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  • richardmitnick 2:15 pm on August 14, 2018 Permalink | Reply
    Tags: , , , Cosmic Web, , Early Opaque Universe Linked to Galaxy Scarcity, ,   

    From UC Riverside: “Early Opaque Universe Linked to Galaxy Scarcity” 

    UC Riverside bloc

    From UC Riverside

    August 14, 2018
    Iqbal Pittalwala

    1
    Computer simulation of a region of the universe wherein a low-density “void” (dark blue region at top center) is surrounded by denser structures containing numerous galaxies (orange/white). The research done by Becker and his team suggests that early in cosmic history, these void regions would have been the murkiest places in the universe even though they contained the least amount of dark matter and gas. Image credit: TNG Collaboration.

    A team of astronomers led by George Becker at the University of California, Riverside, has made a surprising discovery: 12.5 billion years ago, the most opaque place in the universe contained relatively little matter.

    It has long been known that the universe is filled with a web-like network of dark matter and gas. This “cosmic web” accounts for most of the matter in the universe, whereas galaxies like our own Milky Way make up only a small fraction.

    Cosmic web Millenium Simulation Max Planck Institute for Astrophysics

    Today, the gas between galaxies is almost totally transparent because it is kept ionized— electrons detached from their atoms—by an energetic bath of ultraviolet radiation.

    Over a decade ago, astronomers noticed that in the very distant past — roughly 12.5 billion years ago, or about 1 billion years after the Big Bang — the gas in deep space was not only highly opaque to ultraviolet light, but its transparency varied widely from place to place, obscuring much of the light emitted by distant galaxies.

    Then a few years ago, a team led by Becker, then at the University of Cambridge, found that these differences in opacity were so large that either the amount of gas itself, or more likely the radiation in which it is immersed, must vary substantially from place to place.

    “Today, we live in a fairly homogeneous universe,” said Becker, an expert on the intergalactic medium, which includes dark matter and the gas that permeates the space between galaxies. “If you look in any direction you find, on average, roughly the same number of galaxies and similar properties for the gas between galaxies, the so-called intergalactic gas. At that early time, however, the gas in deep space looked very different from one region of the universe to another.”

    To find out what created these differences, the team of University of California astronomers from the Riverside, Santa Barbara, and Los Angeles campuses turned to one of the largest telescopes in the world: the Subaru telescope on the summit of Mauna Kea in Hawaii.


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    Using its powerful camera, the team looked for galaxies in a vast region, roughly 300 million light years in size, where they knew the intergalactic gas was extremely opaque.

    For the cosmic web more opacity normally means more gas, and hence more galaxies. But the team found the opposite: this region contained far fewer galaxies than average. Because the gas in deep space is kept transparent by the ultraviolet light from galaxies, fewer galaxies nearby might make it murkier.

    “Normally it doesn’t matter how many galaxies are nearby; the ultraviolet light that keeps the gas in deep space transparent often comes from galaxies that are extremely far away. That’s true for most of cosmic history, anyway,” said Becker, an assistant professor in the Department of Physics and Astronomy. “At this very early time, it looks like the UV light can’t travel very far, and so a patch of the universe with few galaxies in it will look much darker than one with plenty of galaxies around.”

    This discovery, reported in the August 2018 issue of the Astrophysical Journal, may eventually shed light on another phase in cosmic history. In the first billion years after the Big Bang, ultraviolet light from the first galaxies filled the universe and permanently transformed the gas in deep space. Astronomers believe that this occurred earlier in regions with more galaxies, meaning the large fluctuations in intergalactic radiation inferred by Becker and his team may be a relic of this patchy process, and could offer clues to how and when it occurred.

    “There is still a lot we don’t know about when the first galaxies formed and how they altered their surroundings,” Becker said.

    By studying both galaxies and the gas in deep space, astronomers hope to get closer to understanding how this intergalactic ecosystem took shape in the early universe.

    The research was funded by the National Science Foundation and NASA.

    Becker was joined in the research by Frederick B. Davies of UC Santa Barbara; Steven R. Furlanetto and Matthew A. Malkan of UCLA; and Elisa Boera and Craig Douglass of UCR.

