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  • richardmitnick 4:43 pm on March 5, 2015 Permalink | Reply
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    From MIT: “Why isn’t the universe as bright as it should be?” 


    MIT News

    March 4, 2015
    Jennifer Chu | MIT News Office

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    This Hubble Space Telescope image of galaxy NGC 1275 reveals the fine, thread-like filamentary structures in the gas surrounding the galaxy. The red filaments are composed of cool gas being suspended by a magnetic field, and are surrounded by the 100-million-degree Fahrenheit gas in the center of the Perseus galaxy cluster. The filaments are dramatic markers of the feedback process through which energy is transferred from the central massive black hole to the surrounding gas. Courtesy of NASA (edited by Jose-Luis Olivares/MIT)

    A handful of new stars are born each year in the Milky Way, while many more blink on across the universe. But astronomers have observed that galaxies should be churning out millions more stars, based on the amount of interstellar gas available.

    Now researchers from MIT, Columbia University, and Michigan State University have pieced together a theory describing how clusters of galaxies may regulate star formation. They describe their framework this week in the journal Nature.

    When intracluster gas cools rapidly, it condenses, then collapses to form new stars. Scientists have long thought that something must be keeping the gas from cooling enough to generate more stars — but exactly what has remained a mystery.

    For some galaxy clusters, the researchers say, the intracluster gas may simply be too hot — on the order of hundreds of millions of degrees Celsius. Even if one region experiences some cooling, the intensity of the surrounding heat would keep that region from cooling further — an effect known as conduction.

    “It would be like putting an ice cube in a boiling pot of water — the average temperature is pretty much still boiling,” says Michael McDonald, a Hubble Fellow in MIT’s Kavli Institute for Astrophysics and Space Research. “At super-high temperatures, conduction smooths out the temperature distribution so you don’t get any of these cold clouds that should form stars.”

    For so-called “cool core” galaxy clusters, the gas near the center may be cool enough to form some stars. However, a portion of this cooled gas may rain down into a central black hole, which then spews out hot material that serves to reheat the surroundings, preventing many stars from forming — an effect the team terms “precipitation-driven feedback.”

    “Some stars will form, but before it gets too out of hand, the black hole will heat everything back up — it’s like a thermostat for the cluster,” McDonald says. “The combination of conduction and precipitation-driven feedback provides a simple, clear picture of how star formation is governed in galaxy clusters.”

    Crossing a galactic threshold

    Throughout the universe, there exist two main classes of galaxy clusters: cool core clusters — those that are rapidly cooling and forming stars — and non-cool core clusters — those have not had sufficient time to cool.

    The Coma cluster, a non-cool cluster, is filled with gas at a scorching 100 million degrees Celsius.

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    A Sloan Digital Sky Survey [SDSS]/Spitzer Space Telescope mosaic of the Coma Cluster in long-wavelength infrared (red), short-wavelength infrared (green), and visible light. The many faint green smudges are dwarf galaxies in the cluster. Credit: NASA/JPL-Caltech/GSFC/SDSS

    Sloan Digital Sky Survey Telescope
    SDSS telescope

    NASA Spitzer Telescope
    Spitzer

    To form any stars, this gas would have to cool for several billion years. In contrast, the nearby Perseus cluster is a cool core cluster whose intracluster gas is a relatively mild several million degrees Celsius. New stars occasionally emerge from the cooling of this gas in the Perseus cluster, though not as many as scientists would predict.

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    Chandra X-ray Observatory observations of the central regions of the Perseus galaxy cluster. Image is 284 arcsec across. RA 03h 19m 47.60s Dec +41° 30′ 37.00″ in Perseus. Observation dates: 13 pointings between August 8, 2002 and October 20, 2004. Color code: Energy (Red 0.3-1.2 keV, Green 1.2-2 keV, Blue 2-7 keV). Instrument: ACIS.

    NASA Chandra Telescope
    Chandra

    “The amount of fuel for star formation outpaces the amount of stars 10 times, so these clusters should be really star-rich,” McDonald says. “You really need some mechanism to prevent gas from cooling, otherwise the universe would have 10 times as many stars.”

    McDonald and his colleagues worked out a theoretical framework that relies on two anti-cooling mechanisms.

    The group calculated the behavior of intracluster gas based on a galaxy cluster’s radius, mass, density, and temperature. The researchers found that there is a critical temperature threshold below which the cooling of gas accelerates significantly, causing gas to cool rapidly enough to form stars.

    According to the group’s theory, two different mechanisms regulate star formation, depending on whether a galaxy cluster is above or below the temperature threshold. For clusters that are significantly above the threshold, conduction puts a damper on star formation: The surrounding hot gas overwhelms any pockets of cold gas that may form, keeping everything in the cluster at high temperatures.

    “For these hotter clusters, they’re stuck in this hot state, and will never cool and form stars,” McDonald says. “Once you get into this very high-temperature regime, cooling is really inefficient, and they’re stuck there forever.”

    For gas at temperatures closer to the lower threshold, it’s much easier to cool to form stars. However, in these clusters, precipitation-driven feedback starts to kick in to regulate star formation: While cooling gas can quickly condense into clouds of droplets that can form stars, these droplets can also rain down into a central black hole — in which case the black hole may emit hot jets of material back into the cluster, heating the surrounding gas back up to prevent further stars from forming.

    “In the Perseus cluster, we see these jets acting on hot gas, with all these bubbles and ripples and shockwaves,” McDonald says. “Now we have a good sense of what triggered those jets, which was precipitating gas falling onto the black hole.”

    On track

    McDonald and his colleagues compared their theoretical framework to observations of distant galaxy clusters, and found that their theory matched the observed differences between clusters. The team collected data from the Chandra X-ray Observatory and the South Pole Telescope [SPT] — an observatory in Antarctica that searches for far-off massive galaxy clusters.

    South Pole Telescope
    SPT

    The researchers compared their theoretical framework with the gas cooling times of every known galaxy cluster, and found that clusters filtered into two populations — very slowly cooling clusters, and clusters that are cooling rapidly, closer to the rate predicted by the group as a critical threshold.

    By using the theoretical framework, McDonald says researchers may be able to predict the evolution of galaxy clusters, and the stars they produce.

    “We’ve built a track that clusters follow,” McDonald says. “The nice, simple thing about this framework is that you’re stuck in one of two modes, for a very long time, until something very catastrophic bumps you out, like a head-on collision with another cluster.”

