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  • richardmitnick 4:21 pm on April 12, 2018 Permalink | Reply
    Tags: , , , Cataclysmic variable stars (CVs) in the globular cluster 47 Tucanae, CfA, , Exotic Binary Stars   

    From CfA: “Exotic Binary Stars” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    A Chandra X-ray Observatory image of the globular cluster 47 Tucanae. The image is about ten light-years across, and shows many cataclysmic variables (CVs), white dwarf stars that accrete from a companion star. Astronomers have discovered twenty-two new CVs in the cluster, and used the statistics to argue that, unlike many clusters which have bright, recently formed CVs, the ones here are older or even primordial.
    NASA/CXC/Michigan State/A.Steiner et al. 2014.

    NASA/Chandra Telescope

    Cataclysmic variable stars (CVs) are white dwarf stars that are accreting from an orbiting, low mass binary companion star. The accretion is facilitated by the proximity of the stars; typical orbital periods range from about one to ten hours. Although the family of these exotic CV binaries is heterogeneous, there are, roughly speaking, four classes characterized by the accretion physics, eruptions caused by occasional accretion events, flaring from activity on the white dwarf’s surface, and the appearance of hydrogen lines in the companion star.

    CVs are found in many galactic environments, but their presence in globular clusters, whose distances and populations are well characterized, allows a more precise comparative study of their properties. CVs can affect the evolution of the cluster while themselves being influenced by the dense stellar environment in a cluster. Evolutionary models of globular cluster evolution imply that after about ten billion years, a cluster with a million stars should have about two hundred CVs – many more than have been seen so far in any cluster. Identifying them, however, is not easy because they can be faint and because they exist in such crowded environments.

    CfA astronomers Maureen van den Berg and Josh Grindlay and their colleagues detected twenty-two new CVs in the nearby globular cluster 47 Tucanae (47 Tuc) using Chandra X-ray Observatory and Hubble measurements, bringing the total known to forty-three, the largest sample in any globular cluster so far.

    NASA/ESA Hubble Telescope

    The scientists find that 47 Tuc has fewer bright CVs than had been expected. Many globular clusters show a steep increase in stellar density near their centers (the so-called “core collapse” scenario). The scientists argue that the high central densities in these core-collapsed clusters has led to frequent close encounters between stars, which in turn has resulted in the formation of younger and brighter CVs. The cluster 47 Tuc has not experienced core collapse, which could explain the relative lack of such bright CVs. These new results imply that the CV population in 47 Tuc is therefore a combination of primordial CVs and others formed dynamically early in the evolution of the cluster.

    Science paper:
    New Cataclysmic Variables and Other Exotic Binaries in the Globular Cluster 47 Tucanae
    MNRAS

    See the full article here .

    Please help promote STEM in your local schools.

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    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 4:33 pm on April 4, 2018 Permalink | Reply
    Tags: , , , Black Hole study finds many in Milky Way, CfA, ,   

    From NPR and CfA: “Center Of The Milky Way Has Thousands Of Black Holes, Study Shows” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    NPR

    National Public Radio (NPR)

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

    The supermassive black hole lurking at the center of our galaxy appears to have a lot of company, according to a new study that suggests the monster is surrounded by about 10,000 other black holes.

    For decades, scientists have thought that black holes should sink to the center of galaxies and accumulate there, says Chuck Hailey, an astrophysicist at Columbia University. But scientists had no proof that these exotic objects had actually gathered together in the center of the Milky Way.

    “This is just kind of astonishing that you could have a prediction for such a large number of objects and not find any evidence for them,” Hailey says.

    He and his colleagues recently went hunting for black holes, using observations of the galactic center made by a NASA telescope called the Chandra X-ray Observatory.

    NASA/Chandra Telescope

    Isolated black holes are almost impossible to detect, but black holes that have a companion — an orbiting star — interact with that star in ways that allow the pair to be spotted by telltale X-ray emissions. The team searched for those signals in a region stretching about three light-years out from our galaxy’s central supermassive black hole.

    “So we’re looking at the very, very, very center of our galaxy. It’s a place that’s filled with a huge amount of gas and dust, and it’s jammed with a huge number of stars,” Hailey says.

    What they found there: a dozen black holes paired up with stars, according to a report in the journal Nature.

    Finding so many in such a small region is significant, because until now scientists have found evidence of only about five dozen black holes throughout the entire galaxy, says Hailey, who points out that our galaxy is 100,000 light-years across. (For reference, one light-year is just under 5.88 trillion miles.)

