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  • richardmitnick 1:05 pm on January 16, 2017 Permalink | Reply
    Tags: , , , Cosmology, , , ,   

    From Motherboard: “An Earth-Sized Telescope is About to ‘See’ a Black Hole For the First Time” 

    motherboard

    Motherboard

    January 13, 2017
    William Rauscher

    We were perched dizzyingly high in the Chilean Andes, ringed by a herd of sixty-six white giants. Through the broad windows of the low, nondescript building in which we stood, we could see massive white radio antennas outside against the Martian-red soil of the desolate Chajnantor Plateau, their dishes thrust towards a pure blue sky.

    This is the Atacama Large Millimeter Array, also known as ALMA—one of the world’s largest radio telescope arrays, an international partnership that spans four continents. In spring of 2017, ALMA, along with eight other telescopes around the world, will aim towards the center of the Milky Way, around 25,000 light years from Earth, in an attempt to capture the first-ever image of a black hole. This is part of a daring astronomy project called the Event Horizon Telescope (EHT).

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

    My partner Dave Robertson and I took turns huffing from a can of oxygen to stave off the altitude sickness that can come on at 16,500 feet. Our guide Danilo Vidal, an energetic Chilean who wore his dark hair in a ponytail, pointed to a grey metal door with a glass window. “If we open that door,” said Vidal, “everyone in science will hate us for the rest of our lives.” Confused by this cryptic statement, I took another hit from the oxygen and peered through the glass, into the heart of the experiment.

    Among a small forest of processors, I could see an eggshell-white box that resembled a dorm room refrigerator. Inside was the brand-new maser, an ultraprecise atomic clock that syncs up every antenna on-site, and then syncs ALMA itself to the Event Horizon Telescope’s global network, lending so much dish-space and processing power that it effectively doubles the entire network’s resolution.

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    Christophe Jacques of the NRAO inspects the wiring on ALMA’s new hydrogen maser atomic clock during installation. Image: Carlos Padilla/NRAO/AUI/NSF

    To keep equipment from overheating, the room is kept at an absurdly low temperature—very close to absolute zero. If we opened the door, Vidal explained, emergency systems would instantly shut down the maser to protect it, and ALMA’s beating heart would stop, ruining multiple international astronomy projects, including the EHT.

    Claudio Follert, an ALMA fiber-optic specialist in his mid-fifties, was there in 2014 when the maser first arrived—he told me it was a machine he had never seen before, carried in by strange men. The men were sent by the EHT, which is based out of MIT.

    The EHT is made possible by the maser’s astonishing precision—about one billion times more precise than the clock in your smartphone.

    Designed by an international team led by MIT scientist Shep Doeleman, the EHT is the first of its kind-a global telescope network that uses a technique called interferometry to synthesize astronomical data from multiple sources, each with its own maser—including ALMA in Chile, the Large Millimeter Telescope atop the Sierra Negra volcano in Mexico, and the National Radio Astronomy Observatory in Virginia.

    Together, these telescopes create a super-telescope that is quite literally the size of the Earth, with enough resolution to photograph an orange on the Moon.

    With ALMA recently added to this Avengers-like team of radio telescopes, the network is ten times more sensitive. As a result, Doeleman’s group believes it has the firepower to penetrate the interstellar gases that cloak their targets: supermassive black holes. Drawn into orbit by the black holes’ gravity, these gases form gargantuan clouds that yield nothing to optical telescopes.

    Faint radio signals from the black holes, on the other hand, slip through the gas clouds and are ultimately detected on Earth.

    Black holes are the folk legends of outer space. Since no light can escape them, they’re invisible to the eye, and we have no confirmation that they actually exist—only heaps of indirect evidence, particularly the gravitational wobbles in orbits of nearby stars, the behavior of interstellar gas clouds, and the gaseous jets that spew into space when an unseen source of extreme gravity appears to rip cosmic matter to shreds.

    Black holes challenge our most fundamental beliefs about reality. Visionary scientific minds, including the theoretical physicists Stephen Hawking and Kip Thorne, have devoted entire books to unpacking the hallucinatory scenarios thought to be induced by black holes’ gravitational forces—imagine the bottom of your body violently wrenched away from the top, physically stretching you like a Looney Tunes character, a scenario that Thorne’s Black Holes and Time Warps paints in stomach-churning detail.

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    An image from the heart of the Milky Way from NASA’s Chandra X-ray Observatory. The supermassive black hole is at the center. Image: NASA/CXC/MIT/F. Baganoff et al.

    NASA/Chandra Telescope
    NASA/Chandra Telescope

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

    Black holes are thought to lurk at the centers of galaxies including our own. Prove the existence of Sagittarius A*, the supermassive black hole at the heart of the Milky Way, and you are one step closer to solving another mystery: the origin of humankind, and all life as we know it.

    “The black hole at the center of our galaxy has everything to do with our own origin,” said Violette Impellizzeri, an ALMA astronomer collaborating with Event Horizon Telescope. Supermassive black holes are thought to regulate the stars that surround them, influencing their formation and orbit. “Understanding how our galaxy was formed leads to our own origin directly,” she said.

    Scientists estimate the mass of Sagittarius A* to be four million times that of our Sun, yet its diameter is roughly equal to the distance from our sun to Mercury—not much, in cosmic terms. The resulting density produces gravity so strong that space and time distort around it, making it invisible.

    The current theory, espoused by Thorne, is that the distance from the center of a black hole, known as the singularity, to its edge, known as the event horizon, becomes so warped that it nears infinite length, and light simply runs out of energy as it tries to escape.

    It took Doeleman, the project leader at MIT, to decide that in order to see the unseeable, you would first have to create a new kind of vision. With ALMA as part of the giant EHT network, we can take a radio “photograph” of the matter that orbits Sagittarius A*—called the accretion disk—and finally see the black hole in shadow: its first-ever portrait.

    • Vidal and Follert, the guide and fiber-optic specialist, led us out onto the plateaus. There was work to do: one of the antennas was hobbled by a damaged radio receptor.

    It was blindingly bright and windy, not to mention dry—Chajnantor is located in Chile’s Atacama Desert, the driest place on Earth, if you don’t count the poles. Completely inhospitable for human beings, Chajnantor is an ideal setting for a radio telescope: the elevation puts it closer to the stars, and the strikingly low water vapor keeps the cosmic signals pristine.

    For some, like ALMA’s crew, as well as Doeleman, the extreme environment is part of the attraction. “I just love getting to the telescopes,” he said. At 50, Doeleman is fresh-faced, with glasses and thinning hair that make him look every part the bookish scientist. His outgoing personality and entrepreneurial vigor reflect an explorer’s spirit more at home in the field than behind a desk.

    Doeleman regularly travels to each EHT site around the world, many of them located in extreme environments like the Andes or the Sierra Negra. “The adventure part is what motivates me—driving along dirt roads, up the sides of mountains, to install new instruments, doing observations that have never been done before. It’s a little bit like Jacques Cousteau—we’re not sitting in armchairs in our offices.”

    Outside on Chajnantor, I felt light-headed. I tried to keep my breathing steady: low oxygen can quickly wreck your mental faculties. On the plateau, Dave and I were dwarfed by ALMA’s antennas, which blocked out the desert sun. They felt powerful and eerie, like Easter Island statues. Even when standing directly beneath these behemoths, it wasn’t clear how they were controlled—the white dishes seemed to twist and pivot without warning.

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    Using a technique called interferometry, ALMA’s antennas can be configured to act as one giant antenna, and ALMA itself can be synced up with telescopes worldwide. Image: Dave Robertson

    An ALMA antenna is useless when one of its radio receptors is out of tune. We followed Follert up several steel ladders, boots clanging on metal, until we were in a low-ceilinged maintenance room inside one of the antennas. We helped him remove the damaged receptor, a long metal cylinder resembling a futuristic bazooka.

