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  • richardmitnick 5:14 pm on February 13, 2016 Permalink | Reply
    Tags: Astronomy, , ,   

    From Ethan Siegel: “The Future Of Astronomy: The Giant (25 Meter!) Magellan Telescope” 

    Starts with a bang
    Starts with a Bang

    Giant Magellan Telescope

    The first of the next generation of telescopes is already under construction. Here’s the audacious new science we’re in for!

    “We find them smaller and fainter, in constantly increasing numbers, and we know that we are reaching into space, farther and farther, until, with the faintest nebulae that can be detected with the greatest telescopes, we arrive at the frontier of the known universe.” -Edwin Hubble

    Pillars of Creation
    Pillars of Creation in the Eagle Nebula

    Throughout history, there have been four things that have determined just how much information we can glean about the Universe through astronomy:

    The size of your telescope, which determines both how much light you can gather in a given amount of time and also your resolution.
    The quality of your optical systems and cameras/CCDs, which allow you to maximize the amount of light that becomes usable data.
    The “seeing” through the telescope, which can be distorted by the atmosphere but minimized by high altitudes, still air, cloudless nights and adaptive optics technology.
    And your techniques of data analysis, which can ideally make the most of every single photon of light that comes through.

    There have been tremendous advances in ground-based astronomy over the past 25 years, but they’ve occurred almost exclusively through improvements in criteria 2 through 4. The largest telescope in the world in 1990 was the Keck 10-meter telescope, and while there are a number of 8-to-10 meter class telescopes today, 10 meters is still the largest class of telescopes in existence.

    Keck Observatory
    Keck Observatory Interior
    10 meter Keck Observatory

    Moreover, we’ve really reached the limits of what improvements in those areas can achieve without going to larger apertures. This isn’t intended to minimize the gains in these other areas; they’ve been tremendous. But it’s important to realize how far we’ve come. The charge-coupled devices (CCDs) that are mounted to telescopes can focus on either wide-field or very narrow areas of the sky, gathering all the photons in a particular band over the entire field-of-view or performing spectroscopy — breaking up the light into its individual wavelengths — for up to hundreds of objects at once. We can cram more megapixels into a given surface area. Quite simply, we’re at the point where practically every photon that comes in through a telescope’s mirror of the right wavelength can be utilized, and where we can observe for longer and longer periods of time to go deeper and deeper into the Universe if we have to.

    In addition, we’ve come a long way towards overcoming the atmosphere, without the need to launch a telescope into space. By building our observatories at very high altitudes in locations where the air is still — such as atop Mauna Kea or in the Chilean Andes — we can immediately take a large fraction of atmospheric turbulence out of the equation. The addition of adaptive optics, where a known signal (like a bright star, or an artificial star created by a laser that reflects off of the atmosphere’s sodium layer, 60 kilometers up) exists but appears blurry, can allow us to create the right “mirror shape” to de-blur that image, and hence all the other light that comes along with it. This way, we can further eliminate the turbulent effects of the atmosphere.

    ESO VLT
    ESO Very Large Telescope showing an Adaptive Optics Laser


    Gemini Observatory Adaptive Optics Laser Guide Star
    Download mp4 video here .

    And finally, computational power and data analysis technique have improved tremendously, where more useful information can be recorded and extracted from the same data that we can take. These are tremendous advances, but just like a generation ago, we’re still using the same size telescopes. If we want to go deeper into the Universe, to higher resolution, and to greater sensitivities, we have to go to larger apertures: we need a bigger telescope. There are currently three major projects that are competing to be first: the Thirty-Meter Telescope [TMT] atop Mauna Kea, the (39 meter) [ESO 39 meter] European Extremely Large Telescope [E-ELT] in Chile, and the (25 meter) Giant Magellan Telescope (GMT), also in Chile.

    TMT
    TMT

    ESO E-ELT
    ESO E-ELT

    These represent the next giant leap forward in ground based astronomy, and the Giant Magellan Telescope is probably going to be first, having broken ground at the end of last year and with early operations planned to begin in just 2021, and becoming fully operational by 2025.

    It’s not really technically possible to make a single mirror that large, as the materials themselves will deform at those weights. Some approaches are to use a segmented “honeycomb” shape of mirrors, like the E-ELT plans, with 798 mirrors, but that produces a distinct disadvantage: you get a large number of image artifacts that are difficult to remove where the sharp lines are. Instead, the Giant Magellan Telescope uses just seven mirrors (four are already complete), each a monstrous 8.4 meters (or 28 feet!) in diameter, all mounted together. The circular nature of these mirrors leaves gaps between them, meaning you miss out on a little bit of your light-gathering potential, but the resultant images are much cleaner, easier to work with, and free of those nasty artifacts.

    It’s also being built on a great site: the Las Campanas Observatory, which currently houses the twin [Carnegie Observatory] 6.5-meter Magellan telescopes.

    Carnegie Las Campanas Observatory
    Las Campanas Observatory in Chile

    Magellan 6.5 meter telescopes
    Carnegie Observatory Baade and Clay 6.5 meter telescopes at Las Campanas

    At an altitude of nearly 2,400 meters (~8,000 feet), with clear skies and devoid of light pollution, it’s one of the best places for astronomical observing on Earth. Equipped with the same cutting edge cameras/CCD, spectrograph, adaptive optics, tracking and computerized technology that the world’s best telescopes have today — only scaled up for a 25 meter telescope — the GMT is going to revolutionize astronomy in a number of tremendous ways.

    1.) The first galaxies: in order to go deeper into the Universe, you need to not only compensate for the fact that objects that are twice as far away deliver only one quarter of the light to your eyes, but that the expanding Universe causes that light to redshift, or to get stretched to longer wavelengths. Our atmosphere might only let a few select “windows” of light through, but this actually helps us out in some ways: the ultraviolet radiation that gets blocked by our atmosphere from nearby stars like the Sun can get redshifted all the way into the visible (and even near-infrared) portion of the spectrum at great enough distances. Finding these galaxies is easiest from space, but confirming them requires follow-up spectroscopy, which is best done from the ground. Ideally, the combination of the James Webb Space Telescope [JWST] (last week’s “future of astronomy” article) and the GMT — which can measure the redshift and spectral features of these objects directly and unambiguously — will push the limits of the most distant known galaxies in the Universe out farther than ever, and give us an unprecedented view of how galaxies form and evolve.

    NASA Webb telescope annotated
    NASA/ESA/CSA JWST

    2.) The first stars: even more exciting is the chance to directly observe and ascertain the properties of the first stars ever to form in the Universe. After the Big Bang, when the Universe forms neutral atoms for the first time, there are no heavy elements at all. There’s hydrogen, deuterium, helium-3 and helium-4, and a little bit of lithium-7. That’s it. Absolutely nothing else. And so the first stars that formed in the Universe must have been made out of these materials alone, with none of the heavier elements found in 100% of our Milky Way’s stars. To find these pristine stars — these Population III stars — we have to go to incredibly high redshifts. Whereas today, we’ve barely uncovered one such candidate for these stars, the GMT should be able to discover hundreds of such candidates. In addition, it won’t just discover more, but:

    it should be able to determine the relative elemental abundances within,
    could measure the hydrogen, helium, and possibly even deuterium and lithium concentrations,
    could measure the absorption spectra of the gas clouds between us and them,
    and can discover them before the Universe has been reionized, back when there’s still neutral gas there.

    This applies to the first galaxies as well, but is even more exciting for the first stars, enabling us to see pristine samples of the Universe and understand just how big these earliest stars can get.

    3.) The earliest supermassive black holes: we’ve serendipitously found a large number of these already, in the form of quasars. The largest number of these have been found by large-volume and all-sky surveys like [Sloan Digital Sky Survey, SDSS] and 2dF [2dF Galaxy Redshift Survey] before it, but in order to truly measure these objects well, we need to obtain their spectra, something GMT will be perfect for.

