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  • richardmitnick 3:32 pm on December 15, 2014 Permalink | Reply
    Tags: , , , Cosmic Microwave Background, ,   

    From ESA: “The magnetic field along the Galactic plane” 

    European Space Agency


    ESA/Planck Collaboration


    While the pastel tones and fine texture of this image may bring to mind brush strokes on an artist’s canvas, they are in fact a visualisation of data from ESA’s Planck satellite.

    ESA Planck
    ESA Planck schematic

    The image portrays the interaction between interstellar dust in the Milky Way and the structure of our Galaxy’s magnetic field.

    Between 2009 and 2013, Planck scanned the sky to detect the most ancient light in the history of the Universe – the cosmic microwave background. It also detected significant foreground emission from diffuse material in our Galaxy which, although a nuisance for cosmological studies, is extremely important for studying the birth of stars and other phenomena in the Milky Way.

    Cosmic Microwave Background  Planck
    CMB per ESA/Planck

    Among the foreground sources at the wavelengths probed by Planck is cosmic dust, a minor but crucial component of the interstellar medium that pervades the Galaxy. Mainly gas, it is the raw material for stars to form.

    Interstellar clouds of gas and dust are also threaded by the Galaxy’s magnetic field, and dust grains tend to align their longest axis at right angles to the direction of the field. As a result, the light emitted by dust grains is partly ‘polarised’ – it vibrates in a preferred direction – and, as such, could be caught by the polarisation-sensitive detectors on Planck.

    Scientists in the Planck collaboration are using the polarised emission of interstellar dust to reconstruct the Galaxy’s magnetic field and study its role in the build-up of structure in the Milky Way, leading to star formation.

    In this image, the colour scale represents the total intensity of dust emission, revealing the structure of interstellar clouds in the Milky Way. The texture is based on measurements of the direction of the polarised light emitted by the dust, which in turn indicates the orientation of the magnetic field.

    This image shows the intricate link between the magnetic field and the structure of the interstellar medium along the plane of the Milky Way. In particular, the arrangement of the magnetic field is more ordered along the Galactic plane, where it follows the spiral structure of the Milky Way. Small clouds are seen just above and below the plane, where the magnetic field structure becomes less regular.

    From these and other similar observations, Planck scientists found that filamentary interstellar clouds are preferentially aligned with the direction of the ambient magnetic field, highlighting the strong role played by magnetism in galaxy evolution.

    The emission from dust is computed from a combination of Planck observations at 353, 545 and 857 GHz, whereas the direction of the magnetic field is based on Planck polarisation data at 353 GHz.

    Acknowledgment: M.-A. Miville-Deschênes, >CNRS – Institut d’Astrophysique Spatiale, Université Paris-XI, Orsay, France

    See the full article here.

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 5:42 pm on December 6, 2014 Permalink | Reply
    Tags: , , , Cosmic Microwave Background, , , Princeton SPIDER   

    From Princeton- ” SPIDER: Searching for the Echoes of Inflation” 

    Princeton University
    Princeton University

    Princeton SPIDER Inflation

    December 5, 2014
    Zigmund Kermish
    Zigmund Kermish is an associate research scholar at Princeton University.

    Wait, why am I in Antarctica?

    I realized I’ve not yet written a blog post explaining why my experiment is in Antarctica. Things are temporarily quiet on the Ice while we’ve been waiting for the SPIDER cryostat to cool down, so now’s a good time to make the attempt.

    To get the best results from SPIDER, we have to go to very high and dry locations. This is because water vapor in the atmosphere limits SPIDER’s sensitivity. There are currently two terrestrial locations that are commonly used: the Atacama Desert POLARBEAR and ACTPol
    sit at about 5,200 meters above sea level) and the South Pole (where the South Pole Telescope, the KECK array, and this year BICEP3 operate at 2,800 meters).

    POLARBEAR McGill Telescope

    ACT Telescope
    Princeton Atacama Cosmology Telescope

    South Pole Telescope
    South Pole Telescope (SPT)

    Keck Array
    Keck Array

    BICEP 2
    BICEP 2 interior

    Of course, one can always go beyond terrestrial limits. With a big enough budget and enough time to develop the project, you can launch a dedicated satellite mission to eliminate the atmosphere all together, achieving dramatically improved individual detector sensitivities. Historically, satellite-based instruments have provided the definitive measurements of various aspects of the cosmic microwave background (the faint signal left over from the Big Bang), but they usually build upon the groundbreaking discoveries made closer to Earth. These discoveries have been made from the ground and from one other platform: balloons.

    Balloon-borne instruments have one big advantage: they allow us to get above nearly all of the atmosphere, approaching the detector sensitivity of satellite-based instruments at a fraction of the cost of a satellite mission.

    Princeton SPIDER instrument

    This increased detector sensitivity has two advantages: you can observe a larger fraction of the sky for a significantly shorter amount of time and still get a higher fidelity map than what you can do from the ground (observing for days rather than years) and you can observe in frequency channels that are difficult (if not impossible) to use from the ground. Both of these features, multiple frequencies and larger sky coverage, are necessary to ultimately demonstrate the ‘cosmological nature’ of the signals we’re looking for – to show that it’s not just a signal from some foreground in our local galaxy and that it has the required statistical properties across the sky we expect from proposed theories.

    As shown in the below gif, SPIDER can observe a large fraction of the ‘clean’ sky (the white outline) for 20 days and get nearly the same sensitivity over that region as a ground based experiment like the BICEP2 project had on their smaller region (green outline) after several years of observation.


    A map of the dust intensity seen in the sky, the bright center band the emission from our own Milky Way galaxy. The overlay that is fading in shows several things: The colored diamonds show the most recent data about the *polarization* strength of the dust signal, blue being less polarized dust, the outlines on the overlay show the regions observed (or to be observed shortly!) by BICEP2 (green), POLARBEAR (red), and SPIDER (white).

    Ok, so that’s why we want to dangle our instrument from a balloon. But why Antarctica? Why don’t we just launch our balloon from New Jersey?

    Well, for one, at some point, we need to bring the instrument back down to Earth, and that involves literally letting it fall to the ground so that we can recover it. That’s why scientific payload balloon flights only happen in places with low population density. In the US, payloads are flown out of Fort Sumner, New Mexico. They used to fly out of Palestine, Texas as well. Payloads flown out of these locations are limited to flights anywhere from a few hours to a few days because they eventually start getting too close to population centers.

    Antarctica doesn’t have any population centers, so rather than being limited by distance, flights are limited by how long the balloons can stay afloat. Currently, that’s about 40 days. Beyond that, weather patterns setup circumpolar winds during the austral summer here.

