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  • richardmitnick 10:54 am on February 6, 2021 Permalink | Reply
    Tags: "JADES will go deeper than the Hubble Deep Fields", , , , Cosmic Dark Ages, , , In the case of light we perceive changes in wave frequency as changes in color not changes in pitch., , It took 11.3 days for the Hubble Space Telescope to collect these ancient photons for the Hubble Ultra Deep Field image., JADES- James Webb Space Telescope Advanced Deep Extragalactic Survey., LaGrange Points via NASA, , , , The Hubble Ultra Deep Field, The infrared Spitzer Space Telescope which recently went into retirement., The main goal is to see far away in space – and thus far back into the very young universe – and image it just at the end of the so-called Cosmic Dark Ages., To conduct the new survey the Webb telescope will be staring at a small point of space for nearly 800 hours., Webb will be able to image-in infrared at the same resolution-detail -that Hubble could obtain in the optical part of the spectrum.   

    From EarthSky: “JADES will go deeper than the Hubble Deep Fields” 

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    From EarthSky

    January 31, 2021 [Just this morning in social media.]
    Theresa Wiegert

    Astronomers announced this month that a new deep-field survey called JADES will be carried out with the James Webb Space Telescope, Hubble’s much-anticipated successor. The Webb is due to launch later this year.

    NASA/ESA/CSA James Webb Space Telescope annotated.

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    The Hubble Ultra Deep Field (in its eXtreme version) is the deepest view of the universe yet obtained … and will be, until JADES takes over. It stretches approximately 13 billion light-years and includes approximately 10,000 galaxies. It took 11.3 days for the Hubble Space Telescope to collect these ancient photons. We’re seeing these galaxies as they were billions of years ago. How might they look today? Credit: NASA/ ESA/ S. Beckwith (STScI)/ HUDF team.

    Astronomers announced a new deeper-than-ever sky survey this month (January 15, 2021), to be conducted with the James Webb Space Telescope, the Hubble telescope’s successor, scheduled for launch in October of this year. The new survey is abbreviated JADES, which is short for James Webb Space Telescope Advanced Deep Extragalactic Survey. The survey will be like the Hubble Deep Fields, but deeper still. Its main goal is to see far away in space – and thus far back into the very young universe – and image it just at the end of the so-called , that is, at the time when gas in the universe went from being opaque to transparent. This is also the time when the very first stars were forming – very large, massive and bright stars – in a veritable firestorm of star birth when the young universe was less than 5% of its current age.

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    Milestones in the history of the universe (not to scale). Gas was in a neutral state from about 300,000 years after the Big Bang until light from the first generation of stars and galaxies began to ionize it, that is, strip atoms in the gas of their electrons. A new study examines the universe at 800 million years (yellow box) to investigate when and how this transformation occurred. Image via NAOJ/NOIRLab NOAO.

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    Webb will be able to see back to when the first bright objects (stars and galaxies) were forming in the early universe. Credit: STScI.

    The Webb telescope will be located near the second Lagrange point – a relatively stable region of space, gravitationally speaking, known as L2 – some 930,000 miles (1.5 million km) from Earth.

    LaGrange Points map. NASA.

    To conduct the new survey, the Webb telescope will be staring at a small point of space for nearly 800 hours (approximately 33 days) to be able to see fainter objects than those ever seen before and thus to find the first generation of galaxies. Astronomers want to know, among other things, how fast did these galaxies form, and how fast did their stars form? They also want to look for the very first supermassive black holes, which are thought to lie at the hearts of nearly all large galaxies, including our Milky Way.

    The long-anticipated launch of the James Webb Space Telescope has been postponed a number of times for a variety of reasons, most recently because of effects of the Covid-19 pandemic. It is the formal successor to the Hubble Space Telescope, but is equipped with instrumentation able to image further into the infrared part of the electromagnetic spectrum than Hubble could.

    This capability also makes it a worthy successor to the infrared Spitzer Space Telescope which recently went into retirement.

    NASA/Spitzer Infrared telescope no longer in service. Launched in 2003 and retired on 30 January 2020. Credit: NASA.

    What makes the infrared part of the spectrum so important for surveys like JADES? If you look really deep, you will also look back in time, and the farther back in time you look, the more redshifted the galaxies are (the farther away they are, the faster they move away from us, and the more their light has been shifted towards the red part of the spectrum).

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    Redshift. Credit: Wikimedia Commons.

    Astronomers use redshifts to measure how the universe is expanding, and thus to determine the distance to our universe’s most distant (and therefore oldest) objects. What is a redshift? It’s often compared to the high-pitched whine of an ambulance siren coming at you, which drops in pitch as the ambulance moves past you and then away from you. That change in the sound of an ambulance is due to what’s called the Doppler effect. It’s a good comparison because both sound and light travel in waves, which are affected by their movement through air and space.

    Sound can only move so fast through the air; sound travels at about 750 miles (1,200 kilometers) per hour. As an ambulance races forward and blares its siren, the sound waves in front of the ambulance get squished together. Meanwhile, the sound waves behind the ambulance get spread out. This means the frequency of the sound waves is higher ahead of the ambulance (more sound waves will strike a listener’s ear, over a set amount of time) and lower behind it (fewer sound waves will strike a listener’s ear, over a set amount of time). Our brains interpret changes in the frequency of sound waves as changes in pitch.

    Like sound, light is also a wave traveling at a fixed speed: 186,000 miles (300,000 km) per second, or some one billion kilometers per hour. Light, therefore, plays by similar rules as sound.

    But, in the case of light, we perceive changes in wave frequency as changes in color, not changes in pitch.

    This means that the light we want to observe, originally in the optical (visible) part of the electromagnetic spectrum, might not even show much in the optical part anymore. Instead, it’s been shifted to longer wavelengths, into the infrared regime.

    In other words, the use of infrared cameras is necessary to be able to see the light from the first generation of galaxies. Daniel Eisenstein, a professor of astronomy at Harvard University, said:

    “Galaxies, we think, begin building up in the first billion years after the Big Bang, and sort of reach adolescence at 1 to 2 billion years. We’re trying to investigate those early periods. We must do this with an infrared-optimized telescope because the expansion of the universe causes light to increase in wavelength as it traverses the vast distance to reach us. So even though the stars are emitting light primarily in optical and ultraviolet wavelengths, that light is shifted quite relentlessly out into the infrared. Only Webb can get to the depth and sensitivity that’s needed to study these early galaxies.”