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    AAO Anglo Australian Telescope Exterior
    AAO Anglo Australian Telescope Interior
    3.9 meter Anglo-Australian telescope used in the 2dF Galaxy Redshift Survey conducted by the Anglo-Australian Observatory (AAO)

    The difference between spectroscopy and photometry is a little bit like the difference between a black-and-white TV and a color TV: they can both show you a picture, but with spectroscopy, the level of detail and the amount of information you get increases more than a thousand-fold, as we can learn what’s inside (and how much) via spectroscopy, while without it we can only make assumptions. GMT will not only give us follow-up spectroscopy on what the future EUCLID and WFIRST missions will find — the most distant quasars over huge regions of the sky — but will enable us to find more distant quasars (and hence younger, smaller and earlier supermassive black holes) than anything else in (and out of) this world.

    ESA Euclid spacecraft
    ESA/EUCLID

    NASA WFIRST telescope
    NASA/WFIRST

    4.) The Lyman-alpha forest: when we look at the most distant quasars and galaxies, we not only see that distant light, but we see every intervening gas cloud there is between that object and ourselves, along the line-of-sight. By measuring the absorption features along the way, we can see how the structure and composition of the Universe evolves, which tells us all sorts of things about components of the Universe that would otherwise be invisible, like neutrinos and dark matter.

    Lyman-Alpha Forest
    ESO Lyman-alpha forest

    Of course, there’s all the “normal” astronomy we can do with it as well, including planet-finding, understanding stellar and galaxy evolution, measuring supernovae and their remnants, planetary nebulae and star forming regions, clusters, interstellar and intergalactic gas and so much more.

    Supernova remnant Crab nebula
    Crab Nebula supernova remnant

    Planetary nebula Cat's Eye
    Cat’s Eye planetary nebula

    Perhaps most exciting will be the advances that we don’t know are coming. No one could’ve predicted that Edwin Hubble would discover the expanding Universe when the 100-inch Hooker telescope was first commissioned; no one could’ve predicted how the Hubble Deep Field would open up the Universe when that image was first taken. What will GMT find in the ultra-distant Universe?

    Mt Wilson 100 inch Hooker Telescope Interior
    100 inch Hooker telescope on Mt Wilson

    NASA Hubble Deep Field
    Hubble Deep Field

    NASA Hubble Telescope
    NASA/ESA Hubble

    This is why we look, and this is what science at the frontiers is. The Giant Magellan Telescope will do all the things from the ground that space-based telescopes can’t do as well, and will do them better than any other telescope in existence. Unlike the other large ground-based telescopes planned, it’s completely privately funded, there are no political controversies over it, and construction on it has already begun. The future of any scientific endeavor — and perhaps astronomy in particular — requires you to be ambitious, and to invest in looking for the unknown. We’ll never learn what lies beyond our current frontiers of knowledge unless we search, and the GMT is one major step towards looking where no one has ever looked before.

    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 3:52 pm on February 13, 2016 Permalink | Reply
    Tags: Astronomy, , Extinction possibilities,   

    From Ethan Siegel: “Are We Due For An Extinction Event On Earth?” 

    Starts with a bang
    Starts with a Bang

    2.13.16
    Ethan Siegel

    Extinction shot Ethan Siegel
    Image credit: Don Davis (work commissioned by NASA)

    Are comets and asteroids periodic, and are we due?

    “Biological diversity is messy. It walks, it crawls, it swims, it swoops, it buzzes. But extinction is silent, and it has no voice other than our own.”
    -Paul Hawken

    While a great many people argue about how and whether the human race will end, there’s no doubt as to the primary cause and catalyst of the last major extinction here on Earth: a massive, large body from outer space colliding with Earth. Some 65 million years ago, an asteroid about 5–10 kilometers in diameter struck what is now the Gulf of Mexico, wiping out roughly 30–50% of the species on our world and ending the age of the dinosaurs. Are we headed for another such event in the near future? Reader David Bertone wants to know:

    I have a question for you regarding [this article I read on] how our galaxy’s disc displaces comets in the Oort cloud every 26–30 million years, causing periodic extinctions and bombardment of comets on Earth… I was wondering if we are in any danger of this happening in our lifetimes, and if the theory itself is credible?

    To be honest, there’s always a danger of a mass extinction, but the key is quantifying that danger accurately.

    Extinction threats in our Solar System — from cosmic bombardment — generally come from two sources: the asteroid belt in between Mars and Jupiter, and the Kuiper belt and Oort cloud out beyond the orbit of Neptune.

    Oort Cloud
    Kuiper Belt and Oort Cloud. Image credit: NASA and William Crochot.

    For the asteroid belt, the suspected (but not the certain) origin of the dinosaur-killer, our odds of getting hit by a large object significantly decrease over time. There’s a good reason for this: the amount of material in between Mars and Jupiter gets depleted over time, with no mechanism for replenishing it. We can understand this by looking at a few things: young Solar Systems, early models of our own Solar System, and most airless worlds without particularly active geologies: the Moon, Mercury and most moons of Jupiter and Saturn.

    We can see, for example, the Moon’s cratering history by looking at it. Where the lunar highlands are — the lighter spots — we can see a longstanding history of heavy cratering, dating all the way back to the earliest days in the Solar System: more than 4 billion years ago. There are a great many large craters with smaller and smaller craters inside: evidence that there was an incredibly high level of impact activity early on. However, if you look at the dark regions (the lunar maria), you can see far fewer craters inside. Radiometric dating shows that most of these areas are between 3 and 3.5 billion years old, and even that is different enough that the amount of cratering is far less. The youngest regions, found in Oceanus Procellarum (the largest mare on the moon), are only 1.2 billion years old, and are the least cratered.

    What this all means is that the asteroid belt is getting sparser and sparser over time. It’s arguable that we haven’t reached it yet (although we may have), but at some point over the next few billion years, the Earth should experience its very final large asteroid strike, and if there’s still life on the world, the last mass extinction event arising from such a catastrophe.

    But the Oort cloud and the Kuiper belt are different stories.

    Out beyond Neptune in the outer Solar System, there’s a huge catastrophic potential out there. Hundreds of thousands — if not millions — of large ice-and-rock chunks wait in a tenuous orbit around our Sun, where a passing mass (which could be Neptune, another Kuiper belt/Oort cloud object, or a different Solar System) has the potential to gravitationally disrupt it. The disruption could have any number of outcomes, but one of them is to hurl it towards the inner Solar System, where it could arrive as a brilliant comet, but where it could also collide with our world, resulting in a catastrophe.

    Milky Way map
    Milky Way Galaxy.

    The interactions with Neptune or other objects in the Kuiper belt/Oort cloud are random and independent of anything else going on in our galaxy, but it’s possible that passing through a star-rich region — such as the galactic disk or one of our spiral arms — could enhance the odds of a comet storm, and the chance of a comet strike on Earth. The recent American Scientist paper that David asks about claims that there’s a roughly 26–30 million year “periodic” pattern in the extinctions on Earth, which correlates roughly with the 28–32 million year period of when the Solar System passes through the Milky Way’s galactic plane! Coincidence, or could this be the cause of the extinctions?

    The answer can be found in the data. We can look at the major extinction events on Earth as evidenced by the fossil record. By counting the number of genera (one step more generic than “species” in how we classify living beings; for human beings, the “homo” in homo sapiens is our genus) at any given time, something we can do going back more than 500 million years (thanks to sedimentary rock), we can see what percent both existed and also died off at any given interval.

