Tagged: First Light Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 5:22 pm on June 4, 2017 Permalink | Reply
    Tags: , , , , First Light, , ,   

    From WIRED: “Cosmic Discoveries Fuel a Fight Over the Universe’s Beginnings” 

    Wired logo

    06.04.17
    Ashley Yeager

    1
    Light from the first galaxies clears the universe. ESO/L. Calçada

    Not long after the Big Bang, all went dark. The hydrogen gas that pervaded the early universe would have snuffed out the light of the universe’s first stars and galaxies. For hundreds of millions of years, even a galaxy’s worth of stars—or unthinkably bright beacons such as those created by supermassive black holes—would have been rendered all but invisible.

    Eventually this fog burned off as high-energy ultraviolet light broke the atoms apart in a process called reionization.

    Reionization era and first stars, Caltech

    But the questions of exactly how this happened—which celestial objects powered the process and how many of them were needed—have consumed astronomers for decades.

    Now, in a series of studies, researchers have looked further into the early universe than ever before. They’ve used galaxies and dark matter as a giant cosmic lens to see some of the earliest galaxies known, illuminating how these galaxies could have dissipated the cosmic fog. In addition, an international team of astronomers has found dozens of supermassive black holes—each with the mass of millions of suns—lighting up the early universe. Another team has found evidence that supermassive black holes existed hundreds of millions of years before anyone thought possible. The new discoveries should make clear just how much black holes contributed to the reionization of the universe, even as they’ve opened up questions as to how such supermassive black holes were able to form so early in the universe’s history.

    First Light

    In the first years after the Big Bang, the universe was too hot to allow atoms to form. Protons and electrons flew about, scattering any light. Then after about 380,000 years, these protons and electrons cooled enough to form hydrogen atoms, which coalesced into stars and galaxies over the next few hundreds of millions of years.

    Starlight from these galaxies would have been bright and energetic, with lots of it falling in the ultraviolet part of the spectrum. As this light flew out into the universe, it ran into more hydrogen gas. These photons of light would break apart the hydrogen gas, contributing to reionization, but as they did so, the gas snuffed out the light.

    2
    Lucy Reading-Ikkanda/Quanta Magazine

    To find these stars, astronomers have to look for the non-ultraviolet part of their light and extrapolate from there. But this non-ultraviolet light is relatively dim and hard to see without help.

    A team led by Rachael Livermore, an astrophysicist at the University of Texas at Austin, found just the help needed in the form of a giant cosmic lens.

    Gravitational Lensing NASA/ESA

    These so-called gravitational lenses form when a galaxy cluster, filled with massive dark matter, bends space-time to focus and magnify any object on the other side of it. Livermore used this technique with images from the Hubble Space Telescope to spot extremely faint galaxies from as far back as 600 million years after the Big Bang—right in the thick of reionization.

    NASA/ESA Hubble Telescope

    In a recent paper that appeared in The Astrophysical Journal, Livermore and colleagues also calculated that if you add galaxies like these to the previously known galaxies, then stars should be able to generate enough intense ultraviolet light to reionize the universe.

    Yet there’s a catch. Astronomers doing this work have to estimate how much of a star’s ultraviolet light escaped its home galaxy (which is full of light-blocking hydrogen gas) to go out into the wider universe and contribute to reionization writ large. That estimate—called the escape fraction—creates a huge uncertainty that Livermore is quick to acknowledge.

    In addition, not everyone believes Livermore’s results. Rychard Bouwens, an astrophysicist at Leiden University in the Netherlands, argues in a paper submitted to The Astrophysical Journal that Livermore didn’t properly subtract the light from the galaxy clusters that make up the gravitational lens.

    6

    As a result, he said, the distant galaxies aren’t as faint as Livermore and colleagues claim, and astronomers have not found enough galaxies to conclude that stars ionized the universe.

    If stars couldn’t get the job done, perhaps supermassive black holes could. Beastly in size, up to a billion times the mass of the sun, supermassive black holes devour matter. They tug it toward them and heat it up, a process that emits lots of light and creates luminous objects that we call quasars. Because quasars emit way more ionizing radiation than stars do, they could in theory reionize the universe.

    The trick is finding enough quasars to do it. In a paper posted to the scientific preprint site arxiv.org last month, astronomers working with the Subaru Telescope announced the discovery of 33 quasars that are about a 10th as bright as ones identified before.


