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  • richardmitnick 5:07 pm on February 15, 2019 Permalink | Reply
    Tags: , , , CfA, , Energetic Particles Can Bombard Exoplanets, TRAPPIST-1 is a system of seven Earth-sized worlds orbiting an ultra-cool dwarf star about 120 light-years away   

    From Harvard-Smithsonian Center for Astrophysics: “Energetic Particles Can Bombard Exoplanets” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    February 15, 2019

    TRAPPIST-1 is a system of seven Earth-sized worlds orbiting an ultra-cool dwarf star about 120 light-years away.

    A size comparison of the planets of the TRAPPIST-1 system, lined up in order of increasing distance from their host star. The planetary surfaces are portrayed with an artist’s impression of their potential surface features, including water, ice, and atmospheres. NASA

    The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

    The star, and hence its system of planets, is thought to be between five-to-ten billion years old, up to twice as old as our own solar system. For scientists seeking evidence for life elsewhere, the advanced age provides more time for chemistry and evolution to operate than the Earth had. On the other hand, the planets are all close to the star (in fact they are probably tidally locked to the star with one side always facing it), and consequently would have soaked up billions more year’s-worth of high energy radiation from the star’s winds, adversely affecting any atmospheres they host.

    In a new paper in The Astrophysical Journal, CfA astronomers Federico Fraschetti, Jeremy Drake, Julian Alvardo-Gomez, Sofia Moschou, and Cecilia Garraffo and a colleague carry out theoretical simulations of the effects of high-energy protons from a stellar wind on nearby exoplanets. These particles are produced by stellar flares or by shock waves driven by magnetic events in the stellar corona. Measurements of solar eruptive events provide the scientists with a basis for their simulations.

    The astronomers calculate the first realistic simulation of the propagation of energetic particles through the turbulent magnetic field environment of an M dwarf star and its wind, and they tailored the details to the TRAPPIST-1 system. They find that particles are trapped within the star’s magnetic field and are directed into two polar streams focused onto the planets’ orbital plane – independent of many of the details. The scientists conclude that the innermost putative habitable planet in the system, TRAPPIST-1e, is bombarded by a proton flux up to a million times larger than that experienced by the present-day Earth. Nevertheless, there are many variables at play, for example the angle between the magnetic field and the rotation axis of the star, and consequently a large uncertainty remains in how these effects actually are manifest in individual situations.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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.

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  • richardmitnick 5:41 pm on January 25, 2019 Permalink | Reply
    Tags: A Primordial Star Forming Galaxy, , , , CfA, , Luminous galaxy G09_83808   

    From Harvard-Smithsonian Center for Astrophysics: “A Primordial Star Forming Galaxy” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    January 25, 2019

    1
    A Hubble image of an ultraluminous infrared galaxy in the relatively nearby universe. Astronomers studying ultraluminous galaxies in the remote, early universe have spotted one dating from the epoch only one billion years after the big bang and found, surprisingly, that is it similar to modern ones like this. NASA/ESA Hubble

    Galaxies with extremely high rates of star formation (from hundreds to thousands of solar-masses worth of stars per year) are rare. Our Milky Way, for example, makes only about one star a year. The process of star formation heats up dust to emit in the infrared, and extreme starburst galaxies that make this many per year shine so brightly they can be spotted at cosmological distances. When gravitational lensing by a fortuitously intervening galaxy or cluster of galaxies magnifies the signal, even farther away and cosmically earlier galaxies can be detected.

    Gravitational Lensing NASA/ESA

    To date only a handful of these extreme starburst galaxies have been confirmed from the universe’s first billion years of existence. Although still a small sample, they offer important insights into how stars were made at primordial times when most chemical elements were less abundant. They also help astronomers understand star formation in cases where the physical processes are so dramatic when compared to the process in our galaxy.

    Far infrared and submillimeter sky surveys identified the first extreme galaxies from the emission of dust heated by their star formation activity. The rate of star formation is inferred from the luminosity of the galaxy, and this is calculated from the observed brightness and distance. As usual in astronomy, the distance parameter is key but difficult to measure. For these remote monsters it is generally obtained from the redshift of some strong lines emitted by the galaxy in the far infrared or submillimeter, typically from carbon monoxide (an abundant molecule) and/or from singly ionized atomic carbon.