    The researchers hope to look deeper into the theory to see whether the mechanisms regulating star formation in clusters also apply to individual galaxies. Preliminary evidence, he says, suggests that is the case.

    “If we can use all this information to understand why or why not stars form around us, then we’ve made a big step forward,” McDonald says.

    “[These results] look very promising,” says Paul Nulsen, an astronomer at the Harvard-Smithsonian Center for Astrophysics who was not involved in this research. “More work will be needed to show conclusively that precipitation is the main source of the gas that powers feedback. Other processes in the feedback cycle also need to be understood. For example, there is still no consensus on how the gas falling into a massive black hole produces energetic jets, or how they inhibit cooling in the remaining gas. This is not the end of the story, but it is an important insight into a problem that has proved a lot more difficult than anyone ever anticipated.”

    This research was funded in part by the National Science Foundation and NASA.

    See the full article here.

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  • richardmitnick 4:17 pm on March 5, 2015 Permalink | Reply
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    From ALMA: “ALMA Gains New Capability in its First VLBI Observation “ 

    ESO ALMA Array
    ALMA

    Thursday, 05 March 2015
    Contact:

    Valeria Foncea
    Education and Public Outreach Officer
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 467 6258
    Cell: +56 9 75871963
    Email: vfoncea@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 434.242.9559
    E-mail: cblue@nrao.edu

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory Tokyo, Japan
    Tel: +81 422 34 3630
    E-mail: hiramatsu.masaaki@nao.ac.jp

    1
    ALMA, the Atacama Large Millimeter/submillimeter Array, has successfully combined its immense collecting area and sensitivity with that of APEX (Atacama Pathfinder Experiment) to create a new, single instrument through a process known as Very Long Baseline Interferometry (VLBI). This first successful observation using VLBI with ALMA used a baseline of 2.1 km, and was an essential proof-of-concept test for the planned Event Horizon Telescope, which eventually will include a global network of millimetre-wavelength telescopes. Crédito: Clem & Adri Bacri-Normier (wingsforscience.com)/ESO

    The Atacama Large Millimeter/submillimeter Array (ALMA) recently combined its immense collecting area and sensitivity with that of the APEX (Atacama Pathfinder Experiment) Telescope to create a new, single instrument through a process known as Very Long Baseline Interferometry (VLBI). In VLBI, data from two independent telescopes are combined to form a virtual telescope that spans the geographic distance between them, yielding extraordinary magnifying power.

    ESO APEX
    ESO/APEX

    The new ALMA/APEX observation, which took place on January 13, was an essential proof-of-concept test for the planned Event Horizon Telescope (EHT), which eventually will include a global network of millimeter-wavelength telescopes.

    Event Horizon Telescope
    EHT

    When fully assembled, the EHT – with ALMA as the largest and most sensitive site – will form an Earth-size telescope with the magnifying power required to see details at the edge of the supermassive black hole at the center of the Milky Way.

    For this first-of-its-kind observation, ALMA and the nearby APEX telescope simultaneous studied a quasar known as 0522-364 – a distant galaxy commonly used for testing in radio astronomy due to its remarkable brightness. To ensure the telescopes were in sync, ALMA used its newly installed and exquisitely precise atomic clock (see ALMA announcement) to time-code the data as it was collected. This is essential for VLBI because it enables data taken at different geographical locations on different telescopes to be precisely matched and accurately integrated.

    The full dataset from the observing run was captured on hard drives and flown back to MIT where it will undergo full analysis. Due to the vast amount of information collected, air travel is the fastest means of data transmission, even faster than the fastest international Internet connection.

    “The entire team is immensely gratified at achieving this success on the first VLBI attempt with ALMA. It marks a huge step toward making first images of a black hole with the Event Horizon Telescope,” said Shep Doeleman, the principal investigator of the ALMA Phasing Project and assistant director of the Massachusetts Institute of Technology’s Haystack Observatory.

    This most recent work was carried out by a team made up of members from the ALMA Phasing Project, the Joint ALMA Observatory, the Smithsonian Astrophysical Observatory and the APEX Telescope.

    See the full article here.

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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  • richardmitnick 3:36 pm on March 5, 2015 Permalink | Reply
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    From Keck: “Thermonuclear Supernova Ejects Galaxy’s Fastest Star” 

    Keck Observatory

    Keck Observatory

    Keck Observatory

    March 5, 2015
    Steve Jefferson
    Communications Officer
    W. M. Keck Observatory
    808.881.3827
    sjefferson@keck.hawaii.edu

    1
    An artist impression of the mass-transfer phase followed by a double-detonation supernova that leads to the ejection of US 708. While this illustration shows the supernova (bottom center) and the ejected star (left) at the same time, in reality the supernova would have been faded away long before the star reached that position.

    Scientists using the W. M. Keck Observatory and Pan-STARRS1 telescopes on Hawaii have discovered a star that breaks the galactic speed record, traveling with a velocity of about 1,200 kilometers per second or 2.7 million miles per hour. This velocity is so high, the star will escape the gravity of our galaxy. In contrast to the other known unbound stars, the team showed that this compact star was ejected from an extremely tight binary by a thermonuclear supernova explosion. These results will be published in the March 6 issue of Science.

    Pann-STARSR1 Telescope
    Pann-STARRS1 interior
    Pan-STARRS1

    Stars like the Sun are bound to our Galaxy and orbit its center with moderate velocities. Only a few so-called hypervelocity stars are known to travel with velocities so high that they are unbound, meaning they will not orbit the galaxy, but instead will escape its gravity to wander intergalactic space.

    A close encounter with the supermassive black hole at the centre of the Milky Way is typically presumed the most plausible mechanism for kicking these stars out of the galaxy.

    A team of astronomers led by Stephan Geier (European Southern Observatory, Garching) observed the known high-velocity star know as US 708 with the Echellette Spectrograph and Imager instrument on the 10-meter, Keck II telescope to measure its distance and velocity along our line of sight.

    Keck Eschellette Spectrograph
    Echellette Spectrograph and Imager instrument

    By carefully combining position measurements from digital archives with newer positions measured from images taken during the course of the Pan-STARRS1 survey, they were able to derive the tangential component of the star’s velocity (across our line of sight).

    Putting the measurements together, the team determined the star is moving at about 1,200 kilometers per second – much higher than the velocities of previously known stars in the Milky Way galaxy. More importantly, the trajectory of US 708 means the supermassive black hole at the galactic center could not be the source of US 708’s extreme velocity.