    So if you launch a balloon at the right time, it’ll come back close to where it started, making recovery of the instrument easier (it takes about a week to ‘boomerang’ back around). This is especially important for an experiment like ours since we need to physically recover our data off the drives that fly with the instrument. The bandwidth of in-flight communications limits us to only getting a small fraction of the data from the instrument during flight. One of the many ballooning challenges is to make the system as autonomous as possible so minimal human intervention based on the limited information we decide to ‘downlink’ to the ground is needed.

    The other fundamental challenges of ballooning that make this a very different game from ground-based experiments I’ve worked on: weight and power constraints. Having to fly the batteries you need to power the experiment, the solar panels to keep them charged, the cryogenic system to keep the everything cool and all the readout and control electronics systems while still staying below the maximum mass limits current balloons can float makes a project like this a fun problem to solve. The absence of day-night cycles during the austral summer in Antarctica helps address the power and weight constraints by giving us a continual source of solar power. This means we only need to fly a few heavy batteries to provide a non-variable power source and we can dedicate more of our mass budget to the scientific instruments. More compromises have to be made when designing payloads to fly at mid-latitudes, where enough batteries need to fly to power the payload throughout the night. There are many advantages to these mid-latitude flights though: larger available sky and longer (100 day!) flights with NASA’s new, soon-to-launch-with-science-payloads super pressure balloon platform (SPB).

    The CMB Cosmology group at Case is led by Prof. John Ruhl. The current members of our group are (GS = Graduate Student, UGS = Undergraduate Student):

    Tom Montroy (Senior Research Assoc.)
    Rick Bihary (Technician of Everything)
    Sean Bryan (GS, Spider)
    J.T. Sayre (GS, SPT)
    Ben Saliwanchik (GS, SPT)
    Adam Stohs (UGS)
    Dane Pittock (UGS)

    Phone numbers (all have 216 area code):

    Rock 117 lab: 368-1153
    Rock 117a lab: 368-3608
    Rock 117a fax: 368-0952
    Rock 114 lab and GS office: 368-2489
    Physics Student Shop: 368-3053
    Prof. Ruhl’s office: 368-4049

    We are located in Rockefeller Hall, on the main quad campus of Case Western Reserve University. Our shipping address is:

    Physics Dept, Rockefeller Hall
    Case Western Reserve University
    10900 Euclid Ave.
    Cleveland, OH 44106-7079

    Spider is a balloon-borne instrument designed to search for the signature of primordial gravity waves that is (hopefully) encoded in the polarization of the CMB. The design consists of six independent telescopes operating at three frequencies (100, 150, and 220GHz), with the optics cooled to 4 Kelvin and the bolometric detectors cooled to 0.25K.

    Gravitational Wave Background

    Spider’s first test flight will be in the fall of 2009, from Alice Springs, Australia. The test flight will be 2-4 nights duration, limited by the requirement that the balloon be brought down before it leaves the continent. The full “around the world” flight will be a year later, if all goes well.
    There are two publications describing Spider:

    “Spider Optimization: Probing the Systematics of a Large Scale B-Mode Experiment”, C. J. MacTavish etal, arXiv:0710.0375, submitted to ApJ. (This discusses Spider’s potential systematics and scan strategies).
    “SPIDER: a new balloon-borne experiment to measure CMB polarization on large angular scales”, T. E. Montroy etal, Proceedings of the SPIE, ed L. M. Step, v 6267, p62670R, (2006). (This describes the Spider instrument as originally conceived.)

    In addition to the effort at Case, the Spider collaboration includes groups at Caltech, JPL, U. Toronto, UBC, NIST, Cardiff, and the Imperial College of London. The main SPT website is maintained at Caltech, at http://www.astro.caltech.edu/~lgg/spider_front.htm.
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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 12:25 pm on December 5, 2014 Permalink | Reply
    Tags: , , , , , Cosmic Microwave Background, , ,   

    From physicsworld: “Planck offers another glimpse of the early universe” 


    Dec 4, 2014
    Tushna Commissariat

    Results of four years of observations made by the Planck space telescope provide the most precise confirmation so far of the Standard Model of cosmology, and also place new constraints on the properties of potential dark-matter candidates. That is the conclusion of astronomers working on the €700m mission of the European Space Agency (ESA). Planck studies the intensity and the polarization of the cosmic microwave background (CMB), which is the thermal remnant of the Big Bang. These latest results will no doubt frustrate cosmologists, because Planck has so far failed to shed much light on some of the biggest mysteries of physics, including what constitutes the dark matter and dark energy that appears to dominate the universe.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe)

    ESA Planck
    ESA Planck schematic

    Cosmic Background Radiation Planck
    Cosmic Background Radiation per Planck

    NASA/WMAP spacecraft

    Cosmic Background Radiation per WMAP
    Cosmic Background Radiation per WMAP

    Planck ran from 2009–2013, and the first data were released in March last year, comprising temperature data taken during the first 15 months of observations. A more complete data set from Planck will be published later this month, and is being previewed this week at a conference in Ferrara, Italy (Planck 2014 – The microwave sky in temperature and polarization). So far, Planck scientists have revealed that a previous disagreement of 1–1.5% between Planck and its predecessor – NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) – regarding the mission’s “absolute-temperature” measurements has been reduced to 0.3%.

    Winnowing dark matter

    Planck’s latest measurement of the CMB polarization rules out a class of dark-matter models involving particle annihilation in the early universe. These models were developed to explain excesses of cosmic-ray positrons that have been measured by three independent experiments – the PAMELA mission, the Alpha Magnetic Spectrometer and the Fermi Gamma-Ray Space Telescope.

    INFN PAMELA spacecraft


    NASA Fermi Telescope

    The Planck collaboration also revealed that it has, for the first time, “detected unambiguously” traces left behind by primordial neutrinos on the CMB. Such neutrinos are thought to have been released one second after the Big Bang, when the universe was still opaque to light but already transparent to these elusive particles. Planck has set an upper limit (0.23 eV/c2) on the sum of the masses of the three types of neutrinos known to exist. Furthermore, the new data exclude the existence of a fourth type of neutrino that is favoured by some models.

    Planck versus BICEP2

    Despite the new data, the collaboration did not give any insights into the recent controversy surrounding the possible detection of primordial “B-mode” polarization of the CMB by astronomers working on the BICEP2 telescope.

    BICEP 2
    BICEP 2 interior
    BICEP 2 with South Pole Telescope

    If verified, the BICEP2 observation would be “smoking-gun” evidence for the rapid “inflation” of the early universe – the extremely rapid expansion that cosmologists believe the universe underwent a mere 10–35 s after the Big Bang. A new analysis of polarized dust emission in our galaxy, carried out by Planck earlier in September, showed that the part of the sky observed by BICEP2 has much more dust than originally anticipated, and while this did not completely rule out BICEP2’s original claim, it established that the dust emission is nearly as big as the entire BICEP2 signal. Both Planck and BICEP2 have since been working together on joint analysis of their data, but a result is still forthcoming.


    See the full article here.

