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  • richardmitnick 2:35 pm on December 7, 2016 Permalink | Reply
    Tags: , , Cosmology, , ESO Supernova exhibition — “The Living Universe”   

    From ESO: “A sneak preview of the images used for the ESO Supernova exhibition — “The Living Universe” 

    ESO 50 Large

    European Southern Observatory

    12.7.16

    This post is dedicated to ESO’s O.S., a great science communicator.

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    Solar system black hole

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    ESO telescopes and instruments

    3
    The three fates of the universe

    4
    Crowd of ice cores in the Kuiper Belt

    4
    Black hole passing by earth

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    Cosmic collapse

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    Different shades of shadow

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    First ever birthday

    8
    An outside perspective on a solar eclipse

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    Probing the early universe

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    Creating the star cluster NGC 3532

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    The habitable zone (artist’s impression)

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    Chemical spectra of a transiting explanet

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    Star formation in the Pillars of Creation

    See the full article here .

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    LaSilla

    ESO VLT
    VLT

    ESO Vista Telescope
    VISTA

    ESO NTT
    NTT

    ESO VLT Survey telescope
    VLT Survey Telescope

    ALMA Array
    ALMA

    ESO E-ELT
    E-ELT

    ESO APEX
    Atacama Pathfinder Experiment (APEX) Telescope

     
  • richardmitnick 2:28 pm on December 4, 2016 Permalink | Reply
    Tags: , , Cold brown dwarfs, Cosmology,   

    From Science: “Alien life could thrive in the clouds of failed stars” 

    ScienceMag
    Science Magazine

    1
    The comfortably warm atmosphere of a brown dwarf is an underappreciated potential home for alien life, scientists say. Mark Garlick/Science Source

    Dec. 2, 2016
    Joshua Sokol

    There’s an abundant new swath of cosmic real estate that life could call home—and the views would be spectacular. Floating out by themselves in the Milky Way galaxy are perhaps a billion cold brown dwarfs, objects many times as massive as Jupiter but not big enough to ignite as a star. According to a new study, layers of their upper atmospheres sit at temperatures and pressures resembling those on Earth, and could host microbes that surf on thermal updrafts.

    The idea expands the concept of a habitable zone to include a vast population of worlds that had previously gone unconsidered. “You don’t necessarily need to have a terrestrial planet with a surface,” says Jack Yates, a planetary scientist at the University of Edinburgh in the United Kingdom, who led the study.

    Atmospheric life isn’t just for the birds. For decades, biologists have known about microbes that drift in the winds high above Earth’s surface. And in 1976, Carl Sagan envisioned the kind of ecosystem that could evolve in the upper layers of Jupiter, fueled by sunlight. You could have sky plankton: small organisms he called “sinkers.” Other organisms could be balloonlike “floaters,” which would rise and fall in the atmosphere by manipulating their body pressure. In the years since, astronomers have also considered the prospects of microbes in the carbon dioxide atmosphere above Venus’s inhospitable surface.

    Yates and his colleagues applied the same thinking to a kind of world Sagan didn’t know about. Discovered in 2011, some cold brown dwarfs have surfaces roughly at room temperature or below; lower layers would be downright comfortable. In March 2013, astronomers discovered WISE 0855-0714, a brown dwarf only 7 light-years away that seems to have water clouds in its atmosphere. Yates and his colleagues set out to update Sagan’s calculations and to identify the sizes, densities, and life strategies of microbes that could manage to stay aloft in the habitable region of an enormous atmosphere of predominantly hydrogen gas. Sink too low and you are cooked or crushed. Rise too high and you might freeze.

    On such a world, small sinkers like the microbes in Earth’s atmosphere or even smaller would have a better chance than Sagan’s floaters, the researchers will report in an upcoming issue of The Astrophysical Journal. But a lot depends on the weather: If upwelling winds are powerful on free-floating brown dwarfs, as seems to be true in the bands of gas giants like Jupiter and Saturn, heavier creatures can carve out a niche. In the absence of sunlight, they could feed on chemical nutrients. Observations of cold brown dwarf atmospheres reveal most of the ingredients Earth life depends on: carbon, hydrogen, nitrogen, and oxygen, though perhaps not phosphorous.

    The idea is speculative but worth considering, says Duncan Forgan, an astrobiologist at the University of St. Andrews in the United Kingdom, who did not participate in the study but says he is close to the team. “It really opens up the field in terms of the number of objects that we might then think, well, these are habitable regions.”

    So far, only a few dozen cold brown dwarfs have been discovered, though statistics suggest there should be about 10 within 30 light-years of Earth. These should be ripe targets for the James Webb Space Telescope (JWST), which is sensitive in the infrared where brown dwarfs shine brightest.

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

    After it launches in 2018, the JWST should reveal the weather and the composition of their atmospheres, says Jackie Faherty, an astronomer at the Carnegie Institution for Science in Washington, D.C. “We’re going to start getting gorgeous spectra of these objects,” she says. “This is making me think about it.”

    Testing for life would require anticipating a strong spectral signature of microbe byproducts like methane or oxygen, and then differentiating it from other processes, Faherty says. Another issue would be explaining how life could arise in an environment that lacks the water-rock interfaces, like hydrothermal vents, where life is thought to have begun on Earth. Perhaps life could develop through chemical reactions on the surfaces of dust grains in the brown dwarf’s atmosphere, or perhaps it gained a foothold after arriving as a hitchhiker on an asteroid. “Having little microbes that float in and out of a brown dwarf atmosphere is great,” Forgan says. “But you’ve got to get them there first.”