    Vidal drove us back down the mountain to the Operations Support Facility (OSF), ALMA’s headquarters, so we could see the lab where receptors are maintained.

    Per strict international regulations, Vidal was required to breathe through an oxygen tube as he drove, lest the high altitude cause him to lose consciousness behind the wheel.

    As we descended, Vidal radioed at regular intervals to identify our location. All around us the mountain slopes were red, rocky and barren—no wonder that NASA regularly deploys expeditions to this desert to replicate conditions on Mars.

    Located at 9,000 ft, the OSF is where ALMA’s staff call home: a total of 600 scientists working in shifts are based here, including engineers and technicians, from over 20 countries. The working conditions can be extreme. Staff hole up in weeklong shifts separated from friends and family, and endure the short and long-term health risks of high elevation, including a stroke or pulmonary edema, where fluid fills your lungs and you suffocate.

    It is thus maybe not surprising to find out that the entire staff are monitored regularly by medical personnel, and that emergency oxygen and a hyperbaric chamber are on-hand.

    They unwind by exercising and watching movies, although certain sci-fi flicks are frowned upon. “We need a break from space sometimes,” said Follert. Alcohol consumption on site is strictly forbidden—have even a tipple and you risk amplifying the physical effects of high elevation.

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    Aerial picture of ALMA’s Operations Support Facility. Image: Carlos Padilla/NRAO/AUI/NSF

    The close teamwork at ALMA is absolutely essential for the life of the observatory. Detecting cosmic radio signals, including those sent from a black hole, requires constant cooperation across teams, who must obsessively calibrate, maintain and repair their instruments to fend off unwanted noise.

    ALMA and the other telescopes on the EHT will soon turn towards the center of the Milky Way to tune in to the black hole’s narrow radio frequency. The data that ALMA collects will be so large, it cannot be transferred online. Instead, physical hard drives will shipped by “sneakernet”: loaded into the belly of a 747 and flown directly to MIT.

    When ALMA’s data is correlated with the other telescopes later this year, Sagittarius A* should appear against the glowing gas of the accretion disk. Maybe.

    Actually, said Doeleman, “we don’t know what we’re going to see. Nature can be cruel. We may see something boring. But we’re not married to one outcome—we’re going to see nature the way nature is.”

    See the full article here .

    The full EHT:

    Event Horizon Telescope Array

    Event Horizon Telescope map

    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

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

    ESO/APEX
    Atacama Pathfinder EXperiment (APEX)

    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 NOEMA interferometer
    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 Hawaii SAO
    Submillimeter Array Hawaii SAO

    Future Array/Telescopes

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

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

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    The future is wonderful, the future is terrifying. We should know, we live there. Whether on the ground or on the web, Motherboard travels the world to uncover the tech and science stories that define what’s coming next for this quickly-evolving planet of ours.

    Motherboard is a multi-platform, multimedia publication, relying on longform reporting, in-depth blogging, and video and film production to ensure every story is presented in its most gripping and relatable format. Beyond that, we are dedicated to bringing our audience honest portraits of the futures we face, so you can be better informed in your decision-making today.

     
  • richardmitnick 10:39 am on January 16, 2017 Permalink | Reply
    Tags: , , , Cosmology, There are at least two trillion galaxies in the universe ten times more than previously thought,   

    From U Nottingham: “There are at least two trillion galaxies in the universe, ten times more than previously thought” 

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    University of Nottingham

    13 Oct 2016 [Just turned up in a social media search]
    Lindsay Brooke
    Media Relations Manager
    lindsay.brooke@nottingham.ac.uk
    +44 (0)115 951 5751
    Location: University Park

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    Image of the HST GOODS-South field, one of the deepest images of the sky but covering just one millionth of its total area. The new estimate for the number of galaxies is ten times higher than the number seen in this image. Credit: NASA / ESA / The GOODS Team / M. Giavalisco (UMass., Amherst)

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    Astronomers have long sought to determine how many galaxies there are in the universe. This is a fundamental question that we have only been able to address with any certainty due to new scientific results.

    During the past 20 years very deep Hubble Space Telescope images have found a myriad of faint galaxies, and it was approximated that the observable Universe contains about 100 billion galaxies in total.

    Now, an international team, led by Christopher Conselice, Professor of Astrophysics at The University of Nottingham, has shown that the actual number is much higher than this.

    Professor Conselice and his team has shown that the number of galaxies in our universe is at least two trillion – ten times more than previously thought – the often quoted value of around 100 Billion.

    Current astronomical technology allows us to study a fraction of these galaxies– just 10%.

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

    It means that over 90% of the galaxies in our universe have yet to be discovered, and will only be seen once bigger and better telescopes are developed.

    ESO 50 Large
    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile
    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile

    LSST
    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC
    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.
    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes

    TMT-Thirty Meter Telescope, proposed for Mauna Kea, Hawaii, USA
    TMT-Thirty Meter Telescope, proposed for Mauna Kea, Hawaii, USA

    Giant Magellan Telescope, Las Campanas Observatory, to be built  some 115 km (71 mi) north-northeast of La Serena, Chile
    Giant Magellan Telescope, Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    NASA/WFIRST telescope
    NASA/WFIRST telescope

    The research – The Evolution of Galaxy number density at Z < 8 and its implications – is published today (October 13, 2016) in the Astrophysical Journal – the foremost research journal in the world dedicated to recent developments, discoveries and theories about astronomy and astrophysics.

    The results have clear implications for galaxy formation, and also help solve an ancient astronomical paradox — why is the sky dark at night?

    Professor Conselice said: “We are missing the vast majority of galaxies because they are very faint and far away. The number of galaxies in the universe is a fundamental number we would like to know, and it boggles the mind that over 90% of the galaxies in the universe have yet to be studied.

    Who knows what interesting properties we will find when we study these galaxies with the next generation of telescopes. These galaxies will likely hold the clues to many outstanding astrophysical issues.”

    Intergalactic archaeological dig

    Professor Conselice’s research is the culmination of 15 year’s work. His team converted pencil beam images of deep space from telescopes around the world, and especially from the Hubble telescope into 3D maps to calculate the volume as well as the density of galaxies of one tiny bit of space after another.

    This painstaking research enabled him to establish how many galaxies we have missed – much like an intergalactic archaeological dig.

    The results of this study are based on the measurements of the number of galaxies at different epochs – different instances in time – through the universe’s history.

    When Professor Conselice and his team at Nottingham, in collaboration with scientists from the Leiden Observatory at Leiden University in the Netherlands and the Institute for Astronomy at the University of Edinburgh, examined how many galaxies there were in a given value they found that this increased significantly at earlier times.

    In fact, it appears that there are a factor of 10 more galaxies in a given volume of space when the universe was a few billion years old compared with today. Most of these galaxies are low mass systems with masses similar to those of the satellite galaxies surrounding the Milky Way.

    Professor Conselice said: “This is very surprising as we know that over the 13.7 billion years of cosmic evolution galaxies are growing through star formation and merging with other galaxies. Thus, to find that there were in fact more galaxies in the past implies that that significant evolution in galaxies must have occurred to reduce the number of galaxies through extensive merging of systems. This also gives us a verification of the top-down formation of structure in the universe.”

    Probing cosmic history answers astronomical questions

    By probing deep into space Professor Conselice and his team have been able to go way back in time – more than 13 billion years in the past – to find out how our universe evolved and answer some vexing questions.

    The implications of this research are many, for instance; galaxies are likely to be forming by merging together. This decreases the number of systems as time progresses which provides a possible solution to Oblers’ paradox – why the sky is dark at night?