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    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
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  • richardmitnick 9:44 pm on December 3, 2014 Permalink | Reply
    Tags: , , , , Cosmic Microwave Background, , , ,   

    From Ethan Siegel: “The Moment of Truth for BICEP2″ 

    Starts with a bang
    Starts with a Bang

    Dec 2, 2014
    Ethan Siegel

    “The paradigm of physics — with its interplay of data, theory and prediction — is the most powerful in science.” -Geoffrey West

    Earlier this year, the BICEP2 experiment shook up the world of cosmology, announcing that they had detected gravitational waves originating from before the Big Bang! Not only did they announce this, but they announced that they had done so with a signal in excess of 5σ, which is regarded as the gold standard for a detection in physics.

    BICEP 2
    BICEP 2 interior
    BICEP2 (With South Pole Telescope

    Image credit: BICEP2 Collaboration — P. A. R. Ade et al, 2014 (R).

    But this may all turn out — despite the hoopla — to be absolutely nothing. Or, as it were, nothing more than a phantasm, as the observed signal may have originated from a source as mundane as our own galaxy, and have nothing to do with anything from billions of years ago!

    How did we get into this mess, and how do we get out of it? The answer to both questions is “science,” and it’s a great illustration of how the process and the body of knowledge actually evolves. Put your preconceptions of how it ought to work aside, and let’s dive in!

    Image credit: ESA and the Planck Collaboration.

    This is a snapshot of the cosmic microwave background (CMB), the leftover glow from the Big Bang, as viewed by the Planck satellite. Planck has the best resolution of any all-sky map of the CMB, getting down to resolutions smaller than one tenth of a degree. The temperature fluctuations are minuscule: on the order of just a few tens of microKelvin, less than 0.01% of the actual CMB temperature.

    Image credit: Wikimedia Commons user SuperManu.

    But buried in this signal is another, even more subtle one: the signal of photon polarization.

    Image credit:the BICEP2 collaboration, via http://www.cfa.harvard.edu/news/2014-05.

    Basically, when photons pass through electrically charged particles in certain configurations, their polarizations — or how their electric and magnetic fields are oriented — are affected. If we look at how the two types of polarization, the E-modes and B-modes, are affected on a variety of angular scales, we ought to be able to reconstruct what caused these signals.

    Images credit: Amanda Yoho [Upper]; http://b-pol.org/ [Lower], of an E-mode polarization pattern at left and a B-mode pattern at right.

    A portion of this signal, in addition to charged particles, could also originate from gravitational waves created in the early Universe. There are two main classes of models of inflation that give us a Universe consistent with what we observe in all ways: new inflation, which was actually the second model (and first viable model) ever proposed, and chaotic inflation, which was the third model (and second viable one).

    Images credit: two inflation potentials, with chaotic inflation [Upper] and new inflation [Lower] shown. Chaotic inflation generates very large gravitational waves, while new inflation generates tiny ones. Generated by me, using google graph.

    These two models of inflation make vastly different predictions for gravitational radiation: new inflation predicts gravitational waves (and primordial B-modes) that are extraordinarily tiny, and well beyond the reach of any current or even planned experiment or observatory, while chaotic inflation predicts huge B-modes, some of the largest ones allowable. These signatures have a characteristic frequency spectrum and affect all wavelengths of light identically, so it should be an easy signal to find if our equipment is sensitive to it.

    And that’s where BICEP2 comes in.

    Image credit: Sky and Telescope / Gregg Dinderman, via http://www.skyandtelescope.com/news/First-Direct-Evidence-of-Big-Bang-Inflation-250681381.html.

    Rather than measuring the whole sky, BICEP2 measured just a tiny fraction of the sky — about three fingers held together at arm’s length worth — but were able to tease out both the E-mode and B-mode polarization signals. And based on their analysis of the B-modes, which was very careful and very good, mind you, they claimed the greater-than-5σ detection.

    What this means is that they had enough data so that the odds that what they were seeing was a “fluke” of having observed just a serendipitous patch of sky was tiny, or a one in 1.7 million chance. Flukes happen all the time at the one-in-100 level or the one-in-1,000, but one-in-1.7 million flukes… well, let’s just say you don’t win the lotto jackpot very often.

    But there’s another type of error that they didn’t report. Not a statistical error, which is the kind you can improve on by taking more data, but a systematic error, which could be an effect that causes what you think is your signal, but is actually due to some other source! This type of error normally goes undetected because if you knew about it you’d account for it!

    This is exactly what happened a couple of years ago, if you remember the “faster-than-light-neutrino” business. An experiment at CERN had reported the early arrival by just a few nanoseconds of thousands upon thousands of neutrinos, meaning that they would have exceeded the speed of light by something like 0.003%, a small but meaningful amount. As it turned out, the neutrinos weren’t arriving early; there was a loose cable that accounted for the error!

    Image credit: ESA / Planck Collaboration, via http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1101_planck/news1101_planck-en-print.html.

    Well, one of the things the BICEP2 team didn’t measure was the galactic foreground emission. Polarized light — including light that contains these B-modes — gets emitted by the Milky Way galaxy, and that can contaminate your signal. The BICEP2 team used a very clever trick to try and eliminate this, by interpolating unreleased Planck data about galactic foregrounds, but when the Planck team actually released their data, the foregrounds were significantly different from what BICEP2 had anticipated. And with the new Planck data, the announcement of a “discovery” needed to be walked back; the evidence was now something like a one-in-200 chance of being a fluke.

    Image credit: John Kovac, viahttp://cosmo2014.uchicago.edu/depot/invited-talk-kovac-john.pdf.

    In other words, although gravitational waves could have caused this signal, so could other, far more mundane sources, including just our boring old galaxy!

    Sometime later this month, the Planck team will release their all-sky polarization results, and either at that moment or shortly thereafter, we’ll find out whether there really are gravitational waves from inflation that can be detected with our current generation of telescopes, satellites and observatories. We’ll find out whether chaotic inflation is right, or whether we need to keep searching for the gravitational wave signal from before the Big Bang. We already have the density fluctuation signal, so we can be confident that inflation happened. It’s just a question of which type.

    Image credit: Bock et al. (2006, astro-ph/0604101); modifications by me.

    Stay curious, stay hungry for more knowledge, but always demand that your scientific claims be independently verified, that your possible systematic errors be checked, and that you have overwhelming evidence before believing the extraordinary claims. It’s easy to make a bold statement; it’s hard to start a bona fide scientific revolution!

    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.

  • richardmitnick 7:01 am on December 2, 2014 Permalink | Reply
    Tags: , , , Cosmic Microwave Background, , , ,   

    From NYT: “New Images Refine View of Infant Universe” 

    New York Times

    The New York Times

    DEC. 1, 2014

    NYT Dennis Overbye
    Dennis Overbye

    In a throwback to another era in cosmic history, astronomers on Monday discussed the birth of the universe in a 15th-century palace, the Palazzo Costabili in Ferrara, Italy, where the amenities do not include Internet access.

