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  • richardmitnick 3:49 pm on August 18, 2017 Permalink | Reply
    Tags: , , , CfA, , The Origin of Binary Stars   

    From CfA: “The Origin of Binary Stars” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1

    An image taken at submillimeter wavelengths of a star-forming core, showing that it contains two young stellar embryos. Astronomers have concluded from a systematic study of very young cores that most embryonic stars form in multiple systems, and later some of them separate.
    Sadavoy and Stahler

    The origin of binary stars has long been one of the central problems of astronomy. One of the main questions is how stellar mass affects the tendency to be multiple. There have been numerous studies of young stars in molecular clouds to look for variations in binary frequency with stellar mass, but so many other effects can influence the result that the results have been inconclusive. These complicating factors include dynamical interactions between stars that can eject one member of a multiple system, or on the other hand might capture a passing star under the right circumstances. Some studies, for example, found that younger stars are more likely to be found in binary pairs. One issue with much of the previous observational work, however, has been the small sample sizes.

    CfA astronomer Sarah Sadavoy and her colleague used combined observations from a large radio wavelength survey of young stars in the Perseus cloud with submillimeter observations of the natal dense core material around these stars to identify twenty-four multiple systems. The scientists then used a submillimeter study to identify and characterize the dust cores in which the stars are buried. They found that most of the embedded binaries are located near the centers of their dust cores, indicative of their still being young enough to have not drifted away. About half of the binaries are in elongated core structures, and they conclude that the initial cores were also elongated structures. After modeling their findings, they argue that the most likely scenarios are the ones predicting that all stars, both single and binaries, form in widely separated binary pair systems, but that most of these break apart either due to ejection or to the core itself breaking apart. A few systems become more tightly bound. Although other studies have suggested this idea as well, this is the first study to do so based on observations of very young, still embedded stars. One of their most significant major conclusions is that each dusty core of material is likely to be the birthplace of two stars, not the single star usually modeled. This means that there are probably twice as many stars being formed per core than is generally believed.

    Reference(s):

    Embedded Binaries and Their Dense Cores, Sarah I. Sadavoy and Steven W. Stahler, MNRAS

    See the full article here .

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  • richardmitnick 2:25 pm on August 17, 2017 Permalink | Reply
    Tags: CfA, ,   

    From CfA: “Properties of a Massive Galaxy 800 Million Years after the Big Bang” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    August 11, 2017 [Not brought to social media. Why?]
    No writer credit

    1
    A Hubble image of the galaxy cluster Abell 1689, which acts as a lens to focus the light from much more distant galaxies, including some very dusty star-forming galaxies in the early universe (seen as the nearly point-like blue smudges in this image). A submillimeter study of a different massive dusty galaxy in the early universe uses carbon monoxide gas to characterize the interstellar medium and determine the mass and star-formation rate. NASA/ESA Hubble

    Searches for the most distant galaxies have now probed earlier than the first billion years in the history of the universe, early enough to start seeing the primary effects of the first stars: the reionization of neutral atoms.

    Reionization era and first stars, Caltech

    Astronomers want to understand how galaxies formed and evolved in this period, the timescale over which this reionization took place, the nature of the objects that provided the ionizing photons, and the scenarios in which galaxies and their interstellar medium (ISM) become enriched with atoms made in stellar furnaces. Although galaxies from this era are currently being discovered in deep optical and near-infrared surveys, most of them are low-mass galaxies, very faint, and the enrichment process is difficult to study. More luminous, massive star-forming galaxies are thought to be present and to play a major role in reionization, but because these large objects are difficult to assemble so early in cosmic time there are not many of them.

    Massive star-forming galaxies that contain dust emit strongly radiation at submillimeter wavelengths and these objects can be find using telescopes.

    CfA Submillimeter Array Mauna Kea, Hawaii, USA

    They therefore offer the opportunity to study extreme cases of metal/dust enrichment of the ISM early in the era of reionization. CfA astronomers Matt Ashby and Chris Hayward were members of a large team using the South Pole Telescope to detect a set of these dusty galaxies.

    South Pole Telescope SPTPOL

    They determined their distances using the ALMA telescopes by looking at the redshifted wavelength of carbon monoxide molecule in their ISM.