    It shows relatively weak evidence for a spike with a frequency of 140 million years, and another spike at 62 million years. These spikes look huge, but that’s only relative to the other spikes, which are totally insignificant. In a timeframe of just ~500 million years, you can only fit three possible 140 million year mass extinctions in there, and only about 8 possible 62 million year events. (We don’t see that many; if there is periodicity like this, it doesn’t happen every time.) But as you can clearly see, there’s no evidence for a 26–30 million year periodicity in these extinctions; there’s not even a suggestive bump at those frequencies. What’s even worse is that, of all the impacts that occur on Earth, less than one quarter originate from the Oort cloud! There’s an old saying that “extraordinary claims require extraordinary evidence,” but Christopher Hitchens flipped the script on that, looking at it from the reverse point of view:

    “What can be asserted without evidence can be dismissed without evidence.”

    And I’m happy to report that as we look back on this most recent pass through the galactic plane, there’s no reason at all to suspect any increase in the frequency of catastrophic events. We might still get one, but the odds that the Universe is coming to kill us appear to be lower than they’ve ever been.

    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 9:30 am on February 13, 2016 Permalink | Reply
    Tags: Astronomy, , , , , Planet Formation around Binary Star, HD 142527 binary system   

    From ALMA: “ALMA Unveils Details of Planet Formation around Binary Star” 

    ALMA Array
    ALMA

    13 February 2016
    Nicolás Lira T.
    Education and Public Outreach Coordinator
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 24 67 65 19
    Cell: +56 9 94 45 77 26
    Email: nlira@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 202 236 6324
    E-mail: cblue@nrao.edu

    Richard Hook
    Public Information Officer, ESO

    Garching bei München, Germany

    Tel: +49 89 3200 6655

    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
Tokyo, Japan

    Tel: +81 422 34 3630

    E-mail: hiramatsu.masaaki@nao.ac.jp

    ALMA Planet Formation around Binary Star
    Artist impression of the HD 142527 binary star system based on data from the Atacama Large Millimeter/submillimeter Array (ALMA). The rendition shows a distinctive arc of dust (red) embedded in the protoplanetary disk. The red arc is free of gas, suggesting the carbon monoxide has “frozen out,” forming a layer of frost on the dust grains in that region. Astronomers speculate this frost provides a boost to planet formation. The two dots in the center represent the two stars in the system. Credit: B. Saxton (NRAO/AUI/NSF)

    Using ALMA, astronomers have taken a new, detailed look at the very early stages of planet formation around a binary star. Embedded in the outer reaches of a double star’s protoplanetary disk, the researchers discovered a striking crescent-shape region of dust that is conspicuously devoid of gas. This result, presented at the AAAS meeting in Washington, D.C., provides fresh insights into the planet-forming potential of a binary system.

    Astronomers struggle to understand how planets form in binary star systems. Early models suggested that the gravitational tug-of-war between two stellar bodies would send young planets into eccentric orbits, possibly ejecting them completely from their home system or sending them crashing into their stars. Observational evidence, however, reveals that planets do indeed form and maintain surprisingly stable orbits around double stars.

    To better understand how such systems form and evolve, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) took a new, detailed look at the planet-forming disk around HD 142527, a binary star about 450 light-years from Earth in a cluster of young stars known as the Scorpius-Centaurus Association.

    The HD 142527 system consists of a main star a little more than twice the mass of our Sun and a smaller companion star only about a third the mass of our Sun. They are separated by approximately one billion miles: a little more than the distance from the Sun to Saturn. Previous ALMA studies of this system revealed surprising details about the structure of the system’s inner and outer disks.

    “This binary system has long been known to harbor a planet-forming corona of dust and gas,” said Andrea Isella, an astronomer at Rice University in Houston, Texas. “The new ALMA images reveal previously unseen details about the physical processes that regulate the formation of planets around this and perhaps many other binary systems.”

    ALMA composite  HD 142527 binary star system
    A composite image of the HD 142527 binary star system from data captured by the Atacama Large Millimeter/submillimeter Array shows a distinctive arc of dust (red) and a ring of carbon monoxide (blue and green). The red arc is free of gas, suggesting the carbon monoxide has “frozen out,” forming a layer of frost on the dust grains in that region. Astronomers speculate this frost provides a boost to planet formation. The two dots in the center represent the two stars in the system. Credit: Andrea Isella/Rice University; B. Saxton (NRAO/AUI/NSF); ALMA (NRAO/ESO/NAOJ)

    Planets form out of the expansive disks of dust and gas that surround young stars. Small dust grains and pockets of gas eventually come together under gravity, forming larger and larger agglomerations and eventually asteroids and planets. The fine points of this process are not well understood, however. By studying a wide range of protoplanetary disks with ALMA, astronomers hope to better understand the conditions that set the stage for planet formation across the Universe.

    ALMA’s new, high-resolution images of HD 142527 show a broad elliptical ring around the double star. The disk begins incredibly far from the central star — about 50 times the Sun-Earth distance. Most of it consists of gases, including two forms of carbon monoxide (13CO and C180), but there is a noticeable dearth of gases within a huge arc of dust that extends nearly a third of the way around the star system.

    This crescent-shaped dust cloud may be the result of gravitational forces unique to binary stars and may also be the key to the formation of planets, Isella speculates. Its lack of free-floating gases is likely the result of them freezing out and forming a thin layer of ice on the dust grains.

    “The temperature is so low that the gas turns into ice and sticks to the grains,” Isella said. “This process is thought to increase the capacity for dust grains to stick together, making it a strong catalyst for the formation of planetesimals, and, down the line, of planets.”

    “We’ve been studying protoplanetary disks for at least 20 years,” Isella said. “There are between a few hundred and a few thousands we can look at again with ALMA to find new and surprising details. That’s the beauty of ALMA. Every time you get new data, it’s like opening a present. You don’t know what’s inside.”

    HD 142527 will be the subject of an upcoming paper led by Rice postdoctoral fellow Yann Boehler, who is working in Isella’s group.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon
    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small

    ESO 50 Large

    NAOJ

     
    • richardmitnick 9:50 am on February 13, 2016 Permalink | Reply

      I have requested the full science team from the contacts listed in the article. If I get the listing, the post will be revised to include it.

      Like

  • richardmitnick 7:23 am on February 13, 2016 Permalink | Reply
    Tags: Astronomy, , , Behind the scenes of some Basic Research,   

    From Astronomy: “Supercomputer black hole collisions make fake gravitational waves” 

    Astronomy magazine

    Astronomy Magazine

    [This is an article from 2010, prior to the success of MIT/Caltech Advanced aLIGO. Astronomy has now brought it forward. It illustrates what goes on behind the scenes of the world of Basic Research, so I have deemed it worthy of a new reading.]

    February 10, 2016
    Adam Frank

    Simulating the merger of black holes is no small scientific feat. For one thing, it requires a lot of computing horsepower — the kind you can get only from a supercomputer. It also involves solving complex, multilayered equations of [Albert] Einstein’s theory of general relativity at lightning speed. Using supercomputers, researchers in the field of numerical relativity hope to shed light on the physics of the most violent events in the cosmos. Black hole mergers and colliding neutron stars are two primary candidates.

    But numerical relativity demands that researchers take on Albert Einstein full bore. Solving the equations of general relativity — Einstein’s grand theory of gravity — is a difficult enough problem. Their additional challenge is to digitally animate the most complex behaviors hiding inside those equations.

    Getting results has become urgent. A new kind of telescope — gravitational wave detectors, built to sense ripples in the fabric of space and time — has recently come on line. These gravity observatories were built specifically to detect events like black-hole mergers. But the telescopes need guidance from computer models to know what sort of signal to look for. This special imperative has made numerical relativity the kind of challenge that draws theorists with a special kind of ambition.

    For years, the computer codes at the heart of numerical relativity simulations could do little more than simply crash. All paths seemed blocked; nothing worked. In spite of all the intellectual firepower attracted to the research, and 30 years of work, some theorists were giving up hope. Simulating Einstein’s universe might not just be hard — it might be impossible.

    But recent breakthroughs in computer modeling by numerical relativists mean the simulations work. They found a way to run Einstein’s equations as black holes collide, without crashing their supercomputers. Animations created from the model runs show black holes spiraling into each other and merging while emitting blasts of radiation and rippling gravity waves.

