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  • richardmitnick 12:37 pm on October 16, 2017 Permalink | Reply
    Tags: , , , , CfA, , ,   

    From CfA: “CfA Scientists Weigh in on Historic Gravitational Wave Discovery” and the Press Release 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    October 16, 2017

    Scientists have detected gravitational waves and electromagnetic radiation, or light, from the same event for the first time, as described in our latest press release [see below].

    Thousands of scientists around the world have worked on this result, with researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., playing a pivotal role. A series of eight papers led by CfA astronomers and their colleagues detail the complete story of the aftermath of this event and reveal clues about its origin.

    We conducted interviews with four CfA scientists about their work on this discovery: Professor Edo Berger, who led the work, postdoctoral fellow Matt Nicholl, and graduate students Kate Alexander and Philip Cowperthwaite. Here they describe their reactions to the exciting news that Advanced LIGO had detected gravitational waves from a neutron star merger, and they discuss unanswered questions and prospects for future work.

    How did you hear about LIGO’s detection of a neutron star merger and what were your first thoughts?

    Kate Alexander:

    I saw the e-mail from the LIGO collaboration when I woke up in the morning, and no one was expecting it because LIGO was a week away from shutting down from its current observing run. We all just kind of went “Wow. Oh my goodness! This is actually happening.” Edo called a meeting and we all rushed into his office to prepare our plans for following it up.


    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

    1
    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)

    Edo Berger:

    So, we first got an alert from LIGO on the morning of August 17th. I was actually in the middle of a boring committee meeting. My office phone started ringing, and I ignored it. Then my cell phone started ringing and I ignored it. Then text messages started coming in. At that point I knew that I couldn’t ignore it anymore, so I kicked everybody out of the office and started catching up on this new alert that came from the LIGO observatory saying that they detected the first merger of a neutron star binary system.

    Matt Nicholl:

    As soon as we started observing the sky in Chile we were transferring these images back to computers at Harvard as soon as they came in and we all frantically brought them up on our computer screens and looked for new sources that appeared. Really what we expected was that we wouldn’t find anything in real time and that we’d spend the whole day next day processing these images trying to find some sort of faint little detections of possible candidates. But what actually happened was that one of the first giant galaxies we looked had an obvious new source popping right out at us. This was an incredible moment. I think one of my collaborators saw it first and sent an email that I can’t quite repeat but I will never forget. After that our email inboxes exploded. Every team in the world was looking at this thing and trying to compete to say things first. It was a night unlike any other I’ve had in my career.

    Phil Cowperthwaite:

    I actually heard about it through a very informal email from a colleague. I just woke up that morning and it was there on my phone: “Oh we have a binary neutron star in LIGO with a coincident Fermi detection. It’s insane. It took a moment to process – it didn’t seem real because that was the goal we never expected to happen.”

    What are some unanswered questions and the prospects for future work?

    Kate Alexander:

    The VLA has been invaluable to the science so far.

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

    This is going to continue to be a very interesting target for radio observations going forward. The radio emission that we’re observing is likely to continue to be observable with the VLA for the next several weeks to months, and we’ll be very eager to monitor the radio emission we’ve seen as it slowly fades away. We also predict that several years from now the source should brighten in the radio again as all of the slower moving material that produced the optical light eventually starts producing a shock wave [akin to a sonic boom] with the surrounding medium. Then we’ll have a completely independent second chance to figure out all of these properties of the environment around the neutron star. We don’t know exactly when this will happen, but we certainly will continue to look at it with the VLA for years to come.

    Edo Berger:

    In studying both the gravitational wave signal and the electromagnetic signal what we hope to do is understand the detailed composition of neutron stars. What are they exactly made of? What do they look like on the inside? The only way we get to see the inside of a neutron star is when it collides with another neutron star and then material from the inside spills out. This is what we see in our observations. We also want to understand how pairs of neutron stars actually come into being. How are they actually formed? How are these systems born? How was their life before they ended it in that final catastrophic collision?

    One of the particularly exciting aspects of studying the collisions of neutron stars in both gravitational waves and electromagnetic radiation is that it gives us a completely new way of measuring the Hubble Constant, which is the measurement of how fast the Universe is expanding. So far, we’ve been studying the Hubble Constant using different techniques: supernova explosions or the cosmic microwave background [leftover radiation from the Big Bang].

    CMB per ESA/Planck

    ESA/Planck

    But here, for the first time, we have a completely independent new way of measuring the Hubble Constant. We can measure the distance to the object from the gravitational wave signal and we can then measure the amount of redshifting which tells us how fast the universe is expanding from the electromagnetic signal. And by combining these two measurements we can directly measure the Hubble Constant.

    Matt Nicholl:

    I think the big outstanding questions now are first of all how typical was this event of the general population of neutron star mergers? Maybe we got lucky and we found a very bright one. Maybe the others aren’t going to be so great. But we’ll find this out in the next few years as LIGO detects more and more of these sources. By detecting more sources we can also measure the rate at which they occur. The combination of those two things is very powerful. If we know how diverse they are and how often they occur we can work out the total production of heavy elements in the universe. If we compare this production of heavy elements to the abundances that we measure in our local environment we can show definitively whether all heavy elements come from neutron star mergers.

