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  • richardmitnick 2:31 pm on June 23, 2018 Permalink | Reply
    Tags: Cosmology, , , , , University of Colorado Boulder, Researchers find last of universe's missing ordinary matter   

    From University of Colorado Boulder via phys.org: “Researchers find last of universe’s missing ordinary matter” 

    U Colorado

    From University of Colorado Boulder

    and

    phys.org

    June 20, 2018
    No writer credit

    1
    A simulation of the cosmic web, or diffuse tendrils of gas connecting galaxies across the universe. Credit: NASA, ESA, E. Hallman (CU Boulder)

    Researchers at the University of Colorado Boulder have helped to find the last reservoir of ordinary matter hiding in the universe.

    Ordinary matter, or “baryons,” make up all physical objects in existence, from stars to the cores of black holes. But until now, astrophysicists had only been able to locate about two-thirds of the matter that theorists predict was created by the Big Bang.

    In the new research, an international team pinned down the missing third, finding it in the space between galaxies. That lost matter exists as filaments of oxygen gas at temperatures of around 1 million degrees Celsius, said CU Boulder’s Michael Shull, a co-author of the study.

    The finding is a major step for astrophysics. “This is one of the key pillars of testing the Big Bang theory: figuring out the baryon census of hydrogen and helium and everything else in the periodic table,” said Shull of the Department of Astrophysical and Planetary Sciences (APS).

    The new study, which will appear June 20 in Nature, was led by Fabrizio Nicastro of the Italian Istituto Nazionale di Astrofisica (INAF)—Osservatorio Astronomico di Roma and the Harvard-Smithsonian Center for Astrophysics.

    Researchers have a good idea of where to find most of the ordinary matter in the universe—not to be confused with dark matter, which scientists have yet to locate: About 10 percent sits in galaxies, and close to 60 percent is in the diffuse clouds of gas that lie between galaxies.

    In 2012, Shull and his colleagues predicted that the missing 30 percent of baryons were likely in a web-like pattern in space called the warm-hot intergalactic medium (WHIM). Charles Danforth, a research associate in APS, contributed to those findings and is a co-author of the new study.

    To search for missing atoms in that region between galaxies, the international team pointed a series of satellites at a quasar called 1ES 1553—a black hole at the center of a galaxy that is consuming and spitting out huge quantities of gas. “It’s basically a really bright lighthouse out in space,” Shull said.

    Scientists can glean a lot of information by recording how the radiation from a quasar passes through space, a bit like a sailor seeing a lighthouse through fog. First, the researchers used the Cosmic Origins Spectrograph on the Hubble Space Telescope to get an idea of where they might find the missing baryons. Next, they homed in on those baryons using the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton) satellite.

    NASA/ESA Hubble Telescope

    ESA/XMM Newton

    The team found the signatures of a type of highly-ionized oxygen gas lying between the quasar and our solar system—and at a high enough density to, when extrapolated to the entire universe, account for the last 30 percent of ordinary matter.

    “We found the missing baryons,” Shull said.

    He suspects that galaxies and quasars blew that gas out into deep space over billions of years. Shull added that the researchers will need to confirm their findings by pointing satellites at more bright quasars.

    See the full article here .


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  • richardmitnick 2:09 pm on June 23, 2018 Permalink | Reply
    Tags: , , , Cosmology, Could The Energy Loss From Radiating Stars Explain Dark Energy?,   

    From Ethan Siegel: “Could The Energy Loss From Radiating Stars Explain Dark Energy?” 

    From Ethan Siegel
    June 23, 2018

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    An artist’s conception of what the Universe might look like as it forms stars for the first time. As they shine and merge, radiation will be emitted, both electromagnetic and gravitational. But will the conversion of matter into energy be able to generate an anti-gravitational force? NASA/ESA/ESO/Wolfram Freudling et al. (STECF)

    When it comes to our quest to understand the Universe, there are mysteries out there that no one knows the solution to. Dark matter, dark energy, and cosmic inflation, for example, are all incomplete ideas, where we don’t know which type(s) of particles or fields are responsible for them. It’s even possible, although most of the top professionals don’t think it’s likely, that one or more of these puzzles might have an unconventional solution that isn’t what we’re expecting at all.

    For the first time in Ask Ethan history, we’ve got a question from a Nobel Laureate — John Mather — who wants to know if stars, by virtue of converting mass into energy, might be responsible for the effects we attribute to dark energy:

    What happens to the gravity produced by the mass that is lost, when it’s converted by nuclear reactions in stars and goes out as light and neutrinos, or when mass accretes into a black hole, or when it’s converted into gravitational waves? […] In other words, are the gravitational waves and EM waves and neutrinos now a source of gravitation that exactly matches the prior mass that was converted, or not?

    This is a fascinating idea. Let’s take a look at why.

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    Artist’s illustration of two merging neutron stars. The rippling spacetime grid represents gravitational waves emitted from the collision, while the narrow beams are the jets of gamma rays that shoot out just seconds after the gravitational waves (detected as a gamma-ray burst by astronomers). Mass, in an event like this, gets converted into two types of radiation. NSF / LIGO / Sonoma State University / A. Simonnet

    In Einstein’s theory of General Relativity, there are only a few ways we can model the Universe that give us exact solutions. Make a Universe with nothing in it? We can describe spacetime exactly. Put down a single mass anywhere in that otherwise empty Universe? It’s much more complicated, but we can still write down a solution. Put down a second mass somewhere else in that Universe? It’s unsolvable. All you can do is make estimates, and try and arrive at a numerical answer. This maddeningly difficult property of spacetime, that it’s so hard to characterize exactly, is why it’s taken such tremendous computing power, theoretical work, and so much time in order to properly model the merging black holes and neutron stars that LIGO has seen.

    UC Santa Cruz

    UC Santa Cruz

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    A UC Santa Cruz special report

    Tim Stephens

    Astronomer Ryan Foley says “observing the explosion of two colliding neutron stars” [see https://sciencesprings.wordpress.com/2017/10/17/from-ucsc-first-observations-of-merging-neutron-stars-mark-a-new-era-in-astronomy ]–the first visible event ever linked to gravitational waves–is probably the biggest discovery he’ll make in his lifetime. That’s saying a lot for a young assistant professor who presumably has a long career still ahead of him.

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    The first optical image of a gravitational wave source was taken by a team led by Ryan Foley of UC Santa Cruz using the Swope Telescope at the Carnegie Institution’s Las Campanas Observatory in Chile. This image of Swope Supernova Survey 2017a (SSS17a, indicated by arrow) shows the light emitted from the cataclysmic merger of two neutron stars. (Image credit: 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

    A neutron star forms when a massive star runs out of fuel and explodes as a supernova, throwing off its outer layers and leaving behind a collapsed core composed almost entirely of neutrons. Neutrons are the uncharged particles in the nucleus of an atom, where they are bound together with positively charged protons. In a neutron star, they are packed together just as densely as in the nucleus of an atom, resulting in an object with one to three times the mass of our sun but only about 12 miles wide.

    “Basically, a neutron star is a gigantic atom with the mass of the sun and the size of a city like San Francisco or Manhattan,” said Foley, an assistant professor of astronomy and astrophysics at UC Santa Cruz.

    These objects are so dense, a cup of neutron star material would weigh as much as Mount Everest, and a teaspoon would weigh a billion tons. It’s as dense as matter can get without collapsing into a black hole.

    THE MERGER

    Like other stars, neutron stars sometimes occur in pairs, orbiting each other and gradually spiraling inward. Eventually, they come together in a catastrophic merger that distorts space and time (creating gravitational waves) and emits a brilliant flare of electromagnetic radiation, including visible, infrared, and ultraviolet light, x-rays, gamma rays, and radio waves. Merging black holes also create gravitational waves, but there’s nothing to be seen because no light can escape from a black hole.

    Foley’s team was the first to observe the light from a neutron star merger that took place on August 17, 2017, and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO).


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

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    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    Now, for the first time, scientists can study both the gravitational waves (ripples in the fabric of space-time), and the radiation emitted from the violent merger of the densest objects in the universe.

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    The UC Santa Cruz team found SSS17a by comparing a new image of the galaxy N4993 (right) with images taken four months earlier by the Hubble Space Telescope (left). The arrows indicate where SSS17a was absent from the Hubble image and visible in the new image from the Swope Telescope. (Image credits: Left, Hubble/STScI; Right, 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    It’s that combination of data, and all that can be learned from it, that has astronomers and physicists so excited. The observations of this one event are keeping hundreds of scientists busy exploring its implications for everything from fundamental physics and cosmology to the origins of gold and other heavy elements.


    A small team of UC Santa Cruz astronomers were the first team to observe light from two neutron stars merging in August. The implications are huge.

    ALL THE GOLD IN THE UNIVERSE

    It turns out that the origins of the heaviest elements, such as gold, platinum, uranium—pretty much everything heavier than iron—has been an enduring conundrum. All the lighter elements have well-explained origins in the nuclear fusion reactions that make stars shine or in the explosions of stars (supernovae). Initially, astrophysicists thought supernovae could account for the heavy elements, too, but there have always been problems with that theory, says Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz.

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    The violent merger of two neutron stars is thought to involve three main energy-transfer processes, shown in this diagram, that give rise to the different types of radiation seen by astronomers, including a gamma-ray burst and a kilonova explosion seen in visible light. (Image credit: Murguia-Berthier et al., Science)

    A theoretical astrophysicist, Ramirez-Ruiz has been a leading proponent of the idea that neutron star mergers are the source of the heavy elements. Building a heavy atomic nucleus means adding a lot of neutrons to it. This process is called rapid neutron capture, or the r-process, and it requires some of the most extreme conditions in the universe: extreme temperatures, extreme densities, and a massive flow of neutrons. A neutron star merger fits the bill.

    Ramirez-Ruiz and other theoretical astrophysicists use supercomputers to simulate the physics of extreme events like supernovae and neutron star mergers. This work always goes hand in hand with observational astronomy. Theoretical predictions tell observers what signatures to look for to identify these events, and observations tell theorists if they got the physics right or if they need to tweak their models. The observations by Foley and others of the neutron star merger now known as SSS17a are giving theorists, for the first time, a full set of observational data to compare with their theoretical models.