    CfA astronomer David Wilner was a member of a large team of astronomers that used the Large Millimeter Telescope Alfonso Serrano (LMT) in Mexico to followup the luminous galaxy G09_83808 that was first spotted in Herschel Space Observatory survey images;

    The University of Massachusetts Amherst and Mexico’s Instituto Nacional de Astrofísica, Óptica y Electrónica
    Large Millimeter Telescope Alfonso Serrano, Mexico, at an altitude of 4850 meters on top of the Sierra Negra

    ESA/Herschel spacecraft active from 2009 to 2013

    they also observed it with the ALMA facility to probe its spatial extent and with the Submillimeter Array to measure its carbon line.

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

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    The spectral lines date the galaxy to about one billion years after the big bang, making it one of the first discovered whose unambiguous distance was that far away. Calculations of its star formation rate based on the luminosity corrected for effects of extinction and lensing find it to be about 380 solar-masses per year, comparable in fact to some of the ultra-luminous galaxies in our own cosmic era. This result implies that despite about twelve billion years of cosmic history, this galaxy is making stars in the same way as do extreme galaxies today. The object also has a relatively weak atomic carbon line, a characteristic also found (but still not well understood) to apply in luminous local systems. The new result also confirms that the early universe had luminous galaxies with physical processes that, although not well understood, appear to mirror closely local extreme cases.

    Science Paper:
    “A Dusty Star-Forming Galaxy at z = 6 Revealed by Strong Gravitational Lensing,” Jorge A. Zavala et al.
    Nature Astronomy

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 2:25 pm on January 22, 2019 Permalink | Reply
    Tags: , , , , CfA, , Sagittarius A*   

    From Harvard-Smithsonian Center for Astrophysics: “Lifting the Veil on the Black Hole at the Heart of Our Galaxy” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    January 22, 2019

    Tyler Jump
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    +1 617-495-7462
    tyler.jump@cfa.harvard.edu

    1

    A black hole four million times as massive as our Sun lurks at the center of the Milky Way. This black hole, called Sagittarius A* (Sgr A*), swallows nearby material that glows brightly as it approaches the event horizon.

    SGR A and SGR A* from Penn State and NASA/Chandra

    This galactic furnace is key to understanding black holes, but our view of it is obscured by lumpy clouds of electrons throughout the Galaxy. These clouds stretch, blur, and crinkle the image of Sgr A*, making it appear as though the black hole is blocked by an enormous sheet of frosted glass.

    Now, a team of astronomers, led by Radboud University PhD student Sara Issaoun, have finally been able to see through these clouds and to study what makes the black hole glow. Issaoun completed this work while participating in the Predoctoral Program at the Smithsonian Astrophysical Observatory in Cambridge, MA.

    “The source of the radiation from Sgr A* has been debated for decades,” says Michael Johnson of the Center for Astrophysics | Harvard and Smithsonian (CfA). “Some models predict that the radiation comes from the disk of material being swallowed by the black hole, while others attribute it to a jet of material shooting away from the black hole. Without a sharper view of the black hole, we can’t exclude either possibility.”

    The team used the technique of Very Long Baseline Interferometry (VLBI), which combines many telescopes to form a virtual telescope the size of the Earth. The decisive advance was equipping the powerful ALMA array of telescopes in northern Chile with a new phasing system. This allowed it to join the GMVA, a global network of twelve other telescopes in North America and Europe.

    GMVA The Global VLBI Array

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

    “ALMA itself is a collection of more than 50 radio dishes. The magic of the new ALMA Phasing System is to allow all these dishes to function as a single telescope, which has the sensitivity of a single dish more than 75 meters across. That sensitivity, and its location high in the Andes mountains, makes it perfect for this Sgr A* study,” says Shep Doeleman of the CfA, who was Principal Investigator of the ALMA Phasing Project.

    “The breakthrough in image quality came from two factors,” explains Lindy Blackburn, a radio astronomer at the CfA. “By observing at high frequencies, the image corruption from interstellar material was less significant, and by adding ALMA, we doubled the resolving power of our instrument.”

    The new images show that the radiation from Sgr A* has a symmetrical morphology and is smaller than expected – it spans a mere 300 millionth of a degree. “This may indicate that the radio emission is produced in a disk of infalling gas rather than by a radio jet,” explains Issaoun, who tested computer simulations against the images. “However, that would make Sgr A* an exception compared to other radio-emitting black holes. The alternative could be that the radio jet is pointing almost directly at us.”

    Issaoun’s supervisor Heino Falcke, Professor of Radio Astronomy at Radboud University, was surprised by this result. Last year, Falcke would have considered this new jet model implausible, but recently another set of researchers came to a similar conclusion using ESO’s Very Large Telescope Interferometer of optical telescopes and an independent technique. “Maybe this is true after all,” concludes Falcke, “and we are looking at this beast from a very special vantage point.”

    To learn more will require pushing these telescopes to even higher frequencies. “The first observations of Sgr A* at 86 GHz date from 26 years ago, with only a handful of telescopes. Over the years, the quality of the data has improved steadily as more telescopes join,” says J. Anton Zensus, director of the Max Planck Institute for Radio Astronomy.

    Michael Johnson is optimistic. “If ALMA has the same success in joining the Event Horizon Telescope at even higher frequencies, then these new results show that interstellar scattering will not stop us from peering all the way down to the event horizon of the black hole.”

    The results were published in The Astrophysical Journal.

    See the full article here .

    See also here.


    five-ways-keep-your-child-safe-school-shootings
    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 12:12 pm on January 21, 2019 Permalink | Reply
    Tags: , , , CfA, , , , Making Stars When the Universe was Half Its Age, The Hubble Ultra Deep Field of galaxies   

    From Harvard-Smithsonian Center for Astrophysics: “Making Stars When the Universe was Half Its Age” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    1
    The Hubble Ultra Deep Field of galaxies. A new study of the star formation activity in 179 of the galaxies in this image including many dating from about six billion years ago confirms an earlier puzzling result: lower mass galaxies tend to make stars at a rate slightly slower than expected. NASA, ESA, and S. Beckwith (STScI) and the HUDF Team.

    The universe is about 13.8 billion years old, and its stars are arguably its most momentous handiwork. Astronomers studying the intricacies of star formation across cosmic time are trying to understand whether stars and the processes that produce them were the same when the universe was younger, about half its current age. They already know that from three to six billion years after the big bang stars were being made at a rate roughly ten times faster than they are today. How this happened, and why, are some of the key questions being posed for the next decade of research.

    Star formation in a galaxy is thought to be triggered by the accretion of gas from the intergalactic medium (gas accretion via mergers between galaxies is thought to play a relatively minor role in the total numbers of stars produced). In galaxies that are actively making stars there is a tight relationship between their mass in stars and their rate of forming new stars, and this relationship approximately holds not only locally but even back when the universe was billions of years younger. In contrast, galaxies that are undergoing an active starburst – or the opposite, the quenching of star formation – fall above and below that relation respectively. The relationship supports the general picture of galaxy growth by gas accretion, except that for some reason smaller galaxies – those with fewer than about ten billion stars – seem to make slighter fewer stars than expected for their masses (the Milky Way is right at the turnover, with about ten billion stars and a rate of roughly one new star per year). A particularly significant consequence of this paucity, if real, is that simulations of galaxy growth do not show it, implying that the simulations are incorrect for smaller galaxies and that some physics is missing.

    CfA astronomer Sandro Tacchella is a member of a team that used the Multi Unit Spectroscopic Explorer instrument on the VLT (Very Large Telescope) to obtain optical spectra of galaxies in the famous Hubble Deep Field South image of galaxies.

    ESO MUSE on the VLT on Yepun (UT4)

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

    They measured stellar emission lines in 179 distant galaxies in the field and used them to calculate the star formation behaviors after corrections for effects like dust extinction (which can make some of the optical lines appear weaker than they are). The find that the puzzle of depleted star formation in small galaxies is real at a level of roughly 5% even when accounting for noise and scatter in the data caused, for example, by galaxy evolution effects. The authors suggest that some kind of previously unaccounted for feedback may be responsible.