    See the full article here .

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  • richardmitnick 2:56 pm on December 3, 2016 Permalink | Reply
    Tags: , Cosmology, ,   

    From The Atlantic: “Fancy Math Can’t Make Aliens Real” 

    Atlantic Magazine

    The Atlantic Magazine

    Jun 17, 2016 [Where has this been?]
    Ross Andersen

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    NASA

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

    Inflationary Universe. NASA/WMAP
    Inflationary Universe. NASA/WMAP

    Last week [at the time of this article], The New York Times published an op-ed titled, Yes, There Have Been Aliens. As its headline suggests, the piece makes an extraordinary claim. “While we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy,” its author writes, “we now have enough information to conclude that they almost certainly existed at some point in cosmic history.”

    That we could know such a thing is not inconceivable. For decades now, a small group of “interstellar archaeologists” has pored over star surveys, looking for evidence of long-dead civilizations, in the form of enormous technological structures. Reading that headline in the Times, I wondered: had one of these astronomers seen something extraordinary?

    Alas, I was disappointed.

    Adam Frank, a professor of astrophysics at the University of Rochester, wrote the essay that appeared in the Times. Frank is a gifted scientist, and a thoughtful science writer. He begins the op-ed with an enthusiastic update on the ongoing exoplanet revolution. I must confess I share his enthusiasm. I suspect that future historians of science will wonder what it was like to live in this moment. A little more than two decades ago, we weren’t sure whether there were any planets outside our solar system. Now we have reason to believe that nearly all stars host planets, and that many of them are rocky and wet like our own. No generation of humans has ever gazed up at night skies so pregnant with possibility.

    It is precisely this profusion of planets that gives Frank confidence that ours is not the first intelligent civilization. “Given what we now know about the number and orbital positions of the galaxy’s planets,” he tells us, “the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.” Most of us have heard a version of this argument, late at night, around a campfire: Look at all the stars in the night sky. Is it really possible that all of their planets are sterile, and all of their predecessors, too?

    These arguments have their appeal, but it is an appeal to intuition. The simple fact is that no matter how much we wish to live in a universe that teems with life—and many of us wish quite fervently—we haven’t the slightest clue how often it evolves. Indeed, we aren’t even sure how life arose on this planet. We have our just-so stories about lightning strikes and volcanic vents, but no one has come close to duplicating abiogenesis in a lab. Nor do we know whether basic organisms reliably evolve into beings like us.

    We can’t extrapolate from our experience on this planet, because it’s only one data point. We could be the only intelligent beings in the universe, or we could be one among trillions, and either way Earth’s natural history would look the exact same. Even if we could draw some crude inferences, the takeaways might not be so reassuring. It took two billion years for simple, single-celled life to spawn our primordial lineage, the eukaryotes. And so far as we can tell, it only happened once. It took another billion years for eukaryotes to bootstrap into complex animal life, and hundreds of millions of years more for the development of language and sophisticated tool-making. And unlike the eye, or bodies with legs—adaptations that have arisen independently on many branches of life’s tree—intelligence of the spaceship-making sort has only emerged once, in all of Earth’s history. It just doesn’t seem like one of evolution’s go-to solutions.

    Frank compresses each of these important, billions-of-years-in-the-making leaps in evolution into a single “biotechnical” probability, which is meant to capture the likelihood of the whole sequence. For all we know, each step could be a highly contingent cosmic lottery win. Perhaps eukaryotes “usually” take tens of billions of years to evolve, and we lucked into an early outlier on the distribution curve. Perhaps we have been fortunate at every step of the way. Frank’s argument skips over these probabilities. Or rather, it bundles them up into a single, tidy unknown, that he can hammer with a big italicized number:

    “What our calculation revealed is that even if this probability [that technological civilization evolves] is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.”

    Absent a clear account of how often we can expect planets to spawn technological civilizations, we don’t have any way to evaluate that “10 billion trillion” number. We certainly don’t have grounds to say that the “odds are high” that some civilization preceded ours, or enough evidence to suggest that skepticism about the possibility “borders on the irrational.”

    See the full article here .

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  • richardmitnick 7:45 am on December 3, 2016 Permalink | Reply
    Tags: , , , Classifying Supernovae, Cosmology   

    From astrobites: “Classifying Supernovae” 

    Astrobites bloc

    Astrobites

    Dec 2, 2016
    Ashley Villar

    Supernovae (SNe) are the deaths of stars big and small. Like many older fields of astronomy, the study of supernovae is plagued with dated nomenclature which is largely unrelated to the physics driving these dazzling events. Below is an enumeration of many known supernova subtypes and simple guidelines for classification. These classifications will rely on your knowledge of spectra, so we recommend reading our spectroscopy guide first!

    Thermonuclear Explosions:

    Type Ia: Type Ia supernovae are the most famous type for two reasons: we find them most often, and they can be used to study cosmology. The latter is true due to their striking lack of diversity. The shape of their light curves (the luminosity of the supernovae as a function of time) can be used to measure their maximum luminosity. This means that Type Ia SNe can be used as standard candles to measure distances. Ironically, the origin of these explosions is still uncertain. Type Ia supernovae are likely caused by the thermonuclear explosions of white dwarf stars; however,it’s currently unclear if these explosions are from single white dwarfs or merging white dwarf binaries. In our simple classification, Type Ia supernovae lack hydrogen and have a strong silicon absorption line near its maximum luminosity.