    The subject of Planck 2014, as the meeting is called, is a new baby picture — and all of the accompanying vital statistics — of the universe when it was 380,000 years old and space was as hot as the surface of the sun. The portrait taker was the European Space Agency’s Planck satellite, which spent three years surveying a haze of microwave radiation left over from the last moments of the Big Bang with a bevy of sensitive radio receivers.

    Cosmic Background Radiation Planck

    ESA Planck

    The data will not be published until Dec. 22 in the journal Astronomy & Astrophysics, and the lack of Internet access frustrated astronomers who had planned on watching a webcast of the proceedings but found themselves relying on Twitter feeds instead.

    At least, they reported, the coffee was suitably strong.

    The new data largely confirms and refines the picture from a temperature map of the microwaves that Planck scientists, a multinational collaboration led by Jan Tauber of the European Space Agency, produced in 2013, showing the faint irregularities from which gargantuan features like galaxies would grow. Its microwave portrait reveals a universe 13.8 billion years old that is precisely mysterious, composed of 4.9 percent atomic matter, 26.6 percent mysterious dark matter that is not atomic, and 68.5 percent of even more mysterious dark energy, the glib name for whatever it is that seems to be blowing the universe apart.

    A map of a patch of sky showing the temperature and polarization of cosmic microwaves from the end of the Big Bang, as reflected by dust swirling in the magnetic field of the Milky Way. Credit European Space Agency

    The result is a resounding victory for a sort of Standard Model of Cosmology that has grown up over the last two decades, said Lyman Page, a Princeton astrophysicist, in a phone call from Ferrara. “What we see is pretty impressive,” he said. “It’s amazing that just six parameters describe the universe.”

    Standard Model of Cosmology Inflation Lambda Model
    Lambda-CDM model

    Standard Model of Cosmology
    Another view

    Cosmologists still do not know what dark matter — the material that provides the gravitational scaffolding for galaxies — is, but the Planck results have increased their knowledge of what it is not, according to the French Center for National Scientific Research.

    Recently space experiments like NASA’s Fermi Gamma-ray Space Telescope and Alpha Magnetic Spectrometer have recorded excess cosmic ray emissions that, some say, could be evidence of a certain kind of dark matter particles colliding and annihilating one another.

    NASA Fermi Telescope

    NASA AMS02 device

    After Planck, we need another answer for those experiments, the French agency concluded in a statement.

    Neal Weiner, a particle theorist at New York University, who is not part of Planck, concurred. That model of dark matter, he said in an email, if not completely excluded, now could be severely constrained. “If this holds up, at the very least a possibility to discover dark matter is now diminished.”

    Planck dealt a blow to another possible dark matter candidate, namely a brand of the ghostly particles known as neutrinos. Physicists have known of three types of neutrinos for some time and have wondered if there were any more, whose accumulated mass would affect the evolution of the universe. Planck’s results leave little room for a fourth kind, so-called sterile neutrinos.

    Compounding the frustration of cosmologists in the room in Ferrara and at large was an issue that has galvanized them for the better part of a year: whether astronomers had detected the very beginnings of the Big Bang in the form of space-time ripples known as gravitational waves.

    Gravitational Wave Background
    Gravitational Waves per BICEP2 radio telescope.

    BICEP 2
    BICEP 2 interior
    BICEP 2 with South Pole Telescope

    The added value of the new Planck data is a map showing how the microwaves are polarized, information that could shed light on what was going on when the universe was a trillionth of a trillionth of a trillionth of a second old, and in the grip of forces about which physicists can only speculate.

    Among the hottest topics of speculation these days is the idea — known as inflation — that the universe underwent a violent and brief surge of expansion in the earliest moments, settling the geometry and other aspects of the present universe. Such an explosion, theorists say, would have left faint corkscrew swirls, known technically as B-modes, in the pattern of polarization of the microwaves.

    In March there was much excitement when a team of American astronomers operating a radio telescope at the South Pole called Bicep2 announced they had detected such a pattern. Alan Guth of M.I.T., one of the inventors(?) [theorist would be better] of inflation, was at the news conference at Harvard announcing the results.

    Alan Guth
    Alan Guth

    After three months of spirited debate, the astronomers conceded, however, that their signal could have been caused by interstellar dust, which can also twist the microwaves.

    Enter Planck, which observed the microwaves in nine different frequencies, making it easy to distinguish dust. Bicep2 had only one frequency.

    A preliminary report from Planck in September confirmed that there was enough dust in Bicep2’s patch of sky to account for the twisting, but there are still large uncertainties that leave room for primordial gravitational waves.

    Subsequently, Planck and Bicep agreed to pool their data for a joint analysis.

    Planck scientists have meanwhile published their own polarization maps, which astronomers say will be useful for studying how the anti-gravitational push of dark energy and the gravitational pull of dark matter orchestrated the growth of galaxies and the universe when it was two or three billion years old — a sensitive age.

    The bumps in the microwave maps that eventually grow to galaxies amount to a temperature difference of only about 75-millionths of a Kelvin, in an otherwise uniform hiss. To measure polarization, radio astronomers have to discern temperature differences about a tenth of that.

    The difficulty of doing this research, while the world looks on, can be gauged by the number of missed deadlines. Planck researchers originally hoped to have their polarization studies done this summer. Recently they had set November as their deadline, aiming to present the results at this conference in Ferrara. Likewise, the joint Bicep/Planck paper is now expected this month or in January.

    Asked about this, David Spergel, a Princeton cosmologist and veteran of cosmic microwave studies who had spent the day fielding Twitter messages from Ferrara, said he had adopted an acronym often used by NASA in announcing launch dates: NET, meaning “No Earlier Than.”

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  • richardmitnick 2:31 pm on November 17, 2014 Permalink | Reply
    Tags: , , , Cosmic Microwave Background, ,   

    From SPACE.com: “Big Bang’s Echo May Reveal Skeleton of the Universe” 

    space-dot-com logo


    November 17, 2014
    Calla Cofield

    Scientists may soon get a look at the universe’s skeleton by taking a close look at light left over from the Big Bang, which can be used to reveal the presence of matter like stars, galaxies, black holes and even larger structures in the otherwise empty universe. It’s a lot like an X-ray revealing bones in a body, but on a cosmic scale.


    X-ray machines work by shining light over an entire area and detecting how different materials react. The light passes through tissue, but is stopped by bone.

    In a similar way, scientists with the international POLARBEAR collaboration want to use a diffuse light that fills every corner of the cosmos to indicate where there is matter and where there is none. POLARBEAR studies the cosmic microwave background (CMB) — the surviving light from the infant universe that is normally seen a kind of baby picture of the cosmos. Scientists estimate the universe is about 13.8 billion years old.