    In fact, the James Webb Space Telescope was built specifically for this purpose. Up to now, infrared images are much less resolved – less clear – than optical images, because of their longer wavelength. With its much larger collecting area, the Webb will be able to image, in infrared, at the same resolution – detail – that Hubble could obtain in the optical part of the spectrum.

    Get ready for a whole new set of mind-blowing images of the universe, this time in the infrared, from Webb!

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    After having successfully deployed its solar panels – precisely as it’s supposed to do once it’s in space – the Webb telescope is shown here ready for the final tests on December 17, 2020, at NASA’s Goddard Space Flight Center. Then it will be packed up and transported to French Guyana, to be launched on October 31, 2021, via an Ariane V rocket. Credit: Chris Gunn/NASA.

    The use of deep field surveys is a young science, for two reasons. First, astronomers didn’t have the right instrumentation before Hubble to do them. Second, it’s also because no one initially knew the result of staring into a piece of empty space for a long time. Such a long stare into the unknown would require valuable observation time, and if this long observation didn’t produce any results, it would be considered a waste.

    But in 1995, Robert Williams, then the director of the Space Telescope Science Institute (STScI), which administrates the Hubble telescope, decided to use his “director’s discretionary time” to point the Hubble toward a very small and absolutely empty-looking part of the sky in the direction of the constellation Ursa Major the Great Bear. There were no stars visible from our Milky Way (or extremely few), no nearby galaxies visible in the field, and no visible gas clouds. Hubble collected photons for 10 consecutive days, and the result, the Hubble Deep Field, was a success and a paradigm changer: A patch of sky about as small as the eye of George Washington on an American quarter (25-cent coin) held out at arm’s length, showed a 10 billion-light-years-long tunnel back in time with a plethora of galaxies – around 3,000 of them – at different evolutionary stages along the way. The field of observational cosmology was born.

    This was done again in 1998 with the Hubble telescope pointed to the southern sky (Hubble Deep Field South), and the result was the same. Thus we learned that the universe is uniform over large scales.

    This was done again in 1998 with the Hubble telescope pointed to the southern sky (Hubble Deep Field South), and the result was the same. Thus we learned that the universe is uniform over large scales.

    Next was the installation of a new, powerful camera on Hubble (the Advanced Camera for Surveys) in 2002.

    NASA/ESA/CSA Hubble Advanced Camera for Surveys.

    The incredible Hubble Ultra Deep Field was acquired in 2004, in a similarly small patch of sky near the constellation Orion, about 1/10 of a full moon diameter (2.4 x 3.4 arc minutes, in contrast to the original Hubble Deep Fields north and south, which were 2.6 x 2.6 arc minutes). And so our reach was extended even deeper into space, and even further back in time, showing light from 10 thousand galaxies along a 13-billion-light-years-long tunnel of space. If you’ll remember that the universe is about 13.77 billion years old, you’ll see this is getting us really close to the beginning!

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    In 2013, the Planck space telescope released the most detailed map to date of the cosmic microwave background, the relic radiation from the Big Bang. It was the mission’s first all-sky picture of the oldest light in our universe, imprinted on the sky when it was just 380,000 years old. Now a new, independent study agrees with Planck’s results. That’s good news for astronomers trying to pin down the universe’s age and rate of expansion. Credit ESA/ Planck.

    The Hubble Ultra Deep Field was the most sensitive astronomical image ever made at wavelengths of visible (optical) light until 2012, when an even more refined version was released, called the Hubble eXtreme Deep Field, which reached even farther: 13.2 billion years back in time.

    The JADES survey will be observed in two batches, one on the northern sky and one on the southern in two famous fields called GOODS North and South (abbreviated from Great Observatories Origins Deep Survey).

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    GOODS North. Credit NASA/ESA Hubble.

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    GOODS South. Credit NASA/ESA Hubble.

    Marcia Rieke, a professor of astronomy at the University of Arizona who co-leads the JADES Team with Pierre Ferruit of the European Space Agency (ESA), explained:

    “We chose these fields because they have such a great wealth of supporting information. They’ve been studied at many other wavelengths, so they were the logical ones to do.”

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    Look closely. Every single speck of light in this image is a distant galaxy (except for the very few ones with spikes which are foreground stars). This telescopic field of view is part of the GOODS South field. It’s one of the directions in space that’ll be observed in JADES, a new survey that aims to study the very first galaxies to appear in the infancy of the universe. Image via NASA/ESA Hubble Space Telescope/ NASA/ESA/CSA James Webb Space Telescope site.

    The GOODS fields have been observed with several of the most famous telescopes, covering a great wavelength range from infrared through optical to X-ray. They are not fully as deep (the observations don’t reach as far back) as the Ultra Deep Field, but cover a larger area of the sky (4-5 times larger) and are the most data-rich areas of the sky in terms of depth combined with wavelength coverage. By the way, the first deep field, HDF-N, is located in the GOODS north image, and the Ultra deep field/eXtreme (don’t you love these names?) is located in the GOODS south field.

    There are a large number of ambitious science goals for the JADES program pertaining to the composition of the first galaxies, including the first generation of supermassive black holes. How these came about at such an early time is a mystery. As well, the transition of gas from neutral and opaque to transparent and ionized, something astronomers call the epoch of reionization, is not well understood.

    Epoch of Reionization and first stars. Credit: Caltech.

    JADES team member Andrew Bunker, professor of astrophysics at the University of Oxford (UK), who is also part of the ESA team behind the Webb telescope, said:

    “This transition is a fundamental phase change in the nature of the universe. We want to understand what caused it. It could be that it’s the light from very early galaxies and the first burst of star formation … It is kind of one of the Holy Grails, to find the so-called Population III stars that formed from the hydrogen and helium of the Big Bang.

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    This is an image from NASA’s Spitzer Space Telescope of a region of sky in the constellation Draco, covering about 50 by 100 million light-years (6 to 12 arcminutes). In this image all the stars, galaxies and artifacts were masked out. The remaining background reveals a glow that is not attributed to galaxies or stars. This might be the glow of the first stars in the universe. This pseudocolor image comes from infrared data at a wavelength of 3.6 microns, below what the human eye can detect. Credit: NASA/JPL-Caltech/A. Kashlinsky (GSFC).