    What’s more, the very center of our galaxy surely has far more than these dozen black holes that were just detected. The researchers used what’s known about black holes to extrapolate from what they saw to what they couldn’t see. Their calculations show that there must be several hundred more black holes paired with stars in the galactic center, and about 10,000 isolated black holes.

    “I think this is a really intriguing result,” says Fiona Harrison, an astrophysicist at Caltech. She cautions that there are a lot of uncertainties and the team has found just a small number of X-ray sources, “but they have the right distribution and the right characteristics to be a tracer of this otherwise completely hidden population.”

    “I find black holes really cool,” Hailey says. “Finding large numbers of black holes is just really neat because it’s just a larger population to study. These are really exotic objects. The more that you can have of them, the more fun you can have studying them.”

    He thinks what they’ve found should help theorists make better predictions about how many cosmic smashups might occur and generate detectable gravitational waves. Scientists have only recently started to detect these ripples in space-time, which were predicted by Albert Einstein about a century ago.

    See the full article here .

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

     
  • richardmitnick 5:24 pm on April 2, 2018 Permalink | Reply
    Tags: , , , , CfA, , , , Rings and Gaps in a Developing Planetary System   

    From CfA: “Rings and Gaps in a Developing Planetary System” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    A model of the dust ring around the young star Elias 24, produced from simulations based on new ALMA millimeter images of the system. The model finds that the dust was shaped by a planet with 70% of Jupiter’s mass located about 60 au from the star. Dipierro et al. 2018

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

    The discovery of an exoplanet has most often resulted from the monitoring of a star’s flicker (the transiting method) or its wobble (the radial velocity method).

    Planet transit. NASA/Ames

    Radial Velociity Method. ESO

    Discovery by direct imaging is rare because it is so difficult to spot a faint exoplanet hidden in the glare of its host star. The advent of the new generation of radio interferometers (as well as improvements in near-infrared imaging), however, has enabled the imaging of protoplanetary discs and, in the disc substructures, the inference of orbiting exoplanets. Gaps and ring-like structures are particularly fascinating clues to the presence or ongoing formation of planets.

    Rings of dust have already been identified in many protoplanetary systems from their infrared and submillimeter emission. The origin of these rings is debated. They might have formed from dust “pile-up,” dust settling, gravitational instabilities, or even from variations in the optical properties of the dust. Alternatively, the rings could result dynamically from the orbital motions of planets that have already developed or that are well on their way. Planets will induce waves in the dusty discs which, as they dissipate, can produce gaps or rings. Key to solving the problem is recognizing that different sized dust grains behave differently, with small grains being strongly coupled to the gas and so track the gas mass, whereas larger grains (millimeter-sized or larger) tend to follow pressure gradients and concentrate near gap edges.

    CfA astronomers Sean Andrews and David Wilner were members of a team of scientists who used the ALMA facility to image the dust around the young star Elias 24 with a resolution of about 28 au (one astronomical unit being about the average distance of the Earth from the Sun). The astronomers find evidence for gaps and rings and, assuming these are produced by an orbiting planet, they model the system allowing both the planet’s mass and location and the dust’s density distribution to evolve. Their best model explains the observations quite well: after about forty-four thousand years the inferred planet has a mass 70% of Jupiter’s mass and is located 61.7 au from the star. The result reinforces the conclusion that both gaps and rings are prevalent in a wide variety of young circumstellar disks, and signal the presence of orbiting planets.

    Science paper:
    Rings and gaps in the disc around Elias 24 revealed by ALMA .
    MNRAS

    See the full article here .

    Please help promote STEM in your local schools.

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    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 1:39 pm on March 28, 2018 Permalink | Reply
    Tags: , , , CfA, , NASA Prepares to Launch Next Mission to Search the Sky for New Worlds,   

    From CfA: “NASA Prepares to Launch Next Mission to Search the Sky for New Worlds” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    March 28, 2018
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

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

    1
    NASA TESS

    NASA’s Transiting Exoplanet Survey Satellite (TESS) is undergoing final preparations in Florida for its April 16 launch to find undiscovered worlds around nearby stars, providing targets where future studies will assess their capacity to harbor life.

    “One of the biggest questions in exoplanet exploration is: If an astronomer finds a planet in a star’s habitable zone, will it be interesting from a biologist’s point of view?” said George Ricker, TESS principal investigator at the Massachusetts Institute of Technology (MIT) Kavli Institute for Astrophysics and Space Research in Cambridge, which is leading the mission. “We expect TESS will discover a number of planets whose atmospheric compositions, which hold potential clues to the presence of life, could be precisely measured by future observers.”