    Phil Cowperthwaite:

    You can do all kinds of science that you could not do with just a gravitational wave detection. The gravitational wave detection is great for telling you about the binary, the objects that merged and their properties, but it can’t do other things. For instance, LIGO can’t give you a precise location on the sky. It can do very well, especially with Virgo, but once you have an optical counterpart you know exactly where that event occurred. And then you can do all kinds of other exciting science. We can associate the source with a galaxy. We can learn about where these objects come from. What are their homes like? Understanding all this information will help us understand the behavior of the merger: how much material is produced, which is important for understanding whether or not these events can truly be the source of heavy element production. So, it really is necessary to maximize the science goals.

    Press release:
    Astronomers See Light Show Associated With Gravitational Waves
    October 16, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Marking the beginning of a new era in astrophysics, scientists have detected gravitational waves and electromagnetic radiation, or light, from the same event for the first time. This historic discovery reveals the merger of two neutron stars, the dense cores of dead stars, and resolves the debate about how the heaviest elements such as platinum and gold were created in the Universe.

    To achieve this remarkable result, thousands of scientists around the world have worked feverishly using data from telescopes on the ground and in space. Researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., have played a pivotal role. A series of eight papers led by CfA astronomers and their colleagues detail the complete story of the aftermath of this event and examine clues about its origin.

    “It’s hard to describe our sense of excitement and historical purpose over the past couple of months,” said the leader of the team, CfA’s Edo Berger. “This is a once in a career moment — we have fulfilled a dream of scientists that has existed for decades.”

    Gravitational waves are ripples in space-time caused by the accelerated motion of massive celestial objects. They were first predicted by Einstein’s General Theory of Relativity. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first direct detection of gravitational waves in September 2015, when the merger of two stellar-mass black holes was discovered.

    On 8:41 am EDT August 17, 2017, LIGO detected a new gravitational wave source, dubbed GW170817 to mark its discovery date. Just two seconds later NASA’s Fermi satellite detected a weak pulse of gamma rays from the same location of the sky. Later that morning, LIGO scientists announced that two merging neutron stars produced the gravitational waves from GW170817.

    “Imagine that gravitational waves are like thunder. We’ve heard this thunder before, but this is the first time we’ve also been able to see the lightning that goes with it,” said Philip Cowperthwaite of the CfA. “The difference is that in this cosmic thunderstorm, we hear the thunder first and then get the light show afterwards.”

    A few hours after the announcement, as night set in Chile, Berger’s team used the powerful Dark Energy Camera on the Blanco telescope to search the region of sky from which the gravitational waves emanated. In less than an hour they located a new source of visible light in the galaxy NGC 4993 at a distance of about 130 million light years.

    “One of the first giant galaxies we looked at had an obvious new source of light popping right out at us, and this was an incredible moment,” said Matt Nicholl of the CfA. “We thought it would take days to locate the source but this was like X marks the spot.”

    The CfA team and collaborators then launched a series of observations that spanned the electromagnetic spectrum from X-rays to radio waves to study the aftermath of the neutron star merger.

    In their set of papers, the CfA scientists report their studies of the brightness and spectrum of the optical and infrared light and how it changed over time. They show that the light is caused by the radioactive glow when heavy elements in the material ejected by the neutron star merger are produced in a process called a kilonova.

    “We’ve shown that the heaviest elements in the periodic table, whose origin was shrouded in mystery until today are made in the mergers of neutron stars,” said Edo Berger. “Each merger can produce more than an Earth’s mass of precious metals like gold and platinum and many of the rare elements found in our cellphones.”

    The material observed in the kilonova is moving at high speeds, suggesting that it was expelled during the head-on collision of two neutron stars. This information, independent of the gravitational wave signature, suggests that two neutron stars were involved in GW170817, rather than a black hole and a neutron star.

    Radio observations with the Very Large Array in New Mexico helped confirm that the merger of the two neutron stars triggered a short gamma ray burst (GRB), a brief burst of gamma rays in a jet of high-energy particles. The properties match those predicted by theoretical models of a short GRB that was viewed with the jet initially pointing at a large angle away from Earth. Combining the radio data with observations from NASA’s Chandra X-ray Observatory shows that the jet pointed about 30 degrees away from us.

    “This object looks far more like the theories than we had any right to expect,” said the CfA’s Kate Alexander who led the teams’ VLA observations. “We will continue to track the radio emission for years to come as the material ejected from the collision slams into the surrounding medium,” she continued.

    An analysis of the host galaxy, NGC 4993, and the environment of the cataclysmic merger shows that the neutron star binary most likely formed more than 11 billion years ago.

    “The two neutron stars formed in supernova explosions when the universe was only two billion years old, and have spent the rest of cosmic history getting closer and closer to each other until they finally smashed together,” said Peter Blanchard of the CfA.