    Solutions to this in the past were based on the fact that the universe is finite in size as well as in time. However, if we consider all the undiscovered galaxies then in principle the critiera for Oblers’ paradox is met.

    However, most galaxies in the universe are very distant and their light is absorbed by gas in intergalactic space. Otherwise, we would see the night sky lit up everywhere.

    See the full article here .

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    “The University of Nottingham shares many of the characteristics of the world’s great universities. However, we are distinct not only in our key strengths but in how our many strengths combine: we are financially secure, campus based and comprehensive; we are research-led and recruit top students and staff from around the world; we are committed to internationalising all our core activities so our students can have a valuable and enjoyable experience that prepares them well for the rest of their intellectual, professional and personal lives.”

     
  • richardmitnick 7:30 am on January 15, 2017 Permalink | Reply
    Tags: , , Cosmology, Could the Universe have begun from a Big Bounce,   

    From Ethan Siegel: “Could the Universe have begun from a Big Bounce?” 

    Ethan Siegel
    1.14.17

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    A ‘Big Bounce’ requires a recollapsing phase followed by an expanding phase. Image credit: E. Siegel, derivative from Ævar Arnfjörð Bjarmason under cc-by-2.0.

    And just what did come before — way before — the Big Bang?

    “We are part of the universe that has developed a remarkable ability: We can hold an image of the world in our minds. We are matter contemplating itself.” -Sean Carroll

    Thanks to incredible advances in science over the past century, we’ve been able to determine where our Universe came from in the past, how it got to be the way it is today and where it’s headed into the distant future. But there are still limits to what we can say: there’s a limit to how far back we can gain any sort of information from, and there’s a limit to how far into the future we can predict the Universe’s evolution with any certainty. When you head beyond those limits, that’s where the greatest mysteries of all lie. Katherine Litchin asks us about one of them:

    “After reading your post on the Big Freeze fate of the universe, I was wondering what you think about the Big Bounce scenario?”

    There are three parts to this: what we know, what remains possible, and what we think is most likely (for good reasons).

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    A map of the clumping/clustering pattern that galaxies in our Universe exhibit today. Image credit: Greg Bacon/STScI/NASA Goddard Space Flight Center.

    Our Universe, as it exists right now, is full of stars, galaxies, black holes, dark matter, dark energy and radiation. It has clumps and clusters; it has giant voids. It’s expanding, it’s cooling, and it contain a certain number of particles arranged in a particular way at any given moment. Based on what we know it’s made out of, how it’s expanding and what the laws of physics are known to be, we can both extrapolate the Universe into the past and into the future. When we go into the past, we find it was smoother, hotter, denser, less clumpy, more energetic and more uniform; when we go into the future, we find that it will become clumpier, frozen, sparser, less energetic and emptier. To a very high degree of accuracy, we know this to be true.

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    Our Universe, from the hot Big Bang until the present day, underwent a huge amount of growth and evolution, and continues to do so. Image credit: NASA / CXC / M.Weiss.

    One thing we can look at, to help us understand this in a different way, is by looking at the entropy of the observable Universe. Entropy is difficult to wrap your head around conceptually, but you can think about it in the following way: it’s the number of possible ways you can arrange the states in a particular system. Today, we can calculate the entropy of the Universe and get a number: about 10¹⁰⁴ k, where k is Boltzmann’s constant. It’s mostly due to supermassive black holes at the centers of galaxies, where the entropy of just the Milky Way’s supermassive black hole is 10⁹¹ k. These black holes didn’t exist when the Universe was very young (they hadn’t formed yet), and so the entropy was much lower; in the far future, the Universe will reach an even higher entropy state when they all decay via Hawking radiation (which hasn’t happened yet). When the Universe was dominated by radiation some 13.8 billion years ago, the entropy was only 10⁸⁸ k; when the last black hole decays in the far future, the entropy will be 10¹²³ k. The laws of thermodynamics — where entropy always increases — are consistent with what’s happening in our Universe.

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    The far distant fates of the Universe offer a number of possibilities, but if dark energy is truly a constant, as the data indicates, it will continue to follow the red curve. Image credit: NASA / GSFC.

    So what about what’s possible? Moving forwards, the Universe could continue to expand forever, continue to accelerate and do so forever, but could also rip apart, tunnel to a new quantum state or recollapse to a singularity. Moving backwards, it could have existed in an inflationary state before the hot Big Bang (with an even lower entropy, of no more than ~10¹⁵ k), but with nothing known before the final 10^-33 seconds or so of that. Did it have a singular beginning, where time and space themselves began? Or have they always existed? At the American Astronomical Society’s annual meeting, cosmologist Sean Carroll described four possibilities for a non-singular origin for the Universe in great detail:

    4
    In classical general relativity, singularities are hard to avoid. But in quantum theories of gravity, such as those with extra dimensions, bouncing scenarios are possible. Image credit: Wikimedia Commons user Rogilbert.

    1. A stringy bounce. In General Relativity, if you extrapolate back to an arbitrarily hot, dense or small state, you inevitably arrive at a singularity, and definitions of time and space break down. But in quantum extensions that go beyond GR, like loop quantum gravity, string theory or brane cosmology, you can “bounce” from a pre-existing, collapsing state to a hot, dense, expanding one.
    2. A cyclic cosmology This is like a stringy bounce, except it “bounces” over and over. The Universe expands, reaches a maximum size, contracts — with entropy increasing the entire time — and then recollapses, where it bounces again.
    3. A hibernating cosmology. Instead of expanding rapidly, like our Universe does today or did during inflation, the Universe could have been in a state that remained relatively constant or quiescent for a very long time. This requires something exotic, like “degravitation” (where gravity gets turned off for a time), or a string gas cosmology.
    4. A reproducing cosmology. This last one is where a Universe gets “birthed” from a previously existing spacetime, where this pre-existing spacetime has a variety of locations and properties, but did not begin in a singularity. In this case, one of the offspring Universes grows into our own.

    5
    A huge number of separate regions where Big Bangs occur are separated by continuously inflating space in eternal inflation. Image credit: Karen46 of http://www.freeimages.com/profile/karen46.

    A “big bounce” is certainly a possibility worth considering, and many people do. But there’s a big problem with it, and with scenarios 1, 2 and 3, above: the problem that our Universe needs to be born with low entropy, and we have the second law of thermodynamics. Either the entropy of the Universe must have decreased in the past, which is the biggest violation of the second law of thermodynamics of all, or the entropy was even smaller in the past, finely tuned to be arbitrarily close to zero.

    The first scenario — the stringy bounce — needs to have decreasing entropy; the cyclic bounces need to have entropy always be increasing. This means the last cycle, pre-bounce, needs to have even less entropy than the birth of our Universe did all throughout; that this cycle will have entropy increase all throughout it; and that the next bounce will begin with even greater entropy than our Universe will end with. Of all the scenarios, only the fourth one, the reproducing cosmology, avoids the entropy problem. To imagine how this works, imagine a Universe in some state where there’s a lot of entropy, a lot of variations and a lot of fluctuations.

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    Particles in the lower configuration will very, very rarely spontaneously arrive at the top configuration, but smaller fluctuations or drops in entropy are plausible. Image credit: Wikimedia Commons user Gzahm.

    This is pretty generic; it’s the least finely-tuned initial state we could begin with, and it also has a lot in common with most physical systems that you’d design, like a room filled with gas molecules at a relatively high temperature. You’d never expect all the molecules to wind up on one half of the room at once, leaving the other half empty. That’s not only thermodynamically disfavored, it’s statistically incredibly unlikely. But you wouldn’t be surprised if one fist-sized region had a few billion more-or-fewer molecules than the average amount, or contained slightly more (or less) energy or entropy than the overall average. If you restricted yourself to looking at extremely small regions, like regions the size of a virus (which can be as small as about 5 nanometers), you might find one that had a fluctuation with extremely low, or perhaps even negligible, entropy. The overall entropy of the system must still increase, but a very small region could have a very low — even negligible — entropy at any given time.