    This research has opened a new window on the universe — one in which astronomers can hopefully observe disturbances in space-time as readily as flashes of X rays and visible light.

    Listening for black holes

    On the dusty plains of the Hanford Nuclear Reservation, about 200 miles (320 kilometers) southeast of Seattle stands numerical relativity’s reason for existence. It consists of two long vacuum chambers that meet to form an L-shaped gravity observatory. The facility is called LIGO, the Laser Interferometer Gravitational-wave Observatory.

    The LIGO Hanford Observatory, along with a sister facility, the LIGO Livingston Observatory in Louisiana, represents a new kind of telescope. Engineers designed LIGO to pick up gravitational waves — ripples on the surface of space-time’s ocean that are a key prediction of Einstein’s general theory of relativity.

    Wiggling any mass back and forth produces gravity waves that move across the fabric of space-time. Wiggling a massive, compact object like a black hole creates gravity waves so powerful that scientists hope instruments can detect them across astronomical distances.

    Caltech Ligo
    MIT/Caltech Advanced aLIGO, Hanford, WA, USA

    “Gravity waves are the point of LIGO,” says Scott A. Hughes, a professor of physics at MIT’s Kavli Institute for Astrophysics and Space Research in Cambridge, Massachusetts. “The crossed lasers are designed to detect changes in space-time produced by passing gravity waves. But you have to know what to look for.”

    When people started thinking about LIGO, they realized that the merger of two black holes would produce a strong signal. A binary system of two massive stars orbiting each other sets the stage for the merger. When the stars go supernova, they each leave behind a black hole corpse.

    The black holes remain locked in orbit around each other.

    Cornell SXS teamTwo merging black holes simulation
    Cornell SXS team two merging black holes simulation

    The closer they get, the more they disturb the space-time in their vicinity. The system generates gravity waves that ripple outward. The waves sap orbital energy from the black holes, which then circle each other ever more closely. They eventually merge into a single object in a cataclysm of distorted space-time and radiating gravity waves.

    “LIGO should be able to see these mergers,” Hughes explains. The LIGO project set researchers on the black hole merger problem with a vengeance. For years, scientists have been trying to use general relativity to calculate the signals LIGO scientists should look for in their data. A match would mean LIGO has detected a black hole merger.

    Death spiral

    There are three phases to a black-hole merger. First, “inspiral” occurs as the black holes circle around each other on an ever-tightening orbit. Until they get close, slight modifications of Newtonian gravitational attraction work just fine.

    At the middle phase of the merger, all hell breaks loose. Tracking two black holes as they spiral into collision demands the full-blown equations of general relativity with no tricks or simplifications. The merger also produces the strongest LIGO signal. The melding of two rapidly moving black holes shreds space-time and radiates a torrent of gravity waves from the scene.

    Like the inspiral phase, the merger’s conclusion is relatively easy to calculate. “You end up with a single black hole,” says Hughes. “The event horizon of the merged black hole oscillates for awhile and radiates gravity waves until it stabilizes.” This final phase of a black hole merger is called the ringdown.

    Accurately reproducing the details of a merger and its gravity wave signature is the grand challenge needed to satisfy LIGO. Earlier this decade, a merger was the prize everyone was gunning for. Winning that prize meant Einstein’s equations would have to be wrestled to the mat.

    Columbia Supercomputer at NASA's Advanced Supercomputing Facility at Ames Research Center
    NASA’s Columbia supercomputer is [was] one of the fastest machines of its kind in the world. [Decommissioned March 15, 2013] Tremendous processing power is required to calculate distortions in space-time caused by merging black holes.Tom Trower/NASA Ames Research Center

    Einstein’s impossible legacy

    It’s the complexity of relativity theory that makes numerical relativity so hard. To handle a problem like merging black holes, theorists have to solve 10 interwoven equations simultaneously. Take just a few steps into a calculation and you can end up with hundreds of terms — smaller pieces of equations — to follow. It’s like doing algebra and calculus in the middle of a tornado.

    Theorists had to first think of ways to convert the equations of general relativity into a form that computers could swallow. “The first attempt at numerical relativity came in the 1970s,” says Joan M. Centrella, chief of the gravitational astrophysics laboratory at Goddard Space Flight Center in Greenbelt, Maryland. “It was really a heroic effort.”

    Centrella understands such theoretical heroism. She and her research group have worked on numerical relativity simulations for 20 years. The first efforts focused on direct collisions of black holes. The calculations were crude, but they did point the way for a future generation of re-searchers. To make real progress, scientists would have to figure out how to simulate Einstein’s 4-D space-time on a computer and make it work for the most complicated situations.

    In general relativity, space and time are intrinsically mixed. All objects in space-time, including you and me, have four dimensions. Each of us occupies and moves through the three dimensions of space and, simultaneously, a fourth dimension of time. That means each person’s life history is a four-dimensional object stretching from birth to death. The same principle applies to black holes.

    Black hole weirdness

    To make it possible to run the equations of general relativity in a computer, researchers had to develop a way to accommodate the complexities of four-dimensional objects. Then, they had to develop a way to visualize the data as 2-D and 3-D animations. This left another major challenge: simulating the black holes themselves.

    Every black hole is surrounded by an event horizon, the point beyond which ordinary radiation cannot escape the object’s powerful gravity. The event horizon is the boundary between our universe and the weirdness inside.

    Anything passing through the event horizon exits our world forever. It’s no surprise, then, that trying to simulate the interiors of black holes in computer simulations creates problems.
    Inside of the event horizon is a place simulations can’t go. Yet, without a way of representing black holes in the model, there could be no numerical relativity. Over the years, two strategies emerged to treat the problem. “You can either cut the black holes out of the grid in a process called excising, or you can try and slow the evolution down near the hole and then insert a solution you already know, which is called puncture,” explains physicist Manuela Campanelli, director of the Center for Computational Relativity and Gravitation at the Rochester Institute of Technology (RIT) in New York.

    Each choice has its problems, and neither worked well. The difficulties of computational relativity brought the field to a standstill. Only a few years ago, the situation appeared to be getting desperate. “The codes just crashed and crashed and crashed,” Centrella says. “You couldn’t even get an entire orbit out of them.”

    The inherent mathematical nastiness of general relativity’s equations and the sheer difficulty of translating them into computer code rendered the models wildly unstable. Just a few steps into a calculation, the machines locked up by trying to divide by zero or some other impossibility.

    Campanelli remembers it as a dark time. “People had really lost hope,” she says. “These were scientists who had spent years building their codes. All that work, all that mathematics. No one wanted to toss it away and start again.” Then, in the midst of the melancholy, everything changed. It was a day that numerical relativists are not likely to forget for a long time.

    The lone gunman

    On April 19, 2005, numerical relativists gathered at a conference center in the mountains of Banff, Alberta. Frans Pretorius, a professor of physics at Princeton University, showed up with a secret. “Frans was the classic lone gunman,” Hughes says. “He appeared at a conference and said ‘Watch this.’”

    After describing the mathematical background of his numerical code, Pretorius showed the audience a simulation with five full orbits of a black-hole pair.

    “It was just amazing,” Hughes says. “Frans had solved it. He got it to work. It was like everybody was climbing this mountain only to find Frans on top already waving down at them.”

    In Pretorius’ new method, Einstein’s equations take on a form similar to those describing simple waves. It was a highly abstract, nonintuitive approach. But progress was not immediate. “My first attempt failed,” he recalls. “In the second attempt, things were a little better.”

    News of Pretorius’ achievement leaked out before his talk. The buzz had already started when he arrived at the conference hall. “People were text messaging during my talk,” he recalls. “Some guy set up with a video camera on a tripod and aimed it right at me. It was kind of embarrassing.”