    Following a successful March 15 review of the spacecraft’s launch readiness, TESS will be fueled and encapsulated within the payload fairing of its SpaceX Falcon 9 rocket.

    TESS will lift off from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida. With the help of a gravitational assist from the Moon, the spacecraft will settle into a 13.7-day orbit around Earth. Sixty days after launch, following tests of its instruments, TESS will begin its initial two-year mission.

    The spacecraft will be looking for a phenomenon known as a transit, where a planet passes in front of its star, causing a periodic and regular dip in the star’s brightness. NASA’s Kepler spacecraft used the same method to spot more than 2,600 confirmed exoplanets, most of them orbiting faint stars 300 to 3,000 light-years away

    Dozens of scientists, including graduate students and post-doctoral fellows, at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., will play important roles in TESS and the science the telescope is expected to achieve.

    CfA astronomer David Latham serves as the Project Science Director, and will oversee the TESS Follow-up Observing Program. This program will include measuring the mass of 50 exoplanets with four times the radius of Earth or smaller. Another goal is to foster communication and coordination among the TESS science team and the community.

    “Everyone in the TESS Science Office is excited,” said Latham. “We can’t wait to get our hands on TESS light curves of new transiting planets!”

    TESS will concentrate on stars less than 300 light-years away and 30 to 100 times brighter than Kepler’s targets. The brightness of these target stars will allow researchers to use spectroscopy, the study of the absorption and emission of light, to determine a planet’s mass, density and atmospheric composition. Water and other key molecules in its atmosphere can give us hints about a planets’ capacity to harbor life.

    The CfA will provide follow-up observations of TESS targets using its MEarth telescopes, a pair of robotically-controlled observatories, each comprising eight 40 cm telescopes, located at the Smithsonian’s Fred Lawrence Whipple Observatory (FLWO) outside Tucson, AZ, and on Cerro Tololo in Chile.

    CfA The MEarth Telescopes at the Smithsonian_s Fred Lawrence Whipple Observatory-FLWO outside Tucson, AZ, and on Cerro Tololo in Chile

    Astronomers will also use the CfA’s Keplercam on the 48-inch telescope and the Tillinghast Reflector Echelle Spectrograph (TRES) at FLWO.

    CfA Whipple 48 inch telescope interior, located in Amado, Arizona on Mount Hopkins, Altitude 2,606 m (8,550 ft)

    The MEarth and KeplerCam observations will be used to confirm the star responsible for the transit events identified by TESS, and TRES will be used to track down false positives due to eclipsing binaries. TRES will also provide improved stellar parameters for the host stars, which is important because the radius of a transiting planet is relative to the size of the star it orbits. These observations at FLWO and CTIO will be critical for identifying the best candidates for very precise radial velocity observations with HARPS-N on the Telescopio Nazionale Galileo on La Palma in the Canary Islands, which will be used to derive the orbits and masses of small planets.

    Through the TESS Guest Investigator Program, the worldwide scientific community will be able to participate in investigations outside of TESS’s core mission, enhancing and maximizing the science return from the mission in areas ranging from exoplanet characterization to stellar astrophysics and solar system science.

    TESS is a NASA Astrophysics Explorer mission led and operated by MIT and managed by Goddard. George Ricker, of MIT’s Kavli Institute for Astrophysics and Space Research, serves as principal investigator for the mission. TESS’s four wide-field cameras were developed by MIT’s Lincoln Laboratory. In addition to the CfA, other partners include Orbital ATK, NASA’s Ames Research Center, the Harvard-Smithsonian Center for Astrophysics, and the Space Telescope Science Institute. More than a dozen universities, research institutes and observatories worldwide are participants in the mission.

    For more information on TESS, go to: https://www.nasa.gov/tess

    See the full article here .

    Please help promote STEM in your local schools.

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

     
  • richardmitnick 3:56 pm on March 1, 2018 Permalink | Reply
    Tags: , CfA, , Quantum matter, Rydberg atom, Rydberg molecule, Rydberg polaron   

    From CFA: “One Atom to Rule Them All: A New Class of Quantum Matter Observed” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    March 1, 2018

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

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

    1
    This illustration of a Rydberg molecule, showing the likelihood of finding an electron on top of the ground state atom, with the peaks correspond to where the electron is most likely to be located. This shows an uncanny resemblance to a trilobite, a fossil of an ancient marine creature. When atoms are added to the Rydberg atom orbit, the resulting molecule eventually transforms into a Rydberg polaron, which acts like a single massive particle. Donald Booth (University of Wisconsin)

    Scientists have observed a new class of quantum matter at the very smallest scales in one of the coldest environments ever made. This discovery could pave the way for new technologies including innovations in superconductivity and other cutting-edge fields.