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    Image credit: E. Siegel. Even though inflation may end in more than 50% of any of the regions at any given time (denoted by red X’s), enough regions continue to expand forever that inflation continues for an eternity, with no two Universes ever colliding.

    And perhaps, then, that tiny fluctuating region, where the entropy becomes low enough, could give birth to a new Universe, where inflation occurs.

    8
    Inflation set up the hot Big Bang and gave rise to the observable Universe we have access to, but it’s the fluctuations from inflation that grew into the structure we have today. Image credit: Bock et al. (2006, astro-ph/0604101); modifications by E. Siegel.

    Inflation has this wonderful property that once it begins, it creates more and more space at an incredibly rapid rate that builds upon itself exponentially. There are regions where inflation will end — giving rise to a hot Big Bang and creating a matter/antimatter/radiation-filled space like our part of the observable Universe — but there are regions where it will continue into the future. The Universe may have began from a singularity, where time and space emerged from a state where there was no time and space outside of it (as much as concepts as “emerged” or “outside” make sense with no space or time), but it also may have come from an ultimately non-singular state. However, as long as we have the second law of thermodynamics, which means as long as the overall entropy of a system can never decrease, the “big bounce” ideas have a very large obstacle to overcome. In the absence of any evidence for a recollapse, coupled with the theoretical difficulties a bounce scenario faces, the best that physics has to offer favors a reproducing scenario for our Universe’s ultimate birth.

    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 3:07 pm on January 14, 2017 Permalink | Reply
    Tags: , , , , Cosmology, EurekaAlert, Keck Cosmic Web Imager   

    From Caltech via EurekaAlert: “New Caltech instrument poised to image the cosmic web” 

    Caltech Logo
    Caltech

    1

    EurekaAlert

    12-Jan-2017
    Whitney Clavin
    wclavin@caltech.edu
    626-395-1856

    Keck Cosmic Web Imager ships from Caltech to Keck Observatory

    2
    Hector Rodriguez, senior mechanical technician, works on the Keck Cosmic Web Imager in a clean room at Caltech. Caltech

    An instrument designed to image the vast web of gas that connects galaxies in the universe has been shipped from Los Angeles to Hawaii, where it will be integrated into the W. M. Keck Observatory.

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

    The instrument, called the Keck Cosmic Web Imager, or KCWI, was designed and built by a team at Caltech led by Professor of Physics Christopher Martin. It will be one of the best instruments in the world for taking spectral images of cosmic objects–detailed images where each pixel can be viewed in all wavelengths of visible light. Such high-resolution spectral information will enable astronomers to study the compositions, velocities, and masses of many objects, such as stars and galaxies, in ways that were not possible before.

    One of KCWI’s main goals, and a passion of Martin’s for the past 30 years, is to answer the question: What is the gas around galaxies doing?

    “For decades, astronomers have demonstrated that galaxies evolve. Now we’re trying to figure out how and why,” says Martin. “We know the gas around galaxies is ultimately fueling them, but it is so faint–we still haven’t been able to get a close look at it and understand how this process works.”

    Martin and his team study what is called the cosmic web–a vast network of streams of gas between galaxies. Recently, the scientists have found evidence supporting what is called the cold flow model, in which this gas funnels into the cores of galaxies, where it condenses and forms new stars.

    3
    The forming galaxy with binary quasars as it fits into the timeline of the Universe. We’re seeing it 10 billion years ago, during the epoch of galaxy formation. Credit: Caltech Academic Media Technologies

    Researchers had predicted that the gas filaments would first flow into a large ring-like structure around the galaxy before spiraling into it–exactly what Martin and his team found using the Palomar Cosmic Web Imager, a precursor to KCWI, at Caltech’s Palomar Observatory near San Diego.

    Caltech Palomar Cosmic Web Imager
    Caltech Palomar Cosmic Web Imager

    “We measured the kinematics, or motion, of the gas around a galaxy and found a very large rotating disk connected to a gas filament,” says Martin. “It was the smoking gun for the cold flow model.”

    With KCWI, the researchers will get a closer look at the gas filaments and ring-like structures around galaxies that range from 10 to 12 billion light-years away, an era when our universe was roughly 2 to 4 billion years old. Not only can KCWI take more detailed pictures than the Palomar Cosmic Web Imager, it has other advances such as better mirror coatings. The combination of these improvements with the fact that KCWI is being installed at one of the twin 10-meter Keck telescopes–the world’s largest observatory with some of the darkest known skies on Earth–means that KCWI will have an improved performance by more than an order of magnitude over the Palomar Cosmic Web Imager.

    KCWI will map the gas flowing from the intergalactic medium–the space between galaxies–into many young galaxies, revealing, for the first time, the dominant mode of galaxy formation in the early universe. The instrument will also search for supergalactic winds from galaxies that drive gas back into the intergalactic medium. How gas flows into and out of forming galaxies is the central open question in the formation of cosmic structures.

    “We designed KCWI to study very dim and diffuse objects, our main emphasis being on the wispy cosmic web and the interactions of galaxies with their surroundings,” says Mateusz (Matt) Matuszewski, the instrument scientist for the project.

    KCWI is also designed to be more a general-purpose instrument than the Palomar’s Cosmic Web Imager, which is mainly for studies of the cosmic web. It will study everything from gas jets around young stars to the winds of dead stars and supermassive black holes and more. “The instrument is really versatile,” says Matuszewski. “Observers can configure the optics to adjust the spatial and spectral scales and resolutions to suit their interests.”

    The nuts and bolts of KCWI

    Scientists and engineers have been busy assembling the highly complex elements of the KCWI instrument at Caltech since 2012. The instrument is about the size of an ice cream truck and weighs over 4,000 kilograms. The core feature of KCWI is its ability to capture spectral information about objects, such as galaxies, across a wide image. Typically, astronomers capture spectra using instruments called spectrographs, which have narrow slit-shaped windows. The spectrograph breaks apart light from the slit into each of the colors making up the target object, just like a prism that spreads light into a rainbow. But traditional spectrographs cannot be used to capture spectral information across an entire image.

    “Traditional spectrographs use multiple small slits to capture many stars or the cores of many galaxies,” says Martin. “Now, we want to look at features that are extended across the sky, such as stellar jets and galaxies, which have complex structures, velocities, and gas flows. If you can only look through a slit, you can only see a small part of what is going on. But we want to see the whole picture. That’s why we need an imaging spectrograph, a device that gives you an image for every single wavelength across a wide view.”

    To create a spectrograph that can image more extended objects like galaxies, KCWI uses what is called an integral field design, which basically divides an image up into 24 slits, and gathers all the spectral information at once.

    “If you’re looking at something big in the sky, it’s inefficient to just have one slit and step your way across that object, so an integral field spectrograph combines a number of slit-shaped mirrors together across a continuous field of view,” says Patrick Morrissey, the project scientist for KCWI who now works at JPL. “Imagine looking into a broken mirror–the reflected image is shifted around depending on the angles of the pieces. This is how the integral field spectrograph works. A series of mirrors works together to make a square-shaped stack of slits across an image appear as a single traditional vertical slit.”

    KCWI has the highest spectral resolution of any integral field spectrograph, which means it can better break apart the rainbow of light to see more colors, or wavelengths. The first phase of the instrument, now on its way to Keck, covers the blue side of the visible spectrum, spanning wavelength ranges from 3500 to 5600 Angstroms. A second phase, extending coverage to the red side of the spectrum, out to 10400 Angstroms, will be built next.