    US 708 has another peculiar property in marked contrast to other hypervelocity stars: it is a rapidly rotating, compact helium star likely formed by interaction with a close companion. Thus, US 708 could have originally resided in an ultra compact binary system, transferring helium to a massive white dwarf companion, ultimately triggering a thermonuclear explosion of a type Ia supernova. In this scenario, the surviving companion, i.e. US 708, was violently ejected from the disrupted binary as a result, and is now travelling with extreme velocity.

    These results provide observational evidence of a link between helium stars and thermonuclear supernovae, and is a step towards understanding the progenitor systems of these mysterious explosions.

    ESI (Echellette Spectrograph and Imager) is a medium-resolution visible-light spectrograph that records spectra from 0.39 to 1.1 microns in each exposure. Built at UCO/Lick Observatory by a team led by Prof. Joe Miller, ESI also has a low-resolution mode and can image in a 2 x 8 arcmin field of view. An upgrade provided an integral field unit that can provide spectra everywhere across a small, 5.7 x 4.0 arcsec field. Astronomers have found a number of uses for ESI, from observing the cosmological effects of weak gravitational lensing to searching for the most metal-poor stars in our galaxy.

    See the full article here.

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    Mission
    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
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  • richardmitnick 2:54 pm on March 5, 2015 Permalink | Reply
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    From Hubble: “An explosive quartet” 

    NASA Hubble Telescope

    Hubble

    5 March 2015

    Contacts

    Patrick Kelly
    University of California
    Berkeley, USA
    Tel: + 1 510 859 8370
    Email: pkelly@astro.berkeley.edu

    Jens Hjorth
    Dark Cosmology Centre
    Copenhagen, Denmark
    Email: jens@dark-cosmology.dk

    Steve Rodney
    Johns Hopkins University
    Baltimore, USA
    Email: rodney@jhu.edu

    Tommaso Treu
    University of California
    Los Angeles, USA
    Email: tt@astro.ucla.edu

    Georgia Bladon
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Cell: +44 7816291261
    Email: gbladon@partner.eso.org

    Hubble sees multiple images of a supernova for the very first time

    1

    Astronomers using the NASA/ESA Hubble Space Telescope have, for the first time, spotted four images of a distant exploding star. The images are arranged in a cross-shaped pattern by the powerful gravity of a foreground galaxy embedded in a massive cluster of galaxies. The supernova discovery paper will appear on 6 March 2015 in a special issue of Science celebrating the centenary of Albert Einstein’s theory of general relativity.

    Whilst looking closely at a massive elliptical galaxy and its associated galaxy cluster MACS J1149+2223 — whose light took over 5 billion years to reach us — astronomers have spotted a strange and rare sight. The huge mass of the galaxy and the cluster is bending the light from a much more distant supernova behind them and creating four separate images of it. The light has been magnified and distorted due to gravitational lensing [1] and as a result the images are arranged around the elliptical galaxy in a formation known as an Einstein cross.

    Although astronomers have discovered dozens of multiply imaged galaxies and quasars, they have never before seen multiple images of a stellar explosion.

    “It really threw me for a loop when I spotted the four images surrounding the galaxy — it was a complete surprise,” said Patrick Kelly of the University of California Berkeley, USA, a member of the Grism Lens Amplified Survey from Space (GLASS) collaboration and lead author on the supernova discovery paper. He discovered the supernova during a routine search of the GLASS team’s data, finding what the GLASS group and the Frontier Fields Supernova team have been searching for since 2013 [2]. The teams are now working together to analyse the images of the supernova, whose light took over 9 billion years to reach us [3].

    “The supernova appears about 20 times brighter than its natural brightness,” explains the paper’s co-author Jens Hjorth from the Dark Cosmology Centre, Denmark. “This is due to the combined effects of two overlapping lenses. The massive galaxy cluster focuses the supernova light along at least three separate paths, and then when one of those light paths happens to be precisely aligned with a single elliptical galaxy within the cluster, a secondary lensing effect occurs.” The dark matter associated with the elliptical galaxy bends and refocuses the light into four more paths, generating the rare Einstein cross pattern the team observed.

    This unique observation will help astronomers refine their estimates of the amount and distribution of dark matter in the lensing galaxy and cluster. There is more dark matter in the Universe than visible matter, but it is extremely elusive and is only known to exist via its gravitational effects on the visible Universe, so the lensing effects of a galaxy or galaxy cluster are a big clue to the amount of dark matter it contains.

    When the four supernova images fade away as the explosion dies down, astronomers will have a rare chance to catch a rerun of the explosion. The supernova images do not arrive at the Earth at the same time because, for each image produced, the light takes a different route. Each route has a different layout of matter — both dark and visible — along its path. this causes bends in the road, and so for some routes the light takes longer to reach us than for others. Astronomers can use their model of how much dark matter is in the cluster, and where it is, to predict when the next image will appear as well as using the time delays they observe to make the mass models even more accurate [4].

    “The four supernova images captured by Hubble appeared within a few days or weeks of each other and we found them after they had appeared,” explains Steve Rodney of Johns Hopkins University, USA, leader of the Frontier Fields Supernova team. “But we think the supernova may have appeared in a single image some 20 years ago elsewhere in the cluster field, and, even more excitingly, it is expected to reappear once more in the next one to five years — and at that time we hope to catch it in action.”

    The supernova has been nicknamed Refsdal in honor of Norwegian astronomer Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the Universe. “Astronomers have been looking to find one ever since,” said Tommaso Treu of the University of California Los Angeles, USA, the GLASS project’s principal investigator. “And now the long wait is over!”

    Notes

    [1] Gravitational lensing was first predicted by Albert Einstein. This effect is similar to a glass lens bending light to magnify and distort the image of an object behind it.

    [2] The Frontier Fields is a three-year programme that uses Hubble to observe six massive galaxy clusters to probe not only what is inside the clusters but also what is beyond them through gravitational lensing. The GLASS survey uses Hubble’s capabilities to study remote galaxies using ten massive galaxy clusters as gravitational lenses, including the six in the Frontier Fields.

    [3] The team used the W. M. Keck Observatory on Mauna Kea, in Hawaii, to measure the redshift of the supernova’s host galaxy, which is a proxy to its distance.