    The researchers examined the behavior of matter on the atomic and subatomic scales – known as “quantum matter” – where a large number of particles interact with each other.

    This latest discovery reveals a new state of quantum matter called a “Rydberg polaron,” a relatively giant particle containing many atoms that behaves in some ways like a single massive particle.

    The experiment, initiated by the theoretical work at the Institute for Theoretical Atomic Molecular and Optical Physics (ITAMP) at the Harvard-Smithsonian Center for Astrophysics (CfA) and Harvard Physics, was performed in the laboratory of Thomas Killian at Rice University, where the electrons were given so much energy, on the verge of being pulled away from the nucleus. These highly excited atoms were immersed in a gas that had been cooled to just a millionth of a degree above absolute zero. The result is the creation of a “Rydberg atom,” which is about one hundred billionth of a meter across. This makes it about ten thousand times larger than a typical atom.

    “By putting Rydberg atoms in these conditions, we saw that the atoms and molecules can configure themselves in ways that we’ve never seen before,” said Richard Schmidt of ITAMP, who led the theoretical work, along with Hossein Sadeghpour at ITAMP and Eugene Demler at Harvard Physics.

    In this quantum environment, atoms and molecules can be stacked to form heavier molecules, much in the way Lego pieces are arranged. In the new work, the team applied this process to Rydberg atoms, where increasingly heavy Rydberg molecules were formed by adding large numbers of surrounding atoms until as many as 160 atoms were added to a Rydberg atom.

    “The emergence of complexity in nature is often due to the appearance of new properties or behaviors. However, like an increasingly large and precarious Lego tower, such an arrangement will crumble unless a new property emerges to stabilize the structure,” said co-author Hossein Sadeghpour.

    Quantum interactions – that is similar behavior by different quantum particles – between the Rydberg atom’s electron and surrounding atoms enable this quantum system with many different particles to hold together. In the process, this object changes its character to become what scientists call a “Rydberg polaron”.

    The polaron becomes shrouded by surrounding atoms that move along with it because of these quantum interactions, developing an effective mass that is larger than the mass of the atoms occupying it. At this point, the Ryberg polaron stops behaving like a molecule and starts acting more like a single massive particle. An analogy is that of a horse galloping along and gradually becoming covered in a cloud of dirt particles, which obscures and changes the appearance of the animal.

    “It’s possible to make larger and larger polarons until the objects stops having quantum behavior and starts acting classically,” said Sadeghpour.

    Applications of this work include the potential to gain a better understanding of room-temperature superconductivity and many-body interactions. The work may also aid in designing new materials, and help act as a spectroscopic probe of weak correlations in quantum many-body matter.

    The Physical Review Letter describes the experimental work conducted at Rice University by Tom Killian, and the theoretical work conducted at Harvard University by Eugene Demler, at the Harvard-Smithsonian Center for Astrophysics by Richard Schmidt and Hossein Sadeghpour, Eugene Demler at Harvard Physics, and at Vienna University of Technology. The Physical Review A article explains the details of the theory by generalizing the polaron concept to a much more strongly interacting system, paving the ground to explore the properties of this novel quantum state of matter, such as its effective mass and the nature of interactions between polarons.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

     
  • richardmitnick 5:33 pm on February 26, 2018 Permalink | Reply
    Tags: , , , Black Hole Blasts May Transform "Mini-Neptunes" into Rocky Worlds, CfA,   

    From CfA: “Black Hole Blasts May Transform “Mini-Neptunes” into Rocky Worlds” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 26, 2018

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

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

    1
    This artist’s impression shows the atmosphere of a Neptune-like planet (foreground) being swept backwards by powerful radiation from an outburst in the center of the Milky Way Galaxy (right). The outburst of X-rays and ultraviolet light is produced by material falling towards the supermassive black hole located there. The planet’s host star is shown on the left. M. Weiss/CfA

    A team of astrophysicists and planetary scientists has predicted that Neptune-like planets located near the center of the Milky Way galaxy have been transformed into rocky planets by outbursts generated by the nearby supermassive black hole.

    These findings combine computer simulations with data from recent exoplanet findings, and X-ray and ultraviolet observations of stars and black holes.

    “It’s pretty wild to think of black holes shaping the evolutionary destiny of a planet, but that very well may be the case in the center of our Galaxy,” said Howard Chen of Northwestern University in Evanston, IL, who led the study.