    A long list of observatories were used to study the kilonova, including the SOAR and Magellan telescopes, the Hubble Space Telescope, the Dark Energy Camera on the Blanco, and the Gemini-South telescope.

    The series of eight papers describing these results appeared in the Astrophysical Journal Letters on October 16th. The four papers with first authors from CfA are led by Philip Cowperthwaite about the changes with time of light from the kilonova, one led by Matt Nicholl about the changes with time of the kilonova’s spectrum, another led by Kate Alexander about the VLA observations, and another led by Peter Blanchard about how long the merger took to unfold and the properties of the host galaxy.

    Completing the series of eight papers, Marcelle Soares-Santos from Brandeis University in Waltham MA led a paper about the discovery of the optical counterpart; Ryan Chornock from Ohio University in Athens, OH, led a paper about the kilonova’s infrared spectra, Raffaella Margutti from Northwestern University in Evanston, IL, led a paper about the Chandra observations of the jet, and Wen-fai Fong also from Northwestern led a paper about the comparison between GW170817 and previous short GRBs.

    Graphics and other additional information on this result can be found at http://www.kilonova.org.

    Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

    See the full main article here .
    See the press release here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

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  • richardmitnick 3:51 pm on October 12, 2017 Permalink | Reply
    Tags: , , , CfA, , , NRAO/VLBA - Very Long Baseline Array, The far side of the Milky Way   

    From Max Planck Institute for Radio Astronomy and CfA : “The far side of the Milky Way” 


    Max Planck Institute for Radio Astronomy

    CfA

    October 12, 2017
    Contact
    Dr. Alberto Sanna
    Max Planck Institute for Radio Astronomy, Bonn
    Phone:+49 228 525-304
    asanna@mpifr-bonn.mpg.de

    Prof. Dr. Karl M. Menten
    Max Planck Institute for Radio Astronomy, Bonn
    Phone:+49 228 525-297
    Fax:+49 228 525-435
    kmenten@mpifr-bonn.mpg.de

    Dr. Norbert Junkes
    Max Planck Institute for Radio Astronomy, Bonn
    Phone:+49 228 525-399
    njunkes@mpifr.de

    Astronomers achieve record measurement for an improved picture of our home galaxy.

    Astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and the Harvard-Smithsonian Center for Astrophysics, using the Very Long Baseline Array, have directly measured a distance of more than 66,000 light-years to a star-forming region. This region, known as G007.47+00.05, is on the opposite side of our Milky Way Galaxy from the Sun. The researchers’ achievement reaches deep into the Milky Way’s terra incognita and nearly doubles the previous record for distance measurement within our Galaxy.

    NRAO VLBA


    NRAO/VLBA


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

    Distance measurements are crucial for an understanding of the structure of the Milky Way. Most of our Galaxy’s material, consisting principally of stars, gas, and dust, lies within a flattened disk, in which our Solar System is embedded. Because we cannot see our Galaxy face-on, its structure, including the shape of its spiral arms, can only be mapped by measuring distances to objects elsewhere in the Galaxy.

    The astronomers used a technique called trigonometric parallax, first applied by Friedrich Wilhelm Bessel in 1838 to measure the distance to the star 61 Cygni in the constellation of the Swan. This technique measures the apparent shift in the sky position of a celestial object as seen from opposite sides of the Earth’s orbit around the Sun. This effect can be demonstrated by holding a finger in front of one’s nose and alternately closing each eye — the finger appears to jump from side to side.

    Measuring the angle of an object’s apparent shift in position this way allows astronomers to use simple trigonometry to directly calculate the distance to that object. The smaller the measured angle, the greater the distance is. In the framework of the Bar and Spiral Structure Legacy (BeSSeL) Survey, it is now possible to measure parallaxes a thousand times more accurate than Friedrich Bessel. The Very Long Baseline Array (VLBA), a continent-wide radio telescope system, with ten dish antennas distributed across North America, Hawaii, and the Caribbean, can measure the minuscule angles associated with great distances. In this case, the measurement was roughly equal to the angular size of a baseball on the Moon.

    “Using the VLBA, we now can accurately map the whole extent of our Galaxy,” says Alberto Sanna, of the Max Planck Institute for Radio Astronomy in Germany (MPIfR).

    The new VLBA observations, made in 2014 and 2015, measured a distance of more than 66,000 light-years to the star-forming region G007.47+00.05 on the opposite side of the Milky Way from the Sun, well past the Galaxy’s center in a distance of 27,000 light-years. The previous record for a parallax measurement was about 36,000 light-years.

    2

    Highly complex observations: The calculation of distances is principally simple, but requires highly accurate measurements of the angle of apparent shifts in an object’s position – only the VLBA has the capability to deliver such measurements.
    © Bill Saxton, NRAO/AUI/NSF; Robert Hurt, NASA.