    People have been trying to do this for many decades and results have been inconclusive so far.”

    But, hopefully, not for much longer!

    See the full article here .


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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 11:37 am on January 26, 2021 Permalink | Reply
    Tags: "Astronomers Detect a Surprisingly Huge Galactic Birthplace in The Early Universe", , , , Cosmic Dark Ages, , LAGER-z7od1 protocluster, , Lyman Alpha Galaxies in the Epoch of Reionization survey, , This research can reveal clues about one of the most mysterious stages in the history of the Universe: the Epoch of Reionization.,   

    From University of Science and Technology [中国科学技术大学] (CN) via Science Alert (AU): “Astronomers Detect a Surprisingly Huge Galactic Birthplace in The Early Universe” 

    From University of Science and Technology [中国科学技术大学] (CN)

    via

    ScienceAlert

    Science Alert (AU)

    25 JANUARY 2021
    MICHELLE STARR

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    Artist’s impression of LAGER-z7od1 protocluster. Credit: ESO/M. Kornmesser.

    Back at the dawn of the Universe, astronomers have found a stacks on of cosmic proportions. At least 21 galaxies, forming stars at a tremendous rate, are merging together in the early stages of the formation of a galaxy cluster. And it’s all happening 13 billion light-years away – just 770 million years after the Big Bang itself.

    This is the earliest protocluster discovered yet, named LAGER-z7OD1, and today it has probably evolved into a group of galaxies 3.7 quadrillion times the mass of the Sun.

    Such a large protocluster, so early in the Universe – barely a cosmic eye blink since the curtain was raised on life, the Universe and everything – could contain some vital clues as to how the primordial smoke cleared and the lights switched on, sending light streaming freely through space.

    Our Universe is a massively interconnected place. Galaxies may seem relatively self-contained, but more than half of all galaxies are gravitationally bound together in clusters or groups, huge structures of hundreds to thousands of galaxies.

    Laniakea supercluster. From Nature: The Laniakea supercluster of galaxies Credit:R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    The beginnings of such clusters are not unknown in the early Universe. Protoclusters have been found nearly as far as LAGER-z7OD1, some even much bigger, suggesting that clusters could begin assembling much faster than previously thought possible.

    But LAGER-z7OD1, according to a team of researchers led by astronomer Weida Hu of the University of Science and Technology of China, is special. It can reveal clues about one of the most mysterious stages in the history of the Universe: the Epoch of Reionization.

    Epoch of Reionization and first stars. Credit: Caltech.

    “The total volume of the ionised bubbles generated by its member galaxies is found to be comparable to the volume of the protocluster itself, indicating that we are witnessing the merging of the individual bubbles and that the intergalactic medium within the protocluster is almost fully ionised,” they wrote in their paper.

    “LAGER-z7OD1 thus provides a unique natural laboratory to investigate the reionization process.”

    Space, you see, wasn’t always the lovely, see-through place it is today. For the first 370 million years or so, it was filled with a hot murky fog of ionised gas. Light was unable to travel freely through this fog; it scattered off free electrons and that was that.

    Once the Universe cooled down enough, protons and electrons started to recombine into neutral hydrogen atoms. This meant that light – not that there was much, yet – could finally travel through space.

    As the first stars and galaxies began to form, their ultraviolet light reionized the neutral hydrogen ubiquitous throughout the Universe: first in localised bubbles around the ultraviolet sources, and then larger and larger areas as the ionized bubbles connected and overlapped, allowing the entire spectrum of electromagnetic radiation to stream freely.

    By about 1 billion years after the Big Bang, the Universe was completely re-ionized. This means that it’s more challenging to probe beyond this point (about 12.8 light-years away), but it also means that the reionization process itself is tricky to understand.

    Ideally, you need really bright objects whose ionizing radiation could cut through the neutral hydrogen, and that’s what Hu and his team were looking for with the Lyman Alpha Galaxies in the Epoch of Reionization survey. These are small, early-Universe galaxies forming stars at an insane rate, which means they can be detected at quite large distances, well inside the Epoch of Reionization. This makes them useful probes of the period.

    In their search, the researchers found LAGER-z7OD1, an over dense region of galaxies in a three-dimensional volume of space measuring 215 million by 98 million by 85 million light-years. This volume contained two distinct subprotoclusters merging together into one larger one, with at least 21 galaxies, 16 of which have been confirmed.

    The total volume of ionized space around the galaxies was slightly larger than the volume of LAGER-z7OD1.

    “This demonstrates substantial overlaps between individual bubbles, indicating that the individual bubbles are in the act of merging into one or two giant bubbles,” the researchers wrote.

    So not only does the protocluster represent an excellent example of its kind, providing a new datapoint for studying how these structures form and emerge, as well as star formation in the early Universe, it offers a one-of-a-kind window into the formation and combination of ionised bubbles in the middle of the Epoch of Reionization.

    What insights will emerge are yet to be discovered, though. As the researchers note, that will be the work of future, more powerful telescopes that will better be able to observe the finer details of the reionization process.

    The team’s research has been published in Nature Astronomy.

    See the full article here.

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    University of Science and Technology of China [中国科学技术大学] (CN)

    “The Cradle Of Scientists” In China

    The University of Science and Technology of China [中国科学技术大] (CN) is a prominent university in China and enjoys an excellent reputation worldwide. It was established by the Chinese Academy of Sciences (CAS) in 1958 in Beijing, as a strategic action by the Chinese government, to meet China’s science and technology needs and increases the country’s international competitiveness. CAS integrated its resources with USTC, with the aim of educating top talent in cutting-edge, interdisciplinary science and technology. The establishment of USTC was hailed as “a great event in the history of education and science of China”. In 1970, USTC moved to its current location in Hefei, the capital of Anhui Province.

     
  • richardmitnick 11:18 am on May 7, 2019 Permalink | Reply
    Tags: "A universe is born", , , , , Cosmic Dark Ages, , , , , , , , The Planck epoch   

    From Symmetry: “A universe is born” 

    Symmetry Mag
    From Symmetry

    05/07/19
    Diana Kwon

    Take a (brief) journey through the early history of our cosmos.

    Timeline of the Inflationary Universe WMAP

    The universe was a busy place during the first three minutes. The cosmos we see today expanded from a tiny speck to much closer to its current massive size; the elementary particles appeared; and protons and neutrons combined into the first nuclei, filling the universe with the precursors of elements.