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

     
  • richardmitnick 12:21 pm on August 29, 2017 Permalink | Reply
    Tags: , , , Cosmic Web, , , , ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars, ,   

    From ESO: “ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars” 

    ESO 50 Large

    European Southern Observatory

    26 October 2016 [Just found this. Don’t know how I missed it.]
    Elena Borisova
    ETH Zurich
    Switzerland
    Tel: +41 44 633 77 09
    Email: borisova@phys.ethz.ch

    Sebastiano Cantalupo
    ETH Zurich
    Switzerland
    Tel: +41 44 633 70 57
    Email: cantalupo@phys.ethz.ch

    Mathias Jäger
    Public Information Officer
    Garching bei München, Germany
    Tel: +49 176 62397500
    Email: mjaeger@partner.eso.org

    1
    An international team of astronomers has discovered glowing gas clouds surrounding distant quasars. This new survey by the MUSE instrument on ESO’s Very Large Telescope indicates that halos around quasars are far more common than expected. The properties of the halos in this surprising find are also in striking disagreement with currently accepted theories of galaxy formation in the early Universe.

    An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to study gas around distant active galaxies, less than two billion years after the Big Bang.

    ESO MUSE on the VLT

    These active galaxies, called quasars, contain supermassive black holes in their centres, which consume stars, gas, and other material at an extremely high rate. This, in turn, causes the galaxy centre to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.

    The study involved 19 quasars, selected from among the brightest that are observable with MUSE. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300 000 light-years away from the centres of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed — far more than the two halos that were expected statistically. The team suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.

    “It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries”, says lead author Elena Borisova, from the ETH Zurich.

    The original goal of the study was to analyse the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes [1].

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.

    The 19 newly-detected halos also revealed another surprise: they consist of relatively cold intergalactic gas — approximately 10 000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.

    The discovery shows the potential of MUSE for observing this type of object [2]. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We have exploited the unique capabilities of MUSE in this study, which will pave the way for future surveys. Combined with a new generation of theoretical and numerical models, this approach will continue to provide a new window on cosmic structure formation and galaxy evolution.”

    Notes

    [1] The cosmic web is the structure of the Universe at the largest scale. It is comprised of spindly filaments of primordial material (mostly hydrogen and helium gas) and dark matter which connect galaxies and span the chasms between them. The material in this web can feed along the filaments into galaxies and drive their growth and evolution.

    [2] MUSE is an integral field spectrograph and combines spectrographic and imaging capabilities. It can observe large astronomical objects in their entirety in one go, and for each pixel measure the intensity of the light as a function of its colour, or wavelength.

    This research was presented in the paper Ubiquitous giant Lyα nebulae around the brightest quasars at z ~ 3.5 revealed with MUSE, to appear in The Astrophysical Journal.

    The team is composed of Elena Borisova, Sebastiano Cantalupo, Simon J. Lilly, Raffaella A. Marino and Sofia G. Gallego (Institute for Astronomy, ETH Zurich, Switzerland), Roland Bacon and Jeremy Blaizot (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Nicolas Bouché (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Jarle Brinchmann (Leiden Observatory, Leiden, The Netherlands; Instituto de Astrofísica e Ciências do Espaço, Porto, Portugal), C Marcella Carollo (Institute for Astronomy, ETH Zurich, Switzerland), Joseph Caruana (Department of Physics, University of Malta, Msida, Malta; Institute of Space Sciences & Astronomy, University of Malta, Malta), Hayley Finley (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Edmund C. Herenz (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Johan Richard (Univ Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Joop Schaye and Lorrie A. Straka (Leiden Observatory, Leiden, The Netherlands), Monica L. Turner (MIT-Kavli Center for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), Tanya Urrutia (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Anne Verhamme (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany).

    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
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

     
  • richardmitnick 10:22 am on July 23, 2017 Permalink | Reply
    Tags: , , , , , Cosmic Web, , , FDM-Fuzzy Dark Matter, Lyman-alpha forest   

    From Astro Watch: “Flashes of Light on the Dark Matter” 

    Astro Watch bloc

    Astro Watch

    July 23, 2017
    No writer credit found

    1

    A web that passes through infinite intergalactic spaces, a dense cosmic forest illuminated by very distant lights and a huge enigma to solve. These are the picturesque ingredients of a scientific research – carried out by an international team composed of researchers from the International School for Adavnced Studies (SISSA) and the Abdus Salam International Center for Theoretical Physics (ICTP) in Trieste, the Institute of Astronomy of Cambridge and the University of Washington – that adds an important element for understanding one of the fundamental components of our Universe: the dark matter.

    In order to study its properties, scientists analyzed the interaction of the “cosmic web” – a network of filaments made up of gas and dark matter present in the whole Universe – with the light coming from very distant quasars and galaxies. Photons interacting with the hydrogen of the cosmic filaments create many absorption lines defined “Lyman-alpha forest”. This microscopic interaction succeeds in revealing several important properties of the dark matter at cosmological distances. The results further support the theory of Cold Dark Matter, which is composed of particles that move very slowly. Moreover, for the first time, they highlight the incompatibility with another model, i.e. the Fuzzy Dark Matter, for which dark matter particles have larger velocities. The research was carried out through simulations performed on international parallel supercomputers and has recently been published in Physical Review Letters.