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA

    With such faint quasars, the astronomers should be able to calculate just how much ultraviolet light these supermassive black holes emit, said Michael Strauss, an astrophysicist at Princeton University and a member of the team.

    The researchers haven’t done the analysis yet, but they expect to publish the results in the coming months.

    The oldest of these quasars dates back to around a billion years after the Big Bang, which seems about how long it would take ordinary black holes to devour enough matter to bulk up to supermassive status.

    This is why another recent discovery [ApJ] is so puzzling. A team of researchers led by Richard Ellis, an astronomer at the European Southern Observatory, was observing a bright, star-forming galaxy seen as it was just 600 million years after the Big Bang.

    The galaxy’s spectrum—a catalog of light by wavelength—appeared to contain a signature of ionized nitrogen. It’s hard to ionize ordinary hydrogen, and even harder to ionize nitrogen. It requires more higher-energy ultraviolet light than stars emit. So another strong source of ionizing radiation, possibly a supermassive black hole, had to exist at this time, Ellis said.

    One supermassive black hole at the center of an early star-forming galaxy might be an outlier. It doesn’t mean there were enough of them around to reionize the universe. So Ellis has started to look at other early galaxies. His team now has tentative evidence that supermassive black holes sat at the centers of other massive, star-forming galaxies in the early universe. Studying these objects could help clarify what reionized the universe and illuminate how supermassive black holes formed at all. “That is a very exciting possibility,” Ellis said.

    All this work is beginning to converge on a relatively straightforward explanation for what reionized the universe. The first population of young, hot stars probably started the process, then drove it forward for hundreds of millions of years. Over time, these stars died; the stars that replaced them weren’t quite so bright and hot. But by this point in cosmic history, supermassive black holes had enough time to grow and could start to take over. Researchers such as Steve Finkelstein, an astrophysicist at the University of Texas at Austin, are using the latest observational data and simulations of early galactic activity to test out the details of this scenario, such as how much stars and black holes contribute to the process at different times.

    His work—and all work involving the universe’s first billion years—will get a boost in the coming years after the 2018 launch of the James Webb Space Telescope, Hubble’s successor, which has been explicitly designed to find the first objects in the universe.

    NASA/ESA/CSA Webb Telescope annotated

    Its findings will probably provoke many more questions, too.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 8:26 am on July 17, 2016 Permalink | Reply
    Tags: , First Light, ,   

    From SKA: “MeerKAT joins the ranks of the world’s great scientific instruments through its First Light image” 

    SKA Square Kilometer Array

    SKA

    16 July 2016
    Lorenzo Raynard, SKA SA Communication Manager
    lorenzo@ska.ac.za
    (+27) 71 454 0658

    1
    IMAGE 1: MeerKAT First Light image. Each white dot represents the intensity of radio waves recorded with 16 dishes of the MeerKAT telescope in the Karoo (when completed, MeerKAT will consist of 64 dishes and associated systems). More than 1300 individual objects – galaxies in the distant universe – are seen in this image.

    The MeerKAT First Light image of the sky, released today by Minister of Science and Technology, Naledi Pandor, shows unambiguously that MeerKAT is already the best radio telescope of its kind in the Southern Hemisphere. Array Release 1 (AR1) being celebrated today provides 16 of an eventual 64 dishes integrated into a working telescope array. It is the first significant scientific milestone achieved by MeerKAT, the radio telescope under construction in the Karoo that will eventually be integrated into the Square Kilometre Array (SKA).

    SKA Meerkat telescope, South African design
    SKA Meerkat telescope, South African design

    3
    When fully up and running in the 2020s, the SKA will comprise a forest of 3,000 dishes spread over an area of a square kilometre (0.4 square miles) across remote terrain around several countries. phys.org

    In a small patch of sky covering less than 0.01 percent of the entire celestial sphere, the MeerKAT First Light image shows more than 1300 galaxies in the distant Universe, compared to 70 known in this location prior to MeerKAT. “Based on the results being shown today, we are confident that after all 64 dishes are in place, MeerKAT will be the world’s leading telescope of its kind until the advent of SKA,” according to Professor Justin Jonas, SKA South Africa Chief Technologist.