    By developing clever theories and conducting experiments with particle colliders, telescopes and satellites, physicists have been able to wind the film of the universe back billions of years—and glimpse the details of the very first moments in the history of our cosmic home.

    Take an abridged tour through this history:

    The Planck epoch
    Time: < 10^-43 seconds

    The Planck Epoch https:// http://www.slideshare.net ericgolob the-big-bang-10535251

    Welcome to the Planck epoch, named after the smallest scale of measurements possible in particle physics today. This is currently the closet scientists can get to the beginning of time.

    Theoretical physicists don’t know much about the earliest moments of the universe. After the Big Bang theory gained popularity, scientists thought that in the first moments, the cosmos was at its hottest and densest and that all four fundamental forces—electromagnetic, weak, strong and gravitational—were combined into a single, unified force. But the current leading theoretical framework for our universe’s beginning doesn’t necessarily require these conditions.

    The universe expands
    Time: From 10^-43 seconds to about 10^-36 seconds

    In this stage, which began either at Planck time or shortly after it, scientists think the universe underwent superfast, exponential expansion in a process known as inflation.

    Inflation

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    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    Physicists first proposed the theory of inflation in the 1980s to address the shortcomings of the Big Bang theory, which, despite its popularity, could not explain why the universe was so flat and uniform, and why its different parts began expanding simultaneously.

    During inflation, quantum fluctuations could have stretched out to produce a pattern that later determined the locations of galaxies. It might have been only after this period of inflation the universe became a hot, dense fireball as described in the Big Bang theory.

    The elementary particles are born
    Time: ~10^-36 seconds

    When the universe was still very hot, the cosmos was like a gigantic accelerator, much more powerful than the Large Hadron Collider, running at extremely high energies. In it, the elementary particles we know today were born.

    Scientists think that first came exotic particles, followed by more familiar ones, such as electrons, neutrinos and quarks. It could be that dark matter particles came about during this time.

    3
    Quarks APS/Alan Stonebraker

    The quarks soon combined, forming the familiar protons and neutrons, which are collectively known as baryons. Neutrinos were able to escape this plasma of charged particles and began traveling freely through space, while photons continued to be trapped by the plasma.

    Standard Model of Particle Physics

    The first nuclei emerge
    Time: ~1 second to 3 minutes

    Scientists think that when the universe cooled enough for violent collisions to subside, protons and neutrons clumped together into nuclei of the light elements—hydrogen, helium and lithium—in a process known as Big Bang nucleosynthesis.

    Protons are more stable than neutrons, due to their lower mass. In fact, a free neutron decays with a 15-minute half-life, while protons may not decay at all, as far as we know.

    So as the particles combined, many protons remained unpaired. As a result, hydrogen—protons that never found a partner—make up around 74% of the mass of “normal” matter in our cosmos. The second most abundant element is helium, which makes up approximately 24%, followed by trace amounts of deuterium, lithium, and helium-3 (helium with a three-baryon core).

    Periodic table Sept 2017. Wikipedia

    Scientists have been able to accurately measure the density of baryons in our universe. Most of those measurements line up with theorists’ estimations of what the quantities ought to be, but there is one lingering issue: Lithium calculations are off by a factor of three. It could be that the measurements are off, but it could also be that something we don’t yet know about happened during this time period to change the abundance of lithium.

    The cosmic microwave background becomes visible
    Time: 380,000 years

    Hundreds of thousands of years after inflation, the particle soup had cooled enough for electrons to bind to nuclei to form electrically neutral atoms. Through this process, which is also known as recombination, photons became free to traverse the universe, creating the cosmic microwave background.

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    Today, the CMB is one of the most valuable tools for cosmologists, who probe its depths in search of answers for many of the universe’s lingering secrets, including the nature of inflation and the cause of matter-antimatter asymmetry.

    Shortly after the CMB became detectable, neutral hydrogen particles formed into a gas that filled the universe. Without any objects emitting high-energy photons, the cosmos was plunged into the dark ages for millions of years.

    Dark Energy Camera Enables Astronomers a Glimpse at the Cosmic Dawn. CREDIT National Astronomical Observatory of Japan

    The earliest stars shine
    Time: ~100 million years

    The dark ages ended with the formation of the first stars and the occurrence of reionization, a process through which highly energetic photons stripped electrons off neutral hydrogen atoms.

    Reionization era and first stars, Caltech

    Scientists think that the vast majority of the ionizing photons emerged from the earliest stars. But other processes, such as collisions between dark matter particles, may have also played a role.

    At this time, matter began to form the first galaxies. Our own galaxy, the Milky Way, contains stars that were born when the universe was only several hundred million years old.

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

    Our sun is born
    Time: 9.2 billion years

    3
    NASA

    The sun is one of a few hundred billion stars in the Milky Way. Scientists think it formed from a giant cloud of gas that consisted mostly hydrogen and helium.

    Today
    Time: 13.8 billion years

    Today, our cosmos sits at a cool 2.7 Kelvin (minus 270.42 degrees Celsius). The universe is expanding at an increasing rate, in a manner similar to (but many orders of magnitude slower than) inflation.

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

    Physicists think that dark energy—a mysterious repulsive force that currently accounts for about 70% of the energy in our universe—is most likely driving that accelerated expansion.

    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP)

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 4:43 pm on April 16, 2019 Permalink | Reply
    Tags: , , , Cosmic Dark Ages, , ,   

    From Kavli Institute for Cosmology, Cambridge: “Variations in the ‘fogginess’ of the universe identify a milestone in cosmic history” 

    KavliFoundation

    The Kavli Foundation

    From Kavli Institute for Cosmology, Cambridge

    Apr 16, 2019

    1

    Large differences in the ‘fogginess’ of the early universe were caused by islands of cold gas left behind when the universe heated up after the big bang, according to an international team of astronomers.

    The results, reported in the Monthly Notices of the Royal Astronomical Society, have enabled astronomers to zero in on the time when reionization ended and the universe emerged from a cold and dark state to become what it is today: full of hot and ionised hydrogen gas permeating the space between luminous galaxies.

    Hydrogen gas dims light from distant galaxies much like streetlights are dimmed by fog on a winter morning. By observing this dimming in the spectra of a special type of bright galaxies, called quasars, astronomers can study conditions in the early universe.