    Core-collapse Explosions:

    Type Ib: Type Ib supernovae are formed when a massive star collapses under its own gravity. This star must have its outer envelope of hydrogen stripped away, because we observe no hydrogen in these spectra of these objects. However, we do observe the second ‘onion layer’ of helium.

    Type Ic: Type Ic supernovae are also formed when a massive star collapses under its own gravity. The stars that produce these supernovae have both their hydrogen and helium layers stripped away over the course of their lives. Because of this, we do not see hydrogen or helium in the spectra of Type Ic SNe.

    Type Ic – Broad Lined (Type Ic – BL): Some Type Ic supernovae have very broad lines (a speed of 20,000 km/s for the bulk of the material!) compared to normal Type Ic SNe. As you might expect, these supernovae typically have higher kinetic energies than normal Ic SNe as well. The origin of the increased energy is unclear and a highly debated topic.

    GRB-SNe: Some Type Ic – BL supernovae are associated with another transient phenomenon: gamma-ray bursts. These events have been interpreted as the collapse of a massive star with the formation of a jet pointed in our direction. It’s possible that all Type Ic – BL SNe are associated with GRBs and some are just not pointed towards us, but we’re not sure yet!

    Superluminous Supernovae (Type I/II SLSNe): A subset of all supernovae are found to be 100 times or brighter than most supernovae. This class is therefore called “superluminous supernovae” — clever, right? SLSNe are, like normal SNe, divided into Type I (lacking hydrogen) and Type II (showing hydrogen). Type II SLSNe are typically spectroscopically similar to Type IIn SNe (see below), so they might be extreme versions of the same explosions. However, the mechanics behind Type I SLSNe is highly debated.

    Type IIn: Type IIn supernovae have very narrow (or slow) hydrogen lines in their spectra, superimposed on the typical broad lines. These narrow lines are interpreted as hydrogen which was blown off of the star before it exploded. To support this argument, a few of these Type IIn supernovae, like SN 2009ip, have had extreme outbursts before their final explosion.

    Type IIP/II L: Type IIP/IIL contain relatively broad hydrogen lines. These explosions are thought to be the deaths of red supergiant stars, which are enshrined by their hydrogen envelopes. The light curves of Type IIP and Type IIL supernovae have distinctive shapes, with a long plateau lasting for hundreds of days.

    Type IIb: Type IIb supernovae largely break our classification system, but we have included them to give you a glimpse of how funky this business is. Spectra of Type IIb SNe begin with strong hydrogen lines, putting them in the Type II category. However, at late times they lose this hydrogen emission and instead resemble Type Ib SNe (with helium features). These explosions are likely from stars which have lost part of their hydrogen envelopes.

    Below is a visual guide to classifying supernovae. To be clear: the real classifications of supernovae are a challenging business, and require a complex ruleset. This is especially true as the subclasses become more specialized. In the below image, for example, it is entirely possible for a SLSN to be associated with a long GRB, or a Type Ia to be cloaked in hydrogen.

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    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 3:51 pm on November 30, 2016 Permalink | Reply
    Tags: , , Cosmology, , What If Gravity Isn't Really Fundamental?   

    From Ethan Siegel: “What If Gravity Isn’t Really Fundamental?” 

    Ethan Siegel

    Nov 12, 2016

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    The warping of spacetime by gravitational masses. Image credit: LIGO/T. Pyle.

    Ever since Newton first put forth his theory of universal gravitation, it’s been accepted that the same forces governing gravitation here on Earth also govern motion and formation of the planets, stars, galaxies and even larger-scale structures in the Universe. As our scientific understanding improved, Newton’s gravity was replaced by Einstein’s General Relativity, with a full, quantum theory of gravity expected to someday supersede that. So far, attempts to quantize gravity have been elusive. But what if gravity weren’t a fundamental force at all, and that’s why attempts to quantize it have failed? A great many of you — including Lex Kemper, Mariusz Woloszyn, Pedro Teixeira, Frank Jansen and Tristan du Pree — have all asked about a new paper: Emergent Gravity and the Dark Universe, by Erik Verlinde. Let’s dive in.

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    The four forces (or interactions) of Nature, their force carrying particles and the phenomena or particles affected by them. The three interactions that govern the microcosmos are all much stronger than gravity and have been unified through the Standard Model. Image credit: Typoform/Nobel Media, via https://www.nobelprize.org/nobel_prizes/physics/laureates/2004/popular.html.

    Conventionally, there are four fundamental forces. The particles and interactions of the Standard Model, which contains the quarks, leptons, gauge bosons and the Higgs, describe three of the fundamental forces: electromagnetism and the weak and strong nuclear forces. The other force, described by Einstein’s General Relativity, is gravitation. This effect is taken into account by the curvature of spacetime on one hand and the presence of matter and energy on the other. Effects like gravitational lensing, gravitational radiation and the expansion of the Universe is a consequence of this theory, and it is capable of incorporating both dark matter and dark energy. One of the great hopes of many theoretical physicists (and string theory) — although it’s not a necessity — is that there may exist some overarching framework that unifies all four of these forces together.

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    The fabric of spacetime, illustrated, with ripples and deformations due to mass. Image credit: European Gravitational Observatory, Lionel BRET/EUROLIOS.

    But another approach is to consider that perhaps General Relativity itself, including space, time, and the gravitational force, is not fundamental, but rather emergent. Perhaps General Relativity is merely a stage upon which the gravitational play is performed, and that there’s a more fundamental, underlying cause to what we perceive as gravitation. Verlinde’s approach is to start from the entropy and Hawking temperature of a black hole, and then, using ideas from String Theory, to show there’s a relationship between quantum information theory and the emergence of gravity, space and time.