    Cosmic Background Radiation Planck
    CMB per ESA/Planck

    ESA Planck
    ESA Planck schematic

    “We’re using the light that we’ve usually used to measure the seeds of the structure of the universe, to measure the whole tree,” said Adrian Lee, a professor of physics at the University of California Berkeley, and a lead scientist with POLARBEAR. “But the mechanism [we use] is pretty different. Instead of looking at a baby picture, we’re looking at the distortion of the baby picture.”
    Bending cosmic light

    Just as the bones in a skeleton are not randomly scattered in the body, the mass in the universe is not randomly scattered through space. Forces such as gravity drive the organization of matter, so stars get grouped into galaxies; galaxies herd together into galaxy clusters; and on an even larger scale, scientists think matter in the universe is arranged into a structure resembling a web, with vast regions of emptiness between strings of galaxy groups.

    The gravity of massive objects can bend light. The light moves around the object like water going around a rock in a stream. This bending causes a change in the CMB, and POLARBEAR scientists say they have now detected that change.

    The bending of light by a massive object is called gravitational lensing, and it changes a property of the light called polarization. When sunlight reflects off the surface of water, it often becomes polarized. Polarizing sunglasses can block this polarized light, but they do not block the sunlight coming from above — ideal for water sport fans.

    CMB light that has not been gravitationally lensed — that has never bumped into any type of matter — has a so-called E-mode polarization. New results from the collaboration show that the researchers can detect something called B-mode polarization, which means the CMB has encountered a massive object on the way to Earth.

    POLARBEAR has only just demonstrated that it can detect this polarization, but eventually, it could create a sketch of the large-scale skeleton inside the universal body.

    Huan Tran Telescope
    The Huan Tran Telescope, located in Chile’s Atacama Desert, looks for light left over from the big bang. Scientists with the POLARBEAR collaboration want to use that light to map the location of matter in the universe.
    Credit: POLARBEAR collaboration

    Dark energy and exotic dragons

    Seeing the universe’s skeleton — the location and structure of all matter — could tell scientists if they’ve got the right idea about how matter in the universe is arranged, and if there are yet-unknown forces acting on it in peculiar ways.

    “There’s some possibility [the structure] won’t look the way theorists predict,” Lee said. “[POLARBEAR] could confirm that the universe is acting the way we think it is; that there are no exotic dragons out there changing the signal.”

    The most dominant force in our universe is dark energy, but scientists know very little about it — only that it’s causing our universe to expand like a balloon. They don’t know when dark energy started this expansion, but Lee said it would have had an effect on how structures formed.

    “Gravity wants to pull structures together but dark energy wants to pull them apart,” Lee said. “If dark energy was acting more strongly early on in the universe that would suppress structure formation, because [the dark energy] would be yanking masses away from each other.” Lee said future data from POLARBEAR could help identify when dark energy started pushing the universe apart.
    Flexing BICEP2

    Earlier this year, members of the BICEP2 collaboration announced that they had detected B-mode polarization in the CMB. But that polarization signal comes from a different source than the one detected by POLARBEAR. The BICEP2 polarization may come from gravitational waves, or ripples in space-time, in the early universe.

    BICEP 2
    BICEP 2 interior
    BICEP 2 (Upper picture also shows the South Pole Telescope)

    Gravitational Wave Background
    Gravitational Waves projected by BICEP2

    Detection of this type of B-mode polarization would indirectly demonstrate the existence of gravitational waves, and their presence in our early universe. But following BICEP2’s announcement, observations by the Planck satellite have raised questions about whether the results were contaminated by space dust.

    It’s possible, said Lee, that POLARBEAR could eventually measure polarization created by gravitational waves from the inflating universe. Those polarization patterns are larger on the sky than the lensing polarization that POLARBEAR has measured, but as BICEP2 has shown, they are in some ways more challenging to observe.

    POLARBEAR’s observations alone can provide only a two-dimensional map of the matter in the universe. But with the help of other telescopes, Lee said it would be possible to create a three-dimensional map, and to even determine when the structure appeared in the universe.

    “If we use other data, if we cross correlate, we could look at the structure of matter over the whole history of the universe,” Lee said. “That’s the strength of all the data sets together.”

    See the full article here.

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  • richardmitnick 9:20 am on October 24, 2014 Permalink | Reply
    Tags: , , , Cosmic Microwave Background, , , POLARBEAR Collaboration   

    From phys.org: “POLARBEAR detects curls in the universe’s oldest light” 


    Oct 21, 2014
    Susan Brown

    Cosmologists have made the most sensitive and precise measurements yet of the polarization of the cosmic microwave background.


    The report, published October 20 in the Astrophysical Journal, marks an early success for POLARBEAR, a collaboration of more than 70 scientists using a telescope high in Chile’s Atacama desert designed to capture the universe’s oldest light.

    “It’s a really important milestone,” said Kam Arnold, the corresponding author of the report who has been working on the instrument for a decade. “We’re in a new regime of more powerful, precision cosmology.” Arnold is a research scientist at UC San Diego’s Center for Astrophysics and Space Sciences and part of the cosmology group led by physics professor Brian Keating.

    POLARBEAR measures remnant radiation from the Big Bang, which has cooled and stretched with the expansion of the universe to microwave lengths. This cosmic microwave background, the CMB, acts as an enormous backlight, illuminating the large-scale structure of the universe and carrying an imprint of cosmic history.

    Cosmic Background Radiation Planck
    CMB from Planck

    Arnold and many others have developed sensitive instruments called bolometers to measure this light. Arrayed in the telescope, the bolometers record the direction of the light’s electrical field from multiple points in the sky.

    “It’s a map of all these little directions that the light’s electric field is pointing,” Arnold explained.

    POLARBEAR has now mapped these angles with resolution on a scale of about 3 arcminutes, just one-tenth the diameter of the full moon..

    The team found telling twists called B-Modes in the patterns of polarization, signs that this cosmic backlight has been warped by intervening structures in the universe, including such mysteries as dark matter, composed of substance that remains unknown, and the famously aloof particles called neutrinos, which elude capture making them difficult to study.

    This initial report, the result of the first season of observation, maps B-modes in three small patches of sky.

    Dust in our own galaxy also emits polarized radiation like the CMB and has influenced other measurements. But these patches are relatively clean, Arnold says. And variations in the CMB polarization due to dust occur on so broad a scale that they do not significantly influence the finer resolution B-modes in this report.

    “We are confident that these B-modes are cosmological rather than galactic in origin,” Arnold said.

    Observations continue, and the data stream will ultimately be fed by additional telescopes comprising the Simons Array. Together they will map wider swaths of the sky, making fundamental discoveries possible.