    Science paper:
    The MUSE Hubble Ultra Deep Field Survey XI. Constraining the low-mass end of the stellar mass – star formation rate relation at z < 1
    Astronomy and Astrophysics

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 2:04 pm on January 15, 2019 Permalink | Reply
    Tags: , , , , CfA, , Double Star System Flips Planet-Forming Disk into Pole Position,   

    From Harvard-Smithsonian Center for Astrophysics and U Warwick: “Double Star System Flips Planet-Forming Disk into Pole Position” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    U Warwick

    January 14, 2019

    Tyler Jump
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    +1 617-495-7462
    tyler.jump@cfa.harvard.edu

    Peter Thorley
    Media Relations Manager (Warwick Medical School and Department of Physics)
    Email: peter.thorley@warwick.ac.uk
    Tel: +44 (0)24 761 50868
    Mob: +44 (0) 7824 540863

    1

    New research that included astronomers Luca Matra and David J. Wilner of the Center for Astrophysics | Harvard & Smithsonian has found the first confirmed example of a double star system that has flipped its surrounding disc to a position that leaps over the orbital plane of those stars. The international team of astronomers used the Atacama Large Millimeter/sub-millimeter Array (ALMA) to obtain high-resolution images of the Asteroid belt-sized disc.

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

    The overall system presents the unusual sight of a thick hoop of gas and dust circling at right angles to the binary star orbit. Until now this setup only existed in theorists’ minds, but the ALMA observation proves that polar discs of this type exist, and may even be relatively common.

    The new research is published today (14 January 2019) by Royal Society University Research Fellow Dr. Grant M. Kennedy of the University of Warwick’s Department of Physics and Centre for Exoplanets and Habitability in Nature Astronomy in a paper entitled “A circumbinary protoplanetary disc in a polar configuration.”

    Dr. Grant M. Kennedy of the University of Warwick said:

    Discs rich in gas and dust are seen around nearly all young stars, and we know that at least a third of the ones orbiting single stars form planets. Some of these planets end up being misaligned with the spin of the star, so we’ve been wondering whether a similar thing might be possible for circumbinary planets. A quirk of the dynamics means that a so-called polar misalignment should be possible, but until now we had no evidence of misaligned discs in which these planets might form.

    Dr. Kennedy and his fellow researchers used ALMA to pin down the orientation of the ring of gas and dust in the system. The orbit of the binary was previously known, from observations that quantified how the stars move in relation to each other. By combining these two pieces of information they were able to establish that the dust ring was consistent with a perfectly polar orbit. This means that while the stellar orbits orbit each other in one plane, like two horses going around on a carousel, the disc surrounds these stars at right angles to their orbits, like a giant ferris wheel with the carousel at the centre.

    Dr. Grant M. Kennedy of the University of Warwick added:

    Perhaps the most exciting thing about this discovery is that the disc shows some of the same signatures that we attribute to dust growth in discs around single stars. We take this to mean planet formation can at least get started in these polar circumbinary discs. If the rest of the planet formation process can happen, there might be a whole population of misaligned circumbinary planets that we have yet to discover, and things like weird seasonal variations to consider.

    If there were a planet or planetoid present at the inner edge of the dust ring, the ring itself would appear from the surface as a broad band rising almost perpendicularly from the horizon. The polar configuration means that the stars would appear to move in and out of the disc plane, giving objects two shadows at times. Seasons on planets in such systems would also be different. On Earth they vary throughout the year as we orbit the Sun. A polar circumbinary planet would have seasons that also vary as different latitudes receive more or less illumination throughout the binary orbit.

    The full research team for this paper also included: Dr. Grant M. Kennedy of the University of Warwick’s Department of Physics and Centre for Exoplanets and Habitability as lead author and; Stefano Facchini of the Max-Planck-Institut fur Extraterrestrische Physik; Julien Milli of the European Southern Observatory (ESO); Olja Panic of the School of Physics & Astronomy, University of Leeds; Daniel Price of Monash University’s Centre for Astrophysics (MoCA) and School of Physics and Astronomy; and Mark C. Wyatt, and Ben M. Yelverton of the Institute of Astronomy, University of Cambridge. This press release was first prepared by the University of Warwick.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 1:27 pm on December 22, 2018 Permalink | Reply
    Tags: A New Neptune-Size Exoplanet, , , , CfA, , The exoplanet K2-263b   

    From Harvard-Smithsonian Center for Astrophysics: “A New Neptune-Size Exoplanet” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    Friday, December 14, 2018

    The remarkable exoplanet discoveries made by the Kepler and K2 missions have enabled astronomers to begin to piece together the history of the Earth and to understand how and why it differs from its diverse exoplanetary cousins.