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

    The farthest known dusty galaxy was detected in this way, and subsequent observations of it with other facilities confirmed its cosmological distance. The scientists constrained the properties of the object by modeling the observed continuum and spectral lines, and found that the object has a mass in gas of about 330 billion solar-masses; for comparison, the estimated gas mass of the Milky Way is about five billion solar-masses (most of its mass is in stars). The dusty galaxy is forming new stars at an estimated rate of several thousand per year – although with the assumption that the process is similar to what is seen in nearby galaxies. This rare and distant object offers one of the best probes so far into the activity in galaxies when the universe was very young.

    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 1:56 pm on August 12, 2017 Permalink | Reply
    Tags: , , , CfA, , NASA Arcus X-Ray Mission   

    From CfA: “NASA Selects the Arcus X-Ray Mission for Phase A Study” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    August 10, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

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

    1
    NASA has announced that the Arcus X-ray mission concept has been selected for a “Phase A” study as part of the $250 million Medium-Class Explorer (MIDEX) program.

    Arcus is a high-resolution grating spectrometer mission that combines X-ray optics and gratings to disperse the X-rays, much like how a prism separates sunlight into the colors of the rainbow. This allows for detailed study of the hot gas that is the dominant component of the normal matter in the Universe, much of which has not yet been directly seen. Arcus will measure the mass and velocity of gas accelerated by the gravitational force of black holes, discovering how this material impacts its host galaxy or beyond. Arcus will also study how stars like our Sun form and evolve. Arcus will conduct research on a wide range of astrophysical phenomena – from the tiniest dust grains to the largest black holes in the largest galaxies in the Universe – in X-ray light.

    The selection of Arcus by NASA for this next phase means NASA will provide $2 million to fund a 9-month detailed study of the mission requirements. At the end of this period, the 3 missions selected for Phase A studies will be reviewed and a single mission selected for flight.

    The Principal Investigator for Arcus is Randall Smith of the Smithsonian Astrophysical Observatory in Cambridge, Mass. The project also includes many hardware partners from US and European institutions including NASA’s Ames Research Center and Goddard Space Flight Center, the Massachusetts Institute of Technology, Penn State University, and the Max Planck Institute for Extraterrestrial Physics. Orbital ATK, industry partner for Arcus, will manufacture the spacecraft itself.

    Smithsonian Astrophysical Observatory scientist Gary Melnick is a Co-Investigator on SPHEREX, led by CalTech, also selected for Phase A (http://spherex.caltech.edu/). More information on this and other NASA selections can be found in this announcement: https://www.nasa.gov/press-release/nasa-selects-proposals-to-study-galax…

    More information about Arcus can be found at: http://www.arcusxray.org/

    See the full article here .

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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 9:32 am on August 11, 2017 Permalink | Reply
    Tags: CfA, Explore the Total Solar Eclipse with the CfA   

    From CfA: “Explore the Total Solar Eclipse with the CfA” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    August 8, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

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

    1
    This photo captures a total solar eclipse (gray and white) captured by the Williams College Expedition to Easter Island in the South Pacific on July 11, 2010. A total solar eclipse like this will travel over parts of North America on August 21, 2017. Williams College Eclipse Expedition – Jay M. Pasachoff, Muzhou Lu, and Craig Malamut

    On August 21, 2017, millions of people across North America will experience a total solar eclipse for the first time. Scientists around the world, including several groups at the Harvard-Smithsonian Center for Astrophysics (CfA), are taking advantage of this opportunity to study the Sun for the benefit of the scientific community and the public at large.

    Eclipse-related projects at the CfA range from detailed studies of solar physics to the development of apps to bring the eclipse to the blind and visually impaired community. These projects include the following:

    The Airborne Infrared Spectrometer (AIR-Spec) for Solar Eclipse Observations:
    During the eclipse, a team of CfA scientists will observe the Sun from a Gulfstream aircraft flying at 50,000 feet over Kentucky during the period of totality. They will be carrying instruments designed to take detailed measurements of the Sun’s outer atmosphere, called the corona, in infrared wavelengths.