    After Pretorius showed his animations and finished his talk, the community tried to digest what it had just seen. A few people were hostile. “There was a lot of investment in the methods researchers had been working with,” Pretorius says. “Not everyone was pleased that I had come at it in an entirely different way and succeeded.”

    But most of Pretorius’ colleagues were thrilled. He had proved that numerical relativity was not an impossible dream. What happened next was more than anyone could have expected.

    Changing course

    In the wake of Pretorius’ success, all of the researchers asked themselves the same question. “If Frans got it to work his way,” Centrella explains, “then did we all need to change to Frans’ method?” Some researchers decided to press ahead with their existing codes.

    The RIT group members decided to focus efforts on their puncture method for treating moving black holes. It had been a major source of problems for them, but they came up with a solution.

    Many in the field of numerical relativity believed that a puncture representing a black hole could not move. So researchers would just pin the puncture in the grid and let space-time move around it.

    Campanelli and her colleagues decided to let the puncture move. To their surprise, the method produced spectacular results. Suddenly, Campanelli’s group could track orbiting black holes all the way to merger.

    The researchers presented the new success at the next numerical relativity meeting but met with disbelief. “People saw our simulations but didn’t understand how you could move the black hole across the grid,” Campanelli says.

    It might have gone worse for Campanelli’s group if Joan Centrella’s team hadn’t shown up with simulations that used the same method. “The community was just stunned silent,” Centrella recalls. The simulation of black hole mergers, from inspiral to ringdown, are now routine. “Now there are sessions at the American Astronomical Society meetings dedicated entirely to mergers,” Centrella says. “And just a little while ago, we could not even get an orbit.”

    Black holes, bright future

    Researchers are moving quickly to explore additional black hole merger scenarios, including mergers of black holes of different sizes and spins. “It’s a feeding frenzy right now,” Pretorius says. “And it will still take a few years until all the important cases have been mapped out.”

    Already, new surprises have appeared. Research with computer models shows that after a merger, the new, combined black hole experiences a powerful recoil force. In simulations, black holes blast away after mergers at speeds topping 625 miles (1,000 km) per second.

    Simulated black hole mergers can now provide guidance to LIGO researchers and other gravity-wave observatories around the world. Sometime around 2013, LIGO will be upgraded to a more sensitive design, called Advanced LIGO. The improvements in sensitivity should finally give astronomers a telescope ready to detect black-hole mergers.

    It has been a long, hard climb for LIGO scientists as they ready their detectors to identify passing gravitational waves. Numerical relativists experienced their own hard climb, and they are finally getting some satisfaction. They will be ready and waiting as LIGO turns its ear to the sky to detect the faint ripples of distant cataclysms.

    See the full article here .

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  • richardmitnick 6:37 am on February 13, 2016 Permalink | Reply
    Tags: Astronomy, , ,   

    From U Washington: “Caught in the act: UW astronomers find a rare supernova ‘impostor’ in a nearby galaxy”” 

    U Washington

    University of Washington

    February 12, 2016
    James Urton

    NGC 300
    The galaxy NGC 300, home to the unusual system Binder and her colleagues studied. The spiral galaxy is over 6 million light years away. An ultraviolet image of NGC 300 taken by the Galaxy Evolution Explorer (GALEX) NASA/JPL-Caltech/OCIW

    NASA Galex telescope
    NASA/GALEX

    Breanna Binder, a University of Washington postdoctoral researcher in the Department of Astronomy and lecturer in the School of STEM at UW Bothell, spends her days pondering X-rays.

    As she and her colleagues report in a new paper published Feb. 12 in the Monthly Notices of the Royal Astronomical Society, they recently solved a mystery involving X-rays — a case of X-rays present when they shouldn’t have been. This mystery’s unusual main character — a star that is pretending to be a supernova — illustrates the importance of being in the right place at the right time.

    Such was the case in May 2010 when an amateur South African astronomer pointed his telescope toward NGC300, a nearby galaxy. He discovered what appeared to be a supernova — a massive star ending its life in a blaze of glory.

    “Most supernovae are visible for a short time and then — over a matter of weeks — fade from view,” said Binder.

    After a star explodes as a supernova, it usually leaves behind either a black hole or what’s called a neutron star — the collapsed, high-density core of the former star. Neither should be visible to Earth after a few weeks. But this supernova — SN2010da— still was.

    “SN 2010da is what we call a ‘supernova impostor‘ — something initially thought to be a supernova based on a bright emission of light, but later to be shown as a massive star that for some reason is showing this enormous flare of activity,” said Binder.

    Many supernova impostors appear to be massive stars in a binary system — two stars in orbit of one another. Stellar astrophysicists think that the impostor’s occasional flare-ups might be due to perturbations from its neighbor.

    For SN 2010da, the story appeared to be over until September 2010 — four months after it was confirmed as an impostor — when Binder pointed NASA’s Chandra X-ray Observatory toward NGC300 and found something unexpected.

    NASA Chandra Telescope
    NASA/Chandra

    Supernova impostor SN 2010da circled in green and the X-ray emission indicated by a white cross.
    An image obtained by UW astronomer Breanna Binder’s group using the Hubble Space Telescope, showing the supernova impostor SN 2010da circled in green and the X-ray emission indicated by a white cross. Reproduced from a Royal Astronomical Society publication.Breanna Binder/NASA/Royal Astronomical Society

    “There was just this massive amount of X-rays coming from SN 2010da, which you should not see coming from a supernova impostor,” she said.

    Binder considered a variety of explanations. For example, material from the star’s corona could be hitting a nearby dust cloud. But that would not produce the level of X-rays she had observed. Instead, the intensity of the X-rays coming from SN 2010da were consistent with a neutron star — the dense, collapsed core remnant of a supernovae.

    “A neutron star at this location would be surprising,” said Binder, “since we already knew that this star was a supernova impostor — not an actual supernova.”

    In 2014, Binder and her colleagues looked at this system again with Chandra and, for the first time, the Hubble Space Telescope.

    NASA Hubble Telescope
    NASA/ESA Hubble

    They found the impostor star and those puzzling X-ray emissions. Based on these new data, they concluded that, like many other supernovae impostors, SN 2010da likely has a companion. But, unlike any other supernovae impostor binary reported to date, SN 2010da is probably paired with a neutron star.

    “If this star’s companion truly is a neutron star, that would mean that the neutron star was once a giant, massive star that underwent its own supernova explosion in the past,” said Binder. “The fact that this supernova event didn’t expel the other star, which is 20 to 25 times the mass of our sun, makes this an incredibly rare type of binary system.”

    To understand how this unusual binary system could form, Binder and her colleagues considered the age of the stars in this region of space. Looking at stellar size and luminosity, they discovered that most nearby stars were created in two bursts — one 30 million years ago and the other less than 5 million years ago. But neither SN 2010da nor its presumed neutron star companion could’ve been created in the older burst of starbirth.

    “Most stars that are as massive as these usually live 10 to 20 million years, not 30 million,” said Binder. “The most massive, hottest stars can form, grow, swell, explode and leave a neutron star emitting X-rays in about 5 million years.”

    Surveys of the galaxy as recently as 2007 and 2008 detected no X-ray emissions from the location of SN 2010da. Instead, Binder believes that the X-rays they first found in 2010 represent the neutron star “turning on” for the first time after its formation. The X-rays are likely produced when material from the impostor star is transferred to the neutron star companion.

    “That would mean that this is a really rare system at an early stage of formation,” said Binder, “and we could learn a lot about how massive stars form and die by continuing to study this unique pairing.”

    One mystery solved, Binder would like to keep looking at SN 2010da, seeing what else she can learn about its formation and evolution. Its home galaxy, which has yielded unique pairings previously, is sure to keep her busy. She is also planning a follow-up study of other recent supernova impostors with the help of an undergraduate research assistant at UW Bothell.