    Howard Chen and collaborators from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., examined the environment around the closest supermassive black hole to Earth: the four-million-solar mass black hole known as Sagittarius A*.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    It is well known that material falling into the black hole in occasional feeding frenzies will generate bright flares of X-ray and ultraviolet radiation. Indeed, X-ray telescopes such as NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton have seen evidence for bright outbursts generated in the past by the black hole ranging from about 6 million years to just over a century ago.

    NASA/Chandra Telescope

    ESA/XMM Newton

    “We wondered what these outbursts from Sagittarius A* would do to any planets in its vicinity,” said John Forbes, a co-author from the CfA. “Our work shows the black hole could dramatically change a planet’s life.”

    The authors considered the effects of this high-energy radiation on planets with masses in between Earth and Neptune that are located less than 70 light years away from the black hole.

    They found that the X-ray and ultraviolet radiation would blast away a large amount of the thick, gas atmosphere of such planets near the black hole. In some cases this would leave behind a bare, rocky core. Such rocky planets would be heavier than the Earth and are what astronomers call super-Earths.

    “These super-Earths are one of the most common types of planet that astronomers have discovered outside our Solar System,” said co-author Avi Loeb, also of CfA, “Our work shows that in the right environment they might form in exotic ways.”

    The researchers think that this black hole impact may be one of the most common ways for rocky super-Earths to form close to the center of our Galaxy.

    While some of these planets will be located in the habitable zone of stars like the Sun, the environment they exist within would be challenging for any life to arise. Supernova explosions and gamma ray bursts would buffet these super-Earths, which might damage the chemistry of any atmosphere remaining on these planets. Additional outbursts from the supermassive black hole could provide a knockout punch and completely erode the planet’s atmosphere.

    These planets would also be subjected to the gravitational disruptions of a passing star that could fling the planet away from its life-sustaining host star. Such encounters might occur frequently near the Milky Way’s supermassive black hole since the region is so packed with stars. How crowded is it in the Galactic Center? Within about 70 light years of the center of the Galaxy, astronomers think the average separation between rocky worlds is between about 75 and 750 billion kilometers. By comparison the nearest star to the Solar System is 40,000 billion kilometers away.

    “It is generally accepted that the innermost regions of the Milky Way is not favorable for life. Indeed, even though the deck seems stacked against life in this region, the likelihood of panspermia, where life is transmitted via interplanetary or interstellar contact, would be much more common in such a dense environment,” said Loeb. “This process might give life a fighting chance to arise and survive.”

    There are formidable challenges required to directly detect such planets. The distance to the Galactic Center (26,000 light years from Earth), the crowded region, and the blocking of light by intervening dust and gas all make the observation of such planets very difficult.

    However, these challenges may be met by the next generation of extraordinarily large ground-based telescopes. For example, searches for transits with future observatories like the European Extremely Large Telescope might detect evidence for these planets. Another possibility is searching for stars with unusual patterns of elements in their atmosphere that have migrated away from the center of the galaxy.

    A paper describing these results appeared in the February 22, 2018 issue of The Astrophysical Journal Letters.

    See the full article here .

    Please help promote STEM in your local schools.

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    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 2:45 pm on February 16, 2018 Permalink | Reply
    Tags: , , , CfA, , Magnetic Reconnection in the Sun   

    From CfA: “Magnetic Reconnection in the Sun” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 16, 2018

    1

    An ultraviolet picture of the sun’s chromosphere, the thin layer of solar atmosphere sandwiched between the visible surface, the photosphere, and the corona. Astronomers have developed a simulation to address magnetic reconnection in the chromosphere. The image was taken by the Hinode spacecraft.

    JAXA/NASA HINODE spacecraft


    JAXA/NASA

    The Sun glows with a surface temperature of about 5500 degrees Celsius. On the other hand its hot outer layer, the corona, has a temperature of over a million degrees and ejects a wind of charged particles at a rate equivalent to about one-millionth of the moon’s mass each year. Some of these particles bombard the Earth, producing auroral glows and occasionally disrupting global communications. In between these two regions of the Sun is the chromosphere. Within this complex interface zone, only a few thousand kilometers deep, the density of the gas drops with height by a factor of about one million and the temperature increases. Almost all of the mechanical energy that drives solar activity is converted into heat and radiation within this interface zone.

    Charged particles are produced by the high temperatures of the gas, and their motions produce powerful, dynamic magnetic fields. Those field lines can sometimes break apart forcefully, but movement of the underlying charged particles often leads them to reconnect. There are two important, longstanding, and related questions about the hot solar wind: how is it heated, and how does the corona produce the wind? Astronomers suspect that magnetic reconnection in the chromosphere plays a key role.