    Two still outstanding puzzles include the differences between the formation and evolution of rocky versus non-rocky small planets, and why there seem to be a size gap with very few exoplanets at or about two Earth-radii in size (planets with smaller radii are likely to be rocky or Earth-like in their composition). In order to estimate an exoplanet’s composition its density is needed, requiring a measurement of mass as well as size. While a radius can be estimated from the shape of the planet’s transit curve as it blocks out its host star’s light, a mass is more difficult to determine. In order to develop the emerging picture, however, precise and accurate masses are required for more planets that are similar in size to the Earth.

    The K2 exoplanetary mission is the revived version of the Kepler exoplanetary discovery mission.

    NASA/Kepler Telescope

    Together they have discovered thousands of exoplanets, and uncovered a remarkable and unexpected diversity in the exoplanet population.

    K2 is sensitive only to short-period planets (it has only found a few with periods longer than 40 days). The exoplanet K2-263b orbits a star less massive than the sun (0.86 solar-masses) and located 536 light-years away as measured with the new Gaia satellite.

    2
    K2-263b was originally spotted in data from NASA’s Kepler/K2 mission.

    ESA/GAIA satellite

    This exoplanet has a radius of 2.41 Earth-radii (with a 5% uncertainty). CfA astronomers Maria Lopez-Morales, Dave Charbonneau, Raphaelle Haywood, John Johnson, Dave Latham, David Phillips, and Dimitar Sasselov and their colleagues used the HARPS-N high precision spectrometer on the Telescopio Nazionale Galileo in La Palma, Spain, to measure the periodic velocity of the exoplanet as it orbited and thus to derive its mass.

    Harps North at Telescopio Nazionale Galileo –


    Telescopio Nazionale Galileo a 3.58-meter Italian telescope, located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain, Altitude 2,396 m (7,861 ft)

    The HARPS-N velocity measurements were amazingly precise – uncertain to about a mere eleven miles an hour, about the speed of a slow bicyclist. From the orbital details the scientists obtained an exoplanet mass of 14.8 Earth-masses and a hence a density of about 5.6 grams per cubic centimeter (for comparison, the density of water is one gram per cubic centimeter, and the average density of the rocky Earth is 5.51 grams per cubic centimeter). The scientists conclude that K2-263b most likely contains an equivalent amount of ices compared to rocks, roughly consistent with current ideas about planet formation and the relative abundances in a circumstellar nebula of the building-block elements like iron, nickel, magnesium, silicon, oxygen, carbon and nitrogen.

    Science paper:
    K2-263 b: a 50 d period sub-Neptune with a mass measurement using HARPS-N,” A. Mortier et al.
    https://academic.oup.com/mnras/article-abstract/481/2/1839/5090159?redirectedFrom=fulltext

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 12:59 pm on December 22, 2018 Permalink | Reply
    Tags: , , , CfA, , Intermediate Mass Black Holes Discovered in Galactic Nuclei   

    From Harvard-Smithsonian Center for Astrophysics: “Intermediate Mass Black Holes Discovered in Galactic Nuclei” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    1
    An infrared IRAC/Spitzer image of a dwarf galaxy with an active galactic nucleus that is not supermassive. A new study has found the first ten confirmed intermediate-mass black hole active galactic nuclei (defined as black holes having between about 100 – 300,000 solar-masses). NASA/ Spitzer/IRAC

    The existence of black holes is well established, and observations have found both stellar mass sized objects and giant ones millions to billions times more massive than the sun at the centers of galaxies. But the origin of these massive black holes is a mystery. Small black holes are the ashes of supernovae, but massive ones presumably must start small and grow over time. Such growth is highly constrained, however, because the vary act of accreting material generates radiation that inhibits further inflow, and billions of years are thought to be needed to make billion solar-mass black holes.

    The problem arises because astronomers have now detected quasars with supermassive black holes in the early universe – but there has not been enough time since the big bang for them to grow to supermassive sizes. Stellar mass black holes, furthermore, should have produced many intermediate mass black holes as they grew, yet only a few are candidates and their identification as IMBHs remains controversial.