    Although constituting an important part of our cosmos, the dark matter is not directly observable, it does not emit electromagnetic radiation and it is visible only through gravitational effects. Besides, its nature remains a deep mystery. The theories that try to explore this aspect are various. In this research, scientists investigated two of them: the so-called Cold Dark Matter, considered a paradigm of modern cosmology, and an alternative model called Fuzzy Dark Matter (FDM), in which the dark matter is deemed composed of ultralight bosons provided with a non-negligible pressure at small scales. To carry out their investigations, scientists examined the cosmic web by analyzing the so-called Lyman-alpha forest. The Lyman-alpha forest consists of a series of absorption lines produced by the light coming from very distant and extremely luminous sources, that passes through the intergalactic space along its way toward the earth’s telescopes. The atomic interaction of photons with the hydrogen present in the cosmic filaments is used to study the properties of the cosmos and of the dark matter at enormous distances.

    Through simulations carried out with supercomputers, researchers reproduced the interaction of the light with the cosmic web. Thus they were able to infer some of the characteristics of the particles that compose the dark matter. More in particular, evidence showed for the first time that the mass of the particles, which allegedly compose the dark matter according to the FDM model, is not consistent with the Lyman-alpha Forest observed by the Keck telescope (Hawaii, US) and the Very Large Telescope (European Southern Observatory, Chile).


    Keck Observatory, Maunakea, Hawaii, USA

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Basically, the study seems not to confirm the theory of the Fuzzy Dark Matter. The data, instead, support the scenario envisaged by the model of the Cold Dark Matter.

    The results obtained – scientists say – are important as they allow to build new theoretical models for describing the dark matter and new hypotheses on the characteristics of the cosmos. Moreover, these results can provide useful indications for the realization of experiments in laboratories and can guide observational efforts aimed at making progress on this fascinating scientific theme.

    See the full article here .

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  • richardmitnick 3:49 pm on February 28, 2016 Permalink | Reply
    Tags: , , , , Cosmic Web,   

    From Nautilus: “Cosmic Void Dwarfs Are a Thing and There’s a Problem With Them” 

    Nautilus

    Nautilus

    Feb 28, 2016
    Ian Chant

    Given how absurdly vast the cosmos is, with its hundreds of billions of galaxies, picturing it isn’t easy. You might think it natural, for instance, to see all these galaxies as more or less evenly spread out across the Universe. But you’d be wrong. Following the Big Bang, 13.8 billion years ago, says Robert Kirshner, an astrophysicist at Harvard, matter began to spread out pretty evenly but then started to clump. Matter-rich places eventually became denser and denser, and as they formed and grew, so too did empty spaces. Check it out.

    Cosmic web Millenium Simulation Max Planck Institute foir Astrophysics
    Cosmic web. Millenium Simulation Max Planck Institute for Astrophysics

    Those voids, despite filling up over 60 percent of the Universe, are hard to find, says Kirshner. He’s been looking for them since 1981, when he and his colleagues found the Bootes void, one of the largest known voids to exist. “You have to make a lot of measurements to ensure that what you’re looking at is really a hollow shell,” he says.

    Actually, they’re not completely hollow—matter in voids still manages to coalesce into dwarf galaxies on occasion. This fact presents astronomers with a unique opportunity to view uninterrupted galactic birth and development. “Galaxy formation and evolution is a messy process,” says Kathryn Kreckel, a researcher at the Max Planck Institute for Astronomy. “Voids provide a uniquely calm environment in which to disentangle the effects of some of the many processes that can play a role.” Galaxies in clusters tend to absorb dwarf galaxies, strip gasses from their environment and even collide with them, creating gigantic galaxy mashups—the Milky Way, in a galaxy cluster known as the Local Group, is an example.

    Local Grp II
    The Local Group of galaxies. The Milky Way and Andromeda are the most massive galaxies by far.

    (It’s merged a number of times over the years with other galaxies and, in 500 million years, it will merge again, with the Andromeda galaxy.)

    Andromeda Galaxy
    Andromeda. NASA/ESA Hubble

    NASA Hubble Telescope
    NASA/ESA Hubble

    Scientists using the Sloan Digital Sky Survey [SDSS}—which has “created the most detailed three-dimensional maps of the Universe ever made”—have managed to spot a good amount of dwarf galaxies in voids.