    2
    In the last few years, observations of this specific dimming pattern (called the Lyman-alpha Forest) suggested that the fogginess of the universe varies significantly from one part of the universe to another, but the reason behind these variations was unknown.

    “We expected the light from quasars to vary from place to place at most by factor of two at this time, but it is seen to vary by factor of about 500,” said lead author Girish Kulkarni, who completed the research while a postdoctoral researcher at the Kavli Institute, University of Cambridge. “Some hypotheses were put forward for why this is so, but none were satisfactory.”

    The new study concludes that these variations result from large regions full of cold hydrogen gas present in the universe when it was just one billion years old, a result which enables researchers to pinpoint when reionization ended.

    During reionization, when the universe transitioned out of the cosmic ‘dark ages’, the space between galaxies was filled with a plasma of ionised hydrogen with a temperature of about 10,000˚C. This is puzzling because fifty million years after the big bang, the universe was cold and dark. It contained gas with temperature only a few degrees above absolute zero, and no luminous stars and galaxies. How is it then that today, about 13.6 billion years later, the universe is bathed in light from stars in a variety of galaxies, and the gas is a thousand times hotter?

    Answering this question has been an important goal of cosmological research over the last two decades. The conclusions of the new study suggests that reionization occurred 1.1 billion years after the big bang (or 12.7 billion years ago), quite a bit later than previously thought.

    The team of researchers from India, the UK, Canada, Germany, and France drew their conclusions with the help of state-of-the-art computer simulations performed on supercomputers based at the Universities of Cambridge, Durham, and Paris, funded by the UK Science and Technology Facilities Council (STFC) and the Partnership for Advanced Computing in Europe (PRACE).

    “When the universe was 1.1 billion years old there were still large pockets of the cosmos where the gas between galaxies was still cold and it is these neutral islands of cold gas that explain the puzzling observations,” said Martin Haehnelt of the Kavli Institute, University of Cambridge, who led the group that conducted this research, supported by funding from the European Research Council (ERC).

    “This finally allows us to pinpoint the end of reionization much more accurately than before,” said Laura Keating of the Canadian Institute of Theoretical Astrophysics.

    The new study suggests that the universe was reionized by light from young stars in the first galaxies to form.

    “Late reionization is also good news for future experiments that aim to detect the neutral hydrogen from the early universe,” said Kulkarni, who is now based at the Tata Institute of Fundamental Research in India. “The later the reionisation, the easier it will be for these experiments to succeed.”

    See the full article here .

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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

     
  • richardmitnick 8:40 pm on December 17, 2017 Permalink | Reply
    Tags: , , , Carnegie Institution for Science Las Campanas Observatory, Cosmic Dark Ages, , Earliest Black Hole Gives Rare Glimpse of Ancient Universe, , , ,   

    From Quanta: “Earliest Black Hole Gives Rare Glimpse of Ancient Universe” 

    Quanta Magazine
    Quanta Magazine

    December 6, 2017 [Today in social media]
    Joshua Sokol

    1
    Olena Shmahalo/Quanta Magazine

    2
    The two Carnegie Magellan telescopes: Baade (left) and Clay (right)

    Astronomers have at least two gnawing questions about the first billion years of the universe, an era steeped in literal fog and figurative mystery. They want to know what burned the fog away: stars, supermassive black holes, or both in tandem? And how did those behemoth black holes grow so big in so little time?

    Now the discovery of a supermassive black hole smack in the middle of this period is helping astronomers resolve both questions. “It’s a dream come true that all of these data are coming along,” said Avi Loeb, the chair of the astronomy department at Harvard University.

    The black hole, announced today in the journal Nature, is the most distant ever found. It dates back to 690 million years after the Big Bang. Analysis of this object reveals that reionization, the process that defogged the universe like a hair dryer on a steamy bathroom mirror, was about half complete at that time.

    First Stars and Reionization Era, Caltech

    The researchers also show that the black hole already weighed a hard-to-explain 780 million times the mass of the sun.

    A team led by Eduardo Bañados, an astronomer at the Carnegie Institution for Science in Pasadena, found the new black hole by searching through old data for objects with the right color to be ultradistant quasars — the visible signatures of supermassive black holes swallowing gas. The team went through a preliminary list of candidates, observing each in turn with a powerful telescope at Las Campanas Observatory in Chile.

    4
    Carnegie Institution for Science Las Campanas Observatory telescopes in the southern Atacama Desert of Chile approximately 100 kilometres (62 mi) northeast of the city of La Serena,near the southern end and over 2,500 m (8,200 ft) high.

    On March 9, Bañados observed a faint dot in the southern sky for just 10 minutes. A glance at the raw, unprocessed data confirmed it was a quasar — not a nearer object masquerading as one — and that it was perhaps the oldest ever found. “That night I couldn’t even sleep,” he said.

    3
    Eduardo Bañados at the Las Campanas Observatory in Chile, where the new quasar was discovered. Courtesy of Eduardo Bañados. Baade and Clay in the background.

    The new black hole’s mass, calculated after more observations, adds to an existing problem. Black holes grow when cosmic matter falls into them. But this process generates light and heat. At some point, the radiation released by material as it falls into the black hole carries out so much momentum that it blocks new gas from falling in and disrupts the flow. This tug-of-war creates an effective speed limit for black hole growth called the Eddington rate. If this black hole began as a star-size object and grew as fast as theoretically possible, it couldn’t have reached its estimated mass in time.

    Other quasars share this kind of precocious heaviness, too. The second-farthest one known, reported on in 2011, tipped the scales at an estimated 2 billion solar masses after 770 million years of cosmic time.

    These objects are too young to be so massive. “They’re rare, but they’re very much there, and we need to figure out how they form,” said Priyamvada Natarajan, an astrophysicist at Yale University who was not part of the research team. Theorists have spent years learning how to bulk up a black hole in computer models, she said. Recent work suggests that these black holes could have gone through episodic growth spurts during which they devoured gas well over the Eddington rate.

    Bañados and colleagues explored another possibility: If you start at the new black hole’s current mass and rewind the tape, sucking away matter at the Eddington rate until you approach the Big Bang, you see it must have initially formed as an object heavier than 1,000 times the mass of the sun. In this approach, collapsing clouds in the early universe gave birth to overgrown baby black holes that weighed thousands or tens of thousands of solar masses. Yet this scenario requires exceptional conditions that would have allowed gas clouds to condense all together into a single object instead of splintering into many stars, as is typically the case.