    Eclipse Soundscapes:
    This project will use sound to bring a multisensory eclipse experience to the blind and visually impaired community. With illustrative audio descriptions of the eclipse delivered in real time and an interactive “Rumble Map” which will allow users to hear and feel the physical qualities of the eclipse, the Eclipse Soundscapes app aims to increase scientific engagement by bringing this astronomical event to a larger, more diverse audience. Eclipse Soundscapes is also partnering with the National Park Service, Brigham Young University, and citizen scientists to record environmental sounds before, during, and after the eclipse, in an effort to study how soundscapes change with the event.
    http://www.eclipsesoundscapes.org

    SAO Eclipse App:
    This free mobile app will calculate a user’s view of the eclipse with an interactive map, give a virtual view in an eclipse simulator, and deliver a live NASA stream of the eclipse as it travels across the continental United States. Users will also learn about solar research at the Smithsonian Astrophysical Observatory, part of the CfA, and get even closer to the sun with near-live views from space.
    http://smithsonian-eclipse-app.simulationcurriculum.com/download.html

    MicroObservatory:
    The MicroObservatory is a robotic network of telescopes operated by the CfA for research and public outreach purposes. During the eclipse, MicroObservatory facilities in Massachusetts and Arizona will observe the eclipse from above and below the path of totality. Science education specialists will engage users by creating eclipse animations, and calculating the distance of the moon by comparing the two image sets.
    http://mo-www.cfa.harvard.edu/MicroObservatory/

    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 1:29 pm on August 4, 2017 Permalink | Reply
    Tags: , , , CfA, , , Magnetic Fields in Massive Star Formation Cores,   

    From CfA: “Magnetic Fields in Massive, Star Formation Cores” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    A far-infrared image of the long filament of star formation activity known as DR21, seen here in emission by the Herschel Space Telescope. A study of the magnetic field along the filament and around six star-forming cores within it finds that magnetic effects are primarily important during the early stages of star formation. ESA/Herschel

    ESA/Herschel spacecraft

    Studies of molecular clouds have revealed that star formation usually occurs in a two step process. First, supersonic flows compress the clouds into dense filaments light-years long, after which gravity collapses the densest material in the filament into cores. In this scenario, massive cores (each more than about twenty solar–masses) preferentially form at intersections where filaments cross, producing sites of clustered star formation. The process sounds reasonable and is expected to be efficient, but the observed rate of star formation in dense gas is only a few percent of the rate expected if the material really were freely collapsing. To solve the problem, astronomers have proposed that magnetic fields support the cores against the collapse induced by self-gravity.

    Magnetic fields are difficult to measure and difficult to interpret. CfA astronomers Tao-Chung Ching, Qizhou Zhang, and Josep Girat led a team that used the Submillimeter Array to study six dense cores in a nearby star formation region in Cygnus.

    CfA Submillimeter Array Mauna Kea, Hawaii, USA

    They measured the field strengths from the polarization of the millimeter radiation; elongated dust grains are known to be aligned by magnetic fields and to scatter light with a preferred polarization direction. The scientists then correlated the field direction in these cores with the field direction along the filament out of which the cores developed.

    The astronomers find that the magnetic field along the filament is well-ordered and parallel to the structure, but at the cores themselves the field direction is much more complex, sometimes parallel and sometimes perpendicular. They conclude that during the formation of the cores the magnetic fields, at least at small scales, become unimportant compared to turbulence and infall. Although the field may play an important role as the filament initially collapses, once the dense cores develop the local kinematics from infall and gravitational effects become more important.

    Reference(s):

    Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament,Tao-Chung Ching, Shih-Ping Lai1, Qizhou Zhang, Josep M. Girart, Keping Qiu, and Hauyu B. Liu, ApJ 838, 121, 2017.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

     
  • richardmitnick 2:46 pm on August 3, 2017 Permalink | Reply
    Tags: , , , CfA, , , The Outer Galaxy   

    From CfA: “The Outer Galaxy” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 28, 2017
    No writer credit

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

    The Sun is located inside one of the spiral arms of the Milky Way galaxy, roughly two-thirds of the way from the galactic center to the outer regions. Because we are inside the galaxy, obscuration by dust and the confusion of sources along our lines-of-sight make mapping the galaxy a difficult task. Astronomers think that the galaxy is a symmetric spiral, and about ten years ago CfA astronomers Tom Dame and Pat Thaddeus using millimeter observations of the gas carbon monoxide discovered symmetric components to the spiral arms deep in the inner galaxy that lent support to this model.