    “Most of the stars and gas in our Galaxy are within this newly-measured distance from the Sun. With the VLBA, we now have the capability to measure enough distances to accurately trace the Galaxy’s spiral arms and learn their true shapes,” Sanna explains.

    The VLBA observations measured the distance to a region where new stars are being formed.

    Such regions include areas where molecules of water and methanol act as natural amplifiers of radio signals — masers, the radio-wave equivalent of lasers for light waves. This effect makes the radio signals bright and readily observable with radio telescopes.

    The Milky Way has hundreds of such star-forming regions that include masers. “So we have plenty of ‘mileposts’ to use for our mapping project. But this one is special: Looking all the way through the Milky Way, past its center, way out into the other side”, says the MPIfR’s Karl Menten.

    The astronomers’ goal is to finally reveal what our own Galaxy looks like if we could leave it, travel outward perhaps a million light-years, and view it face-on, rather than along the plane of its disk. This task will require many more observations and much painstaking work, but, the scientists say, the tools for the job now are in hand. How long will it take?

    “Within the next 10 years, we should have a fairly complete picture,” predicts Mark Reid of the Harvard-Smithsonian Center for Astrophysics.

    Science paper:
    Mapping Spiral Structure on the far side of the Milky Way, Science

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.



    MPIFR/Effelsberg Radio Telescope, Germany

    The Max Planck Institute for Radio Astronomy (German: Max-Planck-Institut für Radioastronomie) is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society (German: Max-Planck-Gesellschaft).

    By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

    The institute was founded in 1966 by the Max-Planck-Gesellschaft as the “Max-Planck-Institut für Radioastronomie” (MPIfR).

    The foundation of the institute was closely linked to plans in the German astronomical community to construct a competitive large radio telescope in (then) West Germany. In 1964, Professors Friedrich Becker, Wolfgang Priester and Otto Hachenberg of the Astronomische Institute der Universität Bonn submitted a proposal to the Stiftung Volkswagenwerk for the construction of a large fully steerable radio telescope.

    In the same year the Stiftung Volkswagenwerk approved the funding of the telescope project but with the condition that an organization should be found, which would guarantee the operations. It was clear that the operation of such a large instrument was well beyond the possibilities of a single university institute.

    Already in 1965 the Max-Planck-Gesellschaft (MPG) decided in principle to found the Max-Planck-Institut für Radioastronomie. Eventually, after a series of discussions, the institute was officially founded in 1966.

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

     
  • richardmitnick 12:14 pm on October 7, 2017 Permalink | Reply
    Tags: A Young Protostellar Dust Disk, , , , CfA, , Young protostar known as HH-212   

    From CfA: “A Young Protostellar Dust Disk” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    An artificial color submillimeter image of the disk around the young protostar HH-212. This is the first submillimeter image of the disk around a very early-stage star, and shows a dark lane of cold dense material implying that the small dust grains in the disk have already begun to coalesce. Lee et al., 2017

    Stars form as gravity contracts the gas and dust in an interstellar cloud until cores develop that become dense enough to coalesce into stars. The simple-sounding process is made much more complex by the presence of magnetic fields and rotation, which produce circumstellar disks around the developing star that in turn play a role in controlling the material accreting onto the protostar. Disks as large as 500 astronomical units in radius (one AU is the average distance of the Earth from the Sun) have been detected around Sun-like stars in the later phases of their gestation. Presumably they began forming in the earlier phases, while infalling material was still feeding the infant protostar, and so astronomers have been trying to probe younger protostars. Evidence for the existence of these early stage disks, however, has been slight: a few examples have been found with total radii less than about 150 AU. If there is smaller structure within them, it has not been measurable.

    CfA astronomers Qizhou Zhang and Paul Ho and their four colleagues used the Atacama Large Millimeter/submillimeter Array (ALMA) to spatially resolve the dust disk around the young protostar known as HH-212.

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

    The disk is seen nearly edge-on with a radius of only sixty AU, and has a prominent equatorial dark lane sandwiched between two brighter layers. The astronomers tentatively estimate the mass of the disk to be about fourteen-thousandths of a solar-mass, and combining the results with earlier observations at other wavelengths they model the dust grains as being as large as a millimeter in size. The dark lane along the midplane of the disk has colder, denser dust than in the outer layers. The large grains signal that the coalescence of small grains into larger ones begins earlier in the lifetime of a star than many had previously thought. The new observations also show that direct detection and characterization of small disks around the youngest protostars is possible. The results provide constraints on theories of disk formation. If small disks turn out to be commonplace, then theoretical models in which magnetic effects inhibit disk formation would need significant revision.
    Reference(s):

    First Detection of Equatorial Dark Dust Lane in a Protostellar Disk at Submillimeter Wavelength, Chin-Fei Lee, Zhi-Yun Li, Paul T. P. Ho, Naomi Hirano, Qizhou Zhang, Hsien Shang, Science Advances, 3: e1602935, 2017.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 2:00 pm on September 29, 2017 Permalink | Reply
    Tags: , , , CfA, , , ,   

    From CfA: “New Insights on Dark Energy” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    Inflationary Universe. NASA/WMAP

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

    The universe is not only expanding – it is accelerating outward, driven by what is commonly referred to as “dark energy.”