    According to Ramirez-Ruiz, the observations support the theory that neutron star mergers can account for all the gold in the universe, as well as about half of all the other elements heavier than iron.

    RIPPLES IN THE FABRIC OF SPACE-TIME

    Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity, but until recently they were impossible to observe. LIGO’s extraordinarily sensitive detectors achieved the first direct detection of gravitational waves, from the collision of two black holes, in 2015. Gravitational waves are created by any massive accelerating object, but the strongest waves (and the only ones we have any chance of detecting) are produced by the most extreme phenomena.

    Two massive compact objects—such as black holes, neutron stars, or white dwarfs—orbiting around each other faster and faster as they draw closer together are just the kind of system that should radiate strong gravitational waves. Like ripples spreading in a pond, the waves get smaller as they spread outward from the source. By the time they reached Earth, the ripples detected by LIGO caused distortions of space-time thousands of times smaller than the nucleus of an atom.

    The rarefied signals recorded by LIGO’s detectors not only prove the existence of gravitational waves, they also provide crucial information about the events that produced them. Combined with the telescope observations of the neutron star merger, it’s an incredibly rich set of data.

    LIGO can tell scientists the masses of the merging objects and the mass of the new object created in the merger, which reveals whether the merger produced another neutron star or a more massive object that collapsed into a black hole. To calculate how much mass was ejected in the explosion, and how much mass was converted to energy, scientists also need the optical observations from telescopes. That’s especially important for quantifying the nucleosynthesis of heavy elements during the merger.

    LIGO can also provide a measure of the distance to the merging neutron stars, which can now be compared with the distance measurement based on the light from the merger. That’s important to cosmologists studying the expansion of the universe, because the two measurements are based on different fundamental forces (gravity and electromagnetism), giving completely independent results.

    “This is a huge step forward in astronomy,” Foley said. “Having done it once, we now know we can do it again, and it opens up a whole new world of what we call ‘multi-messenger’ astronomy, viewing the universe through different fundamental forces.”

    IN THIS REPORT

    Neutron stars
    A team from UC Santa Cruz was the first to observe the light from a neutron star merger that took place on August 17, 2017 and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)

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    Graduate students and post-doctoral scholars at UC Santa Cruz played key roles in the dramatic discovery and analysis of colliding neutron stars.Astronomer Ryan Foley leads a team of young graduate students and postdoctoral scholars who have pulled off an extraordinary coup. Following up on the detection of gravitational waves from the violent merger of two neutron stars, Foley’s team was the first to find the source with a telescope and take images of the light from this cataclysmic event. In so doing, they beat much larger and more senior teams with much more powerful telescopes at their disposal.

    “We’re sort of the scrappy young upstarts who worked hard and got the job done,” said Foley, an untenured assistant professor of astronomy and astrophysics at UC Santa Cruz.

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    David Coulter, graduate student

    The discovery on August 17, 2017, has been a scientific bonanza, yielding over 100 scientific papers from numerous teams investigating the new observations. Foley’s team is publishing seven papers, each of which has a graduate student or postdoc as the first author.

    “I think it speaks to Ryan’s generosity and how seriously he takes his role as a mentor that he is not putting himself front and center, but has gone out of his way to highlight the roles played by his students and postdocs,” said Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz and the most senior member of Foley’s team.

    “Our team is by far the youngest and most diverse of all of the teams involved in the follow-up observations of this neutron star merger,” Ramirez-Ruiz added.

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    Charles Kilpatrick, postdoctoral scholar

    Charles Kilpatrick, a 29-year-old postdoctoral scholar, was the first person in the world to see an image of the light from colliding neutron stars. He was sitting in an office at UC Santa Cruz, working with first-year graduate student Cesar Rojas-Bravo to process image data as it came in from the Swope Telescope in Chile. To see if the Swope images showed anything new, he had also downloaded “template” images taken in the past of the same galaxies the team was searching.

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    Ariadna Murguia-Berthier, graduate student

    “In one image I saw something there that was not in the template image,” Kilpatrick said. “It took me a while to realize the ramifications of what I was seeing. This opens up so much new science, it really marks the beginning of something that will continue to be studied for years down the road.”

    At the time, Foley and most of the others in his team were at a meeting in Copenhagen. When they found out about the gravitational wave detection, they quickly got together to plan their search strategy. From Copenhagen, the team sent instructions to the telescope operators in Chile telling them where to point the telescope. Graduate student David Coulter played a key role in prioritizing the galaxies they would search to find the source, and he is the first author of the discovery paper published in Science.

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    Matthew Siebert, graduate student

    “It’s still a little unreal when I think about what we’ve accomplished,” Coulter said. “For me, despite the euphoria of recognizing what we were seeing at the moment, we were all incredibly focused on the task at hand. Only afterward did the significance really sink in.”

    Just as Coulter finished writing his paper about the discovery, his wife went into labor, giving birth to a baby girl on September 30. “I was doing revisions to the paper at the hospital,” he said.

    It’s been a wild ride for the whole team, first in the rush to find the source, and then under pressure to quickly analyze the data and write up their findings for publication. “It was really an all-hands-on-deck moment when we all had to pull together and work quickly to exploit this opportunity,” said Kilpatrick, who is first author of a paper comparing the observations with theoretical models.

    11
    César Rojas Bravo, graduate student

    Graduate student Matthew Siebert led a paper analyzing the unusual properties of the light emitted by the merger. Astronomers have observed thousands of supernovae (exploding stars) and other “transients” that appear suddenly in the sky and then fade away, but never before have they observed anything that looks like this neutron star merger. Siebert’s paper concluded that there is only a one in 100,000 chance that the transient they observed is not related to the gravitational waves.

    Ariadna Murguia-Berthier, a graduate student working with Ramirez-Ruiz, is first author of a paper synthesizing data from a range of sources to provide a coherent theoretical framework for understanding the observations.

    Another aspect of the discovery of great interest to astronomers is the nature of the galaxy and the galactic environment in which the merger occurred. Postdoctoral scholar Yen-Chen Pan led a paper analyzing the properties of the host galaxy. Enia Xhakaj, a new graduate student who had just joined the group in August, got the opportunity to help with the analysis and be a coauthor on the paper.

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    Yen-Chen Pan, postdoctoral scholar

    “There are so many interesting things to learn from this,” Foley said. “It’s a great experience for all of us to be part of such an important discovery.”

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    Enia Xhakaj, graduate student

    IN THIS REPORT

    Scientific Papers from the 1M2H Collaboration

    Coulter et al., Science, Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source

    Drout et al., Science, Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis

    Shappee et al., Science, Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger

    Kilpatrick et al., Science, Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger

    Siebert et al., ApJL, The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational-wave Source

    Pan et al., ApJL, The Old Host-galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational-wave Source

    Murguia-Berthier et al., ApJL, A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a

    Kasen et al., Nature, Origin of the heavy elements in binary neutron star mergers from a gravitational wave event

    Abbott et al., Nature, A gravitational-wave standard siren measurement of the Hubble constant (The LIGO Scientific Collaboration and The Virgo Collaboration, The 1M2H Collaboration, The Dark Energy Camera GW-EM Collaboration and the DES Collaboration, The DLT40 Collaboration, The Las Cumbres Observatory Collaboration, The VINROUGE Collaboration & The MASTER Collaboration)

    Abbott et al., ApJL, Multi-messenger Observations of a Binary Neutron Star Merger

    PRESS RELEASES AND MEDIA COVERAGE


    Watch Ryan Foley tell the story of how his team found the neutron star merger in the video below. 2.5 HOURS.

    Press releases:

    UC Santa Cruz Press Release

    UC Berkeley Press Release

    Carnegie Institution of Science Press Release

    LIGO Collaboration Press Release

    National Science Foundation Press Release

    Media coverage:

    The Atlantic – The Slack Chat That Changed Astronomy

    Washington Post – Scientists detect gravitational waves from a new kind of nova, sparking a new era in astronomy

    New York Times – LIGO Detects Fierce Collision of Neutron Stars for the First Time

    Science – Merging neutron stars generate gravitational waves and a celestial light show

    CBS News – Gravitational waves – and light – seen in neutron star collision

    CBC News – Astronomers see source of gravitational waves for 1st time

    San Jose Mercury News – A bright light seen across the universe, proving Einstein right

    Popular Science – Gravitational waves just showed us something even cooler than black holes

    Scientific American – Gravitational Wave Astronomers Hit Mother Lode

    Nature – Colliding stars spark rush to solve cosmic mysteries

    National Geographic – In a First, Gravitational Waves Linked to Neutron Star Crash

    Associated Press – Astronomers witness huge cosmic crash, find origins of gold

    Science News – Neutron star collision showers the universe with a wealth of discoveries

    UCSC press release
    First observations of merging neutron stars mark a new era in astronomy

    Credits

    Writing: Tim Stephens
    Video: Nick Gonzales
    Photos: Carolyn Lagattuta
    Header image: Illustration by Robin Dienel courtesy of the Carnegie Institution for Science
    Design and development: Rob Knight
    Project managers: Sherry Main, Scott Hernandez-Jason, Tim Stephens

    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 at an altitude of 7200 feet

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    Noted in the vdeo but not in te article:

    NASA/Chandra Telescope

    NASA/SWIFT Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    Prompt telescope CTIO Chile

    NASA NuSTAR X-ray telescope

    See the full article UCSC article here

    3
    It isn’t just the locations and magnitudes of masses that determine how gravity works and spacetime evolves, but rather how those masses move relative to one another and accelerate through a changing gravitational field over time. In General Relativity, a system with more than one mass is not exactly solvable. David Champion, Max Planck Institute for Radio Astronomy

    One of the few cases we can solve exactly is where the Universe is filled with an even amount of “stuff” everywhere and in all directions. It doesn’t matter what that “stuff” is. It could be a collection of particles, a fluid, radiation, a property inherent to space itself, or a field with the right properties. It could be a mix of a bunch of different things, such as normal matter, antimatter, neutrinos, radiation, and even the mysterious dark matter and dark energy.