    CfA astronomer Nicholas Murphy and his three colleagues have completed complex new simulations of magnetic reconnection in hot ionized gas like that present in the solar chromosphere. (The lead author on the study, Lei Ni, was a visitor to the CfA.) The scientists include for the first time the effects of incompletely ionized gas in lower temperature regions, certain particle-particle effects, and other details of the neutral and ionized gas interactions. They find that the neutral and ionized gas is well-coupled throughout the reconnection region, and conclude that reconnection can often occur in the cooler portions of the zone. They also note that new, high-resolution solar telescopes are capable of studying smaller and smaller regions of low ionization for which their results are particularly applicable.

    Science paper:
    Magnetic Reconnection in Strongly Magnetized Regions of the Low Solar Chromosphere, The Astrophysical Journal

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

     
  • richardmitnick 12:21 pm on February 15, 2018 Permalink | Reply
    Tags: , , , , CfA,   

    From CfA: “The Extreme Nucleus of the Galaxy Arp220” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    Arp 220 – two collided spiral galaxies. NASA/ESA Hubble

    NASA/ESA Hubble Telescope

    2
    The compound view shows a new ALMA Band 5 image of the colliding galaxy system Arp 220 (in red) on top of an image from the NASA/ESA Hubble Space Telescope (blue/green). With the newly installed Band 5 receivers, ALMA has now opened its eyes to a whole new section of this radio spectrum, creating exciting new observational possibilities and improving the telescope’s ability to search for water in the Universe.

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

    In the Hubble image, most of the light from this dramatic merging galaxy pair is hidden behind dark clouds of dust. ALMA’s observations in Band 5 show a completely different view. Here, Arp 220’s famous double nucleus, invisible for Hubble, is by far the brightest feature in the whole galaxy complex. In this dense, double centre, the bright emission from water and other molecules revealed by the new Band 5 receivers will give astronomers new insights into star formation and other processes in this extreme environment.
    This image is one of the first taken using Band 5 and was intended to verify the scientific capability of the new receivers. The ALMA image includes data recording emission from water, CS and HCN in the galaxies.
    Date 21 December 2016
    ALMA(ESO/NAOJ/NRAO)/NASA/ESA and The Hubble Heritage Team (STScI/AURA)

    4
    A Chandra X-ray image of the ultraluminous merging galaxy Arp 220. Astronomers studying the X-ray emission have concluded that accretion onto the supermassive black hole nuclei contributes only a modest amount, compared with star formation, to the galaxy’s luminosity. NASA/SAO/CXC/J.McDowell

    The galaxy Arp 220 is ultraluminous (defined as having more than about 300 times the luminosity of our own galaxy) and, at a distance of only about 260 million light-years, is the closest ultraluminous galaxy to our Milky Way. Even more dramatic galaxies can have luminosities as much as ten times brighter, and astronomers are still piecing together the reasons for these huge energy outputs. The two primary suspects for the energetics are bursts of star formation that produce many hot young stars, or the accretion of material onto the supermassive black hole at a galaxy’s nucleus – an active galactic nucleus (AGN). As the closest example, Arp 220 is one of the best places to probe these different scenarios; however, observations are difficult because whatever is powering the activity in Arp220 is heavily shrouded in dust and the nuclear region is invisible at optical wavelengths.

    The starburst explanation should produce many hot young stars with abundant ultraviolet light and supernovae resulting from the deaths of the most massive and short-lived stars. The AGN explanation will produce hotter gas with more X-ray emission and characteristic spectral features. So far signs of both processes have been detected. Astronomers generally have concluded that stars are being made at a rate of about ten thousand solar-masses per year, dominating the luminosity, and that the AGN contributes only modestly to the output, less than 25%.

    Adding to the appeal and mystery of Arp 220, however, is the fact that it is a merger of two galaxies and its two constituent galactic nuclei are approaching coalescence, currently being only about one thousand light-years apart. This makes the relatively small AGN output puzzling: Simulations of galaxy mergers suggest that as the nuclei get close together their accretion soars and their luminosity dominates the emission, even exceeding 80% of the total. Moreover, observations of supermassive black hole nuclei in general find that they are systematically larger in larger galaxies, something that would be expected if, as galaxies grow in a merger, their black holes also grow from accreting matter and radiate as they do so.