    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

    The term is a poetic analogy to label for dark matter, the mysterious material that dominates the matter in the universe and that really is dark because it does not radiate light (it reveals itself via its gravitational influence on galaxies).

    Dark Matter Research

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

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

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

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington

    Two explanations are commonly advanced to explain dark energy. The first, as Einstein once speculated, is that gravity itself causes objects to repel one another when they are far enough apart (he added this “cosmological constant” term to his equations). The second explanation hypothesizes (based on our current understanding of elementary particle physics) that the vacuum has properties that provide energy to the cosmos for expansion.

    For several decades cosmologies have successfully used a relativistic equation with dark matter and dark energy to explain increasingly precise observations about the cosmic microwave background, the cosmological distribution of galaxies, and other large-scale cosmic features.

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

    But as the observations have improved, some apparent discrepancies have emerged. One of the most notable is the age of the universe: there is an almost 10% difference between measurements inferred from the Planck satellite data and those from so-called Baryon Acoustic Oscillation experiments. The former relies on far-infrared and submillimeter measurements of the cosmic microwave background [CMB] and the latter on spatial distribution of visible galaxies.

    BOSS Supercluster Baryon Oscillation Spectroscopic Survey (BOSS)

    CMB per ESA/Planck

    ESA/Planck

    CfA astronomer Daniel Eisenstein was a member of a large consortium of scientists who suggest that most of the difference between these two methods, which sample different components of the cosmic fabric, could be reconciled if the dark energy were not constant in time. The scientists apply sophisticated statistical techniques to the relevant cosmological datasets and conclude that if the dark energy term varied slightly as the universe expanded (though still subject to other constraints), it could explain the discrepancy. Direct evidence for such a variation would be a dramatic breakthrough, but so far has not been obtained. One of the team’s major new experiments, the Dark Energy Spectroscopic Instrument (DESI) Survey…

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    …could settle the matter. It will map over twenty-five million galaxies in the universe, reaching back to objects only a few billion years after the big bang, and should be completed sometime in the mid 2020’s.

    Reference(s):

    Dynamical Dark Energy in Light of the Latest Observations, Gong-Bo Zhao et al. Nature Astronomy, 1, 627, 2017

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 4:23 pm on September 22, 2017 Permalink | Reply
    Tags: A mini-halo is a faint diffuse region of radio emission that surrounds a cluster of galaxies, CfA, , Nature of Galaxy Cluster Mini-Halos,   

    From CfA: “Nature of Galaxy Cluster Mini-Halos” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    A galaxy cluster mini-halo as seen around the galaxy NGC 1275 in the radio, with its main structures labeled: the northern extension, the two eastern spurs, the concave edge to the south, the south-western edge and a plume of emission to the south-south-west. Astronomers used radio and X-ray data to conclude that mini-halos, rather than being simple structures resulting from turbulence, are actually the result of multiple processes. Gendron-Marsolais et al.

    A mini-halo is a faint, diffuse region of radio emission that surrounds a cluster of galaxies. So far about thirty of these cluster mini-halos have been detected via their X-ray and radio emission, the result of radiation from electrons in the ionized gas, including one mini-halo in the nearby Perseus cluster of galaxies. These electrons are thought to arise from activity around a supermassive black hole at a galactic nucleus, which injects steams of particles into the intracluster medium and which also produces turbulence and shocks. One issue puzzling astronomers is that such electrons should rapidly lose their energy, faster than the time it takes for them to reach the mini-halo regions. Suggested solutions include processes in which turbulence reaccelerates the electrons, and in which cosmic rays generate new ones.

    CfA astronomer Reinout van Weeren and his colleagues used the radio Karl G. Jansky Very Large Array (JVLA) to obtain the first detailed study of the structure of the mini-halo in Perseus, and to compare it with Chandra X-Ray images.

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

    NASA/Chandra Telescope

    They find that the radio emission comes primarily from gas behind a cold front as would be expected if the gas is sloshing around within the cluster as particles are re-accelerated. They also detect unexpected, filamentary structures that seem to be associated with edges of X-ray features. The scientists conclude that mini-halos are not simply diffuse structures produced by a single process, but reflect a variety of structures and processes including turbulent re-acceleration of electrons, relativistic activity from the black hole jets, and also some magnetic field effects. Not least, the results demonstrate the sensitivity of the new JVLA and the need to obtain such sensitive images to understand the mini-halo phenomenon.

    Reference(s):

    Deep 230–470 MHz VLA Observations of the Mini-Halo in the Perseus Cluster, M. Gendron-Marsolais, J. Hlavacek-Larrondo, R. J. van Weeren, T. Clarke, A. C. Fabian, H. T. Intema, G. B. Taylor, K. M. Blundell, and J. S. Sanders, MNRAS 469, 3872, 2017.

    See the full article here .