    Simmons Array

    “POLARBEAR is a real tour de force. With a relatively small, but strong, UC-led team we have surpassed the next-nearest competitors by an order of magnitude in sensitivity. We have paved the way towards solving the deepest mysteries in the quest to understand matter and energy at the beginning of time,” said Brian Keating.

    POLARBEAR is a collaboration of scientists from many institutions including experiment founder, Adrian Lee, professor of physics at UC Berkeley.

    See the full article here.

    About Phys.org in 100 Words

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  • richardmitnick 5:45 pm on August 12, 2014 Permalink | Reply
    Tags: , , , Cosmic Microwave Background, ,   

    From SPACE.com: “Planck’s Mystery Cosmic ‘Cold Spot’ May Be an Error” 

    space-dot-com logo


    August 12, 2014
    Ian O’Neill

    The European Planck space telescope detects very faint primordial radiation that was generated after the Big Bang — when the universe was only 380,000 years old. By creating a cosmic map of the slight variations in this cosmic microwave background (CMB) radiation — variations known as “anisotropies” — cosmologists have been able to gain some clue as to the structure of the Universe nearly 14 billion years ago.

    cmb planck
    he European Space Agency’s Planck space telescope mapped the cosmic microwave background.
    Credit: ESA and the Planck Collaboration

    However, several anomalies in the CMB map have confused the scientific community; some mysterious features mapped by Planck don’t agree with established theory as to how the Cosmos works. Is there some exotic new cosmology at play? Or are these features simply observational error?

    Cosmologists in Switzerland and France have now shown that many of these features disappear from the map when observational data is processed differently, potentially erasing features like the mysterious CMB “cold spot.”

    One of the more exotic explanations for the cold spot is that it could be observational evidence for the “multiverse“— a hypothesis with roots in superstring theory where our universe exists in an ocean of other universes — and the cold spot is caused by a neighboring universe pushing up against ours. Unfortunately, the feature might not even be real.

    “Using new techniques to separate the foreground light from the background, and taking into account effects like the motion of our Galaxy, we found that most of the claimed anomalies we studied, like the cold spot, stop being problematic,” said lead researcher Anaïs Rassat, of the Ecole Polytechnique Fédérale de Lausanne, Switzerland.

    ANALYSIS: Will Science Burst the Multiverse’s Bubble?

    Rassat’s team’s work has been published today (Aug. 4) in the Journal of Cosmology and Astroparticle Physics.

    When mapping such faint radiation that has been traveling through space-time for billions of years, it is difficult to separate the primordial signal from other microwave sources. Our galaxy, for example, swamps the universal vista with microwaves and, as we live inside the galactic disk, our microwave view is dominated by Milky Way emissions. It’s a thick cosmic fog that needs to be subtracted.

    Through complex algorithms and foreground emission subtraction techniques, these extraneous microwave sources can be effectively removed. But Rassat’s team gave the data another pass, correcting for the motion of our galaxy and other impacts such as gravitational interference and distortions in the radiation itself.

    Although this study appears to have corrected for previously overlooked effects in Planck observations, some anomalies remain in the data, leaving room for some of the more exotic hypotheses about the origin and nature of our universe. But as for Planck’s “cold spot,” that mystery might be down to observational error and not something real.

    See the full article here.

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  • richardmitnick 11:18 am on July 11, 2014 Permalink | Reply
    Tags: , , , , Cosmic Microwave Background, , South Pole Telescope   

    From BBC- “Cosmic inflation: BICEP2 and Planck to share data” 


    3 July 2014
    Jonathan Amos

    The BICEP2 telescope studied a small patch of sky in detail above the South Pole

    Scientists on rival projects looking for evidence that the early Universe underwent a super-expansion are in discussion about working together.

    The negotiations between the US-led BICEP2 group and Europe’s Planck Collaboration are at an early stage.

    BICEP2 announced in March that its South Pole telescope had found good evidence for “cosmic inflation“.

    South Pole Telescope
    South Pole Telescope

    Cosmic Background Radiation Planck
    CMB from Planck

    But to be sure, it needs the best data on factors that confound its research – data that Planck has been compiling.

    If the two teams come to an arrangement, it is more likely they will hammer down the uncertainties.

    “We’re still discussing the details but the idea is to exchange data between the two teams and eventually come out with a joint paper,” Dr Jan Tauber, the project scientist on the European Space Agency’s Planck satellite, told BBC News.

    This paper, hopefully, would be published towards the end of the year, he added.

    Foreground dust per Planck

    The question of whether the BICEP2 team did, or did not, identify a signal on the sky for inflation has gripped the science world for weeks.

    The group used an extremely sensitive detector in its Antarctic telescope to study light coming to Earth from the very edge of the observable Universe – the famous Cosmic Microwave Background (CMB) radiation.
    Planck artist impression The Planck satellite was launched in 2009 to map the Cosmic Microwave Background

    BICEP2 looked for swirls in the polarisation of the light.

    This pattern in the CMB’s directional quality is a fundamental prediction of inflation – the idea that there was an ultra-rapid expansion of space just fractions of a second after the Big Bang.

    The twists, known as B-modes, are an imprint of the waves of gravitational energy that would have accompanied the violent growth spurt.

    But this primordial signal – if it exists – is expected to be extremely delicate, and a number of independent scientists have expressed doubts about the American team’s finding. And the BICEP2 researchers themselves lowered their confidence in the detection when they formally published their work in a Physical Review Letters paper last month.

    At issue is the role played by foreground dust in our galaxy.

    Nearby spinning grains can produce an identical polarisation pattern, and this effect must be removed to get an unambiguous view of the primordial, background signal.

    The BICEP2 team used every piece of dust information it could source on the part of the sky it was observing above Antarctica.

    What it lacked, however, was access to the dust data being compiled by the Planck space telescope, which has mapped the microwave sky at many more frequencies than BICEP2.

    This allows it to more easily characterise the dust and discern its confounding effects.
    Dust Planck released dust information close to the galactic plane in May

    In May, the Planck Collaboration published dust polarisation information gathered close to the galaxy’s centre – where the grains are most abundant.

    In a few weeks’ time, the Planck team plans to release further information detailing galactic dust in high latitude regions, including the narrow patch of the southern sky examined by BICEP2.

    And then, in late October, the Planck Collaboration is expected to say something about whether it can detect primordial B-modes.

    As Dr Tauber explained, Planck’s approach to the problem is a different one to BICEP2’s.

    “Planck’s constraints on primordial B-modes will come from looking at the whole sky with relatively low sensitivity as compared to BICEP2,” he said.

    “But because we can look at the whole sky, it makes up for some of that [lower sensitivity] at least. On the other hand, we have to deal with the foregrounds – we can’t ignore them at all.

    “At the same time, we will work together with BICEP2 so that we can contribute our data to improve the overall assessment of foregrounds and the Cosmic Microwave Background.

    “We hope to start working with them very soon, and if all goes well then we can maybe publish in the same timeframe as our main result [at the end of October].”