    The galaxy is not perfectly flat. It has a slight warp that allows some distant structures, at least in the direction of the constellations of Scutum and Centaurus, to be seen more distinctly above much of the foreground confusion. In 2011 the same CfA astronomers were the first to discover a large-scale spiral feature within this distant warp which they called the “Outer Scutum–Centaurus Arm (OSC).” Subsequent studies placed the OSC at a distance from the galactic center of over forty thousand light-years; it appears to be a symmetric counterpart to a spiral arm on the opposite side, in the direction of Perseus.

    CfA astronomer Tom Dame has joined with a set of collaborators to probe the extent of massive star formation in the OSC; sadly, his colleague Pat Thaddeus passed away earlier this year. Using radio measurements of ionized gas, which traces the hot ultraviolet from massive young stars, as well as bright emission from masers associated with massive star formation, the scientists observed 140 candidate locations and discovered evidence for massive young stars in about sixty percent of them. The study shows that the OSC is forming new stars, some with as much as forty solar masses each. These stars and their associated ionized environments, at least as far as we know now, mark the outer boundary for massive star formation in the Milky Way.

    Science paper:
    High-mass Star Formation in the Outer Scutum–Centaurus Arm, ApJ

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

     
  • richardmitnick 2:32 pm on August 3, 2017 Permalink | Reply
    Tags: , , CfA, , , SN 2017egm,   

    From CfA: “Astronomers Discover “Heavy Metal” Supernova Rocking Out” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 31, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

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

    1

    Many rock stars don’t like to play by the rules, and a cosmic one is no exception. A team of astronomers has discovered that an extraordinarily bright supernova occurred in a surprising location. This “heavy metal” supernova discovery challenges current ideas of how and where such super-charged supernovas occur.

    Supernovas are some of the most energetic events in the Universe. When a massive star runs out of fuel, it can collapse onto itself and create a spectacular explosion that briefly outshines an entire galaxy, dispersing vital elements into space.

    In the past decade, astronomers have discovered about fifty supernovas, out of the thousands known, that are particularly powerful. These explosions are up to 100 times brighter than other supernovas caused by the collapse of a massive star.

    Following the recent discovery of one of these “superluminous supernovas”, a team of astronomers led by Matt Nicholl from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., has uncovered vital clues about where some of these extraordinary objects come from.

    Cambridge University’s Gaia Science Alerts team discovered this supernova, dubbed SN 2017egm, on May 23, 2017 with the European Space Agency’s Gaia satellite.

    ESA/GAIA satellite


    Nordic Optical telescope, at Roque de los Muchachos Observatory, La Palma in the Canary Islands, Spain


    A team led by Subo Dong of the Kavli Institute for Astronomy and Astrophysics at Peking University used the Nordic Optical Telescope to identify it as a superluminous supernova.

    SN 2017egm is located in a spiral galaxy about 420 million light years from Earth, making it about three times closer than any other superluminous supernova previously seen. Dong realized that the galaxy was very surprising, as virtually all known superluminous supernovas have been found in dwarf galaxies that are much smaller than spiral galaxies like the Milky Way.

    Building on this discovery, the CfA team found that SN 2017egm’s host galaxy has a high concentration of elements heavier than hydrogen and helium, which astronomers call “metals”. This is the first clear evidence for a metal-rich birthplace for a superluminous supernova. The dwarf galaxies that usually host superluminous supernovas are known to have a low metal content, which was thought to be an essential ingredient for making these explosions.

    “Superluminous supernovas were already the rock stars of the supernova world,” said Nicholl. “We now know that some of them like heavy metal, so to speak, and explode in galaxies like our own Milky Way.”

    “If one of these went off in our own Galaxy, it would be much brighter than any supernova in recorded human history and would be as bright as the full Moon,” said co-author Edo Berger, also of the CfA. “However, they’re so rare that we probably have to wait several million years to see one.”

    The CfA researchers also found more clues about the nature of SN 2017egm. In particular, their new study supports the idea that a rapidly spinning, highly magnetized neutron star, called a magnetar, is likely the engine that drives the incredible amount of light generated by these supernovas.

    While the brightness of SN 2017egm and the properties of the magnetar that powers it overlap with those of other superluminous supernovas, the amount of mass ejected by SN 2017egm may be lower than the average event. This difference may indicate that the massive star that led to SN 2017egm lost more mass than most superluminous supernova progenitors before exploding. The spin rate of the magnetar may also be slower than average.

    These results show that the amount of metals has at most only a small effect on the properties of a superluminous supernova and the engine driving it. However, the metal-rich variety occurs at only about 10% of the rate of the metal-poor ones. Similar results have been found for bursts of gamma rays associated with the explosion of massive stars. This suggests a close association between these two types of objects.

    From July 4th, 2017 until September 16th, 2017 the supernova is not observable because it is too close to the Sun. After that, detailed studies should be possible for at least a few more years.

    “This should break all records for how long a superluminous supernova can be followed”, said co-author Raffaella Margutti of Northwestern University in Evanston, Illinois. “I’m excited to see what other surprises this object has in store for us.”

    6
    The CfA team observed SN 2017egm on June 18th with the 60-inch telescope at the Smithsonian Astrophysical Observatory’s Fred Lawrence Whipple Observatory in Arizona.

    A paper by Matt Nicholl describing these results was recently accepted for publication in The Astrophysical Journal Letters, and is available online. In addition to Berger and Margutti, the co-authors of the paper are Peter Blanchard, James Guillochon, and Joel Leja, all of the CfA, and Ryan Chornock of Ohio University in Athens, Ohio.

    See the full article here .

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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 4:20 pm on July 27, 2017 Permalink | Reply
    Tags: , , , CfA, , ,   

    From CfA: “Mapping Dark Matter” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 21, 2017 [Not making it into social media, but I need the work.]

    1
    Abell 2744, a cluster of galaxies whose dark matter halo has imaged more distant galaxies as seen in this Hubble Space Telescope image. Astronomers have compared the image to simulations of dark matter lensing and found excellent agreement, indicating that that current models of dark matter behavior on the large scale are quite good. NASA/ESA/Hubble.

    About eighty-five percent of the matter in the universe is in the form of dark matter, whose nature remains a mystery. The rest of the matter in the universe is of the kind found in atoms. Astronomers studying the evolution of galaxies in the universe find that dark matter exhibits gravity and, because it is so abundant, it dominates the formation of large-scale structures in the universe like clusters of galaxies. Dark matter is hard to observe directly, needless to say, and it shows no evidence of interacting with itself or other matter other than via gravity, but fortunately it can be traced by modeling sensitive observations of the distributions of galaxies across a range of scales.

    Galaxies generally reside at the centers of vast clumps of dark matter called haloes because they surround the clusters of galaxies.

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Dark matter halo Image credit: Virgo consortium / A. Amblard / ESA

    Gravitational lensing of more distant galaxies by dark matter haloes offers a particularly unique and powerful probe of the detailed distribution of dark matter.

    So-called strong gravitational lensing creates highly distorted, magnified and occasionally multiple images of a single source; so-called weak lensing results in modestly yet systematically deformed shapes of background galaxies that can also provide robust constraints on the distribution of dark matter within the clusters.

    Gravitational Lensing NASA/ESA

    Weak gravitational lensing HST

    CfA astronomers Annalisa Pillepich and Lars Hernquist and their colleagues compared gravitationally distorted Hubble images of the galaxy cluster Abell 2744 and two other clusters with the results of computer simulations of dark matter haloes. They found, in agreement with key predictions in the conventional dark matter picture, that the detailed galaxy substructures depend on the dark matter halo distribution, and that the total mass and the light trace each other. They also found a few discrepancies: the radial distribution of the dark matter is different from that predicted by the simulations, and the effects of tidal stripping and friction in galaxies are smaller than expected, but they suggest these issues might be resolved with more precise simulations. Overall, however, the standard model of dark matter does an excellent and reassuring job of describing galaxy clustering.

