What Are Intermediate-Mass Black Holes?", , , , , , , Discover Magazine   

    From Discover Magazine: “What Are Intermediate-Mass Black Holes?” 

    DiscoverMag

    From Discover Magazine

    July 12, 2019
    Jake Parks

    1
    The hunt for intermediate-mass black holes (IMBH) has picked up over recent years, and there are now dozens of promising candidates. This artist’s concept depicts a 2,200 solar mass IMBH suspected to reside in the heart of the globular cluster 47 Tucanae, located some 15,000 light-years from Earth. (Credit: B. Kiziltan/T. Karacan)

    Black holes have long served as fodder for science fiction — and for good reason. These unimaginably dense objects contain so much matter trapped in such a small volume that their gravity prevents even light from escaping their surfaces.

    Although the first prediction of a black hole was made nearly 250 years ago by the English philosopher and clergyman John Michell, the first black hole candidate, Cygnus X-1, wasn’t discovered until 1971. Since then, astronomers have tirelessly chipped away at countless questions related to these once-mythical beasts. But one of the most basic and enduring questions remains: Do they come in all sizes?

    Small and Large, or Small to large?

    Over the past few decades, astronomers have compiled loads of evidence for the existence of black holes at both ends of the mass spectrum. Researchers have uncovered small black holes that weigh just a few to 100 times the mass of the sun, as well as supermassive black holes that can reach billions of times the mass of their star-sized brethren.

    Stellar-mass black holes are thought to form when a relatively massive star dies in spectacular fashion. As the exhausted star burns through its final traces of fuel, its immense gravity causes it to collapse in on itself. If the collapsing star isn’t too big, the infalling material rebounds off the star’s dense core. This causes a supernova explosion, often leaving behind a tiny white dwarf or neutron star. But if the surviving remnant is greater than about three solar masses, not even tightly packed neutrons can prevent the city-sized core from continuing to collapse into a stellar-mass black hole.

    On the other hand, there’s another class of black holes known as supermassive black holes, which serve as the central gravitational anchors of most, if not all, large galaxies. Though supermassive black holes are anywhere from millions to billions of times the mass of the sun, they pack all that matter into a region roughly the size of a single star. There are many lines of evidence that indicate these cosmic behemoths are common throughout the universe, but exactly how and when they formed still remains a mystery.

    But what about the in-betweeners? Shouldn’t there should be a class of mid-sized black holes that split the difference between stellar-mass and supermassive black holes? These cosmic middleweights, which would range from about 100 to 1 million solar masses — though the specific range varies depending on who you ask — are referred to as intermediate-mass black holes (IMBHs). And although astronomers have found several compelling IMBH candidates spread throughout the universe, the jury is still out on whether they truly exist. However, the evidence is beginning to pile up.

    2
    Located roughly 290 million light-years from Earth, the edge-on spiral galaxy ESO 243-49 is thought to harbor one of the first strong candidates for an intermediate-mass black hole, HLX-1. The black hole (circled) was found near the edge of the galaxy within a cluster of young stars. (Credit: NASA/ESA/S. Farrell (University of Sydney and University of Leicester))

    NASA/ESA Hubble Telescope

    Is Proof Out There?

    Though conclusive proof of IMBHs remains elusive, over the past few decades, there have been a number of studies that have uncovered intriguing evidence hinting at the existence of these not-so-big, not-so-small black holes.

    For example, in 2003, researchers used the ESA’s XMM-Newton space observatory to identify two strong, distinct X-rays sources in the nearby starburst galaxy NGC 1313. Because black holes tend to ferociously gobble up material that gets too close and belch out high-energy radiation, they are some of the strongest known emitters of X-rays. And by pinpointing NGC 1313’s X-ray sources and studying how they periodically flash, in 2015, researchers were able to constrain the mass of one of the galaxy’s suspected black holes, known as NGC 1313 X-1 [The Astrophysical Journal Letters]. They calculated it’s about 5,000 times the mass of the Sun, give or take about 1,000 solar masses, which would put it firmly in the mass range of an intermediate-mass black hole.