    If this describes your Universe, and you know how much of each of these different quantities there are, all you need to do is measure the expansion rate of the Universe. Do that, and you immediately know how the Universe expanded over its entire history, including its future history. If you know what the Universe is made of and how it’s expanding today, you can figure out the fate of the entire Universe.

    4
    The expected fates of the Universe (top three illustrations) all correspond to a Universe where the matter and energy fights against the initial expansion rate. In our observed Universe, a cosmic acceleration is caused by some type of dark energy, which is hitherto unexplained. All of these Universes are governed by the Friedmann equations. E. Siegel / Beyond the Galaxy

    When we do this figuring based on the Universe we observe today, we arrive at a Universe that’s made of:

    68% dark energy,
    27% dark matter,
    4.9% normal matter,
    0.1% neutrinos,
    0.01% radiation,

    and a negligible amount of everything else: curvature, antimatter, cosmic strings, and anything else you can imagine. The total uncertainty on all of these, combined, is less than 2%. We also learn the fate of the Universe — that it will expand forever — and the age of the Universe: 13.8 billion years since the Big Bang. It’s a remarkable achievement of modern cosmology.

    4
    An illustrated timeline of the Universe’s history. If the value of dark energy is small enough to admit the formation of the first stars, then a Universe containing the right ingredients for life is pretty much inevitable. We are, thankfully, here to confirm that this occurred where we live. European Southern Observatory (ESO)

    But this assumes that we can approximate the Universe the way we modeled it: with a smooth, even amount of stuff everywhere and in all directions. The real Universe, as you probably noticed, is clumpy. There are planets, stars, clumps of gas and dust, plasmas, galaxies, clusters of galaxies and great cosmic filaments connecting them. There are enormous cosmic voids, sometimes stretching billions of light years across. The mathematical word for a perfectly smooth Universe is homogeneous, and yet our Universe is remarkably inhomogeneous. It’s possible that our assumption that led us to this conclusion is all wrong.

    5
    Both simulations (red) and galaxy surveys (blue/purple) display the same large-scale clustering patterns. The Universe, particularly on smaller scales, is not perfectly homogeneous.
    Gerard Lemson and the Virgo Consortium

    On the largest scales, though, the Universe is homogeneous. If you look at a small scale, like that of a star, galaxy, or even a cluster of galaxies, you’ll find that you have regions that are both way below and way above the average density. But if you look at scales that are closer to 10 billion light years (or more) on a side, the Universe appears roughly the same everywhere, on average. On the largest scales, the Universe is over 99% homogeneous.

    Thankfully, we can quantify how good (or not good) our assumption is by calculating the effects of the inhomogeneities atop this large-scale homogeneous background. I did this for myself back in 2005, and found that the inhomogeneities contribute less than 0.1% to the expansion rate, and they don’t behave like dark energy. You can see this for yourself if you like.

    6
    Fractional contributions of gravitational potential energy W (long-dashed line) and kinetic energy K (solid line) to the total energy density of the universe, plotted as a function of past and future expansion factor for a Universe with matter but no dark energy. The short-dashed line is the sum of contributions from inhomogeneities. The dotted lines show results from linear perturbation theory. E.R. Siegel and J.N. Fry, ApJ, 628, 1, L1-L4.

    But a related possibility is that certain types of energy can transform from one type into another over time. In particular, owing to the

    burning of nuclear fuel inside stars,
    gravitational collapse of clouds into contracted objects,
    mergers of neutron stars and black holes,
    and the inspiraling action of many gravitational systems,

    matter, or mass, can transform into radiation, or energy. In other words, it’s possible to change how the Universe gravitates, and therefore, how it expands (or contracts) over time.

    7
    Although we’ve seen black holes directly merging many separate times in the Universe, we know many more exist. When supermassive black holes merge together, LISA will allow us to predict, up to years in advance, exactly when the critical event will occur. LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

    When two black holes merge together, for example, a significant fraction of mass can be converted into energy: up to about 5%. In the first black hole-black hole merger detected by LIGO, a black hole of 36 solar masses and a black hole of 29 solar masses merged together, but produced a single black hole whose final mass was only 62 solar masses. What happened to the other 3 solar masses? They were converted into pure energy, in the form of gravitational waves, by Einstein’s E = mc2.

    The question, then, becomes how a change from mass into radiation affects the expansion of the Universe? According to a recent paper by Nick Gorkavyi and Alexander Vasilkov, they claim that it can generate a repulsive, anti-gravitational force.

    8
    Computer simulation of two merging black holes producing gravitational waves. When mass converts into radiation, is it possible that we can generate a repulsive force? Werner Benger, cc by-sa 4.0

    Unfortunately, this claim is based in what only appears to be anti-gravity. When you have a certain amount of mass, you experience a certain amount of gravitational attraction towards that mass: this is equally true in both Einstein’s and Newton’s theory of gravity. If you transform that mass into energy and it radiates outward at the speed of light, like all massless radiation, then when that radiation passes by you, you’ll suddenly see less mass to be attracted to.

    The curvature of spacetime changes, and where you once experienced gravitational attraction of a certain amount, you’ll now experience attraction that’s 5% less. It’s equivalent, mathematically, to adding a repulsive, anti-gravitational force to your system. But in reality, you’re experiencing the reduced attraction because you turned mass into energy, and radiation gravitates differently (especially once it passes you by) than matter does.. This has been stated quite clearly.

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    Any object or shape, physical or non-physical, would be distorted as gravitational waves passed through it. Whenever one large mass is accelerated through a region of curved spacetime, gravitational wave emission is an inevitable consequence. However, we can compute the effects of this radiation on space, and it doesn’t cause a repulsion or an accelerated expansion. NASA/Ames Research Center/C. Henze

    In fact, we can go a step further and calculate how this transformation affects the entire Universe! We can quantify both how gravitational waves contribute to the energy density of the Universe and how much of the Universe’s energy is in the form of radiation of all types. Like mass, radiation is quantized, so that as the volume of the Universe increases (by a factor of distance cubed), the particle density decreases (by a factor of one over the distance cubed). But unlike mass, radiation has a wavelength, and as space expands, that wavelength drops as one over the distance as well; radiation becomes less gravitationally important faster than matter does.

    Another thing that you’d need to do is have the correct equation-of-state. Matter and radiation both evolve over time as stated above, but dark energy keeps a constant density throughout all of space as the Universe expands. As we move forward in time, this problem only gets worse; dark energy becomes more dominant while matter and radiation both become less and less important.

    Not only do matter and radiation both result in an attractive force and a decelerating Universe, but neither one can come to dominate the energy density of the Universe so long as it keeps expanding.

    10
    The blue “shading” represent the possible uncertainties in how the dark energy density was/will be different in the past and future. The data points to a true cosmological “constant,” but other possibilities are still allowed. Unfortunately, the conversion of matter into radiation cannot mimic dark energy; it can only cause what was once behaving as matter to now behave as radiation. Quantum Stories.

    If you want to create a Universe where you have an accelerated expansion, to the best of our knowledge, you require a new form of energy over the ones we presently know about. We have given a name to it, dark energy, even though we aren’t 100% sure what the nature of dark energy truly is.

    However, despite our ignorance in that realm, we can very clearly state what dark energy isn’t. It isn’t stars burning through their fuel; it isn’t matter emitting gravitational waves; it isn’t due to gravitational collapse; it isn’t due to mergers or inspirals. It’s possible that there’s a new law of gravity that will eventually replace Einstein, but in the context of General Relativity, there’s no way to explain what we observe with the physics we know today. There’s something truly new to discover out there.

    See the full article here .


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

     
  • richardmitnick 2:32 pm on June 22, 2018 Permalink | Reply
    Tags: A SINFONI of Exoplanets, , , , Cosmology,   

    From ESOblog: “A SINFONI of Exoplanets” 

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    From ESOblog

    1
    Science Snapshots

    22 June 2018

    Exoplanets have fast become a huge research area and astronomers are now trying to study their atmospheres. The possibility of finding an exoplanet with an atmosphere that may be able to support life is incredibly exciting. We spoke to Jens Hoeijmakers, from the Geneva Observatory and the Center for Space Habitability in Bern, Switzerland, to find out more about these distant worlds.

    Q: Let’s start simple: what is an exoplanet?

    A: Since 1995, we have known that many stars other than the Sun have their own “solar systems,” with the majority of stars hosting one or multiple planets. Exoplanetary systems come in all shapes and colours, meaning that they are very diverse. Astronomers have discovered planets ranging from gas giants to smaller, rocky planets. Some planets orbit far away from their star like the gas and ice giants in our Solar System, and some orbit very closely, with surface temperatures greater than 1000°C.

    Q: Why do you think it’s important and exciting to study exoplanets?

    A: The discovery of the existence of exoplanets has evolved as a major branch of astronomy in the past two decades. We now know of the existence of thousands of exoplanets, and this has shown that planets may even be more common than stars in our Universe! This ubiquitous presence of planets all around us begs the question of whether it’s possible for extraterrestrial life to exist. This is a major driving force behind the continued search for exoplanets and the detailed study of those that we’ve already discovered. But besides the exciting prospect of discovering life, the exoplanet population also gives us a unique window into understanding our own Solar System and the possible outcomes of the same planet formation processes that have made our Solar System the way that we see it today — essentially, studying exoplanets can help us understand how we got to be here.

    2
    This composite image represents the close environment of Beta Pictoris as seen in near-infrared light. A very careful subtraction of the much bright stellar halo reveals this very faint environment. The outer part of the image shows the reflected light on the dust disc, as observed with ADONIS on ESO 3.6-metre telescope. The inner part is the innermost part of the system, as seen with NACO on the Very Large Telescope.
    Credit: ESO/A.-M. Lagrange et al.

    3
    ADONIS Infrared Cameras

    ESO/NACO

    Q: Your research looked at one exoplanet in particular: Beta Pictoris b. Why did you choose to look at this system?

    A: Beta Pictoris b is maybe the most famous directly-imaged exoplanet, meaning that astronomers have managed to actually take a snapshot of the planet rather than infer its existence through its indirect effect on its star, as is most commonly done. Beta Pictoris b orbits a bright star about 70 light-years away from Earth, is in a system about 20 to 25 million years old and has a fairly hot surface, about 1700°C.