    MeerKAT will consist of 64 receptors, each comprising a 13.5-metre diametre dish antenna, cryogenic coolers, receivers, digitiser, and other electronics. The commissioning of MeerKAT is done in phases to allow for verification of the system, early resolution of any technical issues, and initial science exploitation. Early science can be done with parts of the array as they are commissioned, even as construction continues. AR1 consists of 16 receptors, AR2 of 32 and AR3 of 64, expected to be in place by late 2017.

    Dr Rob Adam, Project Director of SKA South Africa, says: “The launch of MeerKAT AR1 and its first results is a significant milestone for South Africa. Through MeerKAT, South Africa is playing a key role in the design and development of technology for the SKA. The South African team of more than 200 young scientists, engineers and technicians, in collaboration with industry, local and foreign universities and institutions, has developed the technologies and systems for MeerKAT. These include cutting edge telescope antennas and receivers, signal processing, timing, telescope management, computing and data storage systems, and algorithms for data processing.”

    2
    IMAGE 2: Montage of MeerKAT First Light radio image and four zoomed-in insets. The two panels to the right show distant galaxies with massive black holes at their centers. At lower left is a galaxy approximately 200 million light years away, where hydrogen gas is being used up to form stars in large numbers.

    3
    IMAGE 3: View showing 10% of the full MeerKAT First Light radio image. More than 200 astronomical radio sources (white dots) are visible in this image, where prior to MeerKAT only five were known (indicated by violet circles). This image spans about the area of the Earth’s moon.

    In May 2016, more than 150 researchers and students, two-thirds from South Africa, met in Stellenbosch to discuss and update the MeerKAT science programme. This will consist of already approved “large survey projects”, plus “open time” available for new projects. An engineering test image, produced with only 4 dishes, was made available just before that meeting.

    “The scientists gathered at the May meeting were impressed to see what 4 MeerKAT dishes could do,” says Dr Fernando Camilo, SKA South Africa Chief Scientist. “They will be astonished at today’s exceptionally beautiful images, which demonstrate that MeerKAT has joined the big leagues of world radio astronomy”.

    Pandor today released the MeerKAT First Light image from the telescope site in the Northern Cape. She was accompanied by Ministers and Deputy Ministers from the Presidential Infrastructure Coordination Committee (PICC), as well as other senior officials.

    Minister Pandor says: “South Africa has already demonstrated its excellent science and engineering skills by designing and building MeerKAT. This telescope, which is predominantly a locally designed and built instrument, shows the world that South Africa can compete in international research, engineering, technology and science. Government is proud of our scientists and engineers for pioneering a radio telescope that will lead to groundbreaking research.”

    MeerKAT is a precursor to the Square Kilometre Array (SKA) and follows the KAT-7 telescope which was an engineering test-bed for MeerKAT. MeerKAT is funded by the South African Government and is a South African designed telescope with 75% of its value sourced locally. MeerKAT will be an integral part of SKA Phase 1. An important aspect of the SKA site decision in 2012 was that MeerKAT would be part of the sensitive SKA Phase 1 array, which will be the most sensitive radio telescope in the world. Upon completion at the end of 2017, MeerKAT will consist of 64 dishes and associated instrumentation. SKA1 MID will include an additional 133 dishes, bringing the total number for SKA1 MID to 197.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition

    SKA Banner

    SKA CSIRO  Pathfinder Telescope
    SKA ASKAP Pathefinder Telescope

    SKA Meerkat telescope
    SKA Meerkat Telescope

    SKA Murchison Widefield Array
    SKA Murchison Wide Field Array

    About SKA

    The Square Kilometre Array will be the world’s largest and most sensitive radio telescope. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity, and 10 000 times the survey speed, of the best current-day telescopes. The SKA will be built in Southern Africa and in Australia. Thousands of receptors will extend to distances of 3 000 km from the central regions. The SKA will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of the Universe, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. Construction of phase one of the SKA is scheduled to start in 2016. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and centralise the leadership of the project.

    The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, led by SKA Organisation. The SKA will conduct transformational science to improve our understanding of the Universe and the laws of fundamental physics, monitoring the sky in unprecedented detail and mapping it hundreds of times faster than any current facility.

    Already supported by 10 member countries – Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, The Netherlands and the United Kingdom – SKA Organisation has brought together some of the world’s finest scientists, engineers and policy makers and more than 100 companies and research institutions across 20 countries in the design and development of the telescope. Construction of the SKA is set to start in 2018, with early science observations in 2020.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: