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  • richardmitnick 9:50 am on January 12, 2017 Permalink | Reply
    Tags: , Auroral Displays at Brown Dwarfs, , Brown Dwarf Stars,   

    From astrobites: “Auroral Displays at Brown Dwarfs” 

    Astrobites bloc


    Title: Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
    Authors: G.Hallinan, S. P. Littlefair, G. Cotter, et al.
    First Author’s Institution: California Institute of Technology
    Caltech Logo
    Status: Published in Nature (2015), open access

    Auroras are the spectacular light shows visible in the polar regions at Earth and other planets. In 2015 they were detected for the first time outside of the solar system. Brown dwarfs are objects often described as “failed stars”, meaning they are insufficiently massive to ignite hydrogen fusion in their cores. Today’s paper reports on the remarkable discovery that a particular brown dwarf plays host to auroral displays far more powerful than those found anywhere in the solar system.

    Brown dwarfs

    Artist's concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech
    Artist’s concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech

    Brown dwarfs occupy the region between giant planets and the lowest mass stars. It is generally accepted that they form in a manner similar to stars, i.e. the gravitational collapse of interstellar gas, but never reaching a mass sufficient to sustain hydrogen fusion in the core. As such, brown dwarfs are extremely cool, faint objects, making their detection much more difficult than ordinary stars. However, they provide an excellent opportunity to for us to better understand the physics that differentiates the stellar and planetary domains. Since their discovery many surveys have been performed which have revealed, amongst other things, the existence of complex weather systems and strong global magnetic fields.


    Understanding the interaction of the magnetic field at a brown dwarf with its nearby space environment is a key scientific goal. At Earth, space scientists observe the aurora as a means of revealing the structure and dynamics of the magnetic field, and the plasma which interacts with it. Before turning to auroras at brown dwarfs we shall briefly review at what we know about auroras from our studies at Earth and other solar system planets.

    The vibrant displays that we see are a result of charged particles (i.e. electrons and ions) from the plasma population around the Earth raining down along magnetic field lines, and colliding with molecules in the atmosphere. These collisions excite the atmospheric constituents to a higher energy state, causing the emission of a photon as they return to their original state.

    Auroral emissions aren’t just confined to Earth; they are found at other magnetised planets in the solar system, with Jupiter being a particularly spectacular example.

    JUNE 30, 2016: Astronomers are using NASA’s Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the solar system, Jupiter. The auroras were photographed during a series of Hubble Space Telescope Imaging Spectrograph far-ultraviolet-light observations taking place as NASA’s Juno spacecraft approaches and enters into orbit around Jupiter. The aim of the program is to determine how Jupiter’s auroras respond to changing conditions in the solar wind, a stream of charged particles emitted from the sun. Auroras are formed when charged particles in the space surrounding the planet are accelerated to high energies along the planet’s magnetic field. When the particles hit the atmosphere near the magnetic poles, they cause it to glow like gases in a fluorescent light fixture. Jupiter’s magnetosphere is 20,000 times stronger than Earth’s. These observations will reveal how the solar system’s largest and most powerful magnetosphere behaves. The full-color disk of Jupiter in this image was separately photographed at a different time by Hubble’s Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble project that annually captures global maps of the outer planets.
    Date 30 June 2016
    Source http://hubblesite.org/newscenter/archive/releases/2016/24
    Author NASA, ESA, and J. Nichols (University of Leicester)

    Neither are they confined only to the visible part of the spectrum; auroral emissions occur from radio frequencies through to UV and X-ray.

    Now we return to brown dwarfs. Since 2006 it has been known that a handful of brown dwarfs emit very regular and persistent radio bursts. These burst are pulsed at the rotation period of the dwarf, leading some researchers to suggest that they may be caused by auroras that are generated in a similar manner to Jupiter’s main auroral oval. The pulsing in this case may be due to the magnetic axis being tilted from the spin axis, so that as the dwarf rotates the auroral emission cones into our line of sight. This motivated the authors of today’s paper to target a particular brown dwarf, LSR J1835 + 3259, with simultaneous radio and optical observation, pursuing a possible relation between the two.

    LSR J1835 + 3259. Image: http://images.zeit.de/ http://www.theweeklyobserver.com/ailed-star-shows-dazzling-display-of-northern-lights/5575/

    Radio observations were made using the Very Large Array (VLA) radio telescope, while simultaneously, optical measurements were made with the 5.1 m Hale telescope at the Palomar Observatory with follow-up observations from the 10 m Keck telescope.

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

    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA
    Caltech Hale Telescope at Palomar interior
    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory Interior
    Keck Observatory, Mauna Kea, Hawaii, USA

    The results of the observations are shown in Figure 1, where the light curve from the optical measurements (Fig 1a) shows a clear periodicity of 2.84 h. Observations of the radio emission (Fig 1b) show the same periodicity, with a slight offset in phase causing it to lag slightly behind the optical emission. The authors attribute their findings to auroras which are driven by strong electric currents flowing in the magnetosphere of the dwarf.

    Figure 1: (a) Optical measurements of Balmer line emission of LSR J1835 made using the Hale telescope. (b) Corresponding radio observations of the same object made using the VLA radio telescope. [Figure 1 from Hallinan et al. 2015]

    With this discovery many open questions are presented. What is the mechanism driving the auroras? It may be interaction with the interstellar medium, analogous to the process of the Earth’s magnetosphere interacting with the solar wind. Or it could be due to a continuously replenishing source of plasma mass outflow from within a closed magnetosphere, analogous to the mechanism producing Jupiter’s main auroral oval. Additionally, the source of the required plasma population is unknown, with the cool temperatures (∼2000 K) of brown dwarfs being unable to support significant ionisation of their atmospheres, and the lack of nearby stars restricting the possibility ionisation by stellar irradiation.

    Ultimately it is an exciting prospect that this discovery, along with the arrival of even more sensitive radio telescopes (e.g. the Square Kilometre Array), may pave the way towards detecting auroras at exoplanets.

    SKA Square Kilometer Array

    This which would add a novel technique to the exoplanet-detectors toolkit, and enable us to learn about the magnetic fields and plasma populations around those objects.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 12:03 pm on September 6, 2016 Permalink | Reply
    Tags: , , Brown Dwarf Stars,   

    From Carnegie: “Brown dwarfs hiding in plain sight in our solar neighborhood” 

    Carnegie Institution for Science
    Carnegie Institution for Science

    September 06, 2016
    No writer credit found

    Cool brown dwarfs are a hot topic in astronomy right now. Smaller than stars and bigger than giant planets, they hold promise for helping us understand both stellar evolution and planet formation. New work from a team including Carnegie’s Jonathan Gagné has discovered several ultracool brown dwarfs in our own solar neighborhood. Their findings are published in The Astrophysical Journal.

    Comparison of sizes and effective temperatures of planets, brown dwarfs, and stars. Displayed are the Sun, the red dwarf star Gliese 229A, the young brown dwarf Teide 1, the old brown dwarf Gliese 229B, the very cool brown dwarf WISE 1828+2650, and the planet Jupiter. Graphic after American Scientist/Linda Huff using NASA satellite images (Sun, Jupiter) and NASA artist work (Gliese 229A + B, Teide 1, WISE1828+2650).
    First published in “Joergens, Viki, 50 Years of Brown Dwarfs – From Prediction to Discovery to Forefront of Research, Astrophysics and Space Science Library 401, Springer, ISBN 978-3-319-01162-2.”
    Author MPIA/V. Joergens

    Brown dwarfs are sometimes called failed stars. They are too small to sustain the hydrogen fusion process that powers stars, so after forming they slowly cool, contract, and dim over time. Their temperatures can range from nearly as hot as a star to as cool as a planet and their masses also range between star-like and giant-planet-like.

    They’re fascinating to astronomers for a variety of reasons, mostly because they can serve as a bridge between stars and planets and how the former influences the latter, particular when it comes to composition and atmospheric properties. But much about them remains unknown.

    “Everyone will benefit from the study of brown dwarfs, because they can often be found in isolation, which means that we can more easily gather precise data on their properties without a bright star blinding our instruments,” Gagné said, who is also a collaborator of the Institute for Research on Exoplanets (iREx) at Université de Montréal.

    Discovering new brown dwarfs will help scientists to better quantify the frequency at which they occur both in our solar neighborhood and beyond. Knowing the abundance and distribution of brown dwarfs provides key information on the distribution of mass in the universe, and on the mechanism of brown dwarf formation, for example, whether they form in isolation or instead are ejected from larger planetary systems.

    To that end, the team, led by Jasmin Robert of Université de Montréal, believed that although hundreds of ultracool brown dwarfs have already been discovered, the techniques used to identify them were overlooking those with more-unusual compositions, which would not show up in the color-based surveys generally used.

    So they surveyed 28 percent of the sky and discovered 165 ultracool brown dwarfs, about a third of which have unusual compositions or other peculiarities. When talking about brown dwarfs, ultracool means temperatures under about 3,500 Fahrenheit or 2,200 kelvin

    “The search for ultracool brown dwarfs in the neighborhood of our own Solar System is far from over,” said Gagné. “Our findings indicate that many more are hiding in existing surveys.”