    Cosmic Dark Ages

    2
    Cosmic Dark Ages. ESO.

    Even earlier in the early universe, before any stars or black holes existed, the chaotic scramble of naked protons and electrons came together to make hydrogen atoms. These neutral atoms then absorbed the bright ultraviolet light coming from the first stars. After hundreds of millions of years, young stars or quasars emitted enough light to strip the electrons back off these atoms, dissipating the cosmic fog like mist at dawn.

    3
    Lucy Reading-Ikkanda/Quanta Magazine

    Astronomers have known that reionization was largely complete by around a billion years after the Big Bang.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    At that time, only traces of neutral hydrogen remained. But the gas around the newly discovered quasar is about half neutral, half ionized, which indicates that, at least in this part of the universe, reionization was only half finished. “This is super interesting, to really map the epoch of reionization,” said Volker Bromm, an astrophysicist at the University of Texas.

    When the light sources that powered reionization first switched on, they must have carved out the opaque cosmos like Swiss cheese.

    Inflationary Universe. NASA/WMAP

    But what these sources were, when it happened, and how patchy or homogeneous the process was are all debated. The new quasar shows that reionization took place relatively late. That scenario squares with what the known population of early galaxies and their stars could have done, without requiring astronomers to hunt for even earlier sources to accomplish it quicker, said study coauthor Bram Venemans of the Max Planck Institute for Astronomy in Heidelberg.

    More data points may be on the way. For radio astronomers, who are gearing up to search for emissions from the neutral hydrogen itself, this discovery shows that they are looking in the right time period. “The good news is that there will be neutral hydrogen for them to see,” said Loeb. “We were not sure about that.”

    The team also hopes to identify more quasars that date back to the same time period but in different parts of the early universe. Bañados believes that there are between 20 and 100 such very distant, very bright objects across the entire sky. The current discovery comes from his team’s searches in the southern sky; next year, they plan to begin searching in the northern sky as well.

    “Let’s hope that pans out,” said Bromm. For years, he said, the baton has been handed off between different classes of objects that seem to give the best glimpses at early cosmic time, with recent attention often going to faraway galaxies or fleeting gamma-ray bursts. “People had almost given up on quasars,” he said.

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 4:50 pm on July 11, 2017 Permalink | Reply
    Tags: 800 million years is the current frontier in reionization studies, , , , Cosmic Dark Ages, , , Determining when the first galaxies formed is a challenge, LAEs-Lyman alpha emitting galaxies,   

    From phys.org: “Distant galaxies ‘lift the veil’ on the end of the cosmic dark ages” 

    physdotorg
    phys.org

    July 11, 2017

    1
    False color image of a 2 square degree region of the LAGER survey field, created from images taken in the optical at 500 nm (blue), in the near-infrared at 920 nm (red), and in a narrow-band filter centered at 964 nm (green). The last is sensitive to hydrogen Lyman alpha emission at z ~ 7. The small white boxes indicate the positions of the 23 LAEs discovered in the survey. The detailed insets (yellow) show two of the brightest LAEs; they are 0.5 arcminutes on a side, and the white circles are 5 arcseconds in diameter. Credit: Zhen-Ya Zheng (SHAO) & Junxian Wang (USTC).

    Astronomers studying the distant Universe have found that small star-forming galaxies were abundant when the Universe was only 800 million years old, a few percent of its present age. The results suggest that the earliest galaxies, which illuminated and ionized the Universe, formed at even earlier times.

    Long ago, about 300,000 years after the beginning of the Universe (the Big Bang), the Universe was dark. There were as yet no stars and galaxies, and the Universe was filled with neutral hydrogen gas. At some point the first galaxies appeared, and their energetic radiation ionized their surroundings, the intergalactic gas, illuminating and transforming the Universe.

    While this dramatic transformation is known to have occurred sometime in the interval between 300 million years and 1 billion years after the Big Bang, determining when the first galaxies formed is a challenge. The intergalactic gas, which is initially neutral, strongly absorbs and scatters the ultraviolet light emitted by the galaxies, making them difficult to detect.

    To home in on when the transformation occurred, astronomers take an indirect approach. Using the demographics of small star-forming galaxies to determine when the intergalactic gas became ionized, they can infer when the ionizing sources, the first galaxies, formed. If star forming galaxies, which glow in the light of the hydrogen Lyman alpha line, are surrounded by neutral hydrogen gas, the Lyman alpha photons are readily scattered, much like headlights in fog, obscuring the galaxies. When the gas is ionized, the fog lifts, and the galaxies are easier to detect.

    A new study [ApJ] taking this approach has discovered 23 candidate Lyman alpha emitting galaxies (LAEs) that were present 800 million years after the Big Bang (at a redshift of z~7), the largest sample detected to date at that epoch. The study, “Lyman-Alpha Galaxies in the Epoch of Reionization” (LAGER), was carried out by an international team of astronomers from China, the US, and Chile using the Dark Energy Camera (DECam) on the CTIO 4-m Blanco telescope.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL


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

    2
    Milestones in the history of the Universe (not to scale). The intergalactic gas was in a neutral state from about 300,000 years after the Big Bang until light from the first generation of stars and galaxies began to ionize it. The gas was completely ionized after 1 billion years. The LAGER study takes a close look at the state of the Universe at 800 million years (yellow box) to investigate when and how this transformation occurred. Credit: NAOJ.

    While the study detected many LAEs, it also found that LAEs were 4 times less common at 800 million years than they were a short time later, at 1 billion years (at a redshift of z~5.7). The results imply that the process of ionizing the Universe began early and was still incomplete at 800 million years, with the intergalactic gas about half neutral and half ionized at that epoch. The low incidence rate of LAEs at 800 million years results from the suppression of their Lyman alpha emission by neutral intergalactic gas.

    The study shows that “the fog was already lifting when the universe was 5% of its current age”, explained Sangeeta Malhotra (Goddard Space Flight Center and Arizona State University), one of the co-leads of the survey.

    Junxian Wang (USTC), the organizer of the study, further explained, “Our finding that the intergalactic gas is 50% ionized at z ~ 7 implies that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang.”