    Beta Pictoris b is one of the easier (but still challenging) planets to image directly because it’s young and hot enough to be observed at infrared wavelengths. When stars and planets form in a large disk of gas and dust, known as the protoplanetary disk, the material from which the planets form is very hot. This means that newborn planets start off with very high temperatures, and throughout the first tens of millions of years of their lives, they slowly cool down as they radiate this heat away, making these planets visible at infrared wavelengths. This is the class of planets that we can directly image, and Beta Pictoris b is a typical example of such a young planet, which is why we chose to observe it — and, indeed, why it is one of the most famous directly imaged exoplanets.

    Q: How did you observe Beta Pictoris b and what were you aiming to find?

    A: We used existing data of the planet from the SINFONI spectrograph on ESO’s Very Large Telescope located at the Paranal Observatory in Chile. Our aim was actually to test out the instrument — to investigate to what extent an adaptive-optics-assisted integral field spectrograph like SINFONI can be used to study an exoplanet’s atmosphere.

    ESO/SINFONI

    SINFONI is a special instrument. Not only does it perform the high-contrast imaging necessary to separately image the planet from its brighter host star, but it also simultaneously generates a spectrum of each pixel in that image at a high enough resolution. This allows us to see absorption lines in the spectrum of the planet. These absorption lines are what tell us about the chemicals in the planet’s atmosphere, and also about the planet’s temperature and other physical parameters. In fact, our new technique relies on the fact that the planet’s spectrum has absorption lines that are not present in the star that it orbits. This helps us disentangle the planet from its much brighter star, effectively increasing the contrast on top of the already high-contrast imaging from SINFONI. The instrument was not actually designed to be used in this way, so we’re the first to apply this technique.

    The only other instrument in the world that can currently perform this type of research is the OSIRIS spectrograph at the Keck Observatory in Hawaii.

    UCO Keck OSIRIS being installed

    It is very similar to SINFONI but is located at a much more northern latitude, meaning that SINFONI and OSIRIS can access complementary parts of the sky.

    3
    Molecular maps of carbon dioxide (left) and water (right) around Beta Pictoris. Beta Pictoris b is starkly visible in the lower right side of both maps. The left-side scale is the y-position and the bottom-side scale is the x-position. The scale is in arcseconds. Credit: J. Hoeijmakers.

    4
    Yepun, the fourth Unit Telescope of the VLT, is angled at a very low altitude, revealing the cell holding its main mirror and the SINFONI integral-field spectrograph.
    Credit: ESO

    Q: So what did you and your team find out?

    A: First of all, our analysis of the existing dataset confidently shows the presence of water and carbon monoxide in the atmosphere of Beta Pictoris b. This in itself is not a new result because both species were known (and expected) to be present. However, it is the first time that a high-contrast imaging instrument has been used to directly detect these absorption lines in an exoplanet’s atmosphere, thereby uniquely and robustly confirming their presence.

    Q: Did you face any challenges during your research?

    A: Our analysis was quite challenging because these observations were experimental. SINFONI is not tuned for these kinds of observations, so when the data was initially taken in 2014, it was quickly deemed too challenging even for the detection of the planet, let alone a measurement of its spectrum. In the case of this dataset, our method is more sensitive to the planet, but we also had to overcome the fact that the instrument is simply not designed to image a very faint planet next to a very bright star. This is why we strongly advocate that future, SINFONI-like instruments (such as the planned HARMONI instrument on ESO’s Extremely Large Telescope) should be outfitted with a coronagraph, which blocks out much of the starlight, making such observations even more powerful.

    5
    This composite image shows the movement of Beta Pictoris b around its star, observed by the NACO on the VLT over six years.
    Credit: ESO/A.-M. Lagrange

    Q: What do you personally find most exciting about this research?

    A: This is a clear example of using an existing dataset and instrument in a completely new way and finding exciting results. I think that there is no reason why the same analysis and observations couldn’t have been carried out 10 years ago, achieving the same results — and something similar is true for the entire field of exoplanets! The first exoplanets could have been discovered with technology that was already available over a decade earlier if only astronomers had taken the possibility of the existence of hot Jupiters seriously. That’s why I sometimes wonder what other new discoveries or applications of existing facilities are still hiding under our noses right now.

    Q: What might this research lead to in the future? And what are the next big steps in the field?

    A: The strength of our signal spells good news for the future, when new instruments will come online that are similar to SINFONI but much more powerful in terms of contrast and spectral resolution. For instance, our result came from over two hours of observations with SINFONI, but we calculated that the same result could be obtained using the Extremely Large Telescope in only 90 seconds — for a planet like Beta Pictoris that is five times closer to its host star! In this sense, our result is a clear demonstration of this analysis technique and should encourage ongoing development of these future instruments, especially for making them suitable for the high-contrast imaging of exoplanets.

    See the full article here .


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

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    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 3:29 pm on June 21, 2018 Permalink | Reply
    Tags: ALMA Discover Exciting Structures in a Young Protoplanetary Disk That Support Planet Formation, , , , Cosmology, ,   

    From ALMA: “ALMA Discover Exciting Structures in a Young Protoplanetary Disk That Support Planet Formation” 

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    From ALMA

    20 June, 2018

    Ruobing Dong
    Steward Observatory, University of Arizona, USA
    Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
    +1 609 423 5625
    rbdong@gmail.com

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    nicolas.lira@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    +81 422 34 3630
    hiramatsu.masaaki@nao.ac.jp

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Phone: +1 434 296 0314
    Cell phone: +1 202 236 6324
    cblue@nrao.edu

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Phone: +49 89 3200 6655
    Cell phone: +49 151 1537 3591
    rhook@eso.org

    1
    ALMA image of the 0.87 mm continuum emission from the MWC 758 disk. Credit: ALMA (ESO/NAOJ/NRAO)/Dong et al.

    Since early 2000, rich structures, including gaps and rings, dust clumps, and spiral arm-like features, have been discovered in a few tens of disks surrounding newborn stars. With the belief that planets are forming inside, astronomers named these disks protoplanetary disks.

    The origin of these structures is in hot debate among astronomers. In one scenario, they are thought to be produced by unseen planets forming inside and gravitationally interacting with the host disks, as planets open gaps, shepherd dust clumps, and excite spiral arms.

    Alternative ways to produce observed disk structures that do not invoke planets have also been raised. For examples, large central cavities may be the outcome of photoevaporation, as high energy radiations from the central star evaporate the inner disk. Also, under certain conditions shadows in disks may mimic the spiral arms seen in reflected light.

    The protoplanetary disk around a young star MWC 758 is located at 500 light years from us. In 2012, a pair of near symmetric giant spiral arms was discovered in reflected light. In dust thermal and molecular gas line emission at millimeter wavelengths, a big inner hole and two major dust clumps have been found, too.

    Now with the new ALMA image, the previously known cavity of MWC 758 is shown to be off-centered from the star with its shape well described by an ellipse with one focus on the star. Also, a millimeter dust emission feature corresponds nicely with one of the two spiral arms previously seen in reflected light. Both discoveries are the first among protoplanetary disks.

    “MWC 758 is a rare breed!”, says Sheng-Yuan Liu at ASIAA, co-author of this study, “All major types of disk structures have been found in this system. It reveals to us one of the most comprehensive suites of evidence of planet formation in all protoplanetary disks.”

    Previously in 2015, Dr. Dong and his collaborators proposed that the two arms in the MWC 758 disk can be explained as driven by a super-Jupiter planet just outside the disk.

    “Our new ALMA observations lend crucial support to planet-based origins for all the structures.”, says Dr. Takayuki Muto at Kogakuin University, Japan, co-author of this research, “For example, it’s exciting to see ellipses with one focus on the star. That’s Kepler’s first law! It’s pointing to a dynamical origin, possibly interacting with planets.”

    The off-centered cavity strongly, on the other hand, disfavors alternative explanations such as photoevaporation, which does not have an azimuthal dependence.

    2
    Various disk structures are marked. The green dotted contours mark the boundaries of the disk; the small circle at the center roughly marks the location of the star; the two green solid contours represent the extent of the two bright clumps; the solid, dotted and dashed white arcs trace out the inner, middle, and outer rings, respectively; and the arrow points out the spiral arm. The resolution (beam size, ~6.5 AU) of the image is labeled at the lower left corner. Credit: ALMA (ESO/NAOJ/NRAO)/Dong et al.

    The fact that the south spiral branch is present in the millimeter emission tracing the dust rules that it’s a density arm. Other scenarios, such as shadows, which view the spiral arms as surface features, are not expected to reproduce the observations. The ultra-high resolution achieved in the new ALMA dataset also enables the detection of a slight offset between the arm locations in reflected light and in dust emission, which is consistent with models of planet-induced density wave.

    “These fantastic new details are only made possible thanks to the amazing angular resolution delivered by ALMA”, says co-author Eiji Akiyama at Hokkaido University, Japan, “We took full advantage of ALMA’s long baseline capabilities, and now the MWC 758 disk joins the elite club of ultra-high-resolution ALMA disks alongside only a handful of others.”

    Additional information

    This research was presented in a paper “The Eccentric Cavity, Triple Rings, Two-Armed Spirals, and Double Clumps of the MWC 758 Disk” by Dong et al. to appear in The Astrophysical Journal.

    The team is composed of Ruobing Dong (U. of Arizona, USA; ASIAA, Taiwan), Sheng-yuan Liu (ASIAA, Taiwan), Josh Eisner (University of Arizona, USA), Sean Andrews (Harvard-Smithsonian Center for Astrophysics, USA), Jeffrey Fung (UC Berkeley, USA), Zhaohuan Zhu (UNLV, USA) Eugene Chiang (UC Berkeley, USA), Jun Hashimoto (Astrobiology Center, NINS, Japan), Hauyu Baobab Liu (European Southern Observatory, Germany), Simon Casassus (University of Chile, Chile), Thomas Esposito (UC Berkeley, USA), Yasuhiro Hasegawa (JPL/Caltech, USA), Takayuki Muto (Kogakuin University, Japan), Yaroslav Pavlyuchenkov (Russian Academy of Sciences, Russia), David Wilner (Harvard-Smithsonian Center for Astrophysics, USA), Eiji Akiyama (Hokkaido University, Japan), Motohide Tamura (The University of Tokyo; Astrobiology Center, NINS, Japan), and John Wisniewski (U. of Oklahoma, USA).