    See the full article here.

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  • richardmitnick 2:17 pm on April 1, 2014 Permalink | Reply
    Tags: , , , , Cosmic Microwave Background, , , ,   

    From Symmetry: “The oldest light in the universe” 

    [I know that I have covered this topic before, but Symmetry’s article is the very best that I have seen.]

    April 01, 2014
    Lori Ann White

    The Cosmic Microwave Background, leftover light from the big bang, carries a wealth of information about the universe—for those who can read it.

    Fifty years ago, two radio astronomers [Arno Penzias and Robert Wilson, both Nobel Laureates] from Bell Labs discovered a faint, ever-present hum in their [radio] telescope that they couldn’t identify. After ruling out radio broadcasts, radar signals, a too-warm receiver and even droppings from pigeons nesting inside the scope, they realized they’d found a soft cosmic static that originated from beyond our galaxy. Indeed, it seemed to fill all of space.

    Fast-forward five decades, and the static has a well-known name: the cosmic microwave background, or CMB. Far from a featureless hum, these faint, cold photons, barely energetic enough to boost a thermometer above absolute zero, have been identified as the afterglow of the big bang.

    Cosmic Microwave Background Planck
    Cosmic Microwave Background from ESA/Planck

    ESA Planck

    This light—the oldest ever observed—offers a baby picture of the very early universe. How early? The most recent result, announced on Saint Patrick’s Day 2014 by the researchers of the BICEP2 experiment, used extremely faint signals imprinted on CMB photons to reach back to the first trillionth of a trillionth of a trillionth of a second after the big bang—almost more of a cosmic sonogram than a baby picture. This image offered the first direct evidence for the era of cosmic inflation, when space itself ballooned outward in a turbocharged period of expansion.

    BICEP 2
    BICEP2 at the South Pole Telescope

    BICEP / Keck Array; The BICEP2 detector array under a microscope
    The BICEP2 telescope at the South Pole uses novel technology developed at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. The focal plane shown here is an array of devices that use superconductivity to gather, filter, detect, and amplify polarized light from the cosmic microwave background — relic radiation left over from the Big Bang that created our universe. The microscope is showing a close-up view of one of the 512 pixels on the focal plane, displayed on the screen in the background. Each pixel is made from a printed antenna that collects polarized millimeter-wavelength radiation, with a filter that selects the wavelengths to be detected. A sensitive detector is fabricated on a thin membrane created through a process called micro-machining. The antennas and filters on the focal plane are made from superconducting materials. An antenna is seen on the close-up shot in the background with the green meandering lines. The detector uses a superconducting film as a sensitive thermometer to detect the heat from millimeter-wave radiation that was collected by the antenna and dissipated at the detector. A detector is seen on the close-up shot in the background to the right of the pink square. Finally, a tiny electrical current from the sensor is measured with amplifiers on the focal plane called SQUIDs (Superconducting QUantum Interference Devices), developed at National Institute of Standards and Technology, Boulder, Colo. The amplifiers are the rectangular chips on the round focal plane. The focal planes are manufactured using optical lithography techniques, similar to those used in the industrial production of integrated circuits for computers.

    CMB photons have more to tell us. Combined with theoretical models of cosmic growth and evolution, ongoing studies will expand this view of the very early universe while also looking forward in time. The goal is to create an entire album chronicling the growth of the universe from the very moments of its birth to today.

    Further studies promise clear insight into which of the many different models of inflation shaped our universe, and can also help us understand dark matter, dark energy and the mass of the neutrino—if researchers can read the CMB in enough detail.

    That’s not easy, though, because the afterglow has faded. During its epic 13-billion-year-plus journey, light that originally blazed through the universe has stretched with space itself, its waves growing billions of times longer and cooler and quieter.

    Relic radiation

    The Standard Model of Cosmology says that about 13.8 billion years ago, the universe was born from an unimaginably hot, dense state. Before a single second had ticked away, cosmic inflation [first proposed by Dr. Alan Guth, M.I.T.] increased the volume of the universe by an amount that varies according to the particular model, but always features a 10 followed by about 30 to 80 zeroes.


    When inflation hit the brakes, leftover energy from that expansion created many of the particles we see around us today: gluons, quarks, photons, electrons and their bigger brethren, muons and taus, and neutrinos. Primordial photons scattered off free-floating electrons, bouncing around inside the gas cloud that was the universe. Hundreds of thousands of years later, the cosmic cloud of particles cooled enough that single protons and helium nuclei could capture the electrons they needed to form neutral hydrogen and helium. This rounded up the free electrons, clearing the fog and releasing the photons. The universe began to shine.

    These photons are the cosmic microwave background. Although now weak, they are everywhere; CMB photons bathe the Earth—and every other star, planet, black hole and hunk of rock in the universe—in their cold light.

    Cosmic sonograms

    The latest big discovery coaxed from CMB data peeks back into the earliest moments of the universe.

    Using cutting-edge sensors, the BICEP2 telescope located at the South Pole detected a type of signal that has been predicted at one strength or another by every version of inflation theory out there: a type of polarization to the CMB light called “B-mode polarization.”

    According to the theories, tiny variations in the energy of the pre-inflation universe caused primordial gravitational waves—ripples in the fabric of space-time—that ballooned outward with inflation. Even before they became the CMB, photons interacted with these ripples, causing the photons’ wavelengths to take on a slight twist. It was this twist that the BICEP2 collaboration measured as a swirling polarization pattern.

    “BICEP2 clearly detected B-mode polarization at precisely the angular scales predicted by inflation,” says Chao-Lin Kuo, one of four principal investigators on the experiment. “This is an incredible combination of big theoretical ideas, teamwork, focus and cutting-edge technologies. The development of mass-produced superconducting polarization detectors and quantum current sensors made a real difference to our success in getting to B-modes first.”

    A discovery of this magnitude calls for further confirmation—not of the signals, which were very clear, but of their inflationary origin. If it holds, the B-mode polarization signals will also give scientists more details about the inflationary event that took place. For example, it can tell us about the energy scale of the universe—essentially the amount of energy poured into the instant of inflation. The BICEP2 result puts this at about 1016 billion electronvolts. For comparison, the Large Hadron Collider’s most powerful proton beams smash together at 104 billion electronvolts—a number with 12 fewer zeros than the first.

    Such information can help scientists determine which of the many different models of inflation actually describes the beginning of our universe. To Walt Ogburn, a postdoctoral researcher at Stanford University and a member of the BICEP2 team, the first view of primordial B-mode polarization does more than turn inflationary theory into fact: It breaks through into uncharted territory in high-energy physics. “What drove inflation is not in the Standard Model,” Ogburn says. By definition, proof of inflation offers evidence that there’s something more out there that’s not yet discovered, and that something big we don’t yet fully understand helped drive the evolution of the early universe.