    KCWI to Climb Mauna Kea

    After KCWI arrives in Hawaii on January 18, engineers will guide it up to the top of Mauna Kea, where Keck is perched. A series of checkout and alignment tests is planned, and will be followed in a few months by the first observations through the Keck telescope.

    “There are train tracks around the telescope where the instruments are installed,” says Morrissey. “It’s like one of those old railroad roundhouses where the train would come in and they would spin it to an available space for storage. The telescope turns around, points to the instrument that the astronomer wants to use, and then they roll that instrument on. Soon KCWI will becomes part of the telescope.”

    KCWI is funded by the National Science Foundation, through the Association of Universities for Research in Astronomy (AURA) program, and by the Heising-Simons Foundation, the W.M. Keck Foundation, the Caltech Division of Physics, Mathematics and Astronomy, and the Caltech Optical Observatories.

    See the full article here .

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    Caltech campus
    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.”

     
  • richardmitnick 2:28 pm on January 14, 2017 Permalink | Reply
    Tags: , , , Cosmology, , , Twinkles   

    From Symmetry: “Twinkle, twinkle, little supernova” 

    Symmetry Mag
    Symmetry

    01/12/17
    Ricarda Laasch

    1
    Phil Marshall, SLAC

    Using Twinkles, the new simulation of images of our night sky, scientists get ready for a gigantic cosmological survey unlike any before.

    Almost every worthwhile performance is preceded by a rehearsal, and scientific performances are no exception. Engineers test a car’s airbag deployment using crash test dummies before incorporating them into the newest model. Space scientists fire a rocket booster in a test environment before attaching it to a spacecraft in flight.

    One of the newest “training grounds” for astrophysicists is called Twinkles. The Twinkles dataset, which has not yet been released, consists of thousands of simulated, highly realistic images of the night sky, full of supernovae and quasars. The simulated-image database will help scientists rehearse a future giant cosmological survey called LSST.

    LSST
    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC
    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.
    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST, short for the Large Synoptic Survey Telescope, is under construction in Chile and will conduct a 10-year survey of our universe, covering the entire southern sky once a year. Scientists will use LSST images to explore our galaxy to learn more about supernovae and to shine a light on the mysterious dark energy that is responsible for the expansion of our universe.

    It’s a tall order, and it needs a well prepared team. Scientists designed LSST using simulations and predictions for its scientific capabilities. But Twinkles’ thousands of images will give them an even better chance to see how accurately their LSST analysis tools can measure the changing brightness of supernovae and quasars. That’s the advantage of using simulated data. Scientists don’t know about all the objects in the sky above our heads, but they do know their simulated sky— there, they already know the answers. If the analysis tools make a calculation error, they’ll see it.

    The findings will be a critical addition to LSST’s measurements of certain cosmological parameters, where a small deviation can have a huge impact on the outcome.

    “We want to understand the whole path of the light: From other galaxies through space to our solar system and our planet, then through our atmosphere to the telescope – and from there through our data-taking system and image processing,” says Phil Marshall, a scientist at the US Department of Energy’s SLAC National Accelerator Laboratory who leads the Twinkles project. “Twinkles is our way to go all the way back and study the whole picture instead of one single aspect.”

    Scientists simulate the images as realistically as possible to figure out if some systematic errors add up or intertwine with each other. If they do, it could create unforeseen problems, and scientists of course want to deal with them before LSST starts.

    Twinkles also lets scientists practice sorting out a different kind of problem: A large collaboration spread across the whole globe that will perform numerous scientific searches simultaneously on the same massive amounts of data.

    Richard Dubois, senior scientist at SLAC and co-leader of the software infrastructure team, works with his team of computing experts to create methods and plans to deal with the data coherently across the whole collaboration and advise the scientists to choose specific tools to make their life easier.

    “Chaos is a real danger; so we need to keep it in check,” Dubois says. “So with Twinkles, we test software solutions and databases that help us to keep our heads above water.”

    The first test analysis using Twinkles images will start toward the end of the year. During the first go, scientists extract type 1a supernovae and quasars and learn how to interpret the automated LSST measurements.

    “We hid both types of objects in the Twinkles data,” Marshall says. “Now we can see whether they look the way they’re supposed to.”

    LSST will start up in 2022, and the first LSST data will be released at the end of 2023.

    “High accuracy cosmology will be hard,” Marshall says. “So we want to be ready to start learning more about our universe right away!”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 2:34 pm on January 13, 2017 Permalink | Reply
    Tags: , , , , Cosmology, When Planets Won’t Stay Put   

    From astrobites: “When Planets Won’t Stay Put” 

    Astrobites bloc

    Astrobites

    Title: Dynamical origin of extrasolar planet eccentricity distribution
    Authors: Mario Jurić and Scott Tremaine
    First author’s institution: Department of Astrophysical Sciences, Princeton University, USA
    PrincetonUniversity
    Status: Published in ApJ (2008) [open access]

    If you fill your house with rocks and go away for a while, you may reasonably expect that the rocks will be there, in their original configuration, when you return. This is in the Constitution.

    If you instead choose to decorate with lizards (which are bound not by the Constitution, but by lizard law), you will find your house much changed when you come back. No matter how you arranged them originally, several will have escaped, and the rest will be under your furniture (whence they will need to be chased if you want to salvage your decor).

    Haters may say that planets are more like rocks than like lizards, which is true in the narrow sense that many planets are large rocks with gaseous envelopes, not reptiles with feet and external ears. But get a whole bunch of planets together, and they behave more like a house full of lizards than a house full of rocks. A system of planets placed in orbit around a star and left to its own gravitational devices doesn’t stick to its initial arrangement. Instead, the shapes of the orbits of the planets change over time. They grow more circular or more elongated as each planet feels the gravitational tug of other planets passing close by.

    Curiously, when you average over many planets in many systems with many different initial orbital shapes, this gradual, chaotic, encounter-by-encounter change tends toward a particular final arrangement of orbital shapes, just as lizards tend to congregate under your couch with obnoxious disregard for their original placement.*

    A suitcase full of planets

    The authors begin by taking a supercomputer** and dumping in a few thousand planetary systems. Each system consists of a central star and a handful of orbiting planets–sometimes as few as 3, or as many as 50. They give these planets a whole range of orbital shapes, or eccentricities: for some planets, circles, and for others, exaggerated, elongated ellipses. The orbit shape is determined by a parameter called eccentricity, or e, illustrated in Figure 1. e can range from 0 in the case of a circular orbit all the way up to very nearly 1 in the case of a long, narrow ellipse.

    1
    Figure 1: Three orbits around a star. From left to right, eccentricity e equals 0, 0.5, and 0.95. No image credit.

    They assign the eccentricities for each system according to a few slightly different rules: some systems have planets on circular orbits, while others have a mixture of shapes. (Crucially, they still love all the systems equally.)

    Next, they let their simulated planets orbit, starting from these initial eccentricities, and watch their orbital characteristics change as time goes on. Early on, the systems are a bumper-car disaster of planet-planet and planet-star collisions, with a healthy additional fraction of planets fully ejected from their systems by close encounters (much like if someone in San Diego looked up and saw a few Disneyland bumper cars flying speedily southeast overhead). After a couple dozen million years, an average of only 2-3 planets per system remain, and after a hundred million years, their average orbital properties are stable.

    A surprising convergence

    After this evolution, about half of the systems (Figure 2, bottom panel, colored bands), despite their very different rules for initial eccentricity assignment, converge to astonishingly similar shapes. These are the planetary equivalents of the under-couch lizards. Most of the remaining systems (Figure 2, middle panel, colored bands) appear to approach the same final state, but retain some imprint of their initial eccentricity distributions in the form of a low-eccentricity peak, which is like if you caught a couple of especially slow lizards in the act of moseying over to the couch from their initial perch on your shelf. Only one set of planets, which had completely circular initial orbits, is unchanged from its initial state, and this is the one that least matches a population of real exoplanets. It’s like it wasn’t even trying!