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    Two possible entanglement patterns in de Sitter space, representing entangled bits of quantum information that may enable space, time and gravity to emerge. Image credit: Erik Verlinde, via https://arxiv.org/pdf/1611.02269v2.pdf.

    The basic idea isn’t too hard: imagine you have two quantum “units,” entangled with one another. Throw a matter particle in there, and it has the capacity to interact with one or both of them. That other particle, quite simply, can change the entanglement of the system, and it’s from that change-in-entanglement that gravity can emerge. Because the entropy of a black hole is proportional to a black hole’s surface area, it’s tempting to view space as a network of entangled “units” that allow gravitation to emerge. There’s also the fact that the other element Verlinde starts from, the Hawking temperature of a black hole, is proportional to the gravitational acceleration at the black hole’s event horizon.

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    We don’t know what happens at the singularity inside a black hole, but the information about the event horizon, including entropy and the temperature outside, are well-defined. Image credit: NASA, via http://www.nasa.gov/topics/universe/features/smallest_blackhole.html.

    The hope is, with the right assumptions, a full theory of gravity, which:

    gives you four dimensions of spacetime (three space and one time),
    incorporates dark energy via a positive cosmological constant,
    and explains where the gravitational “differences” between the Standard Model’s predictions and what we observe comes from.

    That’s the big hope, and what Verlinde is working towards. (Others are also working towards it independently.) This paper is an update on how it’s going. So, how’s it going?

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    An illustration of a step in the emergence of gravity-as-we-know-it according to the idea of entropic gravity. Image credit: Erik Verlinde, via https://arxiv.org/pdf/1611.02269v2.pdf.

    There are some successes given very specific assumptions, but there are a lot of problems. The largest problem, quite simply, is that one needs to make a multitude of seemingly arbitrary “interpretation” decisions to wind up with something other than nonsense. For example: the full motivation for this approach is based in anti-de Sitter space (or space with a negative cosmological constant), but our Universe is observed to have a positive cosmological constant (i.e., de Sitter space), and the mathematics of the two spaces have very different properties. For another, you need the entropy to obey a strict area-based law to get the Einstein equations out, but you don’t get a cosmological horizon out if you do. (And our Universe has one.) And finally, if you make all the assumptions you need to in order to get the gravitational acceleration for galaxies out, you destroy all of General Relativity’s successes on larger-than-galaxy scales. (Verlinde, on pp. 39-40, makes the argument that it could succeed, but the observations of colliding galaxy clusters completely undermine his line of thought.)

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    The X-ray (pink) and overall matter (blue) maps of various colliding galaxy clusters show a clear separation between normal matter and dark matter. Image credit: X-ray: NASA/CXC/Ecole Polytechnique Federale de Lausanne, Switzerland/D.Harvey & NASA/CXC/Durham Univ/R.Massey; Optical & Lensing Map: NASA, ESA, D. Harvey (Ecole Polytechnique Federale de Lausanne, Switzerland) and R. Massey (Durham University, UK).

    There are other, more fundamental disappointments. Verlinde’s model allows gravitational mass to emerge, but there is no mention of inertial mass, or why those two are the same. (This is Einstein’s equivalence principle.) For another, many of the intricate assumptions that Verlinde makes can only get the numbers to work out if they apply the Hubble expansion rate as it is today, despite the fact that the Universe’s expansion rate has changed dramatically over its history. He’s also assumed that dark energy was always the dominant form of energy in the Universe in order to make this framework valid, but the truth is that for billions of years, dark energy was negligible. In other words, some of the key cornerstones of modern cosmology — like the large-scale formation of structure or the fluctuations in the cosmic microwave background [CMB] — aren’t sufficiently explained by this work.

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    The fluctuations across the entire sky are imprinted in the cosmic microwave background, the Big Bang’s leftover glow. Image credit: ESA and the Planck collaboration.

    For the most part, though, this is a herculean effort to try and develop a radical new idea: that by starting with the entropy and temperature of fundamental quantum “bits,” you can derive a theory of gravitation, including space and time. Now, there are some problems with it that I would sum up as follows:

    The definitions for entropy and temperature rely on General Relativity to be defined in the first place.
    Many assumptions and interpretations are made along the way with no clear motivation, other than “the math appears to work out this way.”
    The composition and structure of the Universe has changed over time, but the laws of physics have not, which appears to be in conflict with Verlinde’s work.
    And there are a number of open questions this work raises: can the standard cosmological picture be incorporated, including the expansion of the Universe, inflation, and the full suite of dark matter/dark energy observations?

    Inflationary Universe. NASA/WMAP
    Inflationary Universe. NASA/WMAP

    Because as interesting as this idea is, it has to be consistent with the Universe we observe. And in order to have a hope of rising to the level of accepted science, it needs to actually make a prediction that we can go and look for on a matter that hasn’t been decided yet. It has the potential to get there, but it isn’t just a matter of hard work; it has to be right, and whether that’s true or not hasn’t been determined. New ideas are always exciting, and this one might offer some tremendous insights down the road. As Niels Bohr brilliantly said,

    “In our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, as far as possible, relations between the manifold aspects of our experience.”

    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 3:28 pm on November 30, 2016 Permalink | Reply
    Tags: , , Cosmology, Could the Universe be infinite?,   

    From Ethan Siegel: “Could the Universe be infinite?” 