    CfA astronomers Alessandro Paggi, Giuseppina Fabbiano, Guido Risaliti, Margarita Karovska, Martin Elvis, W. Peter Maksym, and Jonathan McDowell and two colleagues obtained new data using the Chandra X-ray Observatory which, combined with archival Chandra data, allowed them to identify in X-rays two locations of extremely hot atomic iron and potassium emission that coincide with the two nuclei. The lines can be produced either in supernovae (a consequence of star formation) or by an AGN. The scientists analyze these and related data to conclude that supernovae are most likely the primary source of the emission, and that, in agreement with earlier results, the AGN contribution is only modest. They also estimate the masses of the two black holes as being relatively modest, only about ten thousand solar-masses each. One implication of this paper is that the merger has not yet progressed to the stage in which active accretion onto the black hole lights up the galaxy.

    Science paper:
    X-Ray Emission from the Nuclear Region of Arp 220

    See the full article here .

    Please help promote STEM in your local schools.

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

     
  • richardmitnick 7:28 am on February 7, 2018 Permalink | Reply
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    From CfA: “Massive Galaxies in the Early Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 2, 2018

    The South Pole Telescope (SPT) is a 10-meter-diameter telescope in the Antarctic that has been operating at millimeter- and submillimeter-waves for a decade; the CfA is an institutional member of the collaboration.

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including the University of Chicago, the University of California, Berkeley, Case Western Reserve University, Harvard/Smithsonian Astrophysical Observatory, the University of Colorado Boulder, McGill University, The University of Illinois at Urbana-Champaign, University of California, Davis, Ludwig Maximilian University of Munich, Argonne National Laboratory, and the National Institute for Standards and Technology. It is funded by the National Science Foundation.

    For the past six years it has been surveying the sky in a search for galaxies in the first few billion years of cosmic history; they are thought to be preferentially detectable at these wavelengths because their dust has been heated by the ultraviolet light of young stars. One of SPT discoveries, the galaxy SPT0311–58, has upon further investigation turned out to date from an epoch a mere 780 million years after the big bang. It is the most distant known case of this postulated but previously undetected population of optically dim but infrared luminous clusters.

    CfA astronomers Chris Hayward, Matt Ashby and Tony Stark are members of the SPT team that made the discovery and then followed up with the Spitzer Space Telescope, the ALMA array, the Hubble Space Telescope, and the Gemini optical/infrared telescope.

    NASA/Spitzer Infrared Telescope

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

    NASA/ESA Hubble Telescope

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

    The scientists were able to determine the cluster’s distance and epoch from the redshift of its spectral features, including a line of ionized carbon, and to characterize the overall emission properties across a wider range of wavelengths. The Spitzer and Hubble images of the source revealed the presence of a foreground galaxy that is acting as a gravitational lens to magnify SPT0311-58 and thus greatly facilitated its detection. The ALMA measurements at high spatial resolution found that the original source is actually two galaxies less than twenty-five thousand light-years apart. The implication is that these two galaxies are in the midst of colliding.

    The masses of the two galaxies are nearly one hundred billion and ten billion solar masses, respectively. The larger one is more massive than any other known galaxy at this early time in cosmic evolution, a period during which many galaxies are thought to be just forming, and is very bright, making new stars at a rate of about 2900 solar masses per year (thousands of times faster than the Milky Way). Although current models of cosmic evolution do not preclude such giant systems from existing at such early times, the observation does push the models to its limits. The results also imply that there should be a dark-matter halo present with more than 400 billion solar masses, among the rarest dark-matter haloes that should exist in the early universe.

    Reference(s):

    Galaxy Growth in a Massive Halo in the First Billion Years of Cosmic History, D. P. Marrone, J. S. Spilker, C. C. Hayward, J. D. Vieira, M. Aravena, M. L. N. Ashby, M. B. Bayliss, M. B’ethermin, M. Brodwin, M. S. Bothwell, J. E. Carlstrom, S. C. Chapman, Chian-Chou Chen, T. M. Crawford;, D. J. M. Cunningham, C. De Breuck, C. D. Fassnacht, A. H. Gonzalez, T. R. Greve, Y. D. Hezaveh, K. Lacaille, K. C. Litke, S. Lower, J. Ma, M. Malkan, T. B. Miller, W. R. Morningstar, E. J. Murphy, D. Narayanan, K. A. Phadke, K. M. Rotermund, J. Sreevani, B. Stalder, A. A. Stark, M. L. Strandet, M. Tang, & A. Weiß, Nature, 553, 51, 2018.