    See the full article here .


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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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  • richardmitnick 2:22 pm on June 21, 2018 Permalink | Reply
    Tags: 'Red Nuggets' are Galactic Gold for Astronomers, , , , Cosmology,   

    From NASA Chandra: “‘Red Nuggets’ are Galactic Gold for Astronomers” 

    NASA Chandra Banner

    NASA/Chandra Telescope


    From NASA Chandra

    June 21, 2018

    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    1
    Credit: X-ray: NASA/CXC/MTA-Eötvös University/N. Werner et al.; Illustration: NASA/CXC/M.Weiss
    Press Image, Caption, and Videos

    The central black holes may be the driving force in how much star formation occurs in a certain type of rare galaxy.

    ‘Red nuggets’ are the relics of the first massive galaxies that formed within a billion years after the Big Bang.

    While most red nuggets merged with other galaxies, some remained untouched throughout the history of the Universe.

    Astronomers used Chandra to learn more about how the black holes in these galaxies affect star formation.

    About a decade ago, astronomers discovered a population of small, but massive galaxies called “red nuggets.” A new study using NASA’s Chandra X-ray Observatory indicates that black holes have squelched star formation in these galaxies and may have used some of the untapped stellar fuel to grow to unusually massive proportions.

    Red nuggets were first discovered by the Hubble Space Telescope at great distances from Earth, corresponding to times only about three or four billion years after the Big Bang. They are relics of the first massive galaxies that formed within only one billion years after the Big Bang. Astronomers think they are the ancestors of the giant elliptical galaxies seen in the local Universe. The masses of red nuggets are similar to those of giant elliptical galaxies, but they are only about a fifth of their size.

    While most red nuggets merged with other galaxies over billions of years, a small number managed to slip through the long history of the cosmos untouched. These unscathed red nuggets represent a golden opportunity to study how the galaxies, and the supermassive black hole at their centers, act over billions of years of isolation.

    For the first time, Chandra has been used to study the hot gas in two of these isolated red nuggets, MRK 1216, and PGC 032673. They are located only 295 million and 344 million light years from Earth respectively, rather than billions of light years for the first known red nuggets. This X-ray emitting hot gas contains the imprint of activity generated by the supermassive black holes in each of the two galaxies.

    “These galaxies have existed for 13 billion years without ever interacting with another of its kind,” said Norbert Werner of MTA-Eötvös University Lendület Hot Universe and Astrophysics Research Group in Budapest, Hungary, who led the study. “We are finding that the black holes in these galaxies take over and the result is not good for new stars trying to form.”

    Astronomers have long known that the material falling towards black holes can be redirected outward at high speeds due to intense gravitational and magnetic fields. These high-speed jets can tamp down the formation of stars. This happens because the blasts from the vicinity of the black hole provide a powerful source of heat, preventing the galaxy’s hot interstellar gas from cooling enough to allow large numbers of stars to form.

    The temperature of the hot gas is higher in the center of the MRK 1216 galaxy compared to its surroundings, showing the effects of recent heating by the black hole. Also, radio emission is observed from the center of the galaxy, a signature of jets from black holes. Finally, the X-ray emission from the vicinity of the black hole is about a hundred million times lower than a theoretical limit on how fast a black hole can grow — called the “Eddington limit” — where the outward pressure of radiation is balanced by the inward pull of gravity. This low level of X-ray emission is typical for black holes producing jets. All these factors provide strong evidence that activity generated by the central supermassive black holes in these red nugget galaxies is suppressing the formation of new stars.

    The black holes and the hot gas may have another connection. The authors suggest that much of the black hole mass may have accumulated from the hot gas surrounding both galaxies. The black holes in both MRK 1216 and PGC 032873 are among the most massive known, with estimated masses of about five billion times that of the Sun, based on optical observations of the speeds of stars near the galaxies’ centers. Furthermore, the masses of the MRK 1216 black hole and possibly the one in PGC 032873 are estimated to be a few percent of the combined masses of all the stars in the central regions of the galaxies, whereas in most galaxies, the ratio is about ten times less.

    In the latest research, astronomers used Chandra to study the hot gas in two of these isolated red nuggets, Mrk 1216, and PGC 032673. (The Chandra data, colored red, of Mrk 1216 is shown in the inset.) These two galaxies are located only 295 million and 344 million light years from Earth respectively, rather than billions of light years for the first known red nuggets, allowing for a more detailed look. The gas in the galaxy is heated to such high temperatures that it emits brightly in X-ray light, which Chandra detects. This hot gas contains the imprint of activity generated by the supermassive black holes in each of the two galaxies.

    An artist’s illustration (main panel) shows how material falling towards black holes can be redirected outward at high speeds due to intense gravitational and magnetic fields. These high-speed jets can tamp down the formation of stars. This happens because the blasts from the vicinity of the black hole provide a powerful source of heat, preventing the galaxy’s hot interstellar gas from cooling enough to allow large numbers of stars to form.

    “Apparently, left to their own devices, black holes can act a bit like a bully,” said co-author Kiran Lakhchaura, also of MTA-Eötvös University.

    “Not only do they prevent new stars from forming,” said co-author Massimo Gaspari, an Einstein fellow from Princeton University, “they may also take some of that galactic material and use it to feed themselves.”

    In addition, the hot gas in and around PGC 032873 is about ten times fainter than the hot gas around MRK 1216. Because both galaxies appear to have evolved in isolation over the past 13 billion years, this difference might have arisen from more ferocious outbursts from PGC 032873’s black hole in the past, which blew most of the hot gas away.

    “The Chandra data tell us more about what the long, solitary journey through cosmic time has been like for these red nugget galaxies,” said co-author Rebecca Canning of Stanford University. “Although the galaxies haven’t interacted with others, they’ve shown plenty of inner turmoil.”

    A paper describing these results in the latest issue of the Monthly Notices of the Royal Astronomical Society. The authors of the paper are Norbert Werner (MTA-Eötvös University Lendület Hot Universe and Astrophysics Research Group in Budapest, Hungary), Kiran Lakhchaura (MTA-Eötvös University), Rebecca Canning (Stanford University), Massimo Gaspari (Princeton University), and Aurora Simeonescu (ISAS/JAXA).

    See the full article here .


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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 4:34 pm on June 20, 2018 Permalink | Reply
    Tags: , , , , Cosmology, Exploring Jets from a Supermassive Black Hole   

    From AAS NOVA: “Exploring Jets from a Supermassive Black Hole” 

    AASNOVA

    From AAS NOVA

    1
    The double-sided jets of the active galaxy NGC 4261, shown here in this composite optical (white) and radio (orange) image, span around 88,000 light-years across. A new study explores the structure and properties of these jets. [HST/NASA/ESA/NRAO]

    What are the feeding — and burping — habits of the supermassive black holes peppering the universe? In a new study, observations of one such monster reveal more about the behavior of its powerful jets.

    Beams from Behemoths

    Across the universe, supermassive black holes of millions to billions of solar masses lie at the centers of galaxies, gobbling up surrounding material. But not all of the gas and dust that spirals in toward a black hole is ultimately swallowed! A large fraction of it can instead be flung out into space again, in the form of enormous, powerful jets that extend for thousands or even millions of light-years in opposite directions.

    2
    Messier 87, shown in this Hubble image, is a classic example of a nearby (55 million light-years distant) supermassive black hole with a visible, collimated jet. Its counter-jet isn’t seen because relativistic effects make the receding jet appear less bright. [The Hubble Heritage Team (STScI/AURA) and NASA/ESA]

    What causes these outflows to be tightly beamed — collimated — in the form of jets, rather than sprayed out in all directions? Does the pressure of the ambient medium — the surrounding gas and dust that the jet is injected into — play an important role? In what regions do these jets accelerate and decelerate? There are many open questions that scientists hope to understand by studying some of the active black holes with jets that live closest to us.

    Eyes on a Nearby Giant

    In a new study led by Satomi Nakahara (The Graduate University for Advanced Studies in Japan), a team of scientists has used multifrequency Very Long Baseline Array (VLBA) and Very Large Array (VLA) images to explore jets emitted from a galaxy just 100 million light-years away: NGC 4261.

    NRAO/VLBA

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    This galaxy’s (relatively) close distance — as well as the fact that we’re viewing it largely from the side, so we can clearly see both of its polar jets — allows us to observe in detail the structure and intensity of its jets as a function of their distance from the black hole. Nakahara and collaborators’ observations span the enormous radial distance of a thousand to a billion times the radius of the black hole, or about 54 light-days to more than a million light-years.

    3
    The width of the jet as a function of radial distance from the black hole, for NGC 4261 (red) compared to the few other jets from nearby supermassive black holes that we’ve measured. NGC 4261’s jets transition from parabolic to conical at around 10,000 times the radius of the black hole (RS). [Nakahara et al. 2018]

    Scale for Change

    The authors’ observations of NGC 4261’s jets indicate that a transition occurs at ~10,000 times the radius of the black hole (that’s a little over a light-year from the black hole). At this point, the jets’ structures change from parabolic (becoming more tightly beamed) to conical (expanding freely). Around the same location, Nakahara and collaborators also see the radiation profile of one of the jets change, suggesting the physical conditions in the jets transition here as well.

    This is the first time we’ve been able to examine jet width this closely for both of the jets emitted from a supermassive black hole. The fact that the structure changes at the same distance for both jets indicates that the shape of these powerful streams is likely governed by global properties of the environment surrounding the galaxy’s nucleus, or properties of the jets themselves, rather than by a local condition.

    The authors next hope to pin down velocities inside NGC 4261’s jets to determine where the jets accelerate and decelerate. This nearby powerhouse is clearly going to be a useful laboratory in the future, helping to unveil the secrets of more distant, feeding monsters.