    Ethan Siegel

    Nov 12, 2016

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    Artist’s logarithmic scale conception of the observable universe. Image credit: Wikipedia user Pablo Carlos Budassi.

    Perhaps the limits of what we can observe aren’t just artificial; perhaps there are no limits to what’s out there at all.

    “Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe.” -Frederick S. Perls, quoting Einstein

    13.8 billion years ago, the Universe began with the hot Big Bang. It’s been expanding and cooling ever since, up through and including the present day. From our point-of-view, we can observe it for some 46 billion light years in all directions, thanks to the speed of light and the expansion of space. Although it’s a huge distance, it’s finite. But that’s just the part we can see. What lies beyond that, and is that possibly infinite? Adam Stephens wants to know:

    [W]hat are your thoughts on the universe being infinite or even existence being so? I’ve been told by many cosmologists that an infinite universe or existence hasn’t been materially proven. How can such be empirically proven anyway?

    First off, what we see tells us more than those 46 billion light years directly reveals to us.

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    Looking out at more and more distant objects in the Universe reveals them to us as they were farther back in time. Image credit: NASA, ESA, and A. Feild (STScI).

    The farther away we look in any direction, the farther back in time we see. The nearest galaxy, some 2.5 million light years away, appears to us as it was 2.5 million years ago, because the light requires that much time to journey to our eyes from when it was emitted. More distant galaxies appear as they were tens of millions, hundreds of millions or even billions of years ago. As we look ever farther away in space, we see light from the Universe as it was when it was younger. So if we look for light that was emitted 13.8 billion years ago, as a relic of the hot Big Bang, we can actually find it: the cosmic microwave background [CMB].

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    Only a few hundred µK separate the hottest regions from the coldest, but the way the fluctuations correlate in scale and magnitude encodes a tremendous amount of information about the early Universe. Image credit: ESA and the Planck Collaboration, via http://crd-legacy.lbl.gov/~borrill/cmb/planck/217poster.html.

    This pattern of fluctuations is incredibly intricate, with different average temperature differences on different angular scales. It also encodes an incredible amount of information about the Universe, including a startling fact: the curvature of space, as best as we can tell, is completely flat. If space were positively curved, like we lived on the surface of a 4D sphere, we would see these distant light rays converge. If it were negatively curved, like we lived on the surface of a 4D saddle, we would see those distant light rays diverge. Instead, distant light rays move in their original direction, and the fluctuations we have indicate perfect flatness.

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    The magnitudes of the hot and cold spots, as well as their scales, indicate the curvature of the Universe. To the best of our capabilities, we measure it to be perfectly flat. Image credit: Smoot Group, LBL, via http://aether.lbl.gov/universe_shape.html.

    From the cosmic microwave background and the large-scale structure of the Universe (via baryon acoustic oscillations) combined, we can conclude that if the Universe is finite and loops back in on itself, it must be at least 250 times the size of the part we observe. Because we live in three dimensions, 250 times the radius means (250)3 times the volume, or more than 15 million times as much space. But, big as that is, it still isn’t infinite. A lower bound of the Universe being at least 11 trillion light years in all directions is tremendous, but it’s still finite.

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    The observable Universe might be 46 billion light years in all directions from our point of view, but there’s certainly more, unobservable Universe just like ours beyond that. Image credit: Wikimedia Commons users Frédéric MICHEL and Azcolvin429, annotated by E. Siegel.

    There’s reason to believe it’s even bigger, though. The hot Big Bang might mark the beginning of the observable Universe as we know it, but it doesn’t mark the birth of space and time itself. Before the Big Bang, the Universe underwent a period of cosmic inflation. Instead of being filled with matter and radiation, and instead of being hot, the Universe was:

    filled with energy inherent to space itself,
    expanding at a constant, exponential rate,
    and creating new space so quickly that the smallest physical length scale, the Planck length, would be stretched to the size of the presently observable Universe every 10–32 seconds.

    6
    Inflation causes space to expand exponentially, which can very quickly result in any pre-existing curved space appearing flat. Images credit: E. Siegel (L); Ned Wright’s cosmology tutorial (R).

    It’s true that in our region of the Universe, inflation came to an end. But there are a few questions we don’t know the answer to that have a tremendous influence on how big the Universe truly is, and whether it’s infinite or not.

    7
    Inflation set up the hot Big Bang and gave rise to the observable Universe we have access to, but we can only measure the last tiny fraction of a second of inflation’s impact on our Universe. Image credit: Bock et al. (2006, astro-ph/0604101); modifications by E. Siegel.

    1.) How big was the region of the Universe, post-inflation, that created our hot Big Bang? Looking at our Universe today, at how uniform the Big Bang’s leftover glow is, at how flat the Universe is, at the fluctuations stretched across the Universe on all scales, etc., there’s quite a bit we can learn. We can learn the upper limit to the energy scale at which inflation occurred; we can learn how much the Universe must have inflated; we can learn a lower limit how long inflation must have gone on for. But the pocket of the inflating Universe that gave rise to us could be much, much bigger than that lower limit! It could be hundreds, or millions, or googols of times larger than what we can observe… or even truly infinite. But without being able to observe more of the Universe than we can presently access, we don’t have enough information to decide.

    8
    Inflation ends (top) when a ball rolls into the valley. But the inflationary field is a quantum one (middle), spreading out over time. While many regions of space (purple, red and cyan) will see inflation end, many more (green, blue) will see inflation continue, potentially for an eternity (bottom). Images credit: E. Siegel.