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    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 2:44 pm on September 21, 2017 Permalink | Reply
    Tags: , , , CfA, ,   

    From CfA: “Fast Radio Bursts May Be Firing Off Every Second” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    September 21, 2017
    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

    1
    This artist’s impression shows part of the cosmic web, a filamentary structure of galaxies that extends across the entire sky. The bright blue, point sources shown here are the signals from Fast Radio Bursts (FRBs) that may accumulate in a radio exposure lasting for a few minutes. The radio signal from an FRB lasts for only a few thousandths of a second, but they should occur at high rates. M. Weiss/CfA

    When fast radio bursts, or FRBs, were first detected in 2001, astronomers had never seen anything like them before. Since then, astronomers have found a couple of dozen FRBs, but they still don’t know what causes these rapid and powerful bursts of radio emission.

    For the first time, two astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) have estimated how many FRBs should occur over the entire observable universe. Their work indicates that at least one FRB is going off somewhere every second.

    “If we are right about such a high rate of FRBs happening at any given time, you can imagine the sky is filled with flashes like paparazzi taking photos of a celebrity,” said Anastasia Fialkov of the CfA, who led the study. “Instead of the light we can see with our eyes, these flashes come in radio waves.”

    To make their estimate, Fialkov and co-author Avi Loeb assumed that FRB 121102, a fast radio burst located in a galaxy about 3 billion light years away, is representative of all FRBs. Because this FRB has produced repeated bursts since its discovery in 2002, astronomers have been able to study it in much more detail than other FRBs. Using that information, they projected how many FRBs would exist across the entire sky.

    “In the time it takes you to drink a cup of coffee, hundreds of FRBs may have gone off somewhere in the Universe,” said Avi Loeb. “If we can study even a fraction of those well enough, we should be able to unravel their origin.”

    While their exact nature is still unknown, most scientists think FRBs originate in galaxies billions of light years away. One leading idea is that FRBs are the byproducts of young, rapidly spinning neutron stars with extraordinarily strong magnetic fields.

    Fialkov and Loeb point out that FRBs can be used to study the structure and evolution of the Universe whether or not their origin is fully understood. A large population of faraway FRBs could act as probes of material across gigantic distances. This intervening material blurs the signal from the cosmic microwave background (CMB), the left over radiation from the Big Bang.

    CMB per ESA/Planck

    ESA/Planck

    A careful study of this intervening material should give an improved understanding of basic cosmic constituents, such as the relative amounts of ordinary matter, dark matter and dark energy, which affect how rapidly the universe is expanding.

    FRBs can also be used to trace what broke down the “fog” of hydrogen atoms that pervaded the early universe into free electrons and protons, when temperatures cooled down after the Big Bang. It is generally thought that ultraviolet (UV) light from the first stars traveled outwards to ionize the hydrogen gas, clearing the fog and allowing this UV light to escape. Studying very distant FRBs will allow scientists to study where, when and how this process of “reionization” occurred.

    Reionization era and first stars, Caltech

    “FRBs are like incredibly powerful flashlights that we think can penetrate thise fog and be seen over vast distances,” said Fialkov. “This could allow us to study the ‘dawn’ of the universe in a new way.”

    The authors also examined how successful new radio telescopes – both those already in operation and those planned for the future – may be at discovering large numbers of FRBs. For example, the Square Kilometer Array (SKA) currently being developed will be a powerful instrument for detecting FRBs.

    SKA Square Kilometer Array

    The new study suggests that over the whole sky the SKA may be able to detect more than one FRB per minute that originates from the time when reionization occurred.

    The Canadian Hydrogen Intensity Mapping Experiment (CHIME), that recently began operating, will also be a powerful machine for detecting FRBs, although its ability to detect the bursts will depend on their spectrum, i.e. how the intensity of the radio waves depends on wavelength.

    CHIME Canadian Hydrogen Intensity Mapping Experiment A partnership between the University of British Columbia McGill University, at the Dominion Radio Astrophysical Observatory in British Columbia

    If the spectrum of FRB 121102 is typical then CHIME may struggle to detect FRBs. However, for different types of spectra CHIME will succeed.

    The paper by Fialkov and Loeb describing these results was published in the September 10, 2017 issue of The Astrophysical Journal Letters.

    See the full article here .

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    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 11:03 am on September 20, 2017 Permalink | Reply
    Tags: , , , CfA, , The Stratosphere of a Hot Exoplanet, WASP-121b   

    From CfA: “The Stratosphere of a Hot Exoplanet” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    An artist’s conception of the hot-Jupiter exoplanet WASP-121b with its star. Astronomers have discovered in this object the first unambiguous signs of a hot stratosphere, heated to a blazing 2400 Celsius. NASA/ESA /G. Bacon, STScI

    The stratosphere of a planetary atmosphere is the layer in which the temperatures rise with altitude, in contrast to the tropospheric layer (near the ground) in which the temperature falls with altitude. On the Earth the stratosphere begins at thirty to sixty thousand feet, depending on the latitude; it terminates at about 160,000 feet. The temperature inversion of the Earth’s stratosphere is caused principally by ozone, which exists at these higher altitudes and absorbs sunlight to heat the layer. A planet’s stratosphere thus contains information about its chemical composition, and astronomers probing the atmospheres of exoplanets have wondered whether any of them show signs of having a stratosphere. The molecules in this warm gas layer should emit diagnostic spectral lines that could be spotted from Earth.