    [4] Measuring the time delays between images offers clues to the type of warped-space terrain the supernova’s light had to cover and will help the astronomers fine tune the models that map out the cluster’s mass.

    The international team of astronomers in this study consists of P. Kelly (University of California, Berkeley, USA); S. Rodney (The Johns Hopkins University, USA); T. Treu (University of California, Los Angeles, USA); R. Foley (University of Illinois at Urbana-Champaign, USA); G. Brammer (Space Telescope Science Institute, USA); K. Schmidt (University of California, Santa Barbara, USA); A. Zitrin (California Institute of Technology, USA); A. Sonnenfeld (University of California, Los Angeles, USA); L. Strolger (Space Telescope Science Institute, USA & Western Kentucky University, USA); O. Graur (New York University, USA), A. Filippenko (University of California, Berkeley, USA), S. Jha (Rutgers, USA); A. Riess (The Johns Hopkins University, USA & Space Telescope Science Institute, USA); M. Bradac (University of California, Davis, USA), B. Weiner (Steward Observatory, USA); D. Scolnic (The Johns Hopkins University, USA); M. Malkan (University of California, Los Angeles, USA); A. von der Linden (Dark Cosmology Centre, Denmark); M. Trenti (University of Melbourne, Australia); J. Hjorth (Dark Cosmology Centre, Denmark); R. Gavazzi (Institut d’Astrophysique de Paris, France); A. Fontana (INAF-OAR, Italy); J. Merten (California Institute of Technology, USA); C. McCully (University of California, Santa Barbara,, USA); T. Jones (University of California, Santa Barbara,, USA); M. Postman (Space Telescope Science Institute, USA); A. Dressler (Carnegie Observatories, USA), B. Patel (Rutgers, USA), S. Cenko (NASA/Goddard Space Flight Center, USA); M. Graham (University of California, Berkeley, USA); and Bradley E. Tucker (University of California, Berkeley, USA).

    See the full article here.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 5:36 am on March 5, 2015 Permalink | Reply
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    From NYT: “Researchers Report Milestone in Developing Quantum Computer” 

    New York Times

    The New York Times

    MARCH 4, 2015
    JOHN MARKOFF

    1
    This device contains nine qubits, the very unstable basic elements of quantum computing equivalent to bits in a regular computer. In the array, each qubit interacts with its neighbors to protect them from error. Credit Julian Kelly/University of California, Santa Barbara, via Google

    Scientists at the University of California, Santa Barbara, and at Google reported on Wednesday in the journal Nature that they had made a significant advance that brings them a step closer to developing a quantum computer.

    Researchers have been pursuing the development of computers that exploit quantum mechanical effects since the 1990s, because of their potential to vastly expand the performance of conventional computers. The goal has long remained out of reach, however, because the computers are composed of basic elements known as qubits that have remained, despite decades of engineering research, highly unstable.

    In contrast to a bit, which is the basic element of a conventional computer and can represent either a zero or a one, a qubit can exist in a state known as superposition, in which it can represent both a zero and a one simultaneously.

    If the qubits are then placed in an entangled state — physically separate but acting with many other qubits as if connected — they can represent a vast number of values simultaneously.

    To date, matrices of qubits that are simultaneously in superposition and entangled have eluded scientists because they are ephemeral, with the encoded information dissipating within microseconds.

    The university and Google researchers reported, however, that they had succeeded in creating an error-correction system that stabilized a fragile array of nine qubits. The researchers said they had accomplished this by creating circuits in which additional qubits were used to observe the state of the computing qubits without altering their state.

    But an important asterisk remains, according to scientists who read an early version of the paper. The Nature paper stated the researchers had succeeded in preserving only the limited “classical” states, rather than the more complex quantum information that would be needed to create a system that outperforms today’s computers.

    The importance of the advance is that the scientists have developed evidence that the system becomes more stable as they interconnect more qubits in the error-checking array. This suggests that far larger arrays of qubits, composed of thousands or tens of thousands of qubits, might be able to control the errors that have until now bedeviled scientists.

    “We have for the first time in the long history of quantum computing an actual device, where we can test all of our ideas about error detection,” said Rami Barends, a quantum electronics engineer at Google and one of the authors of the paper.

    Julian Kelly, another Google quantum electronics engineer, said there remained significant challenges in manufacturing materials for quantum computing.

    In some cases, the scientists are able to rely on existing semiconductor technology, but there are many steps for which they will have to invent approaches.

    The research was reported by scientists working in the laboratory of John M. Martinis, a physicist at the university. In September, Google announced it would join efforts to build a quantum computer as part of the recently established Quantum Artificial Intelligence Laboratory. Under that agreement, Dr. Martinis joined Google while keeping his teaching role, and members of his laboratory became Google employees.

    While the researchers described their new circuit as a significant advance, they acknowledged that they had not yet solved all of the problems that prevented the building of a working quantum computer.

    “While the basic physical processes behind quantum error correction are feasible, many challenges remain, such as improving the logic operations behind error correction and testing protection from phase-flip errors,” the scientists noted in a statement posted on the company’s website.

    In a discussion of the Nature paper on his website, the M.I.T. physicist Scott Aaronson suggested that the achievement represented about half the progress required to build a fully functional quantum computer.

    Google is not the only computing company collaborating with academic researchers in advancing quantum computing. IBM is working with scientists at Yale, and Microsoft is working separately with researchers at the University of California, Santa Barbara, supporting the Station Q research laboratory it created there in 2006.

    See the full article here.

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  • richardmitnick 5:02 am on March 5, 2015 Permalink | Reply
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    From NYT: “Jawbone’s Discovery Fills Barren Evolutionary Period” 

    New York Times

    The New York Times

    MARCH 4, 2015
    JOHN NOBLE WILFORD

    1
    The Ledi-Geraru mandible fossil. Credit William Kimble/Arizona State University

    On the morning of Jan. 29, 2013, Chalachew Seyoum was climbing a remote hill in the Afar region of his native Ethiopia, his head bent, eyes focused on the loose sediment. The site, known as Ledi-Geraru, was rich in fossils. Soon enough, he spotted a telltale shape on the surface — a premolar, as it turned out. It was attached to a piece of a mandible, or lower jawbone. He collected other pieces of a left mandible, and five teeth in all.