    3
    a, Emission in the 157.74-μm fine-structure line of ionized carbon ([C ii]) as measured at 240.57 GHz with ALMA, integrated over 1,500 km s−1 of velocity, is shown with the colour scale. The range in flux per synthesized beam (the 0.25″ × 0.30″ beam is shown in the lower left) is provided at right. The rest-frame 160-μm continuum emission that was measured simultaneously is overlaid, with contours at 8, 16, 32 and 64 times the noise level of 34 μJy per beam. SPT0311−58 E and SPT0311−58 W are labelled. b, The continuum-subtracted, source-integrated [C ii] (red) and [O iii] (blue) spectra. The upper spectra are as observed (‘apparent’) with no correction for lensing, whereas the lensing-corrected (‘intrinsic’) [C ii] spectrum is shown at the bottom. SPT0311−58 E and SPT0311−58 W separate almost completely at a velocity of 500 km s−1. c, The source-plane structure after removing the effect of gravitational lensing. The image is coloured according to the flux-weighted mean velocity, showing that the two objects are physically associated but separated by roughly 700 km s−1 in velocity and 8 kpc (projected) in space. The reconstructed 160-μm continuum emission is shown as contours. The scale bar represents the angular size of 5 kpc in the source plane. d, The line-to-continuum ratio at the 158-μm wavelength of [C ii], normalized to the map peak. The [C ii] emission from SPT0311−58 E is much brighter relative to its continuum than for SPT0311−58 W. e, Velocity-integrated emission in the 88.36-μm fine-structure line of doubly ionized oxygen ([O iii]) as measured at 429.49 GHz with ALMA (colour scale). The data have an intrinsic angular resolution of 0.2″ × 0.3″, but have been tapered to 0.5″ owing to the lower signal-to-noise ratio of these data. f, The luminosity ratio between the [O iii] and [C ii] lines. As for the [C ii] line-to-continuum ratio, a large disparity is seen between SPT0311−58 E and SPT0311−58 W. The sky coordinates and contours for rest-frame 160-μm continuum emission in d–f are the same as in a.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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

     
  • richardmitnick 3:41 pm on January 22, 2018 Permalink | Reply
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    From CfA: “A New Bound on Axions” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    January 19, 2018

    1
    A composite image of M87 in the X-ray from Chandra (blue) and in radio emission from the Very Large Array (red-orange). Astronomers used the X-ray emission from M87 to constrain the properties of axions, putative particles suggested as dark matter candidates. X-ray NASA/CXC/KIPAC/N. Werner, E. Million et al.; Radio NRAO/AUI/NSF/F. Owen.

    NASA/Chandra Telescope

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

    An axion is a hypothetical elementary particle whose existence was postulated in order to explain why certain subatomic reactions appear to violate basic symmetry constraints, in particular symmetry in time. The 1980 Nobel Prize in Physics went for the discovery of time-asymmetric reactions. Meanwhile, during the following decades, astronomers studying the motions of galaxies and the character of the cosmic microwave background [CMB] radiation came to realize that most of the matter in the universe was not visible.

    CMB per ESA/Planck

    Cosmic Background Radiation per Planck

    ESA/Planck

    It was dubbed dark matter, and today’s best measurements find that about 84% of matter in the cosmos is dark. This component is dark not only because it does not emit light — it is not composed of atoms or their usual constituents, like electrons and protons, and its nature is mysterious. Axions have been suggested as one possible solution. Particle physicists, however, have so far not been able to detect directly axions, leaving their existence in doubt and reinvigorating the puzzles they were supposed to resolve.

    CfA astronomer Paul Nulsen and his colleagues used a novel method to investigate the nature of axions. Quantum mechanics constrain axions, if they exist, to interact with light in the presence of a magnetic field. As they propagate along a strong field, axions and photons should transmute from one to the other other in an oscillatory manner. Because the strength of any possible effect depends in part on the energy of the photons, the astronomers used the Chandra X-ray Observatory to monitor bright X-ray emission from galaxies. They observed X-rays from the nucleus of the galaxy Messier 87, which is known to have strong magnetic fields, and which (at a distance of only fifty-three million light-years) is close enough to enable precise measurements of variations in the X-ray flux. Moreover, Me3ssier 87 lies in a cluster of galaxies, the Virgo cluster, which should insure the magnetic fields extend over very large scales and also facilitate the interpretation. Not least, Messier 87 has been carefully studied for decades and its properties are relatively well known.

    The search did not find the signature of axions. It does, however, set an important new limit on the strength of the coupling between axions and photons, and is able to rule out a substantial fraction of the possible future experiments that might be undertaken to detect axions. The scientists note that their research highlights the power of X-ray astronomy to probe some basic issues in particle physics, and point to complementary research activities that can be undertaken on other bright X-ray emitting galaxies.

    Science paper:
    A New Bound on Axion-Like Particles, Journal of Cosmology and Astroparticle Physics.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

     
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