    CfA astronomer Mercedes Lopez-Morales was the Co-Principal Investigator in a large team of international exoplanet hunters who discovered a stratosphere on the exoplanet WASP-121b, the first unambiguous such discovery.

    1
    An illustration of WASP-121b, a super hot gas giant found to have a stratosphere Illustration: Engine House VFX, At-Bristol Science Centre, University of Exeter

    The exoplanet itself, discovered in 2015, is a so-called hot-Jupiter, and orbits its star every 1.27 days. Its mass is slightly larger than Jupiter’s, and it orbits so close to its star that its atmospheric temperature is thought to be heated to about 2200 Celsius (hence the name, “hot Jupiter”).

    The astronomers used the Hubble Space Telescope and the IRAC camera on the Spitzer Space Telescope to study in the planet during its secondary eclipses: as it passed behind the star, its illuminated Earth-facing side can be seen.

    NASA/ESA Hubble Telescope

    NASA/Spitzer Infrared Telescope

    The reflected light from the atmosphere enabled scientists to spot faint emission lines of the molecules present, including in this case water molecules at a temperature of about 2400 Celsius, as well as some other species that are still uncertain. The hot gas is consistent with the presence of a stratospheric layer on the planet. Water had been previously spotted on WASP-121b during a normal transit, but this new result shows that there is water in the stratosphere. The models were able to infer even more detailed information about the atmosphere, for example, that the molecules in that layer absorb about twenty percent of the incident stellar radiation, contributing to the stratosphere being hotter than the general atmosphere.

    Reference(s):

    An Ultrahot Gas-Giant Exoplanet with a Stratosphere, Thomas M. Evans, David K. Sing, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R. Wakeford, Drake Deming, Mark S. Marley, David S. Amundsen, Gilda E. Ballester, Joanna K. Barstow, Lotfi Ben-Jaffel, Vincent Bourrier, Lars A. Buchhave, Ofer Cohen, David Ehrenreich, Antonio García Muñoz, Gregory W. Henry, Heather Knutson, Panayotis Lavvas, Alain Lecavelier des Etangs, Nikole K. Lewis, Mercedes López-Morales, Avi M. Mandell, Jorge Sanz-Forcada, Pascal Tremblin & Roxana Lupu, Nature, 548, 58, 2017.

    See the full article here .

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  • richardmitnick 6:04 pm on September 11, 2017 Permalink | Reply
    Tags: , , , CfA, , Modeling the Radiation of Black Holes, ,   

    From CfA: “Modeling the Radiation of Black Holes” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    August 25, 2017

    1
    An X-ray image of two ultraluminous X-ray sources (ULXs) in the Andromeda galaxy. New calculations confirm that ULXs are usually stellar-mass black holes rapidly accreting material and emitting radiation in a narrow beam. NASA/Swift/Stefan Immler

    NASA/SWIFT Telescope

    Ultraluminous X-ray sources (ULXs) are extremely luminous, compact X-ray sources found in some nearby spiral galaxies. The nature of these mysterious sources is not well understood, but they are thought to be black holes of about ten solar-masses accreting material, and are distinct both in size and character from the supermassive black holes in the nuclei of galaxies that also emit bright X-rays. The class of ULXs appears to contain several physical variants: one subsample shows coherent pulsations and is thought to be composed of neutron stars rather than black holes, while another set might be more massive than a star. Even a single type might change its emission character with time between the several morphological classes identified.

    Astronomers trying to model ULXs face several challenges. The strong gravitational field means that the calculations must be done in a full general relativity context, and moreover the observations indicate that the emission is not spherical but instead is typically highly beamed. Not least, powerful magnetic fields are expected to be present and must in included in the simulations. CfA astronomer Ramesh Narayan and two colleagues used their new computer codes to calculate the emission properties and spatial appearances of ULXs, taking into account the complexities of relativity, magnetic fields, beaming, and varying accretion rates. Their results are in good agreement with previous, less sophisticated calculations. They conclude that observed large luminosities are in part caused by focusing of the emission by the geometry of the system. This raises the question, to be pursued in further research, of whether the observed population of ULXs is only the tip of the iceberg with many more ULXs oriented away from our line-of-sight, and if so, where this large population comes from.
    Reference(s):

    Spectra of Black Hole Accretion Models of Ultra-Luminous X-ray Sources,” Ramesh Narayan, Aleksander Sadowski, Roberto Soria, MNRAS 2017 (in press).

    See the full article here .