    For Zhenya Zheng (Shanghai Astronomical Observatory, CAS), the lead author of the paper describing these results, “800 million years is the current frontier in reionization studies.” While hundreds of LAEs have been found at later epochs, only about two dozen candidate LAEs were known at 800 million years prior to the current study. The new results dramatically increase the number of LAEs known at this epoch.

    “None of this science would have been possible without the widefield capabilities of DECam and its community pipeline for data reduction,” remarked coauthor James Rhoads. “These capabilities enable efficient surveys and thereby the discovery of faint galaxies as well as rare, bright ones.”

    To build on these results, the team is “continuing the search for distant star forming galaxies over a larger volume of the Universe”, said Leopoldo Infante (Pontificia Catolica University of Chile and the Carnegie Institution for Science), “to study the clustering of LAEs.” Clustering provides unique insights into how the fog lifts. The team is also investigating the nature of these distant galaxies.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 12:39 pm on August 8, 2016 Permalink | Reply
    Tags: , , , Cosmic Dark Ages, ,   

    From Astronomy: “When did the lights turn on in the universe?” 

    Astronomy magazine

    Astronomy.com

    August 08, 2016
    Nola Taylor Redd

    1
    A map showing the history of the universe, including the shift from neutral to ionized hydrogen resulting in the universe we see today.
    NAOJ

    The early universe hides behind the cloak of its Dark Ages, a period of time light can’t seem to pierce. Even the length of those unseen years remains uncertain. As part of its efforts to probe the secrets of those hidden years, the European Space Agency’s Planck Satellite recently announced the most precise constraints on the universe’s evasive era, for the first time revealing that the first stars and their galaxies are enough to light up the darkness.

    ESA/Planck
    ESA/Planck

    Trying to pierce the veil of darkness has been a decades-long struggle to look back in time nearly 14 billion years. After the Big Bang, the hot universe quickly cooled down, and the simplest atomic particles formed. The protons and electrons of the early universe constantly collided, creating a hot soup that kept light from passing. The Dark Ages had begun.

    As the gas cooled down, and the expanding galaxy stretched space-time, the particles recombined to form neutral hydrogen. Like the rising dawn, the universe grew gradually more transparent, its gradual glow imprinted on the radio noise scientists recognize as the Cosmic Microwave Background (CMB). The universe remained dark, however, because nothing produced visible light.

    Cosmic Microwave Background per ESA/Planck
    Cosmic Microwave Background per ESA/Planck

    Gravity worked hard to change that. It didn’t take long for the force to begin pulling material together, forming the first stars and galaxies. Bright galaxies know as quasars, whose central supermassive black holes produce powerful jets of light and matter, also populated the early universe. Heat from the young objects broke the neutral hydrogen apart over time in the process known as reionization, with slow-sweeping bubbles of light spreading outward from the bright objects. As the bubbles grew and overlapped, the universe once again became visible, and the Dark Age ended. (The change of state in hydrogen that allowed a visible universe is called the Epoch of Reionization.)

    Perhaps one of the most challenging attributes of the Dark Age is the difficulty inherent in nailing down just when it ended and how long it lasted. Because light didn’t shine from the start of the Dark Age, scientists must rely on the glow from the CMB to provide them with clues to when recombination brought particles together to make the universe gradually more transparent. Observations of early galaxies and quasars, the brightest objects in the universe, help narrow down how long the lights were off.

    Planck’s most recent results suggest that the time of reionization, when light from the first objects began to break apart molecules once again, occurred about 55 million years later than previous studies placed it.

    “It is certainly clear that we are now measuring a later onset of reionization,” says Planck Project Scientist Jan Tauber said by email.

    Planck Scientist Graca Rocha, of the Jet Propulsion Laboratory, stresses that Planck’s measurements have become more precise over time. Rocha, who presented a portion of the research at the American Astronomical Society meeting in San Diego, California in June, pointed to the error bar in the calculations, a number that has grown smaller over time. The most recent results have an error of less than nine-thousandanths.

    “We are narrowing the range of reionization, when the first stars start to form,” Rocha told Astronomy. “People are thrilled about the shift down.”

    Strange objects begone

    The first early estimates suggested that reionization wrapped up extremely fast, requiring unusual astronomical bodies to clear the darkness. Tension mounted as the scientists sought to reconcile multiple forms of observation. Planck’s new numbers helped to relieve some of the pressure as the more precise calculations suggested that novel things were unnecessary after all.

    “Those early measurements required ‘strange objects’ to reionize the universe, but those concerns have now been dissipated by Planck,” Tauber says.

    “We now know that the first galaxies that we can already observe are enough to reionize the universe at the time shown by the [Cosmic Microwave Background].”

    Since its launch in 2009, Planck has probed the early universe, seeking to learn more about when the Dark Ages started and ended. Over three quarters of a decade, the spacecraft has helped to improve the understanding of the unseen era by penetrating the veil of darkness around it.

    The more sophisticated analysis reveals that the first objects didn’t begin to separate the fog of particles until “quite late,” Tauber says. Planck reveals that the universe was no more than 10 percent ionized by the time the universe was 475 million years old. It also demonstrated that the process wrapped up quickly, within about 250 million years.

    “This model is very consistent with observations of the earliest galaxies,” Tauber says.

    These galaxies allow scientists to estimate the total amount of light available to the early universe to split the particles once again.

    “So the Planck- and CMB-based estimates are now in full agreement with direct observations.”

    See the full article here .

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  • richardmitnick 10:12 pm on January 20, 2016 Permalink | Reply
    Tags: , , Cosmic Dark Ages,   

    From Ethan Siegel: “The Universe’s Dark Ages May Hold The Secrets To Dark Matter, Inflation, And Even String Theory” 

    Starts with a bang
    Starts with a Bang

    1.20.16
    Presented by Ethan Siegel
    This post is written by Sabine Hossenfelder, a theoretical physicist specialized in quantum gravity & high energy physics. She also freelance writes about science.

    How the future of astronomy — and something we can’t even see — might open up the dark Universe.

    Temp 1
    Image credit: NASA / WMAP science team.