    2
    Figure 2: The final eccentricity distributions of the simulated planetary systems. Each colored band corresponds to a different rule for assigning initial eccentricities to planetary systems. One rule (that planets must start on circular orbits) yielded systems which hardly changed from the beginning of the simulation to the end (top panel); four others (bottom panel), despite their dramatically different initial conditions, converged on the same final eccentricity distribution, plotted as a smooth black line. The remaining rules (middle panel) appear to yield a mixture or superposition of the other types. The eccentricity distribution of real, observed exoplanets is plotted as a black histogram in each panel.

    Why, and what next?

    An underlying pattern emerges: the systems which converged to the same distribution in the end were tightly packed at the beginning, with little room (on average) between each planet and its nearest orbital neighbor. By the end of the hundred million years, enough of these uncomfortably close planets had collided with each other, been kicked out of their systems, or otherwise spread out that those that remained had some breathing room and no longer underwent frequent close encounters. In contrast, the few systems which maintained their initial eccentricity distribution throughout the simulation were adequately spaced out from the beginning. Our own solar system fits this bill, because the planets are adequately spaced out and all on quite circular orbits—making our solar system, yet again, a little bit different from the norm.

    So what can we do with this information? For one, now that we know that planetary systems are likely to act this way, we can make smarter assumptions to about planet populations in the future. And planet simulators can rest easier knowing that their choices of initial parameters don’t matter so much in the end, except for in systems like ours. Lizards, I suppose, can take this result as celestial validation and go about their decor-ruining business more smugly than ever.

    *Please help me, my apartment is full of uncooperative lizards. I don’t want them to leave, I just need them to listen.

    ** Supercomputer uncredited.

    See the full article here .

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    What do we do?

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

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

     
  • richardmitnick 9:29 am on January 13, 2017 Permalink | Reply
    Tags: , , Cosmology, , New Hubble Image Captures the Collision of Two Galaxies,   

    From Smithsonian: “New Hubble Image Captures the Collision of Two Galaxies” 

    smithsonian
    Smithsonian.com

    A beautiful look at a violent event

    1
    NASA/ESA Hubble

    January 12, 2017
    Danny Lewis

    More than a billion light years away from Earth, two galaxies are locked in a slow-motion collision, throwing countless stars out of whack and whirling about the void of deep space.

    This week, NASA shared a new album of images recently taken by the Hubble spacecraft—one of which captures this slow galactic collision, Christine Lunsford reports for Space.com. Known as IRAS 14348-1447, this whirling object appears to be just a glittery smudge of star stuff.

    2
    IRAS 14348-1447 http://inspirehep.net/record/1226780/plots

    “This doomed duo approached one another too closely in the past, gravity causing them to affect and tug at each other and slowly, destructively, merge into one,” NASA says in a statement.

    The two galaxies forming IRAS 14348-1447 are packed with gas, meaning that it has plenty of fuel to feed the massive emissions radiating from the event—enough to qualify it as an ultraluminous infrared galaxy, Brooks Hays reports for United Press International. In fact, nearly 95 percent of the energy emitted is in the far-IR range, Hays reports. The energy released by these gases also contributes to the object’s swirling appearance, as wisps of gas spiral out from the collision’s epicenter.

    “It is one of the most gas-rich examples known of an ultraluminous infrared galaxy, a class of cosmic objects that shine characteristically—and incredibly—brightly in the infrared part of the spectrum,” NASA says in a statement.

    While witnessing two galaxies collide in such great detail is a fascinating sight, it’s not a rarity in the cosmos. Galaxies collide all the time, with larger ones consuming smaller ones and incorporating new stars into their makeup. While galaxies are often destroyed in the process, these collisions can also fuel the creation of new stars, though that comes at a cost of depleting gas reserves, Matt Williams reports for Universe Today. In fact, this is the same fate our own Milky Way will face billions of years from now, when it eventually collides with the ever-nearing Andromeda Galaxy.

    NAOJ Milky Way merger with Andromeda
    Depiction of Milky Way merger with Andromeda. NAOJ.

    These collisions are dramatic, but it’s unlikely that individual stars are smashing together. Though galaxies may look solid from afar, stars, planets and other matter is so distantly distributed within them that they more often than not simply glide past each other, Williams reports. But even from this distance, the drama of watching two galaxies collide is undeniable.

    See the full article here .

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    Smithsonian magazine and Smithsonian.com place a Smithsonian lens on the world, looking at the topics and subject matters researched, studied and exhibited by the Smithsonian Institution — science, history, art, popular culture and innovation — and chronicling them every day for our diverse readership.

     
  • richardmitnick 3:52 pm on January 11, 2017 Permalink | Reply
    Tags: , , , Cosmology, , , ,   

    From PI via Motherboard: “Dark Matter Hunters Are Hoping 2017 is Their Year” 

    Perimeter Institute
    Perimeter Institute

    Motherboard

    January 3, 2017
    Kate Lunau

    It can be unsettling to realize that only five percent of the universe is made of the kind of matter we know and understand—everything from the planets and stars, to trees and animals and your dining room table.

    Roughly one-quarter is dark matter. This is thought to knit the galaxies together, and has been called the “scaffolding” of the universe, but we’ve never detected it directly. Scientists believe they can see dark matter’s traces in the way that galaxies rotate, but they still have no idea what it is. (Most of the universe, about 70 percent, is dark energy, a mysterious force that permeates space and time. It’s even less well-understood than dark matter.)

    Confirming dark matter’s existence would change humankind’s perspective on the universe. 2016 was a year of dark matter disappointments, as big searches came up empty. Most are looking for WIMPs—weakly interacting massive particles, the leading contender for a dark matter particle.

    2017 might just be the year we finally catch one. And if we don’t, well, it may be that our best theories about dark matter are wrong—that we’re looking in the wrong places, with the wrong instruments. Maybe dark matter, whatever it is, will turn out to be even weirder and more surprising than anyone has so far predicted. Maybe it’s not a WIMP, but some other bizarre kind of particle.

    Then there’s the outside possibility that dark matter doesn’t exist, that it’s an illusion. If that’s the case, we’ll have to consider whether we’ve been fundamentally misreading the universe’s clues.

    Buried deep in a mine near Sudbury in northern Ontario is SNOLAB, a vast underground laboratory where scientists are performing a range of experiments, including looking for dark matter. Often compared to the lair of a Bond villain, it’s an ultra-clean, high-tech facility. Two kilometers of solid rock overhead shield its detectors from cosmic radiation, allowing them to sift for bits of matter from dying stars and the Sun: science done here won the Nobel Prize in Physics, in 2015.

    2
    A scientist works on the deck of DEAP-3600, a dark matter search at SNOLAB. Image: SNOLAB

    I recently travelled to SNOLAB. To get there, I had to don full mining gear (including a hardhat and headlamp), drop down underground in a rattling dark cage, and hike a kilometre or so to reach the gleaming white facility, which is cleaner inside than an operating room—a startling contrast to the dirty nickel mine that surrounds it.

    After the long hike through the mine, anyone who wants to enter SNOLAB has to undress, shower (with soap and shampoo), and put on lint-free clothing and a hairnet. Any bit of dust from the mine, which is naturally radioactive, can mess up the experiments.

    There, I met research scientist Ken Clark, a congenial physicist with a sandy-coloured beard. Like me, he was wearing safety goggles and a hardhat. Clark has worked on high-profile dark matter searches like CDMS and LUX, and collaborates on the IceCube detector at the South Pole in Antarctica.