    Co-authors on the paper included UW astronomy professor Ben Williams, Albert Kong at the National Tsing Hua University, Terry Gaetz and Paul Plucinsky at the Harvard-Smithsonian Center for Astrophysics, Evan Skillman at the University of Minnesota and Andrew Dolphin at Raytheon. Their work was funded by NASA.

    See the full article here .

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    The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.

    So what defines us — the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 4:06 pm on February 10, 2016 Permalink | Reply
    Tags: Astronomy, , , , Earth's magnetosphere, Owens Valley Long Wavelength Array, ,   

    From Caltech: “Chasing Extrasolar Space Weather” 

    Caltech Logo
    Caltech

    02/10/2016
    Lori Dajose

    Earth’s magnetic field acts like a giant shield, protecting the planet from bursts of harmful charged solar particles that could strip away the atmosphere.

    Magnetosphere of Earth
    Earth’s magnetosphere

    Gregg Hallinan, an assistant professor of astronomy, aims to detect this kind of space weather on other stars to determine whether planets around these stars are also protected by their own magnetic fields and how that impacts planetary habitability.

    On Wednesday, February 10, at 8 p.m. in Beckman Auditorium, Hallinan will discuss his group’s efforts to detect intense radio emissions from stars and their effects on any nearby planets. Admission is free.

    What do you do?
    I am an astronomer. My primary focus is the study of the magnetic fields of stars, planets, and brown dwarfs—which are kind of an intermediate object between a planet and a star.

    Brown dwarf
    Brown dwarf

    Stars and their planets have intertwined relationships. Our sun, for example, produces coronal mass ejections, or CMEs, which are bubbles of hot plasma explosively ejected from the sun out into the solar system.

    Solar eruption 2012 by NASA's Solar Dynamic Observatory SDO
    CME

    Radiation and particles from these solar events bombard the earth and interact with the atmosphere, dominating the local “space weather” in the environment of Earth. Happily, our planet’s magnetic field shields and redirects CMEs toward the polar regions. This causes auroras—the colorful light in the sky commonly known as the Northern or Southern Lights.

    Auroras from around the world
    Auroras from around the world

    Our new telescope, the Owens Valley Long Wavelength Array, images the entire sky instantaneously and allows us to monitor extrasolar space weather on thousands of nearby stellar systems.

    Caltech Owens Valley Long Wavelength Array
    Caltech Owens Valley Long Wavelength Array

    When a star produces a CME, it also emits a bright burst of radio waves with a specific signature. If a planet has a magnetic field and it is hit by one of these CMEs, it will also become brighter in radio waves. Those radio signatures are very specific and allow you to measure very precisely the strength of the planet’s magnetic field. I am interested in detecting radio waves from exoplanets—planets outside of our solar system—in order to learn more about what governs whether or not a planet has a magnetic field.

    Why is this important?

    The presence of a magnetic field on a planet can tell us a lot. Like on our own planet, magnetic fields are an important line of defense against the solar wind, particularly explosive CMEs, which can strip a planet of its atmosphere. Mars is a good example of this. Because it didn’t have a magnetic field shielding it from the sun’s solar wind, it was stripped of its atmosphere long ago. So, determining whether a planet has a magnetic field is important in order to determine which planets could possibly have atmospheres and thus could possibly host life.

    How did you get into this line of work?

    From a young age, I was obsessed with astronomy—it’s all I cared for. My parents got me a telescope when I was 7 or 8, and from then on, that was it.

    As a grad student, I was looking at magnetic fields of cool—meaning low-temperature—objects. When I was looking at brown dwarfs, I found that they behave like planets in that they also have auroras. I had the idea that auroras could be the avenue to examine the magnetic fields of other planets. So brown dwarfs were my gateway into exoplanets.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 3:33 pm on February 10, 2016 Permalink | Reply
    Tags: Astronomy, , , ,   

    From Ethan Siegel via Forbes: “What Will It Mean If LIGO Detects Gravitational Waves?” 

    ForbesMag

    Forbes Magazine

    Starts with a bang
    Starts with a Bang

    Feb 9, 2016
    Ethan Siegel

    Cornell SXS teamTwo merging black holes simulation
    Image credit: Bohn et al 2015, SXS team, of two merging black holes and how they alter the appearance of the background spacetime in General Relativity.

    For over a decade, to very little fanfare, a new type of astronomy has been going on: gravitational wave astronomy. Rather than using a telescope to look out at the Universe, a gravitational wave detector uses lasers, fired and reflected perpendicular to one another, and then reconstructed to create a specific interference pattern when they’re reunited. This apparatus — the Laser Interferometer Gravitational-Wave Observatory (LIGO) — demonstrated its proof-of-concept from 2002-2010, and then was shut down for five years while it was upgraded.

    Caltech Ligo
    MIT/Caltech Advanced aLIGO

    In September of 2015, it was turned back on with the new upgrade (Advanced LIGO), and in just two days, the Advanced LIGO collaboration is going to make their first major announcement, and the speculation is this: that they’re going to announce the direct detection of the first gravitational wave. Here’s what that would mean.

    When [Albert] Einstein’s General Relativity was first proposed, it was incredibly different from the concept of space and time that came before. Rather than being fixed, unchanging quantities that matter and energy traveled through, they are dependent quantities: dependent on one another, dependent on the matter and energy within them, and changeable over time. If all you have is a single mass, stationary in spacetime (or moving without any acceleration), your spacetime doesn’t change. But if you add a second mass, those two masses will move relative to one another, will accelerate one another, and will change the structure of your spacetime. In particular, because you have a massive particle moving through a gravitational field, the properties of General Relativity mean that your mass will get accelerated, and will emit a new type of radiation: gravitational radiation.

    pulsar orbiting a binary companion and the gravitational waves (or ripples) in spacetime that ensue as a resul ESO
    Image credit: ESO/L. Calçada, of a pulsar orbiting a binary companion and the gravitational waves (or ripples) in spacetime that ensue as a result.

    This gravitational radiation is unlike any other type of radiation we know. Sure, it travels through space at the speed of light, but it itself is a ripple in the fabric of space. It carries energy away from the accelerating masses, meaning that if the two masses orbit one another, that orbit will decay over time. And it’s that gravitational radiation — the waves that cause ripples through space — that carries the energy away. For a system like the Earth orbiting the Sun, the masses are so (relatively) small and the distances so large that the system will take more than 10^150 years to decay, or many, many times the current age of the Universe. (And many times the lifetime of even the longest-lived stars that are theoretically possible!) But for black holes or neutron stars that orbit each other, those orbital decays have already been observed.

    Neutron stars merging
    Image credit: NASA (L), Max Planck Institute for Radio Astronomy / Michael Kramer, via http://www.mpg.de/7644757/W002_Physics-Astronomy_048-055.pdf.

    We suspect there are even stronger systems out there that we simply haven’t been able to detect, like black holes that spiral into and merge with one another. These should exhibit characteristic signals, like an inspiral phase, a merger phase, and then a ringdown phase, all of which result in the emission of gravitational waves that Advanced LIGO should be able to detect. The way the Advanced LIGO system works is nothing short of brilliant, and it takes advantage of the unique radiation of these gravitational waves. In particular, it takes advantage of how they cause spacetime to respond.

    These ripples work by compressing and then expanding space in directions that are perpendicular to one another, with frequencies and intensities that are dependent on a number of properties of where they come from, such as the two masses that spiral into one another, their distance from one another, and their distance from us. Advanced LIGO shoots two lasers of identical frequencies/wavelengths perpendicular to one another down a shaft four kilometers in either direction, bounces them off of mirrors many times over (effectively increasing the path-length to thousands of kilometers), and then brings them back together, where they create an interference pattern with one another.

    MIT Caltech Advanced aLIGO how it works schematic
    Image credit: public domain / US Government, of a schematic of how LIGO works. Modifications made by Krzysztof Zajączkowski.