    Likewise, in 2009, researchers uncovered even stronger evidence for the existence of a medium-sized black hole [Nature] . Located some 290 million light-years away near the edge of the galaxy ESO 243-49, the team observed an incredibly bright X-ray source called HLX-1 (Hyper-Luminous X-ray source 1) [Astronomy] that did not have an optical counterpart. This suggests the object is not simply a star or background galaxy. Additionally, the researchers found HLX-1’s X-ray signature varied with time, suggesting a black hole is brightening every time a nearby star makes a close approach, feeding gas to the black hole and causing brief outbursts of X-rays that then slowly fade away. Based on the brightness of the observed flashes, the researchers calculated a minimum mass of the black hole of about 500 times the mass of the Sun, though some estimates put its weight closer to 20,000 solar masses [The Astrophysical Letters].

    “Such a detection is essential,” said lead author Sean Farrell of the University of Leicester after the discovery [ScienceDaily]. “While it is already known that stellar-mass black holes are the remnants of massive stars, the formation mechanisms of supermassive black holes are still unknown.” Farrell went on to explain that “the identification of HLX-1 is therefore an important step towards a better understanding of the formation of the supermassive black holes that exist at the center of the Milky Way and other galaxies.

    More recently, astronomers have started to uncover strong evidence of wandering intermediate-mass black holes lurking near the heart of the Milky Way. For example, in January 2019, astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to trace streams of gas orbiting an invisible object, thought to be an IMBH [The Astrophysical Journal Letters] , with an apparent mass of about 32,000 times the mass of the Sun.

    Located a scant 23 light-years from the Milky Way’s supermassive black hole, Sagittarius A*, the discovery suggests the newfound IMBH could merge with the roughly 4-million-solar-mass Sagittarius A* in the not-too-distant future. To help bolster the case for IMBHs wandering through the Milky Way, the researchers hope to use other oddly-orbiting gas clouds to probe our galaxy for more mid-sized black holes tucked away in gas-dominated regions.

    3
    So far, the LIGO and Virgo gravitational-wave detectors have teamed up to uncover 20 stellar-mass black holes in the process of merging to form black holes ranging from about 20 to 80 solar masses. Although LIGO-Virgo has not uncovered any IMBHs (over 100 solar masses), researchers are optimistic about spotting them in the future. (Credit: LIGO-Virgo/Frank Elavsky/Northwestern)

    The Hunt for IMBHs

    Moving forward, researchers will rely on a variety of methods to uncover a slew of more mid-sized black holes. By doing so, they not only hope to prove that IMBHs truly exist, but more importantly, they want to use IMBHs to help piece together how large black holes grow and evolve over time.

    Fortunately, astronomers are now in a prime position to do just that. Thanks to the recent successes of the LIGO-Virgo gravitational-wave project — which has identified 20 stellar-mass black holes [MPIGP] by probing the universe for gravitational waves that are produced when black holes merge — researchers have a new method for searching for small to mid-sized black holes.

    Although the LIGO-Virgo collaboration has yet to uncover gravitational waves from mergers between black holes larger than about 40 solar masses, according to the LIGO website [https://www.ligo.org/science/Publication-O1O2IMBH/index.php], “in [the] future, with improvement in [the] sensitivity of gravitational wave detector[s], we will have a better understanding of the frequency of IMBH mergers. The third observing run has started collecting data from April 1, 2019, and gravitational-wave scientists are very hopeful to observe these elusive sources soon!”

    So stay tuned, because over the next few years, we may find definitive proof of the missing link between small and super-sized black holes. And if we do, it will finally put this cosmic conundrum to rest once and for all. Only then will we be able to stop debating the existence of IMBHs, and instead focus on unraveling their origin stories, as well as those of supermassive black holes.

    See the full article here .

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  • richardmitnick 9:12 am on July 12, 2019 Permalink | Reply
    Tags: , , , , Discover Magazine, ,   

    From Discover Magazine: “Japanese Asteroid Mission Touches Down on Ryugu, Collects Sample” 

    DiscoverMag

    July 11, 2019
    Korey Haynes

    1
    Hayabusa2 has successfully collected its second sample from the surface of asteroid Ryugu. (Credit: Illustration by Akihiro Ikeshita (C), JAXA)

    Hayabusa2’s encounters with asteroid Ryugu have been delightfully action-packed. In February, the Japanese spacecraft collected its first sample by swooping close and firing a bullet into the asteroid’s surface to stir up material it then snagged with a horn-shaped collector. Then, in April, it shot a much larger impactor into Ryugu, creating an artificial crater so it could examine the material churned up from beneath the surface. On Thursday, Hayabusa2 returned to the scene of the crime and fired a second bullet, collecting material from its newly made crater.