    “When their eyes grew dim with looking at unrevealing dials and studying uneventful graphs, they could step outside their concrete cells and renew their dull spirits in communion with the giant mechanism they commanded, the silent, sensing instrument in which the smallest packets of energy, the smallest waves of matter, were detected in their headlong, eternal flight across the universe.” -James Gunn, on Radio Astronomy

    The universe might have started with a bang, but once the echoes faded it took quite some while until the cosmic symphony began. Between the creation of the cosmic microwave background (CMB), where neutral atoms formed for the first time, and the formation of the first stars, there were 100 million years that passed in complete darkness.

    Cosmic Background Radiation Planck
    CMB per ESA/Planck

    ESA Planck
    ESA/Planck

    This “dark age” has so far been entirely hidden from observation, but this situation is soon to change.

    The dark ages may hold the answers to many pressing questions. During this period, most of the universe’s mass was in form of light atoms — primarily hydrogen — and dark matter. The atoms slowly clumped under the influence of gravitational forces, until they finally ignited the first stars.


    Download the mp4 video here .

    Before the first stars, astrophysical processes were few, and so the distribution of hydrogen during the dark ages carries very clean information about structure formation. Details about both the behavior of dark matter and the sizes of the structures that formed are encoded in these hydrogen clouds. But how can we see into this darkness?

    Luckily, these dark ages weren’t entirely dark, just very, very dim. Back then, the hydrogen atoms that filled the universe frequently bumped into each other, which can flip the electron’s spin. If a collision flips the spin, the electron’s energy changes by a tiny amount because the energy depends on whether the electron’s spin is aligned with the spin of the nucleus or whether it points in the opposite direction. This very small energy difference is known as “hyperfine splitting.” Flipping the hydrogen electron’s spin from the aligned state to the anti-aligned one therefore leads to the emission of a very low energy photon. Since high energy means short wavelengths and low energy is long wavelength, you’ll be unsurprised to learn this hyperfine transition produces photons with a wavelength of 21cm. If we can trace the emission of these 21cm photons, we can trace the distribution of hydrogen. But 21 cm is the wavelength of the photons at the time of emission, which was some 13 billion years ago.

    Temp 2
    Image credit: Sabine Hossenfelder.

    Since that time, the universe has expanded significantly and stretched the photons’ wavelength with it. How much the wavelength has been stretched depends on whether it was emitted early or late during the dark ages. The early photons have meanwhile been stretched by a factor of about 1000, resulting in wavelengths of a few hundred meters. Photons emitted towards the end of the dark ages have not been stretched quite as much — they today have wavelengths of “only” a few meters.


    Download mp4 video here .

    The most exciting aspect of 21cm astronomy is that it does not only give us a snapshot at one particular moment — like the CMB — but allows us to continuously map different epochs during the dark ages. By measuring the red-shifted photons at different wavelengths, we can scan through the entire time period. This would give us many new insights about the history of our universe.

    Temp 3
    On the left, the infrared light from the end of the Universe’s dark ages in shown, with the (foreground) stars subtracted out. 21cm astronomy will be able to probe even farther back. Image credit: NASA/JPL-Caltech/A. Kashlinsky (GSFC).

    To begin with, it is not well understood how the dark ages end and the first stars are formed. The dark ages fade away in a phase of reionization, in which the intense UV starlight strips the neutral hydrogen of its electrons once again. This reionization is believed to be caused by radiation from the first stars, but we don’t know exactly what the intricacies of this process are. Since ionized hydrogen can no longer emit the hyperfine line, 21cm astronomy could tell us how the ionized regions grow, teaching us much about the early stellar objects and the behavior of the intergalactic medium. 21 cm astronomy can also help solve the riddle of dark matter. If dark matter self-annihiliates, this affects the distribution of neutral hydrogen, which can be used to constrain or rule out dark matter models.

    Temp 4
    A 3D map of the dark matter distribution in the cosmos. 21 cm astronomy would allow us to probe this structure far more finely and at earlier times than the weak lensing technique used to make this map. Image credit: NASA/ESA/Richard Massey (California Institute of Technology).

    Inflation models too can be probed by this method: The distribution of structures that 21cm astronomy can map carries an imprint of the quantum fluctuations that caused them. These fluctuations in return depend on the type of inflation fields and the shape of those fields’ potentials. Thus, the correlations in the structures which were present already during the dark ages let us narrow down what type of inflation has occurred.

    Perhaps most excitingly, the dark ages might give us a peek at cosmic strings, one-dimensional objects with a high density and high gravitational pull. In many models of string phenomenology, cosmic strings can be produced at the end of inflation, before the dark ages begins. By distorting the hydrogen clouds, the cosmic strings would leave a characteristic signal in the 21cm emission spectrum.

    But measuring photons of this wavelength is not easy. The Milky Way, too, has sources that emit in this regime, which gives rise to an unavoidable galactic foreground that must be understood and subtracted. In addition, the Earth’s atmosphere distorts the signal and some radio broadcasts can interfere with the measurement. Nevertheless, astronomers have risen to the challenge and the first telescopes hunting for the early universe’s 21cm signal are now in operation.

    SKA Murchison Widefield Array
    Image credit: one module in the Murchison Widefield Array (MWA), via Natasha Hurley-Walker under c.c.-by-s.a.-3.0.

    The Low-Frequency Array (LOFAR) went online in late 2012.

    ASTRON LOFAR Radio Antenna Bank
    LOFAR

    Its main telescope is located in the Netherlands, but it combines data from 24 other telescopes in Europe, and is sensitive to wavelengths up to 30m in size. The Murchison Widefield Array (MWA) in Australia, which is sensitive to wavelengths of a few meters, has started taking data in 2013. And in 2025, the Square Kilometer Array is scheduled to be completed. This joint project between Australia and South Africa will be the world’s largest radio telescope.

    Still, the astronomers’ dream would be to get rid of the distortion caused by Earth’s atmosphere altogether. Their most ambitious plan is to put an array of telescopes on the far side of the Moon. But this idea is, unfortunately, still far-fetched — for not to mention underfunded.

    Temp 5
    Image credit: ESO/M. Kornmesser, of an illustration of CR7, the first galaxy detected that’s thought to house Population III stars: the first stars ever formed in the Universe.

    Only a few decades ago, cosmology was a discipline so starved of data that many argued it was closer to philosophy than to science. Today, it is a research area based on high precision measurements with a wealth of data covering the entire electromagnetic spectrum. The progress in technology and in our understanding of the universe’s history has been nothing but stunning, but we have only just begun. The dark ages are next.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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