    The firm identification of IMBHs could help clarify the issue. An alternative suggestion has been advanced to solve the problem. The direct collapse of a large gas cloud in the early universe could produce an intermediate-sized black hole (IMBH) with hundreds to hundreds of thousands of solar masses, leaving plenty of time for them all to grow by now into supermassive objects.

    CfA astronomer Igor Chilingarian led a team that has for the first time identified a set of galaxies with active nuclei hosting intermediate mass black holes.

    They used optical and near-infrared galaxy surveys to identify candidate sources from the intensity and velocities of their atomic emission lines, selecting three hundred and five likely IMBH candidates. They then obtained X-ray measurements from the Chandra and/or XMM missions which confirmed that ten of these nuclei were IMBHs and were actively accreting.

    NASA/Chandra X-ray Telescope

    ESA/XMM Newton

    The least massive IMBH they discovered in their set of ten had thirty-six thousand solar-masses; the largest had about ten times more. Their discovery is remarkable not only because it marks the first conclusive detection of these elusive objects, but because it lends credence to the idea that stellar-mass black holes seeded the early universe, with many of them then growing into the supermassive monsters we see today.

    Science paper:

    A Population of Bona Fide Intermediate-mass Black Holes Identified as Low-luminosity Active Galactic Nuclei,” Igor V. Chilingarian, Ivan Yu. Katkov, Ivan Yu. Zolotukhin, Kirill A. Grishin, Yuri Beletsky, Konstantina Boutsia, and David J. Osip
    http://iopscience.iop.org/article/10.3847/1538-4357/aad184/meta

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 5:42 pm on December 2, 2018 Permalink | Reply
    Tags: "How Do Stellar Binaries Form?, , , , CfA,   

    From Harvard-Smithsonian Center for Astrophysics: “How Do Stellar Binaries Form?” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    November 30, 2018

    1
    An ALMA millimeter-wavelength image of protostellar binary stars early in their formation. (The length scale and the size of the telescope’s beam are shown at the bottom.) Astronomers have studied seventeen multiple systems and found evidence supporting the model of multiple stars developing from disk fragmentation. Tobin et al.

    Most stars with the mass of the sun or larger have one or more companion stars, but when and how these multiple stars form is one of the controversial central problems of astronomy. Gravity contracts the natal gas and dust in an interstellar cloud until clumps develop that are dense enough to coalesce into stars, but how are multiple stars fashioned? Because the shrinking cloud has a slight spin, a disk (possibly a preplanetary system) eventually forms. In one model of binary star formation, this disk fragments due to gravitational instabilities, producing a second star. The other model argues that turbulence in the contracting cloud itself fragments the clumps into multiple star systems. In the first case, simulations show that the two stars should be relatively close together, typically less than about 600 astronomical units (one AU is the average distance of the earth from the sun). If the second mechanism is correct, both close and wide binary pairs can form. A distinguishing feature of the turbulent fragmentation process, and one that facilitates an observational test, is that the seeds for multiplicity are produced early in the pre-stellar phases.

    CfA astronomers Sarah Sadavoy and Mike Dunham were members of a team of astronomers that used the VLA and ALMA radio and millimeter-wave facilities to study seventeen protostellar systems of multiple-stars in the nearby Perseus cloud.

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

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

    The sensitive observations were able to reveal the environments of the systems and determine the presence of any small-scale rotation or surrounding material. Twelve of the systems were spatially resolved, and eight showed dust emission structures surrounding the pair. The slightly more evolved systems in the set showed no evidence for circumbinary dust; they have probably reached the end point of their early evolution and finished accreting material. In summary, about two-thirds of the systems were consistent with the disk fragmentation theory and one third was inconsistent with it. The results show that the disk fragmentation mechanism is an important one but probably not the whole story, and a larger sample should help constrain the processes even further.