    Astronomers hadn’t been certain they’d be able to find a safe spot to touch down in the new crater, and spent the last few months scouting the area and analyzing the images Hayabusa2 sent back. The successful collection of this second sample means the mission has accomplished all its major goals, and can head back to Earth later this year on a positive note.

    Hayabusa2 is just one spacecraft currently surveying an asteroid with the goal of bringing back pieces of its rocky partner. A NASA mission called OSIRIS-REx is similarly investigating the asteroid Bennu.

    NASA OSIRIS-REx Spacecraft

    Astronomers often find fragments of asteroids in the form of meteorites that fall to Earth, but obtaining samples directly from space gives them a clearer picture of where and how these space rocks formed and how they’ve spent the past few billion years of solar system history.

    The mission team behind Hayabusa2 has had to work hard to get their spacecraft to finish the job it started when it launched back in 2014. Its asteroid, Ryugu, proved more jagged and rocky than mission planners had anticipated. The spacecraft must descend all the way to the surface to collect its samples, and it’s not built to handle rough or uneven terrain. The engineering team found that to guarantee a safe touchdown, they had to dramatically increase the accuracy of their touchdown targeting.

    That took longer than they’d planned, and the craft has a schedule to keep. Its mission timeline has it leaving Ryugu in December so it can bring its samples back to Earth for study. It’s also a race against time, as Ryugu’s surface is about to become too warm for Hayabusa2 to handle, meaning it couldn’t just extend its stay indefinitely.

    But the engineering team persevered, and Hayabusa2 has now successfully completed all its main mission objectives. It still has a few months of work left to do in orbit around Ryugu, taking pictures and measurements from afar, before it can return to Earth with its prized samples.

    See the full article here .

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  • richardmitnick 11:49 am on July 10, 2019 Permalink | Reply
    Tags: Chandrayaan-2 lunar mission, Discover Magazine, ISRO-Indian Space Research Organisation, Studying the moon’s little explored south pole   

    From Discover Magazine: “India Set to Launch Moon Rover and Orbiter” 

    DiscoverMag

    From Discover Magazine

    July 9, 2019
    Hailey Rose McLaughlin

    1
    (Credit: ISRO)

    India is expected to launch their second lunar mission, Chandrayaan-2 on July 14. The launch will take up an orbiter, a lander, and a rover, dubbed Pragyan, all designed to study the moon’s little explored south pole.

    Using the Indian Space Research Organization’s (ISRO) most powerful rocket, Chandrayaan-2 will reach Earth’s orbit, where it’ll spend about 16 days before it heads over to the moon.

    After a short time in lunar orbit, the lander and the rover will attempt to touch down on the moon’s surface around September 6 or 7, if all goes as planned.

    For about 14 days, the rover will explore this rarely studied lunar area, collecting samples and performing experiments. Meanwhile, Chandrayaan-2’s orbiter is expected to remain operational for about a year, sending back information about the moon to ISRO.

    The new data should help offer insights into moon’s origin, as well as Earth’s own history. And along the way, the Indian space agency also says it will test new technologies that could be used in future deep space travel.

    During ISRO’s first lunar mission a decade ago, their Chandrayaan-1 orbiter mapped the Moon’s surface for some 300 days. It also smashed an instrument called the Moon Impact Probe into the surface, turning up traces of water.

    If this second mission’s soft landing goes as planned, India will be just the fourth country to gently touch down on the moon, joining Russia, the U.S. and China.

    See the full article here .

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  • richardmitnick 3:03 pm on July 5, 2019 Permalink | Reply
    Tags: California Earthquake, Discover Magazine,   

    From Discover Magazine: “Italian Eruption Turns Deadly and California Rocked by Earthquake” 

    DiscoverMag

    From Discover Magazine

    July 5, 2019
    Erik Klemetti

    1
    Stromboli erupting on July 3, 2019. Image by Anil Charley/Twitter.

    There is the strong tendency in humans to look for patterns, even when none exist. This is amplified by the modern effect of news media, where certain events make headlines for reasons not necessarily related to the severity of the event.

    We see this frequently in geology, where a news-making eruption or earthquake then starts a cascade of reports of other eruptions and earthquakes that follow, even if they aren’t disasters. This feeds into our propensity to construct patterns from things, even when one doesn’d necessarily exist. For example, when read about a bunch of geological events, it’s tempting to think: “Uh oh, the Earth must be getting more active!”