    Bonus

    Curious what these hungry supermassive black holes look like? Check out this artist’s imagining of NGC 4261, which shows how it feeds from a large, swirling accretion disk and emits fast-moving, collimated jets. [Original video credit to Dana Berry, Space Telescope Science Institute]

    Citation

    Satomi Nakahara et al 2018 ApJ 854 148. http://iopscience.iop.org/article/10.3847/1538-4357/aaa45e/meta The Astrophysical Journal

    Related journal articles
    _________________________________________________
    See the full article for further references with links.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 2:19 pm on June 20, 2018 Permalink | Reply
    Tags: , , , Cosmology, , The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes   

    From Ethan Siegel: “The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes” 

    From Ethan Siegel
    June 20, 2018

    1
    In the aftermath of the creation of a neutron star, it can have a variety of masses, many of which are far in excess of the most massive white dwarf. But there is a limit to how massive they can get before becoming a black hole, and a simple nuclear physics experiment on a single proton may have just discovered why. (NASA)

    There’s something very special inside a proton and neutron that holds the key.

    There are few things in the Universe that are as easy to form, in theory, as black holes are. Bring enough mass into a compact volume and it gets more and more difficult to gravitationally escape from it. If you were to gather enough matter in a single spot and let gravitation do its thing, you’d eventually pass a critical threshold, where the speed you’d need to gravitationally escape would exceed the speed of light. Reach that point, and you’ll create a black hole.

    But real, normal matter will very much resist getting there. Hydrogen, the most common element in the Universe, will fuse in a chain reaction at high temperatures and densities to create a star, rather than a black hole. Burned out stellar cores, like white dwarfs and neutron stars, can also resist gravitational collapse and stave off becoming a black hole. But while white dwarfs can reach only 1.4 times the mass of the Sun, neutron stars can get twice as massive. At long last, we finally understand why [Nature].

    2
    Sirius A and B, a normal (Sun-like) star and a white dwarf star. Even though the white dwarf is much lower in mass, its tiny, Earth-like size ensures its escape velocity is many times larger. For a neutron stars, masses can be even larger, with physical sizes in the tens of kilometers. (NASA, ESA and G. Bacon (STScI))

    In our Universe, the matter-based objects we know of are all made of just a few simple ingredients: protons, neutrons, and electrons. Each proton and neutron is made up of three quarks, with a proton containing two up and one down quark, and a neutron containing one up and two downs. On the other hand, electrons themselves are fundamental particles. Although particles come in two classes — fermions and bosons — both quarks and electrons are fermions.

    3
    The Standard Model of particle physics accounts for three of the four forces (excepting gravity), the full suite of discovered particles, and all of their interactions. Quarks and leptons are fermions, which have a host of unique properties that the other (bosons) particles do not possess. (Contemporary Physics Education Project / DOE / NSF / LBNL)

    Standard Model of Particle Physics from Symmetry Magazine

    Why should you care? It turns out that these classification properties are vitally important when it comes to the question of black hole formation. Fermions have a few properties that bosons don’t, including:

    they have half-integer (e.g., ±1/2, ±3/2, ±5/2, etc.) spins as opposed to integer (0, ±1, ±2, etc.) spins,
    they have antiparticle counterparts; there are no anti-bosons,
    and they obey the Pauli Exclusion Principle, whereas bosons don’t.

    That last property is the key to staving off collapse into a black hole.

    4
    The energy levels and electron wavefunctions that correspond to different states within a hydrogen atom. Because of the spin = 1/2 nature of the electron, only two (+1/2 and -1/2 states) electrons can be in any given state at once. (PoorLeno / Wikimedia Commons)

    The Pauli exclusion principle, which only applies to fermions, not bosons, states, explicitly, that in any quantum system, no two fermions can occupy the same quantum state. It means that if you take, say, an electron and put it in a particular location, it will have a set of properties in that state: energy levels, angular momentum, etc.

    If you take a second electron and add it to your system, however, in the same location, it is forbidden from having those same quantum numbers. It must either occupy a different energy level, have a different spin (+1/2 if the first was -1/2, for example), or occupy a different location in space. This principle explains why the periodic table is arranged as it is.

    This is why atoms have different properties, why they bind together in the intricate combinations that they do, and why each element in the periodic table is unique: because the electron configuration of each type of atom is unlike any other.

    Periodic table Sept 2017. Wikipedia

    5
    The three valence quarks of a proton contribute to its spin, but so do the gluons, sea quarks and antiquarks, and orbital angular momentum as well. The electrostatic repulsion and the attractive strong nuclear force, in tandem, are what give the proton its size.(APS/Alan Stonebraker)

    Protons and neutrons are similar. Despite being composite particles, made up of three quarks apiece, they behave as single, individual fermions themselves. They, too, obey the Pauli Exclusion Principle, and no two protons or neutrons can occupy the same quantum state. The fact that electrons are fermions is what keeps white dwarf stars from collapsing under their own gravity; the fact that neutrons are fermions prevents neutron stars from collapsing further. The Pauli exclusion principle responsible for atomic structure is responsible for keeping the densest physical objects of all from becoming black holes.

    6
    A white dwarf, a neutron star or even a strange quark star are all still made of fermions. The Pauli degeneracy pressure helps hold up the stellar remnant against gravitational collapse, preventing a black hole from forming. (CXC/M. Weiss)

    And yet, when you look at the white dwarf stars we have in the Universe, they cap out at around 1.4 solar masses: the Chandrasekhar mass limit. The quantum degeneracy pressure arising from the fact that no two electrons can occupy the same quantum state is what prevents black holes from forming until that threshold is crossed.

    In neutron stars, there should be a similar mass limit: the Tolman-Oppenheimer-Volkoff limit. Initially, it was anticipated that this would be about the same as the Chandrasekhar mass limit, since the underlying physics is the same. Sure, it’s not specifically electrons that are providing the quantum degeneracy pressure, but the principle (and the equations) are pretty much the same. But we now know, from our observations, that there are neutron stars much more massive than 1.4 solar masses, perhaps rising as high as 2.3 or 2.5 times the mass of our Sun.

    7
    A neutron star is one of the densest collections of matter in the Universe, but there is an upper limit to their mass. Exceed it, and the neutron star will further collapse to form a black hole. (ESO/Luís Calçada)

    And yet, there are reasons for the differences. In neutron stars, the strong nuclear force plays a role, causing a larger effective repulsion than for a simple model of degenerate, cold gases of fermions (which is what’s relevant for electrons). For the past 20+ years, calculations of the theoretical mass limit for neutron stars have varied tremendously: from about 1.5 to 3.0 solar masses. The reason for the uncertainty has been the unknowns surrounding the behavior of extremely dense matter, like the densities you’ll find inside an atomic nucleus, are not well known.

    Or rather, these unknowns plagued us for a long time, until a new paper last month changed all of that. With the publication of their new paper in Nature, The pressure distribution inside the proton, coauthors V. D. Burkert, L. Elouadrhiri, and F. X. Girod may have just achieved the key advance needed to understand what’s happening inside neutron stars.

    8
    A better understanding of the internal structure of a proton, including how the “sea” quarks and gluons are distributed, has been achieved through both experimental improvements and new theoretical developments in tandem. These results apply to neutrons as well. (Brookhaven National Laboratory)

    Our models of nucleons like protons and neutrons have improved tremendously over the past few decades, coincident with improvements in both computational and experimental techniques. The latest research uses an old technique known as Compton scattering, where electrons are fired at the internal structure of a proton to probe its structure. When an electron interacts (electromagnetically) with a quark, it emits a high-energy photon, along with a scattered electron and leads to nuclear recoil. By measuring all three products, you can calculate the pressure distribution experienced by the quarks inside the atomic nucleus. In a shocking find, the average peak pressure, near the center of the proton, comes out to 10³⁵ pascals: a greater pressure than neutron stars experience anywhere.

    9
    At large distances, quarks are confined within a nucleon. But at short distances, there’s a repulsive pressure that prevents other quarks-and-nuclei from getting too close to each individual proton (or, by extension, neutron). (The quark-confinement-induced pressure distribution in the proton by V.D. Burkert, L. Elouadrhiri, and F.X. Girod)

    In other words, by understanding how the pressure distribution inside an individual nucleon works, we can calculate when and under what conditions that pressure can be overcome. Although the experiment was only done for protons, the results should be analogous for neutrons, too, meaning that, in the future, we should be able to calculate a more exact limit for the masses of neutron stars.

    10
    The masses of stellar remnants are measured in many different ways. This graphic shows the masses for black holes detected through electromagnetic observations (purple); the black holes measured by gravitational-wave observations (blue); neutron stars measured with electromagnetic observations (yellow); and the masses of the neutron stars that merged in an event called GW170817, which were detected in gravitational waves (orange). The result of the merger was a neutron star, briefly, that swiftly became a black hole. (LIGO-Virgo/Frank Elavsky/Northwestern)

    The measurements of the enormous pressure inside the proton, as well as the distribution of that pressure, show us what’s responsible for preventing the collapse of neutron stars. It’s the internal pressure inside each proton and neutron, arising from the strong force, that holds up neutron stars when white dwarfs have long given out. Determining exactly where that mass threshold is just got a great boost. Rather than solely relying on astrophysical observations, the experimental side of nuclear physics may provide the guidepost we need to theoretically understand where the limits of neutron stars actually lie.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 12:35 pm on June 20, 2018 Permalink | Reply
    Tags: , , , , Cosmology, XMM-Newton Finds Missing Intergalactic Material   

    From Harvard-Smithsonian Center for Astrophysics: “XMM-Newton Finds Missing Intergalactic Material” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    June 20, 2018
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279
    pedmonds@cfa.harvard.edu

    ESA/XMM Newton

    1
    This figure shows the filamentary structure of the hot gas that represents part of the warm-hot intergalactic medium (WHIM). It is based on a simulation extending over more than 200 million light years. The red and orange regions have the highest densities & the green regions have lower densities. Princeton University/Renyue Cen