    Science paper:
    The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Perseus Protostars. VI. Characterizing the Formation Mechanism for Close Multiple Systems
    The Astrophysical Journal John J. Tobin, Leslie W. Looney, Zhi-Yun Li, Sarah I. Sadavoy, Michael M. Dunham, Dominique Segura-Cox, Kaitlin Kratter, Claire J. Chandler, Carl Melis, Robert J. Harris, and Laura Perez

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 3:32 pm on November 25, 2018 Permalink | Reply
    Tags: , , , CfA, , Gravitationally Lensed Quasars, Strong gravitational lensing,   

    From Harvard-Smithsonian Center for Astrophysics: “Gravitationally Lensed Quasars” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    November 16, 2018

    The path of light is bent by mass, an effect predicted by Einstein’s theory of gravity, and when a massive galaxy or cluster lies along our line-of-sight to a more distant galaxy its matter will act as a lens to image the light from that object. So-called strong gravitational lensing creates highly distorted, magnified and often multiple images of a single source.

    Gravitational Lensing NASA/ESA

    Weak gravitational lensing NASA/ESA Hubble

    (Strong lensing is distinct from weak lensing which results in modestly deformed shapes of background galaxies.) Quasars are galaxies with massive black holes at their cores around which vast amounts of energy are being radiated, more than from the rest of the entire host galaxy. Their luminosities allow quasars to be seen at cosmological distances and they are therefore likely candidates for strong lensing, with a few hundred gravitationally lensed quasars known so far. They have provided valuable information not only about quasars and lensing but also on cosmology since the distorted light paths of the distant objects have traveled across cosmological distances.

    CfA astronomer David James was a member of a large international team systematically searching for new gravitationally lensed quasars. They used the WISE infrared all-sky survey to search for candidates whose infrared colors suggested they were galaxies with active nuclei (like quasars). They processed images of these candidates with a sophisticated algorithm looking for evidence of their being multiple components, such as would be expected from a lensed system, and then followed up this subset with spectroscopic and ground-based imaging observations using higher spatial resolution than WISE. Of the original set of fifty-four candidates, they found two whose spectra confirmed that they were gravitationally lensed quasars, one with four sub-images and one with two, each of whose light has been traveling towards us for about ten billion years. The images in these two cases also showed traces of the lensing galaxy, an important verification of the lensing effect, although the galaxies were too faint to obtain measurements of their distances. The scientists also identified another seven objects that are likely to be doubled-quasars, but further research is needed to confirm those results.
    Reference(s):

    “The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 Follow-up Campaign – II. New quasar lenses from double component fitting,” T. Anguita et al. MNRAS 480, 5017, 2018.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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 3:01 pm on November 25, 2018 Permalink | Reply
    Tags: , , “Cherenkov” light, , CfA, CFA/VERITAS is an array of four 12 m diameter optical telescopes located at the SAO's Fred Lawrence Whipple Observatory near Tucson Arizona, , It is common for massive stars to form in binary pairs and so it is not surprising that some pulsars have an orbiting companion that has survived its partner's explosive death, Very high energy (VHE) gamma-ray emitting neutron star-massive star binary pairs   

    From Harvard-Smithsonian Center for Astrophysics: “Once-In-A-Lifetime Observations by Veritas Astronomers Reveal High Energy Gamma-Rays from a Binary Star System” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    November 13, 2018
    Tyler Jump
    Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    +1 617-495-7462
    tyler.jump@cfa.harvard.edu

    CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

    A new discovery reported in The Astrophysical Journal Letters might lay claim to title of the most unusual extreme class of astronomical object: very high energy (VHE) gamma-ray emitting, neutron star-massive star binary pairs. Of the one-hundred billion stars in our galaxy, fewer than ten are in known to be in gamma-ray binary systems, with this discovery being only the second with an identified neutron star. The gamma-ray emission was discovered during an event that will not happen again until 2067.

    A neutron star is the dense remains of a type of supernova, the explosive death of a star that started its life more massive than about eight solar-masses. Containing as much material as the sun but in an object only the diameter of a city, neutron stars are so dense that most of their matter is in the form of neutrons, the uncharged atomic particles found in atomic nuclei. Neutron stars spin rapidly and generate powerful magnetic fields, fast winds and narrow beams that sweep like a lighthouse across the sky as the star rotates. If the Earth happens to lie in the path of one of these beams as it passes, astronomers can detect the radiation as regular pulses at radio and other wavelengths. There are a few thousand of these “pulsars” known, beating at a variety of rates from more than a thousand times a second to less than about once a second.