    The truth is that earthquake and eruption activity does wax and wane, but over time, our planet is not “becoming more restless” than it was 100 or 1,000 or 10,000 years ago. Most earthquakes and eruptions are sprinkled randomly over time and that randomness sometimes produces clusters of events. Flip a coin 100 times and you might get 8 heads in a row, then none for another 10 tosses. That’s clustering in a random distribution.

    Over the last few weeks, it might have felt like the Earth was behaving differently. We’ve had big eruptions at Raikoke, Ulawun, Manam. We’ve had earthquakes felt in across the globe: 14 over M6 on the Richter scale in the past 30 days. Yet, in an average year, these things happen. They might not happen in a span of a fortnight, but then again, sometimes they do.

    People’s perceptions of eruptions can be skewed as well. The eruptions at Raikoke, Ulawun and Manam were all big. They produced some of the tallest ash plumes we’ve seen in a few years, reaching over 12-15 kilometers high (>30,000 feet). They were clearly newsworthy events, especially in the case of the two eruptions on Papua New Guinea, where tens of thousands of people live near the volcanoes.

    Luckily, for all three of those giant blasts, it appears that no one was killed. However, another volcano — this time Stromboli in Italy — erupted in an unexpected fashion. The volcano is one of the most active on Earth, so much so that is has been referred to as the “lighthouse of the Mediterranean.”

    Most of its eruptive activity is fairly tame, confined to small explosions at the summit. This means that lots of tourists like to visit the tiny volcanic island of Italy’s western shores so that they can see this volcano in action.

    2
    Stromboli erupting. Evening Standard

    There is the strong tendency in humans to look for patterns, even when none exist. This is amplified by the modern effect of news media, where certain events make headlines for reasons not necessarily related to the severity of the event.

    We see this frequently in geology, where a news-making eruption or earthquake then starts a cascade of reports of other eruptions and earthquakes that follow, even if they aren’t disasters. This feeds into our propensity to construct patterns from things, even when one doesn’d necessarily exist. For example, when read about a bunch of geological events, it’s tempting to think: “Uh oh, the Earth must be getting more active!”

    The truth is that earthquake and eruption activity does wax and wane, but over time, our planet is not “becoming more restless” than it was 100 or 1,000 or 10,000 years ago. Most earthquakes and eruptions are sprinkled randomly over time and that randomness sometimes produces clusters of events. Flip a coin 100 times and you might get 8 heads in a row, then none for another 10 tosses. That’s clustering in a random distribution.

    Over the last few weeks, it might have felt like the Earth was behaving differently. We’ve had big eruptions at Raikoke, Ulawun, Manam. We’ve had earthquakes felt in across the globe: 14 over M6 on the Richter scale in the past 30 days. Yet, in an average year, these things happen. They might not happen in a span of a fortnight, but then again, sometimes they do.

    People’s perceptions of eruptions can be skewed as well. The eruptions at Raikoke, Ulawun and Manam were all big. They produced some of the tallest ash plumes we’ve seen in a few years, reaching over 12-15 kilometers high (>30,000 feet). They were clearly newsworthy events, especially in the case of the two eruptions on Papua New Guinea, where tens of thousands of people live near the volcanoes.

    Luckily, for all three of those giant blasts, it appears that no one was killed. However, another volcano — this time Stromboli in Italy — erupted in an unexpected fashion. The volcano is one of the most active on Earth, so much so that is has been referred to as the “lighthouse of the Mediterranean.”

    Most of its eruptive activity is fairly tame, confined to small explosions at the summit. This means that lots of tourists like to visit the tiny volcanic island of Italy’s western shores so that they can see this volcano in action.

    This familiarity with the volcano’s usual activity can cause people to think the volcano is more benign than it truly is. Stromboli can produce more explosive eruptions, sometimes unexpectedly. This is what happened on July 3, when the volcano exploded (see above), sending ash, papilla (larger volcanic fragments) and volcanincn bombs across the island, generating a small pyroclastic flow that headed down the side of the volcano into the ocean (see below).

    Many tourists on the volcano had to immediately seek cover and some even jumped into the sea. The eruptions started fires on the slopes of the volcano as well. Unfortunately, one person was killed due to the flying volcanic debris from the blast, the volcano’s largest since 2007.

    Now, compared to Raikoke, Ulawun and Manam, this eruption was very, very small. The ash plume was only 2 kilometers (~6,500 feet). In the geologic record, the Stromboli eruption would likely quickly be lost because so little material actually came out. Yet, because people crawl over the slopes of the volcano, even a small but powerful blast can capture the world’s attention.

    The same might be said for the earthquake that rattled southern California on the July 4 (see below). This was one of the largest earthquakes in southern California over the past few years. There are dozens of M6+ earthquakes globally each year, but with the proximity of the Ridgecrest earthquake epicenter to Los Angeles, the temblor was felt by many, many people. Is there any link to the earthquake and these eruptions? Not really beyond the fact they all happened on Earth.

    3
    In this image taken from video provided by Ben Hood, a firefighter works to extinguish a fire, Thursday, July 4, 2019, following an earthquake in Ridgecrest, Calif. (Ben Hood via AP)

    See the full article here .

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  • richardmitnick 4:27 pm on June 20, 2019 Permalink | Reply
    Tags: , , , , Discover Magazine,   

    From Discover Magazine: “The Event Horizon Telescope’s Possible Next Target? Blazars” 

    DiscoverMag

    From Discover Magazine

    June 20, 2019
    Korey Haynes

    1
    A blazar is an active black hole hurling jets of material directly at Earth. (Credit: NASA/Goddard Space Flight Center/CI Lab)

    The Event Horizon Telescope made history on April 10 when it captured the first image of a supermassive black hole’s event horizon at the heart of galaxy Messier 87.

    2

    While there’s only one other target close enough to image that way – the black hole at the center of our own Milky Way – there are plenty of other targets where EHT’s sharp gaze can still make breakthroughs.

    Astronomers are proposing to use EHT to image the jets of a blazar called PKS 1510-089 more than 4 billion light-years away. A blazar is one of many names for a black hole that is actively consuming material, resulting in high-energy jets shooting out of the top or bottom of the black hole. With a blazar, the jets are pointed almost directly at Earth, making them especially bright.

    This particular blazar is one of the brightest known, and it’s also highly variable, meaning its brightness changes on short time scales. Many blazars vary on the scale of months to days, but PKS 1510-089 varies on the scale of minutes to hours. Scientists think the powerful, variable jets are the result of the black hole twisting magnetic field lines, but they’ve lacked the technology to peer close enough to discern the details — until now.

    Nicholas MacDonald, from Germany’s Max Planck Institute for Radio Astronomy, presented the case for observing PKS 1510-089 with EHT on June 20 at the annual meeting of the Canadian Astronomical Society in Montreal, Quebec, Canada.

    Bright jets

    In 2008, the Fermi Gamma-Ray Telescope launched, opening a new era of exploration of the high-energy universe. “The big discovery of the last decade,” says MacDonald, “was that blazars dominate the gamma-ray sky. These classes of objects are all bright, but [PKS 1510-089] is one of the brightest.”

    That makes it a good target for EHT, which is a network of telescopes spanning the globe, acting together as one giant telescope the size of the planet. MacDonald wants to use EHT plus ALMA, a radio observatory in Chile composed of yet another 66 telescopes networked together. The ALMA array is much smaller in overall size though, spreading out across only between 500 feet and 10 miles, depending on the movable telescopes’ configuration.

    The problem with EHT acting as one telescope the size of the planet is that it’s not actually one telescope. It’s a telescope with massive holes in it, and that makes the data less reliable. Because ALMA is farther south than most of the EHT telescopes, and is composed of a dense cluster of telescopes itself, it can drastically improve EHT’s results by essentially filling in gaps in EHT’s coverage.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    Astronomers ultimately hope to understand what creates the powerful jets they observe, and that means taking the closer look with EHT.

    “The idea is you have a central supermassive black hole, millions of times the mass of the sun,” MacDonald explains. The black hole is not just consuming gas and dust in a whirlpool, but yanking spacetime itself along for the ride. Researchers think the jets are produced when magnetic fields also get caught and twisted up in this motion, launching relativistic beams of charged material. But they don’t know what it looks like in detail.

    D-brief

    « Third Falcon Heavy Launch Set for Next Week A Molecule Long Thought Harmless Plays a Role in Pancreatic Cancer, Could Hint at Cure »
    The Event Horizon Telescope’s Possible Next Target? Blazars
    By Korey Haynes | June 20, 2019 12:30 pm
    1
    flat disk of material with jet shooting out perpindicular
    A blazar is an active black hole hurling jets of material directly at Earth. (Credit: NASA/Goddard Space Flight Center/CI Lab)

    The Event Horizon Telescope made history on April 10 when it captured the first image of a supermassive black hole’s event horizon at the heart of galaxy M87. While there’s only one other target close enough to image that way – the black hole at the center of our own Milky Way – there are plenty of other targets where EHT’s sharp gaze can still make breakthroughs.

    Astronomers are proposing to use EHT to image the jets of a blazar called PKS 1510-089 more than 4 billion light-years away. A blazar is one of many names for a black hole that is actively consuming material, resulting in high-energy jets shooting out of the top or bottom of the black hole. With a blazar, the jets are pointed almost directly at Earth, making them especially bright.

    This particular blazar is one of the brightest known, and it’s also highly variable, meaning its brightness changes on short time scales. Many blazars vary on the scale of months to days, but PKS 1510-089 varies on the scale of minutes to hours. Scientists think the powerful, variable jets are the result of the black hole twisting magnetic field lines, but they’ve lacked the technology to peer close enough to discern the details — until now.

    Nicholas MacDonald, from Germany’s Max Planck Institute for Radio Astronomy, presented the case for observing PKS 1510-089 with EHT on June 20 at the annual meeting of the Canadian Astronomical Society in Montreal, Quebec, Canada.
    Bright jets

    In 2008, the Fermi Gamma-Ray Telescope launched, opening a new era of exploration of the high-energy universe. “The big discovery of the last decade,” says MacDonald, “was that blazars dominate the gamma-ray sky. These classes of objects are all bright, but [PKS 1510-089] is one of the brightest.”

    That makes it a good target for EHT, which is a network of telescopes spanning the globe, acting together as one giant telescope the size of the planet. MacDonald wants to use EHT plus ALMA, a radio observatory in Chile composed of yet another 66 telescopes networked together. The ALMA array is much smaller in overall size though, spreading out across only between 500 feet and 10 miles, depending on the movable telescopes’ configuration.

    The problem with EHT acting as one telescope the size of the planet is that it’s not actually one telescope. It’s a telescope with massive holes in it, and that makes the data less reliable. Because ALMA is farther south than most of the EHT telescopes, and is composed of a dense cluster of telescopes itself, it can drastically improve EHT’s results by essentially filling in gaps in EHT’s coverage.

    Astronomers ultimately hope to understand what creates the powerful jets they observe, and that means taking the closer look with EHT.

    “The idea is you have a central supermassive black hole, millions of times the mass of the sun,” MacDonald explains. The black hole is not just consuming gas and dust in a whirlpool, but yanking spacetime itself along for the ride. Researchers think the jets are produced when magnetic fields also get caught and twisted up in this motion, launching relativistic beams of charged material. But they don’t know what it looks like in detail.

    “Is it highly ordered, or disordered?” MacDonald wonders. The options are that the magnetic field lines are either turbulent and snarled, or, alternatively, highly ordered in a helical structure. Theorists can reproduce the blazar behavior observed by telescopes with either ordered or disordered computer models of the magnetic fields. So they need to look closer to figure out what’s really going on.

    “The big game changer is ALMA,” MacDonald says, and especially ALMA’s cooperation with the other EHT telescopes. “And so we’re able to – for the first time – resolve down to the scales where we can distinguish where the field is ordered or disordered.”

    MacDonald was approved once for these observations, but weather at multiple points around the globe cheated him of his images. He’s trying again, and the observations, if approved, would be taken sometime between October 2019 and September 2020.

    See the full article here .

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  • richardmitnick 3:21 pm on April 30, 2019 Permalink | Reply
    Tags: "What ‘Rock Tides’ Reveal About Movements of the Earth", , Discover Magazine,   

    From Discover Magazine: “What ‘Rock Tides’ Reveal About Movements of the Earth” 

    DiscoverMag

    From Discover Magazine

    April 30, 2019
    Rebecca Boyle

    1
    Rock formations in the Atacama Desert. (Credit: Phil Whitehouse via Flickr)

    Earth’s interior teems with movement and heat, a characteristic that manifests in memorable fashion as volcanoes and earthquakes. But even Earth’s more seemingly stable solid rocks move, too. Understanding just how rocks respond when they are pushed and pulled by natural forces, such as tectonic activity, or human-caused forces, like hydraulic fracturing, can make mining, construction, natural gas production and other projects safer. It can also improve geological monitoring in fault zones.