    Science paper:
    Mapping Substructure in the HST Frontier Fields Cluster Lenses and in Cosmological Simulations 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 4:19 pm on July 26, 2017 Permalink | Reply
    Tags: , , , CfA, , Dynamo, More slowly rotating stars have a magnetic cycle that repeats more quickly, , The Secret of Magnetic Cycles in Stars, The solar cycle, The Sun’s magnetic field flips approximately every 11 years   

    From CfA: “The Secret of Magnetic Cycles in Stars” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    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 combination of images and artist’s impression shows changes in the Sun’s appearance and magnetic fields during part of the solar cycle. The Sun’s magnetic field flips approximately every 11 years, defining this cycle. The switch happens around at the maximum peak of magnetic activity, when sunspot and flare activity reaches its peak. We show images of the Sun captured by NASA’s Solar Dynamics Observatory (SDO) obtained on 10th October 2010 (solar minimum), 25th December 2013 (solar maximum) and on 25th June 2017 (solar minimum), combined with artist’s impressions to show the magnetic field of the Sun. Images: NASA/SDO/A. Strugarek et al; Illustrations: L. Almeida, Federal University of Rio Grande do Norte (UFRN), Brazil.

    NASA/SDO

    Using new numerical simulations and observations, scientists may now be able to explain why the Sun’s magnetic field reverses every eleven years. This significant discovery explains how the duration of the magnetic cycle of a star depends on its rotation, and may help us understand violent space weather phenomena around the Sun and similar stars.

    During what is known as the solar cycle, the magnetic field of the Sun has reversed every 11 years over the past centuries. This flip, where the south magnetic pole switches to north and vice versa, occurs during the peak of each solar cycle and originates from a process called a “dynamo”. Magnetic fields are generated by a dynamo, which involves the rotation of the star as well as convection and the rising and falling of hot gas in the star’s interior.

    For the Sun, scientists know that magnetic fields originate in its turbulent outer layers and have a complex dependency upon how quickly the Sun is rotating. Scientists have also measured magnetic cycles for distant stars with fundamental properties similar to those of the Sun. By studying the characteristics of these magnetic properties, scientists have a very promising way to better understand the magnetic evolution in our Sun associated with the dynamo process.

    An international collaboration that includes the University of Montréal, the Harvard-Smithsonian Center for Astrophysics, the Commissariat à l’énergie atomique et aux énergies alternatives and the Universidade Federal do Rio Grande do Norte, carried out a set of 3D simulations of the interiors of stars similar to the Sun to explain the origin of their magnetic field cycles. The scientists found that the period of the magnetic cycle depends on the rotation rate of a star. The trend is that more slowly rotating stars have a magnetic cycle that repeats more quickly.

    “The trend we found differs from theories developed in the past. This really opens new research avenues for our understanding of the magnetism of stars,” said Antoine Strugarek of the Commissariat à l’énergie atomique et aux énergies alternatives, France, the lead author of a paper published in the July 14th issue of Science Magazine.

    An important advance is that the scientists’ model can explain the cycle of both the Sun and stars that astronomers categorize as Sun-like. Previously scientists thought that the Sun’s cycle might differ in behavior from those of Sun-like stars, with a shorter magnetic cycle than expected.

    “Our work supports the idea that our Sun is an average, middle-aged yellow dwarf star, with a magnetic cycle compatible with cycles from its stellar cousins,” said co-author Jose-Dias Do Nascimento of the Harvard-Smithsonian Center for Astrophysics (CfA) and the University of Rio G. do Norte (UFRN), Brazil. “In other words we confirm that the Sun really is a useful proxy for understanding other stars in many ways.”

    By observing more and more stars and exploring stellar structures different from those of the Sun with numerical simulations, the team of researchers hopes to refine their new scenario for the origin of stellar magnetic cycles.

    One long-term goal of this work is to gain a better understanding of “space weather”, a term used to describe the wind of particles that blows away from the Sun and other stars. The acceleration mechanism for this wind is likely related to magnetic fields in the atmospheres of stars. In extreme cases, space weather can interrupt electrical power on Earth, and it can be very dangerous to satellites and astronauts.

    “The changes throughout a magnetic cycle have effects throughout the Solar System and other planetary systems thanks to the influence of space weather,” said Do Nascimento.