    2
    Astronomers have used ESA’s XMM-Newton space observatory (lower right) to detect the WHIM. The white box encloses the filamentary structure of the hot gas that represents part of the WHIM. It is based on a cosmological simulation extending over more than 200 million light years. The red and orange regions have the highest densities & the green regions have lower densities. The discovery was made using observations of a distant quasar – a supermassive black hole that is actively devouring matter and shining brightly from X-rays to radio waves (upper left). The team found the signature of oxygen in the WHIM lying between the observatory and the quasar, at two different locations along the line of sight (shown in the spectrum in the lower left with green and magenta arrows). The blue arrows are signatures of nitrogen in our Milky Way galaxy.
    Illustrations and composition: ESA / ATG medialab; data: ESA / XMM-Newton / F. Nicastro et al. 2018; cosmological simulation: Princeton University/Renyue Cen

    3
    The mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, and ordinary matter, which makes up everything we see, including galaxies, stars and planets – amounts to only about five percent. However, stars in galaxies across the Universe only make up about seven percent of all ordinary matter and the cold and hot interstellar gas that permeates galaxies and galaxy clusters together accounts for only about 11 percent. Most of the Universe’s ordinary matter, or baryons, lurks in the cosmic web, the filamentary distribution of both dark and ordinary matter that extends throughout the Universe. In the past astronomers were able to locate a good chunk of the cool and warm parts of this intergalactic material (about 43 percent of all baryons in total). Astronomers have now used ESA’s XMM-Newton space observatory to detect the hot component of this intergalactic material along the line of sight to a quasar. The amount of hot intergalactic gas detected in these observations amounts up to 40 percent of all baryons in the Universe, closing the gap in the overall budget of ordinary matter in the cosmos. ESA

    After a nearly twenty-year long game of cosmic hide-and-seek, astronomers using ESA’s XMM-Newton space observatory have finally found evidence of hot, diffuse gas permeating the cosmos, closing a puzzling gap in the overall budget of ‘normal’ matter in the Universe.

    While the mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, the ordinary matter that makes up everything we see – from stars and galaxies to planets and people – amounts to only about five percent.

    But even this five percent turns out to be hard to track down.

    The total amount of ordinary matter, which astronomers refer to as baryons, can be estimated from observations of the Cosmic Microwave Background [CMB], which is the most ancient light in the history of the Universe, dating back to only about 380,000 years after the Big Bang.

    CMB per ESA/Planck

    ESA/Planck 2009 to 2013

    Observations of very distant galaxies allow astronomers to follow the evolution of this matter throughout the Universe’s first couple of billions of years. After that, however, more than half of it seemed to have gone missing.

    “The missing baryons represent one of the biggest mysteries in modern astrophysics,” explains Fabrizio Nicastro, lead author of the paper presenting a solution to the mystery, published today in Nature. Nicastro is from the INAF-Osservatorio Astronomico di Roma, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass.

    “We know this matter must be out there, we see it in the early Universe, but then we can no longer get hold of it. Where did it go?”

    Counting the population of stars in galaxies across the Universe, plus the interstellar gas that permeates galaxies – the raw material to create stars – only gets as far as a mere ten percent of all ordinary matter. Adding up the hot, diffuse gas in the haloes that encompass galaxies and the even hotter gas that fills galaxy clusters, which are the largest cosmic structures held together by gravity, raises the inventory to less than twenty percent.

    This is not surprising: stars, galaxies and galaxy clusters form in the densest knots of the cosmic web, the filamentary distribution of both dark and ordinary matter that extends throughout the Universe. While these sites are dense, they are also rare, so not the best spots to look for the majority of cosmic matter.

    Astronomers suspected that the ‘missing’ baryons must be lurking in the ubiquitous filaments of this cosmic web, where matter is, however, less dense and therefore more challenging to observe. Using different techniques over the years, they were able to locate a good chunk of this intergalactic material – mainly its cool and warm components – bringing up the total budget to a respectable 60 percent, but leaving the overall mystery still unsolved.

    Nicastro and many other astronomers around the world have been on the tracks of the remaining baryons for almost two decades, ever since X-ray observatories such as ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory became available to the scientific community.

    Observing in this portion of the electromagnetic spectrum, they can detect hot intergalactic gas, with temperatures around a million degrees or more, that is blocking the X-rays emitted by even more distant sources.

    For this project, Nicastro and his collaborators used XMM-Newton to look at a quasar – a massive galaxy with a supermassive black hole at its center that is actively devouring matter and shining brightly from X-rays to radio waves. They observed this quasar, whose light takes more than four billion years to reach us, for a total of 18 days, split between 2015 and 2017, in the longest X-ray observation ever performed of such a source.

    “After combing through the data, we succeeded at finding the signature of oxygen in the hot intergalactic gas between us and the distant quasar, at two different locations along the line of sight,” says Nicastro.

    “This is happening because there are huge reservoirs of material – including oxygen – lying there, and just in the amount we were expecting, so we finally can close the gap in the baryon budget of the Universe.”

    This extraordinary result is the beginning of a new quest. Observations of different sources across the sky are needed to confirm whether these findings are truly universal, and to further investigate the physical state of this long-sought-for matter.

    Fabrizio and his colleagues are planning to study more quasars with XMM-Newton and Chandra in the coming years. To fully explore the distribution and properties of this so-called warm-hot intergalactic medium, however, more sensitive instruments will be needed, like ESA’s Athena, the Advanced Telescope for High-Energy Astrophysics, scheduled for launch in 2028.

    ESA/Athena spacecraft depiction

    “The discovery of the missing baryons with XMM-Newton is the exciting first step to fully characterize the circumstances and structures in which these baryons are found,” says co-author Jelle Kaastra from the Netherlands Institute for Space Research.

    “For the next steps, we will need the much higher sensitivity of Athena, which has the study of the warm-hot intergalactic medium as one of its main goals, to improve our understanding of how structures grow in the history of the Universe.”

    “It makes us very proud that XMM-Newton was able to discover the weak signal of this long elusive material, hidden in a million-degree hot fog that extends through intergalactic space for hundreds of thousands of light years,” says Norbert Schartel, XMM-Newton project scientist at ESA.

    “Now that we know these baryons are no longer missing, we can’t wait to study them in greater detail.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 10:14 am on June 20, 2018 Permalink | Reply
    Tags: , , , Cosmology, Dark fusion?, , ,   

    From Science News: “If real, dark fusion could help demystify this physics puzzle” 


    From Science News

    June 6, 2018
    Emily Conover

    1
    DARK CLOUDS Galaxies and galaxy clusters are surrounded by dark matter (illustrated in blue over an image of the cluster Abell 2744; red indicates gas). Dark matter particles may undergo a process called dark fusion, one scientist suggests. XMM-Newton/ESA, WFI/ESO, NASA, CFHT

    Fusion may have a dark side. A shadowy hypothetical process called “dark fusion” could be occurring throughout the cosmos, a new study suggests.

    The standard type of fusion occurs when two atomic nuclei unite to form a new element, releasing energy in the process. “This is why the sun shines,” says physicist Sam McDermott of Fermilab in Batavia, Ill. A similar process — dark fusion — could occur with particles of dark matter, McDermott suggests in a paper published in the June 1, 2018 in Physical Review Letters.

    If the idea is correct, the proposed phenomenon may help physicists resolve a puzzle related to dark matter — a poorly understood substance believed to bulk up the mass of galaxies. Without dark matter, scientists can’t explain how galaxies’ stars move the way they do. But some of the quirks of how dark matter is distributed within galaxy centers remain a mystery.

    Dark matter is thought to be composed of reclusive particles that don’t interact much with ordinary matter — the stuff that makes up stars, planets and living creatures. That introverted nature is what makes the enigmatic particles so hard to detect. But dark matter may not be totally antisocial (SN: 3/3/18, p. 8). “Why wouldn’t the dark matter particles interact with each other? There’s really no good reason to say they wouldn’t,” says physicist Manoj Kaplinghat of the University of California, Irvine.

    Scientists have suggested that dark matter particles might ricochet off one another. But the new study goes a step further, proposing that pairs of dark matter particles could fuse, forming other unknown types of dark matter particles in the process.

    Such dark fusion could help explain why dark matter near the centers of galaxies is more evenly distributed than expected. In computer simulations of galaxy formation, the density of dark matter rises sharply toward a cusp in the center of a galaxy. But in reality, galaxies have a core evenly filled with dark matter.

    Those simulations assume dark matter particles don’t interact with one another. But dark fusion could change how the particles behave, giving them energy that would provide the oomph necessary to escape entrapment in a galaxy’s dense cusp, thereby producing an evenly filled core.

    “You can kick [particles] around through this interaction, so that’s kind of cool,” says physicist Annika Peter of the Ohio State University in Columbus. But, she says, dark fusion might end up kicking the particles out of the galaxy entirely, which wouldn’t mesh with expectations: The particles could escape the halo of dark matter that scientists believe surrounds each galaxy.

    For now, if fusion does have an alter ego, scientists remain in the dark.

    See the full article here .


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    Please help promote STEM in your local schools.

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  • richardmitnick 10:21 pm on June 19, 2018 Permalink | Reply
    Tags: , , , Cosmology, , , NASA's Next Flagship Mission May Be A Crushing Disappointment For Astrophysics   

    From Ethan Siegel: “NASA’s Next Flagship Mission May Be A Crushing Disappointment For Astrophysics” 

    From Ethan Siegel
    Jun 19, 2018

    1
    Various long-exposure campaigns, like the Hubble eXtreme Deep Field (XDF) shown here, have revealed thousands of galaxies in a volume of the Universe that represents a fraction of a millionth of the sky. Ambitious, flagship-class observatories are needed to take the next great leap forward for science. NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

    Every ten years, the field of astronomy and astrophysics undergoes a Decadal Survey. This charts out the path that NASA’s astrophysics division will follow for the next decade, including what types of questions they’ll investigate, which missions will be funded, and what won’t be chosen. The greatest scientific advances of all come when we invest a large amount of resources in a single, ultra-powerful, multi-purpose observatory, such as the Hubble Space Telescope.

    NASA/ESA Hubble Telescope

    These are high-risk, high-reward propositions. If the mission succeeds, we can learn an unprecedented amount about the Universe as never before.