    Under normal circumstances (where no gravitational waves pass through them), these path lengths are equal, and the interference pattern looks normal. But if a gravitational wave does pass through, that interference pattern will shift in a particular set of circumstances, and that shift will tell us the mass of each part of the system, how far apart they are and how distant they are from us.

    We have two Advanced LIGO system set up: one in the northwest United States (in Washington) and one in the southeast United States (in Louisiana), and if both detectors see the same thing, we’ll catch our first gravitational wave! This version of LIGO should be most sensitive to two black holes between 1 and a few hundred solar masses merging together out to many millions of light years: something that’s expected to happen at least a few times a year.

    Advanced aLIGO search range MIT Caltech
    Image credit: Caltech/MIT/LIGO Lab, of the Advanced LIGO search range.

    If the collaboration does announce their first detected event this Thursday, they’ll not only have this information for us, it will be a brand new successful test of Einstein’s General Relativity, and the first direct evidence for gravitational radiation ever. Advanced LIGO is the most advanced gravitational wave observatory ever constructed, and the first one that ought to actually see a true signal. With nearly 1,000 scientists on board, it’s the largest scientific collaboration designed to search for them as well. If all goes as suspected, a new era of astronomy is about to begin.

    MIT Caltech Advanced aLIGO Installing Upgrades
    Installing the Advanced LIGO upgrades. Image credit: Caltech/MIT/LIGO Lab, taken by Cheryl Vorvik.

    I’m very much against doing science by rumor. But if they find a gravitational wave, this is what it’ll teach us: that Einstein’s relativity is right, that gravitational radiation is real, and that merging black holes not only produce them, but that these waves can be detected. It’s a whole new type of astronomy — one that doesn’t use telescopes — and a whole new way to view black holes, neutron stars, and other objects that are otherwise mostly invisible. For the first time, we may be developing eyes for examining the Universe in a way that no living creature has ever examined it before.

    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 1:34 pm on February 10, 2016 Permalink | Reply
    Tags: , Astronomy, , Kilonovas   

    From AAS NOVA: “Can JWST Follow Up on Gravitational-Wave Detections?” 

    AASNOVA

    American Astronomical Society

    10 February 2016
    Susanna Kohler

    Kilanova
    Kilonova. Popular Mechanics

    Bitten by the gravitational-wave bug? While we await Thursday’s press conference, here’s some food for thought: if LIGO were able to detect gravitational waves from compact-object mergers, how could we follow up on the detections?

    Caltech Ligo
    MIT/Caltech Advanced aLIGO

    A new study investigates whether the upcoming James Webb Space Telescope (JWST) will be able to observe electromagnetic signatures of some compact-object mergers.

    NASA Webb telescope annotated
    NASA/ESA/CSA Webb

    Hunting for Mergers

    Studying compact-object mergers (mergers of black holes and neutron stars) can help us understand a wealth of subjects, like high-energy physics, how matter behaves at nuclear densities, how stars evolve, and how heavy elements in the universe were created.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) is searching for the signature ripples in spacetime identifying these mergers, but gravitational waves are squirrelly: LIGO will only be able to localize wave sources to tens of square degrees. If we want to find out more about any mergers LIGO discovers in gravitational waves, we’ll need a follow-up search for electromagnetic counterparts with other observatories.

    The Kilonova Key

    One possible electromagnetic counterpart is kilonovae, explosions that can be produced during a merger of a binary neutron star or a neutron star–black hole system. If the neutron star is disrupted during the merger, some of the hot mass is flung outward and shines brightly by radioactive decay.

    Kilonovae are especially promising as electromagnetic counterparts to gravitational waves for three reasons:

    1.They emit isotropically, so the number of observable mergers isn’t limited by relativistic beaming.
    2.They shine for a week, giving follow-up observatories time to search for them.
    3.The source location can be easily recovered.

    The only problem? We don’t currently have any sensitive survey instruments in the near-infrared band (where kilonova emission peaks) that can provide coverage over tens of square degrees. Luckily, we will soon have just the thing: JWST, launching in 2018!

    JWST’s Search

    n a recent study, a team of authors led by Imre Bartos (Columbia University) evaluate whether JWST will be capable of catching these kilonovae if LIGO finds gravitational wave signals.

    Bartos and collaborators calculate that, given the sensitivity of the different filters on JWST’s Near-Infrared Camera [NIRCAM], the instrument should easily be able to detect a kilonova 200 Mpc away (a typical distance at which LIGO might be able to find a neutron-star binary).

    NASA Webb NIRcam
    JWST NIRCAM

    But there’s a catch: 10 deg^2 is a really big sky area, and it would take JWST an unfeasible amount of time (days!) to fully cover it.

    The authors suggest instead using a targeted search. Since most mergers are expected to be in or near galaxies, JWST could specifically focus the follow-up search on known galaxies within the search area. This approach would bring the total search time down to 12.6 hours, which is within the realm of feasibility. And this time could be reduced even further by concentrating on galaxies most likely to host kilonovae, like those with high star-formation rates.

    The conclusion: if LIGO is able to detect gravitational waves, JWST will provide an excellent means to follow up on the detection in the attempt to identify the source.
    Citation

    I. Bartos et al 2016 ApJ 816 61. doi:10.3847/0004-637X/816/2/61

    See the full article here .

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  • richardmitnick 2:50 am on February 10, 2016 Permalink | Reply
    Tags: Astronomy, , , ,   

    From perth now for CSIRO: “Australian astronomers zero-in on the ‘Great Attractor’ pulling on our Milky Way” 

    perth now

    perth now

    CSIRO bloc

    Commonwealth Scientific and Industrial Research Organisation

    February 9, 2016
    Jamie Seidel

    A STRANGE intergalactic force is drawing our Milky Way galaxy inward. We don’t know what, or why. But a hidden swarm of hundreds of nearby galaxies just discovered by Australian astronomers may help reveal the identity of the ‘Great Attractor’.

    Great Attractor galaxies

    This pack of galaxies has been spotted by International Centre for Radio Astronomy Research (ICRAR) researchers using CSIRO’s Parkes Observatory in NSW.

    CSIRO Parkes Observatory

    The study was published today in Astronomical Journal.

    Despite being ‘just next door’ in astronomical terms — a mere 250 million light years away — these galaxies have remained hidden from view because they are on the opposite side of our own.

    The intensity of stars and dust crowded together along the plane of the Milky Way is directly in the line of sight — masking everything behind it from view.

    That something must be there has been known for some time.

    Its immense gravitational pull — the equivalent of a million billion Suns — has been observed through calculations of strange deviations in the flight path of nearby galaxies.

    And our own.

    In the absence of any indication as to what it may be, astronomers have simply dubbed it the Great Attractor.

    Universe map
    Panoramic view of the entire near-infrared sky. The location of the Great Attractor is shown following the long blue arrow at bottom-right.

    Our Milky Way is just one of hundreds of thousands of local galaxies ensnared by its grasp.

    And we’re hurtling towards the mysterious source of this attraction force at more than two million kilometres per hour.

    GREAT ATTRACTOR

    “We don’t actually understand what’s causing this gravitational acceleration on the Milky Way or where it’s coming from,” says study lead author Professor Lister Staveley-Smith of the University of Western Australia.

    “We know that in this region there are a few very large collections of galaxies we call clusters or superclusters, and our whole Milky Way is moving towards them.”

    Superclusters
    Superclusters

    Essentially, all we know is that there is an immense — but probably diffuse — concentration of mass lurking some 250 million light years away.

    Is it a monster-black hole? Or a whole army of these collapsed points in space-time?

    “Some astronomers think the Great Attractor is a super-supercluster of galaxies; some astronomers think that some regions of the universe are “darker” than others,” Professor Staveley-Smith says, referring to densities of the invisible source of gravity dubbed Dark Matter.

    “Some physicists are even considering the possibility that the mass fluctuations in the universe are so significant that astronomers may be fundamentally misinterpreting the relationship between gravity and motion.”

    It all remains speculation.

    But observing and understanding the distribution and behaviour of the new galaxies may uncover vital clues.

    “The ‘Great Attractor’ lies at the intersection of several large-scale filaments of galaxies,” says Dr Barbel Koribalski of CSIRO Astronomy and Space Science. “One could picture a giant hoover with galaxies near and far slowly streaming towards it. We can’t see much of this hoover, but we can measure the motion of the galaxies.”

    What is doing the hoovering is the issue.

    SUPER SIGHT

    The Parkes radio telescope is a 64-metre dish that was activated in 1961. It was more recently modified with an innovative receiver, allowing the international team of scientists to peer past the ‘interference’ of our galactic core into unexplored space.

    “The Milky Way is very beautiful of course and it’s very interesting to study our own galaxy but it completely blocks out the view of the more distant galaxies behind it,” says Professor Staveley-Smith.

    Not so completely anymore.

    What the survey revealed was a field of 883 galaxies, a third of which had not previously been suspected says Professor Staveley-Smith.

    University of Cape Town astronomer Professor Renée Kraan-Korteweg — also part of the research team — said astronomers have been trying to map the galaxies hidden behind the Milky Way for decades.

    “We’ve used a range of techniques but only radio observations have really succeeded in allowing us to see through the thickest foreground layer of dust and stars,” she said.

    “An average galaxy contains 100 billion stars, so finding hundreds of new galaxies hidden behind the Milky Way points to a lot of mass we didn’t know about until now.”

    So what caused this odd accumulation of galaxies?

    That bit remains the problem.

    BIONIC EYE

    Dr Koribalski says innovative technologies on the Parkes radio telescope had made it possible to survey large areas of the sky quickly. And things are about to get much, much better.

    “Detecting galaxies behind the Milky Way (in the so-called Zone of Avoidance) and measuring their motions is important to pinpoint its location and total mass,” she says. “The Parkes multibeam system made this possible. With this receiver we’re able to map the sky 13 times faster than we could before and make new discoveries at a much greater rate.”

    Copies of this receiver have been purchased from CSIRO by United States and Chinese astronomers to upgrade their own radio telescopes.

    But this receiver is being temporarily removed from the Parkes telescope this week. A new Phased-Array Feed (PAF) is being attached for testing.

    Parkes Phased Array Feed

    “The PAF is a huge technological advance, a breakthrough of major proportion that will be able to do fast and sensitivities surveys of the sky, (and is) bound to make many new discoveries,” Dr Koribalski says. “How to learn more about the Great Attractor? The answer is WALLABY — the upcoming Australian SKA Pathfinder (ASKAP) HI All Sky Survey – which is expected to spot more than 500,000 galaxies.”

    SKA ASKAP telescope
    ASKAP

    This will offer much faster scanning of the skies than current equipment, combined with a twenty-fold increase in resolution.

    Dr Koribalski says she expects the new scope will detect an additional 10,000 galaxies tucked away behind our own.

    It may also, hopefully, paint a trail to the ‘Great Attractor’ itself.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

     
  • richardmitnick 12:43 pm on February 9, 2016 Permalink | Reply
    Tags: Astronomy, , , NGC 253, Suprime-Cam instrument   

    From Subaru: “Galactic Space Oddity Discovered 

    NAOJ

    NAOJ

    February 8, 2016
    No writer credit found

    An international team of researchers led by Aaron Romanowsky of San José State University has used the Subaru Telescope to identify a faint dwarf galaxy disrupting around a nearby giant spiral galaxy. The observations provide a valuable glimpse of a process that is fleeting but important in shaping galaxies.

    “The outer regions of giant galaxies like our own Milky Way appear to be a jumble of debris from hundreds of smaller galaxies that fell in over time and splashed into smithereens,” said Romanowsky. “These dwarfs are considered building blocks of the giants, but the evidence for giants absorbing dwarfs has been largely circumstantial. Now we have caught a pair of galaxies in the act of a deadly embrace.”

    NGC 253-dw2 dwarf galaxy disturbing
    Close-up view of the dwarf galaxy NGC 253-dw2. The closely packed red dots show that it is composed of individual stars.

    The two objects in the study are NGC 253 [Sculpture] , also called the Silver Dollar galaxy, and the newly discovered dwarf NGC 253-dw2.

    NGC 253 Sculpture or Silver Dollar Galaxy
    NGC 253 Sculpture Galaxy

    They are located in the Southern constellation of Sculptor at a distance of 11 million light years from Earth, and are separated from each other by about 160 thousand light years. The dwarf has an elongated appearance that is the hallmark of being stretched apart by the gravity of a larger galaxy.

    “The dwarf has been trapped by its giant host and will not survive intact for much longer,” said team member Nicolas Martin, of the Strasbourg Observatory. “The next time it plunges closer to its host, it could be shredded into oblivion. However, the host may suffer some damage too, if the dwarf is heavy enough.”

    The interplay between the two galaxies may resolve an outstanding mystery about NGC 253, as the giant spiral shows signs of being disturbed by a dwarf. The disturber was previously unseen and presumed to have perished, but now the likely culprit has been found. “This looks like a case of galactic stealth attack,” said Gustavo Morales of Heidelberg University. “The dwarf galaxy has dived in from the depths of space and barraged the giant, while remaining undetected by virtue of its extreme faintness.”

    The discovery of NGC 253-dw2 has an unusual pedigree. It began with a digital image of the giant galaxy taken by astrophotographer Michael Sidonio using a 30 centimeter (12 inch) diameter amateur telescope in Australia. Other members of the international team noticed a faint smudge in the image and followed it up with a larger, 80 centimeter (30 inch) amateur telescope in Chile, led by Johannes Schedler. The identity of the object was still not clear, and it was observed with the 8 meter (27 foot) Subaru Telescope on the summit of Mauna Kea in Hawaii, in December 2014. “In the first image, we weren’t sure if there was really a faint galaxy or if it was some kind of stray reflection,” said David Martínez-Delgado, also from Heidelberg University. “With the high-quality imaging of the Suprime-Cam instrument on the Subaru Telescope, we can now see that the smudge is composed of individual stars and is a bona fide dwarf galaxy. This discovery is a wonderful example of fruitful collaboration between amateur and professional astronomers.”

    NAOJ Subaru Hyper Suprime Camera
    NAOJ Subaru Hyper Suprime Camera

    This discovery is a wonderful example of fruitful collaboration between amateur and professional astronomers.”

    The findings are in research paper published in the Monthly Notices of the Royal Astronomical Society Letters by Oxford University Press, as “Satellite accretion in action: a tidally disrupting dwarf spheroidal around the nearby spiral galaxy NGC 253” by Romanowsky et al., first online on January 23, 2016 (http://mnrasl.oxfordjournals.org/lookup/doi/10.1093/mnrasl/slv207).

    The research team:

    Aaron J. Romanowsky (San José State University and University of California Observatories, USA)
    David Martínez-Delgado (Zentrum für Astronomie der Universität Heidelberg, Germany)
    Nicolas F. Martin (Université de Strasbourg, France and Max-Planck-Institut für Astronomie, Germany)
    Gustavo Morales (Zentrum für Astronomie der Universität Heidelberg, Germany)
    Zachary G. Jennings (University of California, USA)
    R. Jay GaBany (Black Bird Observatory II, USA)
    Jean P. Brodie (University of California Observatories and University of California, USA)
    Eva K. Grebel (Zentrum für Astronomie der Universität Heidelberg, Germany)
    Johannes Schedler (Cerro Tololo Inter-American Observatory, Chile)
    Michael Sidonio (Terroux Observatory, Australia)

    Links:

    http://subarutelescope.org/Pressrelease/2014/07/01/index.html
    http://subarutelescope.org/Pressrelease/2012/02/08/index.htmll

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
    Subaru

    ALMA Array
    ALMA

    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

     
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