    2.) Is the idea of “eternal inflation” correct? If you consider that inflation must be a quantum field, then at any given point during that phase of exponential expansion, there’s a probability that inflation will end, resulting in a Big Bang, and a probability that inflation will continue, creating more and more space. These are calculations we know how to do (given certain assumptions), and they lead to an inevitable conclusion: if you want enough inflation to occur to produce the Universe we see, then inflation will always create more space that continues to inflate compared to the regions that end and produce Big Bangs. While our observable Universe may have come about from inflation ending in our region of space some 13.8 billion years ago, there are regions where inflation continues — creating more and more space and giving rise to more Big Bangs — continuing to the present day. This idea is known as eternal inflation, and is generally accepted by the theoretical physics community. How big, then, is the entire unobservable Universe by now?

    7
    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. Image credit: E. Siegel.

    3.) And how long did inflation go on prior to its end and the resultant hot Big Bang? We can only see the observable Universe created by inflation’s end and our hot Big Bang. We know that inflation must have occurred for at least some ~10–32 seconds or so, but it likely went on for longer. But how much longer? For seconds? Years? Billions of years? Or even an arbitrary, infinite amount of time? Has the Universe always been inflating? Did inflation have a beginning? Did it arise from a previous state that was around eternally? Or, perhaps, did all of space and time emerge from nothingness a finite amount of time ago? These are all possibilities, and yet the answer is untestable and elusive at present.

    8
    A huge number of separate regions where Big Bangs occur are separated by continuously inflating space in eternal inflation. But we have no idea how to test, measure or access what’s out there beyond our own observable Universe. Image credit: Karen46 of http://www.freeimages.com/profile/karen46.

    From our best observations, we know that the Universe is an awful lot bigger than the part we can observe. Beyond what we can see, we strongly suspect that there’s plenty more Universe out there just like ours, with the same laws of physics, the same types of structures (stars, galaxies, clusters, filaments, voids, etc.), and the same chances at complex life. There should also be a finite size and scale to the “bubble” in which inflation ended, and an exponentially huge number of such bubbles contained within the larger, inflating spacetime. But as inconceivably large as that entire Universe (or Multiverse, if you prefer) is, it might not be infinite. In fact, unless inflation went on for a truly infinite amount of time, the Universe must be finite in extent.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
    As vast as our observable Universe is and as much as we can see, it’s only a tiny fraction of what must be out there. Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    The biggest problem of all, though? It’s that we only know how to access the information available inside our observable Universe: those 46 billion light years in all directions. The answer to the biggest of all questions — whether the Universe is finite or infinite — might be encoded in the Universe itself, but we can’t access enough of it to know. Until we either figure it out, or come up with a clever scheme to expand what we know physics is capable of, all we’ll have are the possibilities.

    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 12:11 pm on November 30, 2016 Permalink | Reply
    Tags: , , Cosmology, NIHAO, ,   

    From SPACE.com: “Ultra-Diffuse Ghost Galaxies Float Among Us” 

    space-dot-com logo

    SPACE.com

    November 30, 2016
    Sarah Lewin

    1

    Ultra-diffuse galaxies are as faint as dwarf galaxies, but spread over an area the size of the Milky Way — with about 1/1000th the number of stars. A new simulation suggests many supernovas at the beginning of a galaxy’s life can push the stars and dark matter outward to a great size. Two simulated ultra-diffuse galaxies are pictured here on top of a Hubble Space Telescope image of background galaxies.
    Credit: Arianna Di Cintio, Chris Brook, NIHAO simulations and Hubble Space Telescope

    Like ghosts, ultra-diffuse galaxies often float undetected in the night sky — stretching the size of the Milky Way, but containing only a dwarf galaxy’s worth of stars. Now, a new simulation suggests their explosive origins, and hints that there may be many more than seen so far.

    Researchers uncovered the first ultra-diffuse galaxy in 2015, and were puzzled by how the faint galaxy came to have such a large size with so few stars. Since then, they’ve spotted many more with the most sensitive telescopes, mostly in large clusters of many galaxies. But this new research suggests that internal dynamics in a forming galaxy, rather than processes happening within clusters, can blow a dwarf up to enormous, spread-out size — and thus they may pepper the universe even far from large clusters, hiding in plain sight because of their faintness.

    2
    The ultra-diffuse galaxy Dragonfly 17, shown in comparison to the large Andromeda galaxy and the elliptical dwarf galaxy NGC 205.
    Credit: Schoening/Harvey/van Dokkum/Hubble Space Telescope

    An international collaboration called NIHAO — the Numerical Investigation of a Hundred Astronomical Objects — simulated the formation of 100 galaxies in extreme detail, tracking the way gases, forming stars and dark matter interacted within the systems. Within that 100, they found some that matched the profile of the newly discovered ultra-diffuse galaxies. So they worked backward to discern what had caused them — not big galaxies failing and growing faint, but dwarf galaxies stretched to an extraordinary size.

    “Once stars explode supernovae, they release a lot of energy into the surrounding gas, and this gas can be expelled really, really fast,” Arianna di Cintio, a researcher at University of Copenhagen’s DARK Cosmology Center and lead author on the new work, told Space.com. If dwarf galaxies experience enough of these supernovas early on in their lives, she said, the galaxy can balloon outwards, borne on the outflows of gas.

    “Basically, the dark-matter particles start flying outwards from the center of the galaxy, and this process happens for the stars as well,” di Cintio said. “At the end of the day, you form a galaxy which has few stars, so it’s a dwarf galaxy, but the stars have spread over a large, large surface — something similar to the Milky Way.”