    SDSS Telescope
    SDSS telescope, Apache Point, NM, USA

    Last year, for example, astronomers at Drexel University using the Survey examined “the first statistically-significant sample” of them—2,777 in total. They’re usually found to be in a more youthful state of star formation than dwarf galaxies outside of voids, and tend to be bluer. They also produce stars much more quickly than galaxies in clusters.

    These void dwarfs pose “several interesting riddles and questions,” write Ignacio Ferraras, a cosmic archaeologist at University College London, and Anna Pasquali, an astrophysicist at Heidelberg University. For one, according to the standard theory of how the Universe evolved—the Lambda cold dark matter model—voids should be “teeming with dwarfs and low surface brightness galaxies,” but they’re not. In 2001, Princeton theoretical cosmologist Jim Peebles termed this anomaly “void phenomenon.” This “‘void phenomenon,’” says Kreckel, “suggests that low mass void galaxy formation is somehow suppressed.”

    There are a few guesses as to why voids host less dwarf galaxies than expected. It could be that incoming UV radiation is heating up the cool gasses galaxies need to form, causing them to evaporate; or winds from supernova explosions could be blowing the gasses away, preventing them from condensing. It’s also possible, says Rien van de Weygaert, an astronomer at the University of Groningen, that objects do exist in these voids, but they are too faint to be effectively detected by our instruments. Peebles suggests that the ionizing radiation of the galaxies that first form in voids may prevent others from taking shape nearby. More speculatively, it could be hypothetical particles like warm dark matter that are producing “regions that are quite devoid of gravitational seeds for structure formation,” says van de Weygaert.

    If that’s true, he says, “the dearth of void dwarfs has the possible implication that the standard theory of cosmological structure formation could have a serious flaw.” It’s a worry that’s been nagging theorists for years. Peebles pointed this out over a decade ago in “The Void Phenomenon” : “The apparent inconsistency between theory and observations of void,” he wrote, “is striking enough to be classified as a crisis.”

    See the full article here .

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 2:37 pm on December 29, 2015 Permalink | Reply
    Tags: Another 20 Billion Kilometers Through The Universe, , , Cosmic Web, scientific   

    From SA: “Another Year, Another 20 Billion Kilometers Through The Universe” 

    Scientific American

    Scientific American

    December 29, 2015
    Caleb A. Scharf

    Temp 1
    (M101, NASA, ESA, CXC, SSC, and STScI)

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Chandra Telescope
    NASA/Chandra

    Temp 1

    Another year passes. Another 365 planetary spins completed (14.6 million kilometers of combined distance traveled if you live at the Earth’s equator), and another journey of 940 million kilometers around the Sun. Time is marked off for us by a largely predictable, if not tedious, set of cycles.

    Except, this is by no means all the cosmic traveling we’ve done in the last 31.5 million seconds.

    For one thing, the solar system is not at rest with respect to its host galaxy. The Sun and its planetary entourage are moving in an orbital path within the Milky Way. The generally quoted properties of this motion are that we’re heading around the galactic center at about 220 kilometers a second, but with an additional ‘bobbing’, or sinusoidal, motion perpendicular to this. In other words the solar system is meandering up and down ‘through’ the plane of the galaxy, while making a full circuit roughly every 220 to 250 million years.

    The solar system’s up and down galactic path has intrigued scientists for a long time because it may have a period of anywhere from about 20 to 60 million years. This period is on a par with various claims for distinctly spaced extinction events on the Earth, or episodes of enhanced comet and asteroid bombardment.

    But the truth is that – as is so often the case – the jury is still firmly out on whether there’s a connection between our passage through the galactic plane and what has happened here on Earth. In fact we really don’t even know what the precise up and down motion of our solar system has been during the past 4 billion years. The Milky Way is not a simple, smooth, distribution of mass. It has lumps, and there are other stellar objects buzzing around, so we don’t yet have good enough models to pin down our past galactic trajectory with any real accuracy – despite what anyone says.

    Milky Way map
    NASA/JPL-Caltech/ESO/R. Hurt

    Stepping a little further out in scale; the Milky Way and the Andromeda galaxy are falling towards each other at roughly 110 kilometers a second, from about 2.5 million light years away.

    3
    Andromeda Galaxy. Adam Evans

    So in the past year we’ve got about 3.5 billion kilometers closer to a likely galactic collision in about 4 billion years time. In the meantime, around us, the other 54 or more galaxies of our Local Group have continued to hang together as a gravitationally bound system, resisting the undercurrent of cosmic expansion.