    Mr. Seyoum, a graduate student in paleoanthropology at Arizona State University, had made a discovery that vaulted evolutionary science over a barren stretch of fossil record between two million and three million years ago. This was a time when the human genus, Homo, was getting underway. The 2.8-million-year-old jawbone of a Homo habilis predates by at least 400,000 years any previously known Homo fossils.

    More significant, scientists say, is that this H. habilis lived only 200,000 years after the last known evidence of its more apelike predecessors, Australopithecus afarensis, the species made famous by “Lucy,” whose skeleton was found in the 1970s at the nearby Ethiopian site of Hadar.

    2
    The fossil of Olduvai Hominid 7, includes a partial lower jaw, bones of the brain case and hand bones. Credit John Reader

    William H. Kimbel, director of the Institute of Human Origins at Arizona State, said the Ledi-Geraru jaw “helps narrow the evolutionary gap between Australopithecus and early Homo,” adding that it was an excellent “transitional fossil in a critical time period in human evolution.”

    The discovery was announced Wednesday in two reports for the journal Science by researchers at Arizona State, the University of Nevada, Las Vegas, and Pennsylvania State University. One paleoanthropologist not on the teams, Fred Spoor of University College London and the Max Planck Institute for Evolutionary Anthropology in Germany, endorsed the analysis.

    3
    The Ledi-Geraru mandible fossil. Credit William Kimble/Arizona State University

    Dr. Spoor said in an email that he agreed with the hypothesis that the new Ledi-Geraru mandible “derives from Australopithecus afarensis, and at 2.8 million years shows morphology that is ancestral to all early Homo.”

    How could Dr. Spoor not agree with the interpretation of the findings in the new report by Brian A. Villmoare of the University of Nevada, Las Vegas, and colleagues on the Arizona State team? By coincidence, Dr. Spoor was ready to predict many of the findings in the journal Nature a day before his predictions would have been proved right in the journal Science. When the relationship between the studies became clear, the two journals agreed to simultaneous publication of the articles on Wednesday.

    4
    The hills of the Lee Adoyta region in Ethiopia expose sediments that are less than 2.67 million years old, which helps to date the mandible. Credit Erin DiMaggio/Penn State University

    Dr. Spoor’s predictions were drawn from a digital reconstruction of the disturbed remains of the jaws of the original 1.8-million-year-old Homo habilis specimen found 50 years ago by the legendary fossil hunters Louis and Mary Leakey at Olduvai Gorge in Tanzania.

    The reconstruction, suggesting a plausible evolutionary link between A. afarensis and H. habilis, yielded a remarkably primitive picture of a deep-rooted diversity of a species that emerged much earlier than the 2.3 million years ago suggested by some specimens. The teeth and jaws appeared to be more similar to A. afarensis than to subsequent Homo erectus or Homo sapiens, modern humans that emerged about 200,000 years ago.

    Dr. Spoor’s analysis also seemed to put a new face on H. habilis. He said that individual species of early Homo were more easily recognizable by jaw structure and facial features than by differences in brain size, which tend to be highly variable. Dr. Villmoare and colleagues made similar observations in their article. Both the predictions and the mandible findings called attention to smaller teeth with the emergence of H. habilis and evidence suggesting that the species probably split in different evolutionary lines, only one of which might have been ancestral to later H. erectus and H. sapiens.

    In an email, Dr. Spoor explained that the split occurred sometime before 2.3 million years ago. The lineage leading to H. habilis must have kept the primitive jaw morphology. The Ledi-Geraru specimen kept the primitive, sloping chin that links it to a Lucy-like ancestor. Other lineages must account for the fact that H. erectus and H. habilis existed together for a period more than a million years ago.

    In a second report for the journal Science, Erin N. DiMaggio of Penn State and other geologists examined soil, vegetation and fossils at Ledi-Geraru. They determined that when the H. habilis left its jaw there, the habitat was dominated by mammals that lived in a more open landscape — grasslands and low shrubs — than the more wooded land often favored by A. afarensis.

    But after about 2.8 million years ago, increased African aridity has been cited as a possible result of widespread climate change affecting species changes and extinctions. Kaye E. Reed, co-leader of the Arizona State team, noted that the “aridity signal” had been observed at the Ethiopian fossil site. However, she said, “it’s still too soon to say this means climate change is responsible for the origin of Homo.”

    For that, Dr. Reed said, “we need a larger sample of hominin fossils, and that’s why we continued to come to the Ledi-Geraru area to search.” That, and to learn more about the evolution of our genus, Homo.

    See the full article here.

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  • richardmitnick 4:34 am on March 5, 2015 Permalink | Reply
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    From Gemini: “FAR FROM HOME: WAYWARD CLUSTER IS BOTH TINY AND DISTANT “ 

    NOAO

    Gemini Observatory
    Gemini Observatory

    March 3, 2015
    Media Contacts:

    Peter Michaud
    Public Information and Outreach
    Gemini Observatory, Hilo, HI
    Email: pmichaud”at”gemini.edu
    Cell: (808) 936-6643

    Science Contacts:

    Dongwon Kim
    Australia National University
    Email: dongwon.kim”at”anu.edu.au
    Office: +61 2 6125 8022

    Helmut Jerjen
    Australia National University
    Email: helmut.jerjen”at”anu.edu.au
    Office: +61 2 6125 8038

    1
    GMOS image of Kim 2, in g band. The image is 4 arcminutes across.

    Like the lost little puppy that wanders too far from home, astronomers have found an unusually small and distant group of stars that seems oddly out of place. The cluster, made of only a handful of stars, is located far away, in the Milky Way’s “suburbs.” It is located where astronomers have never spotted such a small cluster of stars before.

    The new star cluster was discovered by Dongwon Kim, a PhD student at the Australian National University (ANU), together with a team of astronomers (Helmut Jerjen, Antonino Milone, Dougal Mackey, and Gary Da Costa) who are conducting the Stromlo Milky Way Satellite Survey* at ANU.

    “This cluster is faint, very faint, and truly in the suburbs of our Milky Way,” said Kim. “In fact, this group of stars is about ten times more distant than the average globular star cluster in the halo of our galaxy — it’s a lost puppy,” Mackey adds. Globular clusters are spherical cities of stars that form a vast, extended halo around the core of our galaxy, the brightest of which are easily seen in amateur telescopes or even binoculars. However, this new discovery required one of the world’s largest telescopes to confirm, “it’s definitely a diminutive oddball,” says Milone.