    LBL SuperCDMS
    LBL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)
    LBL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    LUX Xenon experiment at SURF
    LUX Xenon experiment at SURF, Lead, SD, USA

    U Wisconsin ICECUBE neutrino detector at the South Pole
    IceCube neutrino detector interior
    U Wisconsin ICECUBE neutrino detector at the South Pole

    Now he’s with PICO, a dark matter search that targets the WIMP particle.

    5

    It was launched in 2013 when two other collaborations, called PICASSO and COUPP, merged.

    6
    A multi-bubble image of a neutron scattering in the PICO detector. Image: PICO Collaboration

    PICO is a bubble detector: a tank of superheated fluid kept higher than its natural boiling point. If dark matter bumps into the nucleus of another particle in the detector, it should cause a tiny bubble to form. Dark matter courses through the Earth and right through our bodies, so it will reach the detector underground, even through all that rock overhead. But that’s also part of the challenge—dark matter is thought to only rarely interact with normal matter, if at all, so it’s really tricky to catch.

    Clark believes we might just find dark matter in the next year or two. “It’s exciting times,” he said.

    Other searches are due to turn on soon, he explained, and those that are already up-and-working are getting increasingly sensitive. In 2017, Clark said it’s possible we’ll see new results from PICO, DEAP (a different detector, also at SNOLAB), as well as China’s ambitious PandaX project, and another in Italy called XENON1T. Even more searches will turn on in 2018.

    “Provided the models are correct, we should see something soon,” Clark told me.

    7
    A scientist works on the steel vessel of DEAP-3600. Image: DEAP Collaboration

    Still, there’s no guarantee, and WIMP searches keep turning up empty-handed. For example, in the summer, the highly sensitive LUX—which uses liquid xenon in a South Dakota mine as its detector—announced it had seen zero WIMPs, after looking for more than a year.

    I phoned Lisa Randall, a prominent theoretical physicist and professor at Harvard University, to ask whether she thinks there’s a chance we’ll find dark matter in the next year or two.

    “I would say kind of the opposite,” said Randall, author of Dark Matter and the Dinosaurs. While she agrees that if dark matter is indeed a WIMP, these searches could find it soon, “that’s just one possibility,” she said.

    The WIMP is “lowest-hanging fruit,” Randall continued: this theoretical particle fits snugly within what’s already known about the Standard Model of physics, which explains how the building blocks of the universe interact. And scientists can imagine ways to actually look for WIMPs, unlike some of the more far-out theories, which are much harder to test in experiments.

    “What if it’s not a WIMP?” Randall said. “Could we still learn something about what dark matter is?”

    Other scientists have different strategies for solving the dark matter puzzle.

    Leslie Rosenberg, a professor of physics at the University of Washington in Seattle, is project scientist on the Axion Dark Matter Experiment, or ADMX, which is looking for a theoretical particle called the axion, which is thought to be much lighter than a WIMP.

    ADMX Axion Dark Matter Experiment
    U Washington ADMX
    U Washington ADMX

    It’s being targeted by other searches under development around the world, Rosenberg told me. ADMX, though, is “the only high-sensitivity axion search now,” he said.

    Maybe we’re being fooled into thinking that dark matter is there.

    ADMX, which uses a resonant microwave cavity nested inside a huge superconducting magnet, started out of a collaboration that began in the mid-nineties. It’s been at full sensitivity for about a year now, Rosenberg told me, and will only get better as the team continues to tweak it. He’s hoping they turn up something soon: their next update should come in the summer of 2017.

    “Axions are bound up in our galaxy,” Rosenberg said. “There [should be] an awful lot of them, and we depend on that as the source of our signal.”

    Axions are a mainstream dark matter candidate. Other ideas get weirder.

    “Personally, I’m interested in the idea that dark matter might have nothing to do with the Standard Model,” Randall told me. “One of the possibilities is that it could be some other type of particle. Maybe it interacts [with itself] via its own light, a dark photon.”

    7
    ESA/Gaia’s first sky map of the Milky Way, based on data collected from July 2014 to Sept. 2015. Image: ESA/Gaia/DPAC

    Randall thinks that one of the best ways to learn about dark matter may be to study the structure of galaxies, and watching the universe at work, to understand how it interacts with itself. The European Space Agency’s Gaia mission, which is making a three-dimensional map of over a thousand million stars, could give insight into some of this, Randall said.

    Asimina Arvanitaki, a theoretical physicist at the Perimeter Institute for Theoretical Physics, suggested to me in a Skype call that dark matter might be detectable through resonant-mass detectors, which are used to hunt for gravitational waves. These ripples in spacetime were detected for the first time in 2016, a hundred years after Albert Einstein predicted their existence.

    Dark matter could also be behaving like a wave, “trapped by gravity and oscillat[ing] at a frequency set by the mass,” she said.

    “The funny thing is you could perhaps even hear dark matter,” Arvanitaki said, “depending on the frequency.”

    Over millions of years, humans have come up with ingenious ways to probe the world around us, from Copernicus and Kepler, through the thousands of scientists involved in the search for the Higgs boson particle at the Large Hadron Collider, and those who are now shaking out the endless diversity of exoplanets that populate our galaxy.

    Because of them, our perspective has changed. When we look up at the night sky today, we understand that just about every star we see hosts at least one planet. The first confirmed exoplanet was announced just over two decades ago.

    Nature can still surprise us.

    7
    The Bullet cluster, formed by the collision of two large galaxy clusters, provides some of the best evidence yet for dark matter. Image: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

    “There’s a chance that dark matter isn’t necessarily a particle at all,” Clark told me. “Some [theorists] say there’s no dark matter. It’s just that we don’t understand how gravity works at large scales,” he continued. “If that’s the case, we’re being fooled into thinking that dark matter is there.”

    Clark and the other dark matter hunters continue their search. If it’s real, “we’re not even made of what most of the universe is made of,” Rosenberg told me. In the grand scheme of things, then, it isn’t dark matter that’s really so exotic and strange—it’s us.

    See the full article here .

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    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 12:30 pm on January 11, 2017 Permalink | Reply
    Tags: , , , Cosmology, , Galaxy clusters prove dark matter’s existence   

    From Ethan Siegel: “Galaxy clusters prove dark matter’s existence” 

    Ethan Siegel
    1.10.17

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    A Hubble image of galaxy cluster MACS J0717, which contains a huge amount of information about the cluster itself thanks to the light from background galaxies. Image credit: ESA/Hubble, NASA and

    You don’t have to detect a particle to know that dark matter is real.

    “You may hate gravity, but gravity doesn’t care.” –Clayton Christensen

    In the 1970s, Vera Rubin’s observations showed galactic rotation was too quick at the outskirts for normal matter alone to explain.

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    Vera Rubin in 2009

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    Traceable stars, neutral gas, and (even farther out) globular clusters all point to the existence of dark matter, which has mass but exists in a large, diffuse halo well beyond the normal matter’s location. Image credit: Wikimedia Commons user Stefania.deluca.

    But 40 years prior, Fritz Zwicky observed the motions of individual galaxies within clusters, and found the same effect.

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    Fritz Zwicky

    5
    The Coma cluster of galaxies, whose galaxies move far too quickly to be accounted for by gravitation given the mass observed alone. Image credit: KuriousG of Wikimedia Commons, under a c.c.a.-s.a.-4.0 license.

    Even as we’ve learned to observe gas, dust, plasma, failed stars and planets, normal matter only explains 15% of the gravitational signal we see.

    6
    This image illustrates a gravitational lensing effect due to the distortion of space by mass. Image credit: NASA, ESA, and Johan Richard (Caltech, USA); Acknowledgements: Davide de Martin & James Long (ESA/Hubble).