    5
    Local Group. Andrew Z. Colvin

    But these are all parochial motions, the kind of to-ing and fro-ing that happens in a little village. None of these spins, orbits, circulations, and infalls really get us anywhere in the long term, we’re just stewing in our own gravitational pot. What about our journey across a greater cosmic frame?

    The snag to evaluating such displacement is that on the biggest scales of an expanding and centerless gulf of spacetime, the concept of absolute motion is not terribly useful. If we’re concerned about measuring progress through the universe, what are we actually moving with respect to?

    There is one helpful gauge. The universe is filled with radiation, with photons zinging endlessly across space. These come from stars, supernovae, quasars, hot gas cooling down, and many other sources. In particular, at any instant in time, a cubic centimeter of the universe will contain, on average, about 400 cosmic microwave background [CMB] photons moving in effectively random directions.

    CMB Planck ESA
    CMB per ESA/Planck

    ESA Planck
    ESA/Planck

    This ocean of ancient photons can serve to as a tool for sensing our motion. The blue and red Doppler-shifts of the microwave radiation allow us to build a sky map reflecting our passage through space.

    Given that we know the Earth’s motion around the Sun very well, and the Sun’s motion around our Galactic center quite well, and the Milky Way’s motion with respect to the other galaxies of our Local Group with some confidence, we can factor those velocities out and deduce the true drift of our intergalactic neighborhood with respect to the cosmic microwave background.

    The answer is that our patch of universe, containing the Milky Way, Andromeda, and all the attendant, gravitationally bound galaxies, is moving at about 627 kilometers a second in a direction close to the constellation of Centaurus from our perspective. So in the course of a terrestrial year we make a journey of some 20 billion kilometers ‘through’ the universe.

    Why is this happening? In a nutshell, it’s because the distribution of matter in the universe is not actually uniform – at least not on scales of up to at least several hundred million light years. We’re surrounded by a vast assortment of further galaxies, galaxy clusters, and superclusters.

    7
    Superclusters. Richard Powell

    The direction that our Local Group is moving in is set by the net gravitational pull of all these matter distributions, and that’s somewhat imbalanced – so we’re falling in a direction along the vector sum of all those pulls.

    The precise details of the matter distribution responsible for this – the large-scale cosmic structures – are still unclear, although regions such as the Shapley Supercluster, containing tens of thousands of galaxies, are involved.

    8
    Shapley Supercluster. Richard Powell

    Chances are that we’ve not yet surveyed the full distribution of responsible galaxies (and therefore matter). We may need to go some billion light years out to account for all the ‘pull’ that is acting on our local patch.

    Will we ever reach these regions, embracing the cosmic web of irregularity that surrounds us?

    9
    Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The image is derived from the 2MASS Extended Source Catalog (XSC)—more than 1.5 million galaxies, and the Point Source Catalog (PSC)–nearly 0.5 billion Milky Way stars. The galaxies are color coded by redshift (numbers in parentheses) obtained from the UGC, CfA, Tully NBGC, LCRS, 2dF, 6dFGS, and SDSS surveys (and from various observations compiled by the NASA Extragalactic Database), or photo-metrically deduced from the K band (2.2 μm). Blue/purple are the nearest sources (z < 0.01); green are at moderate distances (0.01 < z < 0.04) and red are the most distant sources that 2MASS resolves (0.04 < z < 0.1). The map is projected with an equal area Aitoff in the Galactic system (Milky Way at center).
    IPAC/Caltech, by Thomas Jarrett

    No, it seems that we will not at our present velocity. The relentless (and accelerating) expansion of the universe will prevent that encounter, eventually isolating our little island.

    Indeed, while we can measure that we’ve traversed 20 billion kilometers of the cosmos in the past year, during that same period any place a hundred million light years away will have further receded from us by some 200 billion kilometers.

    This cosmic indifference to any hopes of progress may leave us feeling a little depressed. After another year, another circuit of the Sun, we’re back in a place very, very similar to the one we left, and that is how it will continue to be.

    Except, the very fact that our minds have figured all of this out, from the spin of the Earth to our modest traversal of an ocean of cosmic photons, is itself remarkable. Whether or not any other sentient beings exist anywhere else in the entire observable universe, here, for a fleeting moment, we can gaze in awe at the cosmos that has allowed our existence. Another 20 billion kilometers through the universe may represent a certain cosmic futility, but at least it is a journey that belongs to us.

    See the full articlehttp://blogs.scientificamerican.com/life-unbounded/another-year-another-20-billion-kilometers-through-the-universe/ .

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    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

     
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