    The oddly small, far-flung, cluster was discovered using the Dark Energy Camera (DECam) on the 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. “This discovery sheds new light on the formation and evolution of the Milky Way,” said Daniel Evans, National Science Foundation program director for Gemini Observatory. “It’s great to see so many telescopes come together to produce this result, not the least being Gemini Observatory with its incredible light-gathering power.”

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    Dark Energy Camera
    4-meter Blanco Telescope and DECam

    The team’s first evidence of the unusually remote star cluster came when they ran detection algorithms on a 500 square-degree imaging data field obtained with DECam. “Such objects are too faint and optically elusive to be seen by eye. The cluster stars are sprinkled so thinly over the image, you look right through them without noticing. They are hiding in the sea of stars from the Milky Way. Sophisticated computer programs are our tools to find them,” said Jerjen.

    Because it is so faint, ultra-deep follow-up observations using the Gemini Multi-Object Spectrograph [GMOS] (in imaging mode) confirmed that the new globular cluster is among the faintest Milky Way globular clusters ever found.

    Gemini Multi Object Spectrograph
    GMOS

    Seven out of 150 known Milky Way globular clusters are comparably faint but none are located as far out toward the edge of the Milky Way. This new globular cluster has 10-20 times fewer stars than any of the other outer halo globular clusters. Also, its star density is less than half of that of other Milky Way globular clusters in the same luminosity (brightness) range.

    The new star cluster, named Kim 2, also shows evidence of significant mass loss over its history. Computer simulations predict that, as a consequence of their evolution over many billions of years, including the slow loss of member stars due to the gravitational pull of the Milky Way, star clusters ought to be arranged such that their more massive stars are concentrated toward their centers. “This ‘mass segregation’ has been difficult to observe, particularly in low mass clusters, but the excellent Gemini data reveal that Kim 2 appears to be mass segregated and has therefore likely lost much of its original mass,” said Da Costa. The finding suggests that a substantial number of low-luminosity globular clusters must have existed in the halo when the Milky Way was younger, but most of them might have evaporated due to internal dynamical processes.

    The observed properties of the new star cluster also raise the question about how such a low luminosity system could have survived until today. One possible scenario is that Kim 2 is not actually a genuine member of the Milky Way globular cluster family, but a star cluster originally located in a satellite dwarf galaxy and was accreted into the Milky Way’s halo. This picture is also supported by the fact that the stars in Kim 2 appear to be more chemically enriched with heavier elements than the other outer halo globular clusters and are young relative to the oldest globular clusters in the Milky Way. As a consequence of spending much of its life in a dwarf galaxy Kim 2 could have largely escaped the destructive influence of tidal forces, thus helping it to survive until the present epoch.

    There are many Milky Way globular clusters formerly and currently associated with satellite dwarf galaxies. It is possible that a significant fraction of the ancient satellite dwarf galaxies were completely disrupted by the tidal field of the Milky Way while the high density of the globular clusters allowed them to survive in our galaxy’s halo. Indeed, Kim 2 is found close to the vast polar structure of Milky Way satellite galaxies, a disc-like region surrounding the Milky Way where satellite galaxies and young halo clusters preferentially congregate. A similar distribution of satellite galaxies is also found in the neighbouring Andromeda Galaxy.

    A large fraction of the Milky Way’s halo is thought to be populated with optically elusive satellite galaxies and star clusters. New discoveries of satellite galaxies and globular clusters will therefore provide valuable information about the formation and the structure of the Milky Way. Previous surveys like the Sloan Digital Sky Survey have contributed to many new discoveries in the northern sky. However, most of the southern sky still remains unexplored to date. The detection of Kim 2 suggests that there are a substantial number of interesting astronomical objects waiting to be discovered in the southern hemisphere and the Stromlo Milky Way Satellite Survey team plans to continue searching for them.

    The team’s paper, accepted for publication in the Astrophysical Journal, is available as a preprint at http://arxiv.org/abs/1502.03952.

    • The Stromlo Milky Way Satellite Survey is led by Australian National University’s Associate Professor Helmut Jerjen. The research team includes Dongwon Kim, Antonino Milone, Dougal Mackey, and Gary Da Costa (all from the Australian National University). See project website at: http://www.mso.anu.edu.au/~jerjen/SMS_Survey.html

    See the full article here.

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    Gemini North
    Gemini North, Hawai’i

    Gemini South
    Gemini South, Chile
    AURA Icon

    The Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on two of the best observing sites on the planet. From their locations on mountains in Hawai‘i and Chile, Gemini Observatory’s telescopes can collectively access the entire sky.
    Gemini was built and is operated by a partnership of six countries including the United States, Canada, Chile, Australia, Brazil and Argentina. Any astronomer in these countries can apply for time on Gemini, which is allocated in proportion to each partner’s financial stake.

     
  • richardmitnick 6:45 pm on March 4, 2015 Permalink | Reply
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    From MIT: “New technique allows analysis of clouds around exoplanets” 


    MIT News

    1
    Analysis of data from the Kepler space telescope has shown that roughly half of the dayside of the exoplanet Kepler-7b is covered by a large cloud mass. Statistical comparison of more than 1,000 atmospheric models show that these clouds are most likely made of Enstatite, a common Earth mineral that is in vapor form at the extreme temperature on Kepler-7b. These models varied the altitude, condensation, particle size, and chemical composition of the clouds to find the right reflectivity and color properties to match the observed signal from the exoplanet.

    Courtesy of NASA (edited by Jose-Luis Olivares/MIT)

    March 3, 2015
    Helen Knight | MIT News

    Meteorologists sometimes struggle to accurately predict the weather here on Earth, but now we can find out how cloudy it is on planets outside our solar system, thanks to researchers at MIT.

    In a paper to be published in the Astrophysical Journal, researchers in the Department of Earth, Atmospheric, and Planetary Sciences (EAPS) at MIT describe a technique that analyzes data from NASA’s Kepler space observatory to determine the types of clouds on planets that orbit other stars, known as exoplanets.

    NASA Kepler Telescope
    Kepler

    The team, led by Kerri Cahoy, an assistant professor of aeronautics and astronautics at MIT, has already used the method to determine the properties of clouds on the exoplanet Kepler-7b. The planet is known as a “hot Jupiter,” as temperatures in its atmosphere hover at around 1,700 kelvins.