    Thus, the galaxies’ few million stars puff up to fill a space that could ordinarily host about 1,000 times that number.

    It’s easier to find ultra-diffuse galaxies in big galaxy clusters because that’s where the most powerful telescopes set their sights — for instance, the National Astronomical Observatory of Japan’s Subaru telescope found 854 of them in the Coma Cluster, according to a statement by the university’s Niels Bohr Institute.

    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA
    NAOJ Subaru Telescope interior
    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA

    Just a few have been found so far floating on their own, di Cintio said.

    The fact that the simulation created these familiar — albeit mysterious — structures is “a very, very nice confirmation of what we think is there — the current cosmological model,” di Cintio said. “This effect of expansion of dark matter and stars, we knew that it existed for a few years, [but] no one connected it yet to ultra-diffuse galaxies because they weren’t observed yet.”

    3
    Some of the 854 ultra-diffuse galaxies found by the Subaru Telescope in the Coma galaxy cluster, about 300 million light-years away. Three hundred and thirty-two of them are Milky Way-size. Credit: NAOJ

    Di Cintio said the next steps are to try and verify more ultra-diffuse galaxies living on their own, outside of big clusters, and to measure their mass — potentially through gravitational lensing — to help verify that they’re really dwarf-galaxy-mass. In general, further research will help researchers discover extremely faint, low-surface-brightness galaxies that may lurk in our telescopes’ fields of view.

    “So far, we were blind, in a certain sense, to these low-surface-brightness and ultra-diffuse galaxies,” di Cintio said. “We may be looking around and finding thousands of galaxies that we didn’t even think about yet.”

    The new work was detailed Nov. 29 in the journal Monthly Notices of the Royal Astronomical Society.

    See the full article here .

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  • richardmitnick 7:06 pm on November 28, 2016 Permalink | Reply
    Tags: , , Cosmology, Researchers propose low-mass supernova triggered formation of solar system, U Minnesota   

    From U Minnesota: “Researchers propose low-mass supernova triggered formation of solar system” 

    u-minnesota-bloc

    University of Minnesota Twin Cities

    1
    About 4.6 billion years ago, a cloud of gas and dust that eventually formed our solar system was disturbed. The ensuing gravitational collapse formed the proto-Sun with a surrounding disc where the planets were born. That cloud might be similar to some region in this much larger complex of gas and dust about 4,500 light-years away in the constellation Cygnus observed by NASA’s Spitzer Telescope. Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

    A research team led by University of Minnesota School of Physics and Astronomy Professor Yong-Zhong Qian uses new models and evidence from meteorites to show that a low-mass supernova triggered the formation of our solar system.

    The findings are published in the most recent issue of Nature Communications, a leading scientific journal.

    About 4.6 billion years ago, a cloud of gas and dust that eventually formed our solar system was disturbed. The ensuing gravitational collapse formed the proto-Sun with a surrounding disc where the planets were born. A supernova—a star exploding at the end of its life-cycle—would have enough energy to compress such a gas cloud. Yet there was no conclusive evidence to support this theory. In addition, the nature of the triggering supernova remained elusive.

    Qian and his collaborators decided to focus on short-lived nuclei present in the early solar system. Due to their short lifetimes, these nuclei could only have come from the triggering supernova. Their abundances in the early solar system have been inferred from their decay products in meteorites. As the debris from the formation of the solar system, meteorites are comparable to the leftover bricks and mortar in a construction site. They tell us what the solar system is made of and in particular, what short-lived nuclei the triggering supernova provided.

    “This is the forensic evidence we need to help us explain how the solar system was formed,” Qian said. “It points to a low-mass supernova as the trigger.”

    Qian is an expert on the formation of nuclei in supernovae. His previous research has focused on the various mechanisms by which this occurs in supernovae of different masses. His team includes the lead author of the paper, Projjwal Banerjee, who is a former Ph.D. student and postdoctoral research associate, and longtime collaborators Alexander Heger of Monash University, Australia, and Wick Haxton of the University of California, Berkeley. Qian and Banerjee realized that previous efforts in studying the formation of the solar system were focused on a high-mass supernova trigger, which would have left behind a set of nuclear fingerprints that are not present in the meteoric record.

    Qian and his collaborators decided to test whether a low-mass supernova, about 12 times heavier than our sun, could explain the meteoritic record. They began their research by examining Beryllium-10, a short-lived nucleus that has 4 protons (hence the fourth element in the periodic table) and 6 neutrons, weighing 10 mass units. This nucleus is widely distributed in meteorites.

    In fact the ubiquity of Beryllium-10 was something of a mystery in and of itself. Many researchers had theorized that spallation—a process where high-energy particles strip away protons or neutrons from a nucleus to form new nuclei—by cosmic rays was responsible for the Beryllium-10 found in meteorites. Qian said that this hypothesis involves many uncertain inputs and presumes that Beryllium-10 cannot be made in supernovae.

    Using new models of supernovae, Qian and his collaborators have shown that Beryllium-10 can be produced by neutrino spallation in supernovae of both low and high masses. However, only a low-mass supernova triggering the formation of the solar system is consistent with the overall meteoritic record.

    “The findings in this paper have opened up a whole new direction in our research,” Qian said. “In addition to explaining the abundance of Beryllium-10, this low-mass supernova model would also explain the short-lived nuclei Calcium-41, Palladium-107, and a few others found in meteorites. What it cannot explain must then be attributed to other sources that require detailed study.”