    This work was supported by the Fonds de Recherche Québécois-Nature et Technologie and the Natural Science and Engineering Research Council of Canada.

    See the full article here .

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    Carnegie Institution of Washington Bldg

    Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile.
    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile

  • richardmitnick 12:21 pm on June 27, 2016 Permalink | Reply
    Tags: , , Brown Dwarf Stars,   

    From Carnegie: “When it comes to brown dwarfs, “how far?” is a key question” 

    Carnegie Institution for Science
    Carnegie Institution for Science

    June 27, 2016
    Alan Boss

    Brown dwarfs are sometimes called failed stars. They’re stars’ dim, low-mass siblings and they fade in brightness over time. They’re fascinating to astronomers for a variety of reasons, but much about them remains unknown. New work from a Carnegie-led team reports the distances of a number of brown dwarfs, as well as low-mass stars, in The Astronomical Journal.

    Brown dwarfs are too small to sustain the hydrogen fusion process that powers stars. Their temperatures can range from nearly as hot as a star to as cool as a planet, and their masses also range between star-like and giant planet-like. They are of particular interest to scientists because they can offer clues to star-formation processes.

    The intrinsic brightness of brown dwarfs, particularly cool brown dwarfs, is poorly known, but this key parameter can only be determined once an object’s distance has been measured. Intrinsic brightness is a determination of how bright an object would be if observed at a common distance, eliminating the fact that a bright star can seem dimmer if it is far away and a dim star can seem brighter if it is close.

    An ongoing planet-hunting survey run by Carnegie co-authors Alycia Weinberger, Alan Boss, Ian Thompson, Sandy Keiser, and others has yielded the distances to 134 low mass stars and brown dwarfs, of which 38 had not been previously measured.

    “Accurate distances are the foundation upon which we can determine the physical properties and luminosities of brown dwarfs and low mass stars,” Weinberger said.

    The team built a special instrument for precisely measuring the locations of stars over time, the CAPSCam—the Carnegie Astrometric Planet Search Camera—and they use it at the DuPont Telescope at our Las Campanas Observatory in Chile.

    Las Campanas Dupont telescope exterior
    Las Campanas Dupont telescope interior
    Carnegie Las Campanas Dupont telescope, Atacama Desert, Chile

    The primary goal of the CAPS project is to search for extrasolar planets by the astrometric method, where the planet’s presence can be detected indirectly through the wobble of the host star around the center of mass of the system. But CAPSCam also measures parallaxes to stars and brown dwarfs, including the 134 objects published in this study.

    Parallax may sound like a word straight out of science fiction, but it’s something you’ve almost certainly experienced yourself. Hold a pen up in front of your face and look at it first with just your right eye and then just your left eye. It appears to be moving in regard to background objects as you switch from eye to eye, even though you know it isn’t moving at all. That’s parallax!


    What’s more, if you hold the pen further from your face, it appears to move less when you switch eyes than it did when it was closer to you. In the same way, closer stars have larger parallactic motion.

    What does it have to do with astronomy? It’s the only direct way to measure astronomical distances and the CAPSCam is capable of doing so very precisely. By measuring the shift in an object’s position from different viewpoints in the Earth’s orbit relative to something fixed in the background, astronomers can use geometry to calculate how far away the object is.

    “There is still so much about brown dwarfs that remains unknown,” explained Weinberger. “As we learn more about them, it could improve our knowledge about the star formation process and possibly also refine our understanding of the distribution of matter in the universe, since it seems that there are far more brown dwarfs than initially thought.”

    The study revealed some other useful distance measurements in addition to the brown dwarf discoveries.

    The team used the motion of two stars and compared them to others in two different stellar groups to confirm the age of the two stars age, between 30 and 50 million years old for one and 100 million years old for the other. This is because distance measurements can tell researchers about the location of a star in 3-D, not just the star’s position in 2-D on the sky, and let them measure the star’s velocity. Finding groups of young stars moving together lets astronomers study them in aggregate and better estimate how old they are and learn about their evolution.

    The team also reported the first parallax for a star that is notable for hosting a Neptune-sized planet. Relatively few giant planets orbiting low-mass stars are known, so every instance is of interest to planet hunters. Using this measurement the team refined the radius and density estimates for the planet, finding it to be about half as dense as Neptune, closer to Saturn’s density.

    “In 2007, we began our long-term search for gas giant planets and brown dwarfs orbiting nearby low mass dwarf stars,” said Boss. “We’re excited to have such a wealth of measurements to publish from our CAPSCam project.”

    The study’s other co-authors are: Guillem Anglada-Escude, a former Carnegie fellow now at Queen Mary University of London and Gregory Burley of the National Research Council of Canada.

    The Carnegie Astrometric Planet Search Camera at the DuPont Telescope at Carnegie’s Las Campanas Observatory in Chile, courtesy of Greg Burley of SBS, who built the camera, along with Carnegie’s Ian Thompson.

    The researchers used the SIMBAD and Vizier databases, operated at CDS; data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing an Analysis Center/California Institute of Technology, funded by NASA and the NSF; data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California Los Angeles and the Jet Propulsion Laboratory/California Institute of Technology, funded by NASA; the Mikulski Archive for Space Telescopes, operated by the Association of Universities for Research in Astronomy Inc. under a NASA contract, with support provided by the NASA Office of Space Science as well as other grants and contracts.

    See the full article here .

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    Carnegie Institution of Washington Bldg

    Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

  • richardmitnick 6:17 pm on June 13, 2016 Permalink | Reply
    Tags: , , Brown Dwarf Stars, U Delaware   

    From U Delaware: “Failed star creates its own spotlight in the universe” 

    U Delaware bloc

    University of Delaware

    John Gizis has discovered an “ultracool” brown dwarf star that can generate flares stronger than the sun’s. Evan Krape

    June 13, 2016
    Tracey Bryant

    23-million-year-old brown dwarf flashes brighter than the sun’s most powerful flares

    Although astronomers often refer to brown dwarfs as “failed stars,” scientists at the University of Delaware have discovered that at least one of these dim celestial objects can emit powerful flashes of light.

    Brown Dwarf 2M1207A and companion 2M120B
    Brown Dwarf 2M1207A and companion 2M120B

    A research team led by John Gizis, professor in UD’s Department of Physics and Astronomy, discovered an “ultracool” brown dwarf known as 2MASS 0335+23, with a temperature of only 4400°F that can generate flares stronger than the sun’s. Gizis reported on the finding on June 13 at the annual meeting of the American Astronomical Society in San Diego.

    “This brown dwarf is very young by star standards — only 23 million years old,” Gizis said. “It has lots of flares that are as hot as or hotter than the flares coming off full-fledged stars. This shows that the warmer brown dwarfs can generate flares from magnetic field energy just like stars. Our work shows, however, that colder brown dwarfs cannot generate flares even though they also have magnetic fields.”

    Brown dwarfs actually begin life just as stars do, from collapsing clouds of gas and dust, but they don’t get big enough and hot enough for hydrogen and helium to fuse at their core, generating the nuclear reactions that keep a star burning bright for millions and billions of years.

    Gizis and his team, including doctoral student Rishi Paudel, and collaborators from the University of California, San Diego and Harvard University, made the findings using NASA’s Kepler space telescope, which monitored the brown dwarf every minute for three months.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

    Poring through thousands of images the size of a postage stamp, the team searched for spikes in brightness. Suddenly, the brown dwarf would get twice as bright for two to four minutes. This happened a dozen times over the three-month period.

    “These flares are very powerful — stronger than the sun’s. They show what the sun could do when it was younger. It’s like its acne is going away,” Gizis said wryly of the sun, which is “middle-aged” now, at 4½ billion years old, 200 times older than this brown dwarf.

    Gizis actually discovered the brown dwarf in 1999 when he was a postdoctoral fellow at the University of Massachusetts at Amherst working on NASA’s 2MASS (Two Micron All Sky Survey) project. It is now known to be part of the Beta Pictoris moving group, an association of stars born at the same time and all moving in parallel in space some 63 light years away.

    Caltech 2MASS Telescope
    Caltech 2MASS telescope interior
    Caltech 2MASS Telescope

    2MASS LSS chart-NEW NASA

    It is now known to be part of the Beta Pictoris moving group, an association of stars born at the same time and all moving in parallel in space some 63 light years away.

    They were all originally part of an interstellar cloud, an amalgamation of dust, gas and space plasma. When this cloud collapsed, the brown dwarfs got scattered into space like the seeds of a dandelion in a puff of wind.

    Gizis said he hopes to learn more about ordinary stars by studying the most unusual and extreme ones like brown dwarfs.

    Among their most unique features, brown dwarfs do a complete spin every five hours — now that’s a very short day.

    “In some respects, brown dwarfs are a lot like planets, especially Jupiter, the gas giant in our solar system,” Gizis said. “They end up being a similar size because they are failed stars, and they get colder and colder with time like a planet does. They also have clouds on them. With Kepler, you can see what the clouds do for several months. You can see how much change occurs—that’s the type of thing we’re trying to figure out.”

    Gizis is looking for evidence of clouds, and for planets, too. The brightness dims when a planet comes in front of a brown dwarf or other star. Flares also can impact planets, as space weather watchers well know.

    When the sun blasts out a massive X-class solar flare, releasing energy equivalent to a billion hydrogen bombs exploding at the same time, Earth can feel the effects, in damaged satellites and communications systems to electrical power grids.

    “We think there are probably planets around brown dwarfs, so the flares generated by brown dwarfs could be a problem for them,” Gizis said. “But as to whether such a planet might be a habitable one like Earth, Gizis thinks that’s a long shot.

    “It would be more like Mercury, which is pretty much fried,” he said. “There’s some debate about that. I guess we’ll find out.”

    See the full article here .

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    U Delaware campus

    One of the oldest universities in the U.S., the University of Delaware traces its roots to 1743 when a petition by the Presbytery of Lewes expressing the need for an educated clergy led the Rev. Dr. Francis Alison to open a school in New London, Pennsylvania.

    Alison’s first class was “possibly the most distinguished in terms of the later achievements of its members, taken as a whole, of any class in any school in America,” wrote historian John Munroe.

    Those first students would go on to become statesmen, doctors, merchants and scholars. Thomas McKean, George Read and James Smith signed the Declaration of Independence, and Read also signed the U.S. Constitution.

    By 1765, Alison’s school relocated to Newark. NewArk College opened as a degree-granting institution in 1834 and was renamed Delaware College in 1843. In 1867, the college was designated one of the nation’s historic Land Grant colleges.

    A women’s college opened in 1914 with 58 students, and in 1921, the two colleges joined to become the University of Delaware.

    Since 1950, UD has quadrupled its enrollment and greatly expanded its faculty and academics and its influence in the world.

    In 2009, the University purchased a 272-acre parcel of land adjacent to the Newark campus that previously had been a Chrysler Plant. That site, now the Science, Technology and Advanced Research (STAR) Campus, is home to the University’s Health Sciences Complex and is being developed as a space combining business, research, education and more.

  • richardmitnick 5:33 am on April 21, 2016 Permalink | Reply
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    From JPL: “Lone Planetary-Mass Object Found in Family of Stars” 

    NASA JPL Banner


    April 19, 2016
    Whitney Clavin
    Jet Propulsion Laboratory, Pasadena, California

    A sky map taken by NASA’s Wide-field Infrared Survey Explorer, or WISE, shows the location of the TW Hydrae family, or association, of stars, which lies about 175 light-years from Earth and is centered in the Hydra constellation. Image credit: NASA/JPL-Caltech

    A young, free-floating world sits alone in space in this illustration. The object, called WISEA J114724.10?204021.3, is thought to be an exceptionally low-mass “brown dwarf,” which is a star that lacked enough mass to burn nuclear fuel and glow like a star. Image credit: NASA/JPL-Caltech

    In 2011, astronomers announced that our galaxy is likely teeming with free-floating planets. In fact, these lonely worlds, which sit quietly in the darkness of space without any companion planets or even a host sun, might outnumber stars in our Milky Way galaxy. The surprising discovery begged the question: Where did these objects come from? Are they planets that were ejected from solar systems, or are they actually light-weight stars called brown dwarfs that formed alone in space like stars?

    A new study using data from NASA’s Wide-field Infrared Survey Explorer, WISE, and the Two Micron All Sky Survey, or 2MASS, provides new clues in this mystery of galactic proportions.

    NASA/Wise Telescope
    NASA/Wise Telescope

    Caltech 2MASS Telescope
    Caltech 2MASS telescope interior
    Caltech 2MASS Telescope

    Scientists have identified a free-floating, planetary-mass object within a young star family, called the TW Hydrae association.

    ALMA protoplanetary  disk  Sun-like star TW Hydrae.
    ALMA protoplanetary disk Sun-like star TW Hydrae

    The newfound object, termed WISEA J114724.10-204021.3, or just WISEA 1147 for short, is estimated to be between roughly five to 10 times the mass of Jupiter.

    WISEA 1147 is one of the few free-floating worlds where astronomers can begin to point to its likely origins as a brown dwarf and not a planet.

    Artist's concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech
    Artist’s concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech

    Because the object was found to be a member of the TW Hydrae family of very young stars, astronomers know that it is also very young — only 10 million years old. And because planets require at least 10 million years to form, and probably longer to get themselves kicked out of a star system, WISEA 1147 is likely a brown dwarf. Brown dwarfs form like stars but lack the mass to fuse atoms at their cores and shine with starlight.

    “With continued monitoring, it may be possible to trace the history of WISEA 1147 to confirm whether or not it formed in isolation,” said Adam Schneider of the University of Toledo in Ohio, lead author of a new study accepted for publication in The Astrophysical Journal.

    Of the billions of possible free-floating worlds thought to populate our galaxy, some may be very low-mass brown dwarfs, while others may in fact be bona fide planets, kicked out of nascent solar systems. At this point, the fraction of each population remains unknown. Tracing the origins of free-floating worlds, and determining whether they are planets or brown dwarfs, is a difficult task, precisely because they are so isolated.

    “We are at the beginning of what will become a hot field – trying to determine the nature of the free-floating population and how many are planets versus brown dwarfs,” said co-author Davy Kirkpatrick of NASA’s Infrared Processing and Analysis Center, or IPAC, at the California Institute of Technology in Pasadena.

    Astronomers found WISEA 1147 by sifting through images taken of the entire sky by WISE, in 2010, and 2MASS, about a decade earlier. They were looking for nearby, young brown dwarfs. One way to tell if something lies nearby is to check to see if it’s moved significantly relative to other stars over time. The closer an object, the more it will appear to move against a backdrop of more distant stars. By analyzing data from both sky surveys taken about 10 years apart, the close objects jump out.

    Finding low-mass objects and brown dwarfs is also well suited to WISE and 2MASS, both of which detect infrared light. Brown dwarfs aren’t bright enough to be seen with visible-light telescopes, but their heat signatures light up when viewed in infrared images.

    The brown dwarf WISEA 1147 was brilliantly “red” in the 2MASS images (where the color red had been assigned to longer infrared wavelengths), which means that it’s dusty and young.

    “The features on this one screamed out, ‘I’m a young brown dwarf,'” said Schneider.

    After more analysis, the astronomers realized that this object belongs to the TW Hydrae association, which is about 150 light-years from Earth and only about 10 million years old. That makes WISEA 1147, with a mass between about five and 10 times that of Jupiter, one of the youngest and lowest-mass brown dwarfs ever found.

    Interestingly, a second, very similar low-mass member of the TW Hydrae association was announced just days later (2MASS 1119-11) by a separate group led by Kendra Kellogg of Western University in Ontario, Canada.

    Another reason that astronomers want to study these isolated worlds is that they resemble planets but are easier to study. Planets around other stars, called exoplanets, are barely perceptible next to their brilliant stars. By studying objects like WISEA 1147, which has no host star, astronomers can learn more about their compositions and weather patterns.

    “We can understand exoplanets better by studying young and glowing low-mass brown dwarfs,” said Schneider. “Right now, we are in the exoplanet regime.”

    Other authors of the study include: James Windsor and Michael Cushing of the University of Toledo; and Ned Wright of UCLA, who was also the principal investigator of the WISE mission.

    The 2MASS mission was a joint effort between the California Institute of Technology, Pasadena; the University of Massachusetts, Amherst; and JPL. Caltech manages JPL for NASA.

    WISE, NEOWISE and 2MASS data are archived at IPAC.

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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    NASA image

  • richardmitnick 11:05 am on April 7, 2016 Permalink | Reply
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    From ND: “Notre Dame physicists discover rare brown dwarf, essential for testing theoretical models” 

    Notre Dame bloc

    Notre Dame University

    April 06, 2016
    Gene Stowe

    A team led by Justin Crepp has discovered HD 4747 B, a rare brown dwarf. As a new mass, age and metallicity benchmark, HD 4747 B will serve as a laboratory for precision astrophysics to test theoretical models.

    A team led by Justin Crepp, the Frank M. Freimann Assistant Professor of Physics at the University of Notre Dame, has discovered a rare brown dwarf, a faint object with properties in between that of a star and planet.

    Artist's concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech
    Artist’s concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech

    In addition to taking its picture for the first time, Crepp’s team also determined the brown dwarf’s mass, age and composition — essential information that can be used to “benchmark” the study of these elusive objects.

    Brown dwarfs are objects thought to have initially begun the process of forming a star but were somehow interrupted before they accumulated sufficient mass and core pressure to ignite nuclear fusion — the process by which the Sun ultimately releases energy in the form of light. An important developmental bridge between bona fide stars and exoplanets, brown dwarfs are very difficult to study because their faint glow fades with time due to a lack of sustained nuclear reactions. The discovery of the object, which goes by the name HD 4747 B, was facilitated by 18 years of precise spectral measurements of the star that indicated it hosts an orbiting companion.

    “We suspect that these companions form at the same time and from the same material,” Crepp said. “As such, you can infer physical properties of the brown dwarf from its parent star, like age and composition. There are no other objects for which we know the mass, age and the metallicity simultaneously and also independent of the light that the companion gives off. We can therefore use HD 4747 B as a test-bed to study brown dwarfs, enabling precision astrophysics studies for a directly imaged substellar object.”

    In the past, brown dwarf masses have been estimated using theoretical evolutionary models. Crepp’s team instead calculated the mass of HD 4747 B directly using observations of its orbit in an attempt to help refine brown dwarf models. It is expected that this work will in turn help to inform models for extrasolar planets. Based on a three-dimensional orbit analysis, HD 4747 B has a mass of about 60 Jupiters (a mass of 80 Jupiters is required to ignite nuclear fusion), well below the theoretical estimate of 72 Jupiters, although still within uncertainties. Forthcoming measurements acquired by Crepp’s team will provide yet more stringent tests of the models used by astronomers for brown dwarfs.

    “This field is transitioning from ‘Hey, I found something neat’ to ‘Hey, I know the mass to within a few percent.’ Now, we can test theoretical models,” Crepp said.

    The team detected the object using the Keck telescopes in Hawaii, and published their results in a paper describing the discovery.

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory Interior
    Keck Observatory, Mauna Kea, Hawaii, USA

    The study has been submitted to the Astrophysical Journal. Co-authors of the study include Erica Gonzales and Eric Bechter, both in the Department of Physics at the University of Notre Dame; Benjamin Montet at the Harvard-Smithsonian Center for Astrophysics and the California Institute of Technology; John Asher Johnson at the Harvard-Smithsonian Center for Astrophysics; Danielle Piskorz at the Division of Geological and Planetary Sciences at the California Institute of Technology; Andrew Howard at the Institute for Astronomy at the University of Hawaii; and Howard Isaacson at the University of California Berkeley.

    Science paper:
    The TRENDS High-Contrast Imaging Survey. VI. Discovery of a Mass, Age, and Metallicity Benchmark Brown Dwarf

    Science team:
    Justin R. Crepp 1, Erica J. Gonzales 1, Eric B. Bechter 1, Benjamin T. Montet 2,3, John Asher
    Johnson 2, Danielle Piskorz 3, Andrew W. Howard 4, Howard Isaacson 5

    1 Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN, 46556, USA
    2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
    3 Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd., Pasadena, CA 91125
    4 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822
    5 Department of Astronomy, University of California, Berkeley, CA 94720

    See the full article here .

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    Notre Dame Campus

    The University of Notre Dame du Lac (or simply Notre Dame /ˌnoʊtərˈdeɪm/ NOH-tər-DAYM) is a Catholic research university located near South Bend, Indiana, in the United States. In French, Notre Dame du Lac means “Our Lady of the Lake” and refers to the university’s patron saint, the Virgin Mary.

    The school was founded by Father Edward Sorin, CSC, who was also its first president. Today, many Holy Cross priests continue to work for the university, including as its president. It was established as an all-male institution on November 26, 1842, on land donated by the Bishop of Vincennes. The university first enrolled women undergraduates in 1972. As of 2013 about 48 percent of the student body was female.[6] Notre Dame’s Catholic character is reflected in its explicit commitment to the Catholic faith, numerous ministries funded by the school, and the architecture around campus. The university is consistently ranked one of the top universities in the United States and as a major global university.

    The university today is organized into five colleges and one professional school, and its graduate program has 15 master’s and 26 doctoral degree programs.[7][8] Over 80% of the university’s 8,000 undergraduates live on campus in one of 29 single-sex residence halls, each of which fields teams for more than a dozen intramural sports, and the university counts approximately 120,000 alumni.[9]

    The university is globally recognized for its Notre Dame School of Architecture, a faculty that teaches (pre-modernist) traditional and classical architecture and urban planning (e.g. following the principles of New Urbanism and New Classical Architecture).[10] It also awards the renowned annual Driehaus Architecture Prize.

  • richardmitnick 5:59 pm on February 19, 2016 Permalink | Reply
    Tags: , , Brown Dwarf Stars,   

    From Gemini Observatory: “Are the Coolest Brown Dwarfs Loners?” 


    Gemini Observatory
    Gemini Observatory

    February 18, 2016

    Astronomers use Gemini’s high-resolution multi-conjugate adaptive optics system to look for elusive companions to the lowest mass brown dwarfs.

    Y-type brown dwarfs, the coolest type of brown dwarfs known, provide an important link in the study of objects between stars and planets.

    Brown dwarf
    Brown dwarf

    While the fraction of binary systems associated with warmer and brighter brown dwarfs is well-established, because the Y spectral class is so new (the first Y-type brown dwarfs were only confirmed in 2011) there is little known about what fraction of Y dwarfs have companions. The Y dwarfs are generally lower in mass than the warmer brown dwarfs. For the warmer brown dwarfs, the frequency of binary systems diminishes with brown dwarf mass, and companions tend to be closer to their host and lower in mass themselves. Scientists wonder if this same trend continues for the Y dwarfs.

    A research team, led by Daniela Opitz (University of New South Wales), utilized the high spatial resolution and infrared sensitivity of the Gemini Multi-Conjugate Adaptive Optics System (GeMS) to help fill this gap in our understanding.

    Gemini GeMS

    Their work, recently accepted for publication in The Astrophysical Journal and available on astro-ph, uses GeMS on five Y dwarfs discovered by the NASA Wide-field Infrared Survey Explorer (WISE) to look for evidence of companions.

    NASA Wise Telescope

    The team found no evidence for equal-mass binaries with separations greater than 0.5-1.9 Astronomical Units, which is consistent with what is observed in the warmer and brighter brown dwarfs.

    While more studies are needed to fully understand the binary fractions of Y-type brown dwarfs, this work establishes a solid foundation for future work at Gemini and other infrared optimized telescopes.

    Paper Abstract
    The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to have smaller separations and are more frequently detected in near-equal mass configurations. The binary statistics for Y-type brown dwarfs, however, are sparse, and so it is unclear if the same trends that hold for L- and T-type brown dwarfs also hold for Y-type ones. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results for binary properties of a sample of five WISE Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System (GeMS). We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or equal-mass) binaries with separations larger than 0.5-1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e. 1011 erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs.

    See the full article here .

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    Gemini North
    Gemini North, Hawai’i

    Gemini South
    Gemini South, Chile
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    Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

    The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

    The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

  • richardmitnick 2:41 pm on August 28, 2014 Permalink | Reply
    Tags: , , , Brown Dwarf Stars, ,   

    From Phys.org: Astronomers find evidence of water clouds in brown dwarf atmosphere 


    Aug 27, 2014
    Bob Yirka

    A team of researchers, led by space scientist Jacqueline Faherty, has found evidence of water clouds in the atmosphere of a brown dwarf situated just 7.3 light years away. In their paper to be published in The Astrophysical Journal Letters, the team describes how they found evidence of the water clouds and where the research is headed next.

    WISE J0855-0714, a brown dwarf was first spotted by astronomer Kevin Luhman after studying pictures taken by NASA’s WISE telescope over the period 2010-2011. A brown dwarf is a star that failed to progress to a point where it could sustain nuclear reactions. Instead of growing, such stars fade and grow colder. WISE J0855-0714’s atmosphere is believed to be just below the freezing point.

    NASA Wise Telescope

    Since the discovery of the brown dwarf, scientists have been studying it to learn more about such objects—in some respects they are easier to study then exoplanets because they don’t have a nearby star and its associated emissions. In this latest effort, the researchers pored over infrared images taken by Chile’s Magellan Baade telescope over three nights this past May. Colors observed in the images matched those of models developed to show what a brown dwarf would look like if it had water clouds in its atmosphere. If further evidence can prove conclusively that the finding is truly water clouds, it would mark the first such instance in a body outside of our solar system.

    Magellan 6.5 meter telescopes
    Magellan Telescopes

    WISE J0855-0714 is approximately the size of Jupiter, but has three times its mass—it’s also the coldest known brown dwarf. The infrared images also indicate that it’s only partly cloudy, which is a relatively new phenomenon, at least from a known perspective, and offers astronomers a unique opportunity to study how it occurs on other celestial bodies. In our solar system, only Earth and Mars have water clouds. And while some exoplanets have been found to have water vapor in their atmosphere, none have been found to have water clouds.

    Space scientists won’t know for sure if the evidence from the infrared images really shows water clouds until researchers with the James Webb space telescope can get a good look at WISE J0855-0714 sometime within the next ten years.

    A ∼ 45′′ x 25′′ region of the final mosaic image at J3 created from three nights of observing the source W0855 with the FourStar imager. Credit: arXiv:1408.4671 [astro-ph.SR]

    Magellan Four Star Imager Camera
    FourStar Infrared Camera on Magellan

    Read more at: http://phys.org/news/2014-08-astronomers-evidence-clouds-brown-dwarf.html#jCp

    See the full article here.

    About Phys.org in 100 Words

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

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