    NASA’s Kepler spacecraft was designed to search for Earth-like planets orbiting other stars. It was pointed at a fixed patch of space, constantly monitoring the brightness of 145,000 stars. An orbiting exoplanet crossing in front of one of these stars causes a temporary dimming of this brightness, allowing researchers to detect its presence.

    Researchers have previously shown that by studying the variations in the amount of light coming from these star systems as a planet transits, or crosses in front or behind them, they can detect the presence of clouds in that planet’s atmosphere. That is because particles within the clouds will scatter different wavelengths of light.

    Modeling cloud formation

    To find out if this data could be used to determine the composition of these clouds, the MIT researchers studied the light signal from Kepler-7b. They used models of the temperature and pressure of the planet’s atmosphere to determine how different types of clouds would form within it, says lead author Matthew Webber, a graduate student in Cahoy’s group at MIT.

    “We then used those cloud models to determine how light would reflect off the atmosphere of the planet [for each type of cloud], and tried to match these possibilities to the actual observations from the Kepler mission itself,” Webber says. “So we ran a large set of models, to see which models fit best statistically to the observations.”

    By working backward in this way, they were able to match the Kepler spacecraft data to a type of cloud made out of vaporized silicates and magnesium. The extremely high temperatures in the Kepler-7b atmosphere mean that some minerals that commonly exist as rocks on Earth’s surface instead exist as vapors high up in the planet’s atmosphere. These mineral vapors form small cloud particles as they cool and condense.

    Kepler-7b is a tidally locked planet, meaning it always shows the same face to its star — just as the moon does to Earth. As a result, around half of the planet’s day side — that which constantly faces the star — is covered by these magnesium silicate clouds, the team found.

    “We are really doing nothing more complicated than putting a telescope into space and staring at a star with a camera,” Cahoy says. “Then we can use what we know about the universe, in terms of temperatures and pressures, how things mix, how they stratify in an atmosphere, to try to figure out what mix of things would be causing the observations that we’re seeing from these very basic instruments,” she says.

    A clue on exoplanet atmospheres

    Understanding the properties of the clouds on Kepler-7b, such as their mineral composition and average particle size, tells us a lot about the underlying physical nature of the planet’s atmosphere, says team member Nikole Lewis, a postdoc in EAPS. What’s more, the method could be used to study the properties of clouds on different types of planet, Lewis says: “It’s one of the few methods out there that can help you determine if a planet even has an atmosphere, for example.”

    A planet’s cloud coverage and composition also has a significant impact on how much of the energy from its star it will reflect, which in turn affects its climate and ultimately its habitability, Lewis says. “So right now we are looking at these big gas-giant planets because they give us a stronger signal,” she says. “But the same methodology could be applied to smaller planets, to help us determine if a planet is habitable or not.”

    The researchers hope to use the method to analyze data from NASA’s follow-up to the Kepler mission, known as K2, which began studying different patches of space last June. They also hope to use it on data from MIT’s planned Transiting Exoplanet Survey Satellite (TESS) mission, says Cahoy.

    NASA TESS
    TESS

    “TESS is the follow-up to Kepler, led by principal investigator George Ricker, a senior research scientist in the MIT Kavli Institute for Astrophysics and Space Research. It will essentially be taking similar measurements to Kepler, but of different types of stars,” Cahoy says. “Kepler was tasked with staring at one group of stars, but there are a lot of stars, and TESS is going to be sampling the brightest stars across the whole sky,” she says.

    This paper is the first to take circulation models including clouds and compare them with the observed distribution of clouds on Kepler-7b, says Heather Knutson, an assistant professor of planetary science at Caltech who was not involved in the research.

    “Their models indicate that the clouds on this planet are most likely made from liquid rock,” Knutson says. “This may sound exotic, but this planet is a roasting hot gas-giant planet orbiting very close to its host star, and we should expect that it might look quite different than our own Jupiter.”

    See the full article here.

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  • richardmitnick 6:18 pm on March 4, 2015 Permalink | Reply
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    From CMU: “Intermediary Neuron Acts as Synaptic Cloaking Device, Says Carnegie Mellon Study” 

    Carnegie Mellon University logo
    Carnegie Mellon university

    February 26, 2015
    Jocelyn Duffy / 412-268-9982

    1

    Neuroscientists believe that the connectome, a map of each and every connection between the millions of neurons in the brain, will provide a blueprint that will allow them to link brain anatomy to brain function. But a new study from Carnegie Mellon University has found that a specific type of neuron might be thwarting their efforts at mapping the connectome by temporarily cloaking the synapses that link a wide field of neurons.

    If you’re a Star Trek fan, think of it as a Romulan or Klingon cloaking device, which hides a warship. The cloaked ship is invisible, until it fires at an enemy. In the study published in the March 16 issue of Current Biology, the researchers found that a class of inhibitory neurons, called somatostatin cells, send out a signal — much like a cloaking device — that silences neighboring excitatory neurons. Synapses, like a cloaked warship, can’t be seen if they aren’t firing; activating the somatostatin cells makes the synapses and local network of neurons invisible to researchers.

    Furthermore, by silencing certain parts of the neuronal network, the activity of the somatostatin neurons also can change the way the brain functions, heightening some perceptual pathways and silencing others.

    “It was totally unexpected that these cells would work this way,” said Alison Barth, professor of biological sciences and a member of BrainHubSM, Carnegie Mellon’s neuroscience research initiative. “Changing the activity of just this one cell type can let you change the brain’s circuit structure at will. This could dramatically change how we look at — and use — the connectome.”

    The Carnegie Mellon researchers discovered this synaptic cloaking device, much in the same way Starfleet would detect a cloaked Klingon warship — they were conducting their normal research and noticed that something just didn’t look quite right.

    Joanna Urban-Ciecko, a research scientist in Barth’s lab, noticed that the synapses in her experiments were not behaving the way that previous experimenters had reported. Prior studies reported that the synapses should be strong and reliable, and that they should always grow and strengthen in response to a stimulus. But the neurons Urban-Ciecko looked at were weak and unreliable.

    The difference between Urban-Ciecko’s research and the previously completed work was that her research was being done under real-life conditions. Prior research on synapse function was done under conditions optimized for observing synapses. However, such experimental conditions don’t reflect the noisy brain environment in which synapses normally exist.

    “There’s this big black box in neuroscience. We know how to make synapses stronger in a dish. But what’s going on in the brain to initiate synaptic strengthening in real life?” Barth asked.