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  • richardmitnick 5:54 pm on September 11, 2017 Permalink | Reply
    Tags: CfA, , SPHEREx   

    From CfA: “CfA Plays Key Role in SPHEREx” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    On August 9, NASA announced that SPHEREx is among three Medium-Class Explorer (MIDEX) missions selected for a “Phase A” study.

    1
    NASA/JPL

    The SPHEREx team, along with the two other chosen MIDEX mission teams, has 9 months and $2 million to refine the mission concept and report back to NASA. NASA anticipates making its final selection by the end of 2018, with a launch expected in 2022 at the earliest. Medium-Class Explorer mission costs are capped at $250 million each, excluding the launch vehicle.

    If approved, during its nominal 27-month mission, the passively cooled SPHEREx telescope will conduct four all-sky surveys, obtaining background-limited infrared spectra of every 6 arcsec x 6 arcsec region of the sky, or about 14 billion spectra per survey. The instrument, which has no moving parts, will cover the wavelength range between 0.75 and 5.0 microns, enabling a wide range of science goals. The SPHEREx team itself will focus on three important science themes:

    1) Constraining the physics of inflation by studying its imprints on the three-dimensional large-scale distribution of matter,
    2) Tracing the history of galactic light production through a deep multi-band measurement of large-scale clustering, and
    3) Mapping the abundance and distribution of water and other biogenic ices throughout the Milky Way with a focus on the early phases of star formation and planet-forming disks.

    SPHEREx will, however, enable a wide range of other scientific investigations with its full-sky spectroscopy roughly two magnitudes deeper than 2MASS in every spectral element. The SPHEREx Principal Investigator is Jamie Bock of the California Institute of Technology; however, a group of CfA scientists, led by Gary Melnick, are responsible for the third science theme. SPHEREx Co-Investigators Matthew Ashby and Volker Tolls are also part of the CfA water/biogenic ices team, and SPHEREx collaborator Karin Öberg will be responsible for interpreting near-infrared spectra in light of present and future laboratory measurements.

    For more about SPHEREx, including the instrument design, the main science themes, and a wider array of scientific questions that SPHEREx will address, follow this link to the official SPHEREx website:

    http://spherex.caltech.edu/index.html

    See the full article here .

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  • richardmitnick 3:39 pm on September 8, 2017 Permalink | Reply
    Tags: A black hole X-ray binary (BHXB) is a black hole orbiting a normal star, , , , CfA, , Extreme Jets, V404 Cygni, X-rays are produced when the black hole's gravity pulls matter in from the normal star   

    From CfA: “Extreme Jets” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    September 8, 2017

    1
    V404 Cygni is a binary star system in which a sun-like star is orbited by a black hole. X-rays are produced when the black hole’s gravity pulls matter in from the normal star. In this X-ray image, V404 Cyg is the bright point source at the center and the bright rings are X-ray “echoes” produced by walls of dust. Astronomers have modeled the recent flare as a combination of eight discrete ejections.
    Andrew Beardmore (Univ. of Leicester) and NASA/Swift

    NASA/SWIFT Telescope

    A black hole X-ray binary (BHXB) is a black hole orbiting a normal star. When matter from the normal star accretes onto the black hole, a jet of charged particles is ejected at relativistic (near-light) speeds, and these particles emit strong X-ray radiation. The processes involved are thought to be similar to ones active under the more dramatic conditions in active galactic nuclei. Most known BHXBs are located in our galaxy, and being much closer to us they can be studied in more detail than their more distant cousins.

    Black hole X-ray binaries occasionally flare in outbursts that can last days to weeks, offering an opportunity to probe how their jets evolve. Two different types of relativistic jets are known, depending on the accretion rate of mass in the system. At low mass accretion rates, the magnetic fields bend the compact jet, prompting it to emit radiation. At high accretion rates, discrete jet ejecta are launched that can interfere with this process in several ways, resulting in more complex emission characteristics. (A very rare third type of emission displays quasi-periodic oscillations.) There are usually a few bright BHXB events each year, but the more powerful kind occurs only about once a decade.

    On June 15, 2015, the BHXB V404 Cygni underwent just such a rare, active outburst, and CfA astronomers Glen Petitpas and Mark Gurwell were members of a team that obtained simultaneous radio through submillimeter observations of the emission using the Submillimeter Array along with the Very Large Array and the James Clerk Maxwell Telescope (SCUBA-2).

    CfA Submillimeter Array Mauna Kea, Hawaii, USA

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

    East Asia Observatory James Clerk Maxwell telescope, Mauna Kea, Hawaii, USA

    They tracked the activity over four hours, during which time they saw multiple, rapidly changing flares that were bright at all the frequencies they observed. The scientists best-fitting model worked well with eight discrete, bipolar, jet ejection events. The model also estimated the speed, structural properties, geometry, and energetics of the jets. These unprecedented coordinated observations of a BHXB highlight the importance of multi-band observations in studying BHXB jet emission.

    Science paper:
    Extreme Jet Ejections from the Black Hole X-ray Binary V404 Cygni MNRAS

    See the full article here .

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    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.

     
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