    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 1:47 pm on July 19, 2017 Permalink | Reply
    Tags: , , , CfA, , , Scientists Are Using the Universe as a "Cosmological Collider", Standard Model of Particle Physics   

    From CfA: “Scientists Are Using the Universe as a “Cosmological Collider” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 19, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

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

    1

    Physicists are capitalizing on a direct connection between the largest cosmic structures and the smallest known objects to use the universe as a “cosmological collider” and investigate new physics.

    The three-dimensional map of galaxies throughout the cosmos and the leftover radiation from the Big Bang – called the cosmic microwave background (CMB) – are the largest structures in the universe that astrophysicists observe using telescopes.

    CMB per ESA/Planck

    ESA/Planck

    Subatomic elementary particles, on the other hand, are the smallest known objects in the universe that particle physicists study using particle colliders.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    A team including Xingang Chen of the Harvard-Smithsonian Center for Astrophysics (CfA), Yi Wang from the Hong Kong University of Science and Technology (HKUST) and Zhong-Zhi Xianyu from the Center for Mathematical Sciences and Applications at Harvard University has used these extremes of size to probe fundamental physics in an innovative way. They have shown how the properties of the elementary particles in the Standard Model of particle physics may be inferred by studying the largest cosmic structures. This connection is made through a process called cosmic inflation.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Inflationary Universe. NASA/WMAP

    Cosmic inflation is the most widely accepted theoretical scenario to explain what preceded the Big Bang. This theory predicts that the size of the universe expanded at an extraordinary and accelerating rate in the first fleeting fraction of a second after the universe was created.

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

    It was a highly energetic event, during which all particles in the universe were created and interacted with each other. This is similar to the environment physicists try to create in ground-based colliders, with the exception that its energy can be 10 billion times larger than any colliders that humans can build.

    Inflation was followed by the Big Bang, where the cosmos continued to expand for more than 13 billion years, but the expansion rate slowed down with time. Microscopic structures created in these energetic events got stretched across the universe, resulting in regions that were slightly denser or less dense than surrounding areas in the otherwise very homogeneous early universe. As the universe evolved, the denser regions attracted more and more matter due to gravity. Eventually, the initial microscopic structures seeded the large-scale structure of our universe, and determined the locations of galaxies throughout the cosmos.

    In ground-based colliders, physicists and engineers build instruments to read the results of the colliding events. The question is then how we should read the results of the cosmological collider.

    “Several years ago, Yi Wang and I, Nima Arkani-Hamed and Juan Maldacena from the Institute of Advanced Study, and several other groups, discovered that the results of this cosmological collider are encoded in the statistics of the initial microscopic structures. As time passes, they become imprinted in the statistics of the spatial distribution of the universe’s contents, such as galaxies and the cosmic microwave background, that we observe today,” said Xingang Chen. “By studying the properties of these statistics we can learn more about the properties of elementary particles.”

    As in ground-based colliders, before scientists explore new physics, it is crucial to understand the behavior of known fundamental particles in this cosmological collider, as described by the Standard Model of particle physics.

    “The relative number of fundamental particles that have different masses – what we call the mass spectrum – in the Standard Model has a special pattern, which can be viewed as the fingerprint of the Standard Model,” explained Zhong-Zhi Xiangyu. “However, this fingerprint changes as the environment changes, and would have looked very different at the time of inflation from how it looks now.”

    The team showed what the mass spectrum of the Standard Model would look like for different inflation models. They also showed how this mass spectrum is imprinted in the appearance of the large-scale structure of our universe. This study paves the way for the future discovery of new physics.

    “The ongoing observations of the CMB and large-scale structure have achieved impressive precision from which valuable information about the initial microscopic structures can be extracted,” said Yi Wang. “In this cosmological collider, any observational signal that deviates from that expected for particles in the Standard Model would then be a sign of new physics.”

    The current research is only a small step towards an exciting era when precision cosmology will show its full power.

    “If we are lucky enough to observe these imprints, we would not only be able to study particle physics and fundamental principles in the early universe, but also better understand cosmic inflation itself. In this regard, there are still a whole universe of mysteries to be explored,” said Xianyu.

    This research is detailed in a paper published in the journal Physical Review Letters on June 29, 2017, and the preprint is available online.

    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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