    To find out, Urban-Ciecko looked at neurons in the brain’s neocortex that were functioning under normal, noisy conditions. She took paired-cell recordings from pyramidal cells, a type of excitatory neuron, and found that many of the synapses between the neurons were not functioning, or functioning at an unexpectedly low level. Urban-Ciecko then recorded the activity of somatostatin cells, a type of inhibitory neuron, and found that those neurons were much more active than expected.

    “The somatostatin cells were so active, I wondered if they could possibly be driving the inhibition of synapses,” Urban-Ciecko said.

    To test her hypothesis, Urban-Ciecko turned to optogenetics, a technique that controls neurons with light. She used light to trigger an enzyme that activated and deactivated the somatostatin neuron. When the somatostatin cells were turned off, synapses grew big and strong. When the cells were turned on, the synapses became weaker and in some cases, disappeared entirely.

    “You have inputs coming at you all the time, why do you remember one thing and not the other? We think that somatostatin neurons may be gating whether synapses are used, and whether they can be changed during some important event, to enable learning,” said Barth, who is also a member of the joint CMU/University of Pittsburgh Center for the Neural Basis of Cognition (CNBC).

    The researchers found that when the somatostatin neurons were turned on, this triggered the cloaking device. The neuron activated the GABAb receptors on hundreds of excitatory neurons in the immediate area. Activating this receptor suppressed the excitatory neurons, which prevented them from creating and strengthening synapses — and made them invisible to researchers.

    The researchers next plan to see if the somatostatin cells behave similarly in other areas of the brain. If they do, it could represent a novel target for studying and improving learning and memory.

    Erika E. Fanselow, a research biologist formerly with Carnegie Mellon and the CNBC, also contributed to this paper.
    The research was funded by the McKnight Foundation and the National Institutes of Health (DA0171-88).

    As the birthplace of artificial intelligence and cognitive psychology, Carnegie Mellon has been a leader in the study of brain and behavior for more than 50 years. The university has created some of the first cognitive tutors, helped to develop the Jeopardy-winning Watson, founded a groundbreaking doctoral program in neural computation, and completed cutting-edge work in understanding the genetics of autism. Building on its strengths in biology, computer science, psychology, statistics and engineering, CMU recently launched BrainHubSM, a global initiative that focuses on how the structure and activity of the brain give rise to complex behaviors.

    See the full article here.

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    Carnegie Mellon Campus

    Carnegie Mellon University (CMU) is a global research university with more than 12,000 students, 95,000 alumni, and 5,000 faculty and staff.
    CMU has been a birthplace of innovation since its founding in 1900.
    Today, we are a global leader bringing groundbreaking ideas to market and creating successful startup businesses.
    Our award-winning faculty members are renowned for working closely with students to solve major scientific, technological and societal challenges. We put a strong emphasis on creating things—from art to robots. Our students are recruited by some of the world’s most innovative companies.
    We have campuses in Pittsburgh, Qatar and Silicon Valley, and degree-granting programs around the world, including Africa, Asia, Australia, Europe and Latin America.

     
  • richardmitnick 6:05 pm on March 4, 2015 Permalink | Reply
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    From Chandra: “Abell 2597: NASA’s Chandra Observatory Finds Cosmic Showers Halt Galaxy Growth” 

    NASA Chandra

    March 4, 2015

    Media contacts:
    Felicia Chou
    Headquarters, Washington
    202-358-0257
    felicia.chou@nasa.gov

    Janet Anderson
    Marshall Space Flight Center
    256-544-6162
    janet.l.anderson@nasa.gov

    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    New research shows how an unusual form of cosmic precipitation can affect the growth and evolution of galaxies. Over 200 galaxy clusters were surveyed in this new study using X-ray data from Chandra. These results provide evidence that this precipitation can slow down star formation in galaxies with giant black holes.

    1
    Composite

    2
    X-ray

    3
    H-alpha

    4
    Optical
    Credit X-ray: NASA/CXC/Michigan State Univ/G.Voit et al; Optical: NASA/STScI & DSS; H-alpha: Carnegie Obs./Magellan/W.Baade Telescope
    Release Date March 4, 2015

    This galaxy cluster comes from a sample of over 200 that were studied to determine how giant black holes at their centers affect the growth and evolution of their host galaxy, as reported in our latest press release. This study revealed that an unusual form of cosmic precipitation enables a feedback loop of cooling and heating, stifling star formation in the middle of these galaxy clusters.

    Abell 2597, shown here, is a galaxy cluster located about one billion light years from Earth. This image contains X-rays from NASA’s Chandra X-ray Observatory (blue), optical data from the Hubble Space Telescope and the Digitized Sky Survey (yellow) and emission from hydrogen atoms (red) from the Walter Baade Telescope in Chile.

    NASA Hubble Telescope
    Hubble

    Magellan 6.5 meter telescopes
    Magellan 6.5 meter Interior
    Walter Baade Telescope

    According to this new study, the regulation of the largest black hole and their host galaxies works as follows: in some galaxies, such as NGC 2597, hot gas is able to quickly cool through radiation and energy loss, in a process called precipitation. The clouds of cool gas that result then fall into the central supermassive black hole, producing jets that heat the gas and prevent further cooling.

    The researchers used Chandra data to estimate how long it should take for the gas to cool at different distances from the black holes in the study. Using that information, they were able to accurately predict the “weather” around each of the black holes.

    They found that the precipitation feedback loop driven by energy produced by the black hole jets prevents the showers of cold clouds from getting too strong. The Chandra data indicate that the regulation of this precipitation has been going on for the last 7 billion years or more.

    While a rain of cool clouds appears to play a key role in regulating the growth of some galaxies, the researchers have found other galaxies where the cosmic precipitation had shut off. The intense heat in these central galaxies, possibly from colliding with another galaxy cluster, likely “dried up” the precipitation around the black hole.

    Evidence was also found, in a few galaxy clusters, that strong bursts of outflows from regions near the black hole may have temporarily shut down precipitation, but the heating is not strong enough to result in conduction. In these cases, further cooling of gas should occur and active precipitation should resume in a few hundred million years.

    A pre-print of the Nature study by Mark Voit (Michigan State University), Megan Donahue (Michigan State), Greg Bryan (Columbia University), and Michael McDonald (Massachusetts Institute of Technology) is available online; the study builds on work by Voit and Donahue that was published in the January 20th, 2015 issue of The Astrophysical Journal Letters and is available online.

    See the full article here.

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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
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