    2
    Star birth in the Carina Nebula, in the optical (top) and the infrared (bottom). Our willingness to invest in fundamental science is directly related to how much we can learn about the Universe. NASA, ESA and the Hubble SM4 ERO Team

    Even though the mission proposals go through NASA, its the National Research Council and the National Academy of Sciences that ultimately make the recommendations. Since the inception of NASA in the 1960s, these Decadal Surveys have shaped the field of astronomy and astrophysics research. They brought us our greatest ground-based and space-based observatories. On the ground, radio arrays like the Very Large Array and the Very Long Baseline Array, as well as the Atacama Large Millimeter Array, owe their origins to the decadal surveys.

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    NRAO VLBA

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Space-based missions include NASA’s great observatories: the Hubble Space Telescope, the Chandra X-ray observatory, the Spitzer Space Telescope, and the Compton Gamma-Ray Observatory Even though the mission proposals go through NASA, its the National Research Council and the National Academy of Sciences that ultimately make the recommendations. Since the inception of NASA in the 1960s, these Decadal Surveys have shaped the field of astronomy and astrophysics research. They brought us our greatest ground-based and space-based observatories. On the ground, radio arrays like the Very Large Array and the Very Long Baseline Array, as well as the Atacama Large Millimeter Array, owe their origins to the decadal surveys. Space-based missions include NASA’s great observatories: the Hubble Space Telescope, the Chandra X-ray observatory, the Spitzer Space Telescope, and the Compton Gamma-Ray Observatory in the 1990s and early 2000s.

    NASA/Chandra X-ray Telescope


    NASA/Spitzer Infrared Telescope

    NASA Compton Gamma Ray Observatory

    4
    NASA’s Fermi Satellite has constructed the highest resolution, high-energy map of the Universe ever created. Without space-based observatories such as this one, we could never learn all that we have about the Universe. NASA/DOE/Fermi LAT Collaboration

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    More recent Decadal Surveys, conducted this millennium, will bring us the James Webb Space Telescope, the WFIRST observatory designed to probe dark energy and exoplanets, and the Large Synoptic Survey Telescope (LSST), among others.

    NASA/ESA/CSA Webb Telescope annotated

    NASA/WFIRST

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    They’ve identified the major, most important science goals of astronomy and astrophysics, including dark energy, exoplanets, supernovae, mergers of extreme objects, and the formation of the first stars and the large-scale structure of the Universe. But there was a warning issued in 2001’s report that hasn’t been heeded, and now it’s creating an enormous problem.

    5
    The 2010 NASA mission timeline doesn’t just show a planned James Webb, but an enormous suite of missions that require ongoing funding. Without a commensurate increase in funds, that means fewer resources available for new missions. NASA Astrophysics Division.

    While a robust astronomy program has many benefits for the nation and the world, it’s vital to have a diverse portfolio of missions and observatories. Prior Decadal Surveys have simultaneously stressed the importance of the large flagship missions that drive the field forward like no other type of mission can, while warning against investing too much in these flagships at the expense of other small and medium-sized missions.

    They’ve also stressed the importance of providing additional funding or securing external funding to support ongoing missions, facilities, and observatories. Without it, the development of new missions is hamstrung by the need to continually fund the existing ones.

    6
    As a percentage of the federal budget, investment in NASA is at a 58 year low; at only 0.4% of the budget, you have to go back to 1959 to find a year where we invested a smaller percentage in our nation’s space agency. Office of Management & Budget.

    Many austerity proponents and budget-hawks — both in politics and among the general public — will often point to the large cost of these flagship missions, which can balloon if unexpected problems arise. The far greater problem, however, would arise if one of these flagship missions failed.

    When Hubble launched with its flawed mirror, unable to properly focus the light it gathered, fixing it became mandatory [Soon after Hubble began sending images from space, scientists discovered that the telescope’s primary mirror had a flaw called spherical aberration. The outer edge of the mirror was ground too flat by a depth of 4 microns (roughly equal to one-fiftieth the thickness of a human hair). The flaw resulted in images that were fuzzy because some of the light from the objects being studied was being scattered.After this discovery, scientists and engineers developed COSTAR, corrective optics that functioned like eyeglasses to restore Hubble’s vision. By placing small and carefully designed mirrors in front of the original Hubble instruments, COSTAR –installed during the 1993 First Servicing Mission — successfully improved their vision to their original design goals (Thank you, Sandy Faber)]. Yes, it was expensive, but the far greater cost — to science, to society, and to humanity — would have been not to fix it. Our choice to invest in repairing (and upgrading) Hubble directly led to some of our greatest discoveries of all-time.

    James Webb, similarly, is now over budget, and will require additional funds to complete. But the small, additional cost to get it right enormously outweighs the cost we’d all bear if we cheated ourselves and didn’t finish this incredible investment. [Also, here, we have commitments from CSA and ESA]

    7
    The science instruments aboard the ISIM module being lowered and installed into the main assembly of JWST in 2016. The telescope must be folded and properly stowed in order to fit aboard the Ariane 5 rocket which will launch it, and all its components must work together, correctly, to deliver a successful mission outcome. NASA / Chris Gunn.

    Now, the 2020 Decadal Survey approaches. The future course of astronomy and astrophysics will be charted, and one flagship mission will be selected as the top priority for a premiere mission of the 2030s. (James Webb was that mission for the 2010s; WFIRST will be it for the 2020s.) Unfortunately, a memorandum was just released by the astronomy & astrophysics director, Paul Hertz, of NASA’s Science Mission Directorate. In it, each of the four finalist teams were instructed to develop a second architechture: a lower-cost, scientifically-inferior option.

    8
    This figure shows the real stars in the sky for which a planet in the habitable zone can be observed. The color coding shows the probability of observing an exoEarth candidate if it’s present around that star (green is a high probability, red is a low one). Note how the size of your telescope/observatory in space impacts what you can see. C. Stark and J. Tumlinson, STScI.

    It flies in the face of what a flagship mission actually is. Speaking at this year’s big American Astronomical Society meeting, NASA Associate Administrator Thomas Zurbuchen said,

    “What we learn from these flagship missions is why we study the Universe. This is civilization-scale science… If we don’t do this, we aren’t NASA.”

    8
    A simulated view of the same part of the sky, with the same observing time, with both Hubble (L) and the initial architecture of LUVOIR (R). The difference is breathtaking, and represents what civilization-scale science can deliver. G. Snyder, STScI /M. Postman, STScI.

    And yet, these scaled-down architectures are by definition not as ambitious. It’s an indication from NASA that, unless the budget is increased to accommodate the actual costs of doing civilization-scale science, we won’t be doing it. Each of the four finalists has been instructed to propose an option with a total cost of below $5 billion, which will severely curtail the capabilities of such an observatory.

    9
    The concept design of the LUVOIR space telescope would place it at the L2 Lagrange point, where a 15.1-meter primary mirror would unfold and begin observing the Universe, bringing us untold scientific and astronomical riches. NASA / LUVOIR concept team; Serge Brunier (background)

    As an example, one of the proposals, LUVOIR, was designed to be the ultimate successor to Hubble: 40 times as powerful with a diameter of up to ~15 meters. It was designed to tackle problems in our Solar System, measure molecular biosignatures on exoplanets, to perform a cosmic census of stars in every type of galaxy in the Universe, to achieve the sensitivity capable of seeing every galaxy in the Universe, to directly image and map the gas in galaxies everywhere, and to measure the rotation of galaxies (and better understand dark matter) for every galaxy in the Universe.

    But the new architecture would be only half the diameter, half the resolution, and with a quarter of the light-gathering power of the original design. It would basically be an optical version of the James Webb Space Telescope. The sweeping ambition of the original project, with the potential to revolutionize our view of the Universe, would be lost.

    9
    A simulated image of what Hubble would see for a distant, star-forming galaxy (L), versus what a 10-15 meter class telescope would see for the same galaxy (R). With a telescope of half the size, the resolution would be halved, and the light-gathering time would need to be four times as great to create that inferior image. NASA / Greg Snyder / LUVOIR-HDST concept team.

    The other three proposals are more easily scaled-down, but again lose their power. HabEx, designed to directly image Earth-like planets around other stars, loses 87.5% of the interesting planets it can survey if its size is reduced in half. It might not offer much more than the other suites of missions that will fly, like WFIRST (especially if WFIRST gets a starshade), to justify being the flagship mission with such a reduction. LYNX, designed to be a next-generation X-ray observatory that’s vastly superior to Chandra and XMM-Newton, might not be much superior to the ESA’s upcoming Athena mission on such a budget. Its spatial and energy resolution were supposed to be its big selling points; on a reduced budget, it’s hard to see how it will achieve those.

    10
    An artist’s concept of the Origins Space Telescope, with the (architecture 1) 9.1 meter primary mirror. At lower resolutions and sizes, it still offers a tremendous improvement over current-and-previous far-IR observatories. NASA/GSFC

    The best bet might be OST: the Origins Space Telescope, which would represent a huge upgrade over Spitzer: the only other far-infrared observatory NASA’s ever sent to space. Its 9.1 meter design is likely impossible at that price point, but a reduction in size is less devastating to this mission. At a lower price tag, it can still teach us a huge amount about space, from our Solar System to exoplanets to black holes to distant, early galaxies. There is no NASA or European counterpart to compete with, and unlike the optical part of the spectrum, it’s notoriously challenging to attempt astronomy in this wavelength from the ground. The closest we have is the airplane-borne SOFIA, which is fantastic, but has a number of limitations.

    11
    NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) with open telescope doors. This joint partnership between NASA and the German organization DLR enables us to take a state-of-the-art infrared telescope to any location on Earth’s surface, allowing us to observe events wherever they occur. NASA / Carla Thomas

    This is NASA. This is the pre-eminent space agency in the world. This is where science, research, development, discovery, and innovation all come together. The spinoff technologies alone justify the investment, but that’s not why we do it. We are here to discover the Universe. We are here to learn all that we can about the cosmos and our place within it. We are here to find out what the Universe looks like and how it came to be the way it is today.

    It’s time for the United States government to step up to the plate and invest in fundamental science in a way the world hasn’t seen in decades. It’s time to stop asking the scientific community to do more with less, and give them a realistic but ambitious goal: to do more with more. If we can afford an ill-thought-out space force, perhaps we can afford to learn about the greatest unexplored natural resource of all. The Universe, and the vast unknowns hiding in the great cosmic ocean.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “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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