    It is common for massive stars to form in binary pairs, and so it is not surprising that some pulsars have an orbiting companion that has survived its partner’s explosive death. Both the pulsar and its companion are likely to have disks of material around them. The rapidly spinning pulsar and its wind can in some cases slam into the disk and wind of the companion star as the two periodically approach in their orbital dance. The energetic collision can produce intense shocks that accelerate charged particles to energies high enough to produce very high energy (VHE) gamma ray radiation by accelerating the particles to nearly the speed of light. When light scatters off such energetic particles it too becomes energized and becomes VHE gamma ray photons each one of which can pack a billion times more energy than a photon of optical light. The precise timing of the radio pulses allows astronomers to use the radio signals to deduce some parameters of the stars and their orbit. Although there are plenty of pulsars, until now most of the explanation was speculation, with only one known case of a binary pulsar system exhibiting VHE gamma-ray emission.

    An international team of astronomers began intensively tracking a second, possible VHE gamma-ray pulsar system in 2016. Located about five thousand light-years away in a massive stellar nursery in the direction of the constellation Cygnus, the pulsar was identified as having a massive stellar companion that orbited it every 50 years in an extreme elliptical orbit. At their closest approach the two were expected to come within a mere one astronomical unit of each other (one AU is the average distance of the Earth from the sun), and the scientists had calculated that this would happen on November 13, 2017 – exactly one year ago.

    CfA astronomers Wystan Benbow, Gareth Hughes, and Michael Daniel direct VERITAS operations and enabled the VERITAS collaboration’s participation in the program to monitor the behavior of this bizarre object before, after and during its expected closest approach. VERITAS is an array of four 12 m diameter optical telescopes located at the SAO’s Fred Lawrence Whipple Observatory near Tucson, Arizona. VERITAS detects gamma rays via the extremely brief flashes of blue “Cherenkov” light created when gamma rays are absorbed in the Earth’s atmosphere. The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland. VERITAS scientists were joined by a team using the two 17 m MAGIC Cherenkov telescopes located at El Roque de Los Muchachos on the island of La Palma, Spain.

    As the binary system is embedded in a larger, diffuse region of VHE gamma-ray emission, the international team of astronomers anxiously awaited the event to see whether the VHE gamma-rays emission brightened near the pulsar. According to Alicia López Oramas, a researcher with MAGIC at the Instituto de Astrofísica de Canarias (IAC), and one of the corresponding authors of the study, “such a unique system was expected to emit very-high-energy gamma rays during this approach, and this opportunity could not be missed.” Graduate student Tyler Williamson and his advisor Professor Jamie Holder, both from University of Delaware’s Department of Physics and Astronomy, played leading roles in the VERITAS campaign, together with Ralph Bird, a post-doctoral researcher at the University of California, Los Angeles.

    Initial observations, in 2016, revealed weak gamma-ray emission, consistent with earlier results. “This low-level, steady emission is most likely from a nebula which is being continuously powered by the pulsar,” explains Dr. Bird. Starting in September 2017, the results became much more exciting. “The gamma-ray flux we observed in September was twice the previous value,” says Williamson. But the fireworks were just beginning. “During the closest approach between the star and the pulsar, in November 2017, the flux increased 10 times in just a single night.”

    In an attempt to explain not only the strength of the gamma rays, but also their gradual variability and then sudden flaring, the team tried to match a recent theoretical model to their observations. The model contains the latest ideas about pulsars, the binary disk and wind environment, the nature of the ionized nebulosity around the object, the spectrum of emission and tries to refine the orbital parameters of the binary. It was unsuccessful and so the scientists conclude that significant revision is needed to the models in order to fit the observations, including better information about the geometry of the encounter. Since information about the structure of disks and winds around pulsars depends on many diverse yet key parameters like magnetic field strength and environmental history, this object – if it can be successfully modeled – offers to be a potential Rosetta Stone about the birth and evolution of compact objects, and so includes all compact objects produced in supernovae, pulsars without companions, and even many black hole binary systems. In the coming years the scientists plan to continue to monitor this and other pulsars to monitor the exotic behavior of these most unusual and extreme cosmic characters. Wystan Benbow from the CfA states that “continued investment in the operation of unique, leading edge facilities like VERITAS is critical and will ensure further opportunities to achieve transformative science.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    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.

     
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