    Now, a new technique uses the fingerprints of the moon, sun and surf to pin down rock behavior.

    Rocks feel solid, but their slight imperfections and cracks give them elastic tendencies, which change when the rock is under some sort of external stress, whether from heat or water or the tidal pull of the moon and sun, said Nicholas van der Elst, a seismologist at the U.S. Geological Survey who was not involved in the new work.

    “For the most part, rocks are elastic in that they change shape when you apply force, but they recover completely when the force is removed. There’s also a small amount of squishy deformation, which takes some time to recover,” he said. These shape changes are captured in a measurement called strain, which can give direct information about rock properties like strength and stiffness. But strain is difficult to measure away from Earth’s surface, van der Elst said.

    Scientists can expose small samples to titanic pressure and heat in lab settings or conduct field measurements of induced seismic activity — like mini-quakes set off by explosive charges — but both these approaches have key limitations such as high costs or questions about how well they replicate the natural environment.

    In the new study [no citation], researchers in Germany were able to link rock strain to seismic velocity changes, using a long-term seismometer station. The seismic velocity measurements serve as a proxy for strain, van der Elst said. And instead of having to squeeze the rock themselves, the scientists let the moon and sun do it for them.

    Christoph Sens-Schönfelder of the GFZ German Research Centre for Geosciences in Potsdam and Tom Eulenfeld of the University of Jena in Germany sifted through 11 years of data from a seismic monitoring station in the Atacama Desert of northern Chile. The Patache station rests on a hillcrest along the Pacific coast, less than 2 kilometers from the shore, in an area where nothing grows save for microbes living in salt rock. The only signs of life are occasional lichen flakes and seabird burrows, and distant lights from copper and salt mines sprinkled through the Atacama. The station keeps tabs on seismic activity in an area known for earthquakes. But it can detect more sensitive ambient movements, too.

    As the moon and sun perpetually tug on Earth, the tides slosh water back and forth all over the planet, causing shorelines to shrink or swell. But not only the water moves: Earth’s insides are strained, too. In this way, the tides serve as a controlled deformation experiment, Sens-Schönfelder said.

    He and Eulenfeld analyzed the Patache recordings for seismic echoes — waves that struck the detector, bounced off the surrounding rock, and then hit the detector again. When they plotted the echo patterns, they could see variations related to the pounding of surf from the Pacific Ocean, a couple kilometers away. They also noticed patterns that repeated every day or half day. They realized the half-day oscillations actually represented two signals, corresponding to 12.42 and 12.56 hours. The 12.42-hour period precisely matches the lunar tide, while the longer oscillation matches the elliptical orbit of Earth’s satellite. The elliptic orbit is the same effect that leads to an occasional “supermoon” when the moon is closer to Earth.

    “We were surprised to see the effects of the tides so clearly,” Sens-Schönfelder said. What’s more, the rocks don’t respond instantaneously, meaning the rock takes some time to relax after it is pushed and pulled.

    The researchers also found something unexpected: The sun was producing a greater effect on the rock tides than they thought it would. Though the sun does contribute to Earth’s tides, its pull is greatly outshone by that of the moon — so why would the one-day seismic signal be so strong? The researchers decided it was related to the sun’s warmth, heating the surface during the day, only to disappear at night and allow the surface to cool and contract.

    “The most surprising thing was that we found an interaction between the tidal and thermal effects. They modulate each other and cause distinct peaks in the spectrum,” Sens-Schönfelder said. The researchers are not sure how these two signals are interacting.

    Van der Elst said the rock deformation and relaxation, or “squishiness,” is faster than the timescales of the tides, which makes it a difficult measurement outside of a controlled lab setting. “It’s a real achievement to have measured this rock property in the field with such precision,” he said.

    Sens-Schönfelder said the researchers were able to separate the effects of temperature and tides by looking at the cycles of the sun and moon — “and the fact that the moon does not cause any heating,” he added. “Disentangling both effects from the sun alone would be much more difficult.”

    Still, the results are precise enough that others should be able to perform similar measurements almost anywhere, and use the signals of the moon and the sun to measure the pulse of the Earth.

    See the full article here .

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