    Qian said the group would like to examine the remaining mysteries surrounding short-lived nuclei found in meteorites. The first step, however is to further corroborate their theory by looking at Lithium-7 and Boron-11 that are produced along with Beryllium-10 by neutrino spallation in supernovae. Qian said they may examine this in a future paper and urged researchers studying meteorites look at the correlations among these three nuclei with precise measurements.

    The research is funded by the Department of Energy Office of Nuclear Physics. Qian, Banerjee, and Heger are also scientific participants of the Joint Institute for Nuclear Astrophysics-Center for the Evolution of the Elements, a National Science Foundation Physics Frontier Center.

    See the full article here .

    Please help promote STEM in your local schools.

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    We are Minnesota’s research university. We change lives—through research, education, and outreach.
    Research

    We seek new knowledge that can change how we all work and live.

    At the University of Minnesota, students do research alongside top professors in all majors.
    Education

    We prepare students to meet the great challenges facing our state, our nation, and our world.

    As a U of M student you’ll engage with your professors and fellow students from the very beginning. And you’ll develop your strengths with beyond-the-classroom experiences.
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    We apply our expertise to meet the needs of Minnesota, our nation, and the world.

     
  • richardmitnick 6:20 pm on November 28, 2016 Permalink | Reply
    Tags: , , , Cosmology, Matching Supernovae to Galaxies,   

    From AAS NOVA: “Matching Supernovae to Galaxies” 

    AASNOVA

    American Astronomical Society

    28 November 2016
    Susanna Kohler

    1
    Not every supernova’s host galaxy is as easy to identify as that of SN 1994D, seen in the outskirts of galaxy NGC 4526 in this Hubble image. Automated matching of supernovae to their host galaxies will likely be necessary for large upcoming surveys. [NASA/ESA]

    One of the major challenges for modern supernova surveys is identifying the galaxy that hosted each explosion. Is there an accurate and efficient way to do this that avoids investing significant human resources?

    Why Identify Hosts?

    2
    One problem in host galaxy identification. Here, the supernova lies between two galaxies — but though the centroid of the galaxy on the right is closer in angular separation, this may be a distant background galaxy that is not actually near the supernova. [Gupta et al. 2016]

    Supernovae are a critical tool for making cosmological predictions that help us to understand our universe. But supernova cosmology relies on accurately identifying the properties of the supernovae — including their redshifts. Since spectroscopic followup of supernova detections often isn’t possible, we rely on observations of the supernova host galaxies to obtain redshifts.

    But how do we identify which galaxy hosted a supernova? This seems like a simple problem, but there are many complicating factors — a seemingly nearby galaxy could be a distant background galaxy, for instance, or a supernova’s host could be too faint to spot.

    3
    The authors’ algorithm takes into account “confusion”, a measure of how likely the supernova is to be mismatched. In these illustrations of low (left) and high (right) confusion, the supernova is represented by a blue star, and the green circles represent possible host galaxies. [Gupta et al. 2016]

    Turning to Automation

    Before the era of large supernovae surveys, searching for host galaxies was done primarily by visual inspection. But current projects like the Dark Energy Survey’s Supernova Program is finding supernovae by the thousands, and the upcoming Large Synoptic Survey Telescope will likely discover hundreds of thousands. Visual inspection will not be possible in the face of this volume of data — so an accurate and efficient automated method is clearly needed!

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera [DECam]. Built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo

    LSST
    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC

    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST telescope, currently under construction at Cerro Pachón Chile

    To this end, a team of scientists led by Ravi Gupta (Argonne National Laboratory) has recently developed a new automated algorithm for matching supernovae to their host galaxies. Their work builds on currently existing algorithms and makes use of information about the nearby galaxies, accounts for the uncertainty of the match, and even includes a machine learning component to improve the matching accuracy.

    Gupta and collaborators test their matching algorithm on catalogs of galaxies and simulated supernova events to quantify how well the algorithm is able to accurately recover the true hosts.

    4
    The matching algorithm’s accuracy (“purity”) as a function of the true supernova-host separation, the supernova redshift, the true host’s brightness, and the true host’s size. [Gupta et al. 2016]

    Successful Matching

    The authors find that when the basic algorithm is run on catalog data, it matches supernovae to their hosts with 91% accuracy. Including the machine learning component, which is run after the initial matching algorithm, improves the accuracy of the matching to 97%.

    The encouraging results of this work — which was intended as a proof of concept — suggest that methods similar to this could prove very practical for tackling future survey data. And the method explored here has use beyond matching just supernovae to their host galaxies: it could also be applied to other extragalactic transients, such as gamma-ray bursts, tidal disruption events, or electromagnetic counterparts to gravitational-wave detections.

    Citation

    Ravi R. Gupta et al 2016 AJ 152 154. doi:10.3847/0004-6256/152/6/154

    See the full article here .

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  • richardmitnick 9:01 am on November 28, 2016 Permalink | Reply
    Tags: , , Cosmography of the Local Universe, Cosmology, Institut de Physique Nucleaire de Lyon   

    From Institut de Physique Nucleaire de Lyon: “Cosmography of the Local Universe” 

    ipnl-bloc

    Institut de Physique Nucleaire de Lyon

    Cosmography of the Local Universe using Cosmicflows-1 Dataset. Ref: arxiv.org/abs/1306.0091 in Press in Astronomical Journal. By Helene Courtois, Daniel Pomarede, Brent Tully, Yehuda Hoffman and Denis Courtois.

    Watch, enjoy, learn.

    See the full article here .

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