    The key to understanding gravitational observations arises from gravitational lensing, where mass bends the background starlight.

    7
    Six examples of the strong gravitational lenses the Hubble Space Telescope discovered and imaged. Image credit: NASA, ESA, C. Faure (Zentrum für Astronomie, University of Heidelberg) and J.P. Kneib (Laboratoire d’Astrophysique de Marseille).

    Under serendipitous configurations, background galaxies are deformed into arcs and multiple, distorted images.

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    The galaxy cluster Abell 68, and its many lensed and distorted background galaxies. Image credit: NASA & ESA. Acknowledgement: N. Rose.

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    Any configuration of background points of light — stars, galaxies or clusters — will be distorted due to the effects of foreground mass via weak gravitational lensing. Even with random shape noise, the signature is unmistakeable. Image credit: Wikimedia Commons user TallJimbo.

    Even without optimal configurations, weak gravitational lensing causes a well-defined distortion in the shape of background galaxies.

    10
    The galaxy cluster SDSS J1004+4112 severely distorts the light from background galaxies, allowing us to measure its mass. Image credit: ESA, NASA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech).

    With numerous enough galaxy counts — obtainable anywhere with deep telescope observations — the total mass of any galaxy cluster can be reconstructed.

    11
    The overlay in the lower left hand corner represents the distortion of background images due to gravitational lensing expected from the dark matter “haloes” of the foreground galaxies, indicated by red ellipses. The blue polarization “sticks” indicate the distortion. Image credit: Mike Hudson, of shear and weak lensing in the Hubble Deep field. His research page is at http://mhvm.uwaterloo.ca/.

    Consistently, about five times too much mass is needed compared to the existing normal matter.

    12
    Four colliding galaxy clusters, showing the separation between X-rays (pink) and gravitation (blue), indicative of dark matter. Images credit: X-ray: NASA/CXC/UVic./A.Mahdavi et al. Optical/Lensing: CFHT/UVic./A. Mahdavi et al. (top left); X-ray: NASA/CXC/UCDavis/W.Dawson et al.; Optical: NASA/ STScI/UCDavis/ W.Dawson et al. (top right); ESA/XMM-Newton/F. Gastaldello (INAF/ IASF, Milano, Italy)/CFHTLS (bottom left); X-ray: NASA, ESA, CXC, M. Bradac (University of California, Santa Barbara), and S. Allen (Stanford University) (bottom right).

    No alternative gravity theory explains all this. We need dark matter.

    13
    On the largest scales, the way galaxies cluster together observationally (blue and purple) cannot be matched by simulations (red) unless dark matter is included. Image credit: Gerard Lemson & the Virgo Consortium, with data from SDSS, 2dFGRS and the Millennium Simulation, via http://www.mpa-garching.mpg.de/millennium/.

    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 12:09 pm on January 11, 2017 Permalink | Reply
    Tags: , , , Cosmology, , ,   

    From Ethan Siegel: “The James Webb Space Telescope Will Truly Do What Hubble Only Dreamed Of” 

    Ethan Siegel
    Jan 10, 2017

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    In 1990, NASA launched the Hubble Space Telescope. This observatory would come to revolutionize not only our scientific understanding of the Universe, but would reveal to humanity, for the first time, what our Universe actually looked like. We could peer inside the densest, most gas-and-dust-rich star forming nebulae, and see exactly how and were stars were beginning to form.

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

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    The pillars of creation, as taken for Hubble’s 25th anniversary. Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

    We could look out at dying stars, reaching the end of their lives, and see exactly what their final moments in the Universe looked like.

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    Four individual planetary nebulae — He 2-47, NGC 5315, IC 4593, and NGC 5307 — were imaged by Hubble in February of 2007. Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA).

    We could look out at distant galaxies, and reveal their shapes, ages, stellar populations and histories with simply a glimpse.

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    The irregular, interacting galaxy pair Arp 230. Image credit: ESA/Hubble & NASA. Acknowledgement: Flickr user Det58.

    We could look out at the largest gravitationally bound structures in the Universe, and see how mass bent starlight, giving us a firsthand, visual look at the stunning phenomenon of gravitational lensing.

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    Gravitational lensing in galaxy cluster Abell S1063, showcasing the bending of starlight by the presence of matter and energy. Image credit: NASA, ESA, and J. Lotz (STScI).

    And perhaps most importantly of all, we were able to look into the vast abyss of nothingness, photographing what lies beyond our visual reach for hours, days or even weeks at a time. What we wound up seeing changed our view of everything.

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    The full UV-visible-IR composite of the Hubble eXtreme Deep Field; the greatest image ever released of the distant Universe. Image credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI).

    Thanks to Hubble, we now know how stars are born, live and die. We know how galaxies form and grow in the Universe. We know what the ultimate fate of our Universe will be, and where we’re headed in the future. But even without any of this scientific knowledge, Hubble taught us something absolutely incredible: it showed us that this is what our Universe looks like.

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    The James Webb Space Telescope vs. Hubble in size (main) and vs. an array of other telescopes (inset) in terms of wavelength and sensitivity. Image credit: NASA / JWST team.

    By the same token, the James Webb Space Telescope will teach us an incredible amount about the Universe, including further details about how stars form, what the earliest stellar populations look like, will show us gas giants and rogue planets in unprecedented detail and will tell us what made up the Universe at any given time in the past. It will show us a whole slew of things that Hubble cannot, by virtue of it reaching to much longer wavelengths of light than Hubble could ever hope to see. And with its huge, large-aperture primary mirror, it will be able to collect more light in a single day than Hubble could in a week. The most exciting things, of course, will be the unexpected: the things we’ll discover that we don’t even know to look for yet.

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    An artist’s conception of what the Universe might look like as it forms stars for the first time. Image credit: NASA/JPL-Caltech/R. Hurt (SSC).

    But even if you don’t learn about any of the science that James Webb will bring to us, there’s one thing it will deliver that everyone can enjoy: the James Webb Space Telescope will show us how the Universe grew up.

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    An illustration of CR7, the first galaxy detected that’s thought to house Population III stars: the first stars ever formed in the Universe. JWST will reveal actual images of this galaxy and others like it. Image credit: ESO/M. Kornmesser.

    It will show us how the Universe went from the hot Big Bang and a state with no stars, no planets and no galaxies into the Universe we have today. It will reveal the very first populations of stars, which were created out of the pristine elements — hydrogen and helium alone — which provided the first light in the Universe.

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    On the left, the infrared light from the end of the Universe’s dark ages is shown, with the (foreground) stars subtracted out. JWST will be able to probe all the way back to the very first stars of all. Image credit: NASA/JPL-Caltech/A. Kashlinsky (GSFC).

    It will reveal how these first stars grew into star clusters, dwarf galaxies and eventually massive behemoths like our own. It will show us how the neutral atoms became ionized, and transparent to visible light. It will show us when and where the Universe became filled with oxygen, carbon and nitrogen: the elements essential to life. In short, it will tell us how the Universe went from being an inhospitable, smooth complex of pristine gas to the rich, diverse set of planets, stars, galaxies, clusters and great cosmic voids we enjoy today.

    11
    The biggest ‘big idea’ that JWST has is to reveal to us the very first luminous objects in the Universe, including stars, supernovae, star clusters, galaxies, and luminous black holes. Image credit: Karen Teramura, UHIfA / NASA.

    Hubble showed us what the Universe looks like; James Webb will show us how the Universe came to be the way it is today. Don’t ever say that James Webb is the “next Hubble,” it isn’t and it should never be. Instead, it’s the first James Webb, and when it starts returning images of the Universe, you may never look at your place in the Cosmos the same way again.

    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

     
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