    Baby picture

    The detection of B-mode polarization is the latest in a long string of scientific discoveries base on information coaxed from these scarce, faint photons.

    The first successes in probing the CMB came almost two decades after it was identified. Beginning with Relikt-1, a Soviet satellite-based experiment launched in 1983, and continuing all the way up to the present, a variety of balloons and satellites have mapped the temperature of the CMB. They found it was 2.7 kelvin across the whole of the sky, with only small, scattered variations in temperature of about one part in 100,000.

    In that temperature map cosmologists saw the image of the infant universe.

    “We’ve learned an enormous amount from the temperature [patterns],” says Lyman Page, also a cosmologist at Princeton. Page was one of the original researchers on what, until this year, was probably the best-known CMB instrument, the Wilkinson Microwave Anisotropy Probe [WMAP]. He now focuses on the Atacama Cosmology Telescope, and few people know more about how to make the CMB give up its secrets.

    ACT Telescope
    Princeton ACT

    Page explains that both the overall sameness of the temperature and the pattern of these minor variations told cosmologists that when the universe began, it was compact enough to be in thermal equilibrium: a dense, nearly featureless plasma of immense energies. But within that plasma, quantum fluctuations caused tiny variations in energy density.

    Then, during cosmic inflation, space grew enormously in all directions. This magnified the variations like an inflating balloon expands ink spots sprayed on it into larger and larger blotches.

    This is the same process that generated the gravitational waves imaged by BICEP2. The gravitational waves left telltale swirling polarization patterns in the CMB without doing much else. However, the dense areas—“blotches” on the otherwise smooth map of the sky—became important seeds of all structures in the universe.

    They grew and cooled, morphed from variations in energy density to variations in matter density. The denser regions attracted more matter as the universe continued to expand, eventually building up large-scale structures we see stitched across the universe today.

    When combined with other theories and measurements, Page says, the temperature variations provide strong evidence that our universe began with the big bang. They have also helped cosmologists improve estimates for how much dark matter and dark energy existed in the early universe (and likely still exist today), and backed the notion that the geometry of the universe is flat.

    “The CMB is really a beautiful signal,” says the University of Chicago’s John Carlstrom, who, like Page, is an expert in extracting information from a few faint photons. He leads the South Pole Telescope project, which uses several instruments mounted on a telescope not too far from BICEP2, to learn more about the CMB. The signal, he continues, offers “very precise measurements of conditions at recombination,” which is the name given to the time when the CMB photons escaped from the primordial cloud of cooling plasma.

    South Pole Telescope
    South Pole Telescope

    These temperature maps—in combination with the primordial B-mode signals detected by BICEP2—cover a time period from a tiny fraction of a second after the birth of the universe to about 380,000 years after that. In the coming years, cosmologists want to expand that picture to include everything that’s happened in the more than 13 billion years since recombination. Many predictions exist for what happened during this huge span of time, but scientists need rock-solid empirical data to compare their theoretical models against.

    BICEP2 revealed a faint but distinctive twist in the polarization pattern of the CMB. Here the lines represent polarization; the red and blue shading show the degree of the clockwise and counter-clockwise twist. Courtesy of: BICEP2

    Filling in the photo album

    CMB photons have more important information to offer, and a new generation of experiments is listening to what they have to say. Situated mostly on the high, dry, cold deserts of the South Pole and the Atacama Plateau in Chile, or in high-flying balloons that rise above much of the atmosphere, new instruments use the CMB to refine our knowledge of how the universe has evolved.

    As the CMB photons traveled through the universe, they were pulled this way and that by gravity, bearing witness to everything that happened on their way from the beginning to now. Using these photons as messengers, the new instruments are helping scientists carefully tease out the story of what the photons saw along their journey.

    Interactions with the hot gas that surrounded and infused galaxy clusters, for example, left a mark on some of the photons in the form of a tiny boost in energy, which is detectable as a very slight adjustment to the temperature map.

    The new instruments also measure a different type of B-mode polarization, added to the CMB photons long after inflation. This type of twist occurs when the photons brush up against the gravity of large-scale cosmic structures comprising both regular matter and dark matter, and it was detected for the first time just last year by SPTpol, a polarization-sensitive microwave camera mounted on the South Pole Telescope.


    Taken together, these measurements of tiny temperature differences and polarization can help scientists map matter distributions over time and improve estimates of how much of the universe is made up of dark matter versus the normal matter we see in stars and planets. It can also help tease apart the difference between expansion due to the momentum left from the big bang and expansion due to dark energy. This will yield an accurate four-dimensional map of the universe, revealing the movement of matter through space and time.

    Further measurements are poised to reveal more information about the contributions to our cosmos of a tiny particle with big implications: the neutrino. Its mass is currently not known to any respectable precision, yet this number is of great importance to predictions regarding the neutrinos’ influence on the growing universe.

    Experiments so far have seen three types of neutrinos [electron neutrinos, muon neutrinos and tau neutrinos, yet some theories predict a fourth type, called a sterile neutrino, as well.

    “Neutrinos are the second most plentiful particle in the universe—after photons,” says Bradford Benson, a scientist at Fermilab and a member of the SPTpol team. “The total mass of all the neutrinos in the universe should at least equal the mass of all the stars.”

    When the universe was smaller, that neutrino mass could have had a significant influence on the universe’s developing structure. As the universe expanded, two things happened: Clumps of heavier, slower-moving particles grew even bigger by pulling in more matter, while the light, speedy neutrinos escaped; and space expanded while the number of neutrinos stayed the same such that, as their density decreased, their gravitational influence decreased as well.

    As they traveled among the growing cosmic structures, the CMB photons recorded these changes in the relative density of neutrinos. Scientists are now mining this record to determine how the influence of neutrinos has evolved over time, and can use the information to estimate their mass. Combined with CMB measurements of dark matter and expansion due to dark energy, scientists expect this research to refine their view of the universe past and present, revealing how matter and energy interacted in the early universe to make the universe we see today.

    Old light, new science

    Using the CMB to discover primordial gravitational waves has been a tremendous step forward. “What’s truly amazing is that the CMB may still hide more secrets even after we found the holy grail,” says Kuo, referring to BICEP2’s discovery.

    Temperature maps, scattered photons and twisted light still have more to tell us. Over the next decade, CMB measurements are poised to help us understand the immense forces of the big bang, illuminate the physics of the early universe and explain the matter and energy we see around us today.

    “Having this signal has helped turn cosmology into a precision science,” Carlstrom says. “We’ve gone from being told, ‘You guys don’t really know what you’re measuring’ to having inde-pendent measurements with levels of precision that rival particle physics.”

    And the benefits are only set to increase. “The study of the CMB is a fantastic field, a very rich field,” Page says. “The microwave background is still going to be a useful tool in 20 years.”

    That’s not bad for a few frigid photons.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

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