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  • richardmitnick 1:37 pm on June 16, 2020 Permalink | Reply
    Tags: "Supergiant Atmosphere of Antares Revealed by Radio Telescopes", , NRAO VLA, Red supergiant stars- like Antares and its more well-known cousin Betelgeuse- are huge relatively cold stars at the end of their lifetime.   

    From ALMA: “Supergiant Atmosphere of Antares Revealed by Radio Telescopes” 

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

    From ALMA

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Bárbara Ferreira
    ESO Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: pio@eso.org

    Iris Nijman
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Cell phone: +1 (434) 249 3423
    Email: alma-pr@nrao.edu

    From NRAO.

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    Radio images of Antares with ALMA [above] and the VLA.

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

    ALMA observed Antares close to its surface in shorter wavelengths, and the longer wavelengths observed by the VLA revealed the star’s atmosphere further out. In the VLA image a huge wind is visible on the right, ejected from Antares and lit up by its smaller but hotter companion star Antares B. Credit: ALMA (ESO/NAOJ/NRAO), E. O’Gorman; NRAO/AUI/NSF, S. Dagnello.

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    Artist impression of the atmosphere of Antares. As seen with the naked eye (up until the photosphere), Antares is around 700 times larger than our sun, big enough to fill the solar system beyond the orbit of Mars (Solar System scale shown for comparison). But ALMA and VLA showed that its atmosphere, including the lower and upper chromosphere and wind zones, reaches out 12 times farther than that. Credit: NRAO/AUI/NSF, S. Dagnello.

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    Artist impression of red supergiant star Antares Credit: NRAO/AUI/NSF, S. Dagnello.

    An international team of astronomers has created the most detailed map yet of the atmosphere of the red supergiant star Antares. The unprecedented sensitivity and resolution of both the Atacama Large Millimeter/submillimeter Array (ALMA) and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) revealed the size and temperature of Antares’ atmosphere from just above the star’s surface, throughout its chromosphere, and all the way out to the wind region.

    Red supergiant stars, like Antares and its more well-known cousin Betelgeuse, are huge, relatively cold stars at the end of their lifetime. They are on their way to run out of fuel, collapse, and become supernovae. Through their vast stellar winds, they launch heavy elements into space, thereby playing an important role in providing the essential building blocks for life in the universe. But it is a mystery how these enormous winds are launched. A detailed study of the atmosphere of Antares, the closest supergiant star to Earth, provides a crucial step towards an answer.

    The ALMA and VLA map of Antares is the most detailed radio map yet of any star, other than the Sun. ALMA observed Antares close to its surface (its optical photosphere) in shorter wavelengths, and the longer wavelengths observed by the VLA revealed the star’s atmosphere further out. As seen in visible light, Antares’ diameter is approximately 700 times larger than the Sun. But when ALMA and the VLA revealed its atmosphere in radio light, the supergiant turned out to be even more gigantic.

    “The size of a star can vary dramatically depending on what wavelength of light it is observed with,” explained Eamon O’Gorman of the Dublin Institute for Advanced Studies in Ireland and lead author of the study published in the June 16 edition of the journal Astronomy & Astrophysics. “The longer wavelengths of the VLA revealed the supergiant’s atmosphere out to nearly 12 times the star’s radius.”

    The radio telescopes measured the temperature of most of the gas and plasma in Antares’ atmosphere. Most noticeable was the temperature in the chromosphere. This is the region above the star’s surface that is heated up by magnetic fields and shock waves created by the vigorous roiling convection at the stellar surface – much like the bubbling motion in a pot of boiling water. Not much is known about chromospheres, and this is the first time that this region has been detected in radio waves.

    Thanks to ALMA and the VLA, the scientists discovered that the star’s chromosphere extends out to 2.5 times the star’s radius (our Sun’s chromosphere is only 1/200th of its radius). They also found that the temperature of the chromosphere is lower than previous optical and ultraviolet observations have suggested. The temperature peaks at 3,500 degrees Celsius (6,400 degrees Fahrenheit), after which it gradually decreases. As a comparison, the Sun’s chromosphere reaches temperatures of almost 20,000 degrees Celsius.

    “We found that the chromosphere is ‘lukewarm’ rather than hot, in stellar temperatures,” said O’Gorman. “The difference can be explained because our radio measurements are a sensitive thermometer for most of the gas and plasma in the star’s atmosphere, whereas past optical and ultraviolet observations were only sensitive to very hot gas and plasma.”

    “We think that red supergiant stars, such as Antares and Betelgeuse, have an inhomogeneous atmosphere,” said co-author Keiichi Ohnaka of the Universidad Católica del Norte in Chile who previously observed Antares’ atmosphere in infrared light. “Imagine that their atmospheres are a painting made out of many dots of different colors, representing different temperatures. Most of the painting contains dots of the lukewarm gas that radio telescopes can see, but there are also cold dots that only infrared telescopes can see, and hot dots that UV telescopes see. At the moment we can’t observe these dots individually, but we want to try that in future studies.”

    In the ALMA and VLA data, astronomers for the first time saw a clear distinction between the chromosphere and the region where winds start to form. In the VLA image, a huge wind is visible, ejected from Antares and lit up by its smaller but hotter companion star Antares B.

    “When I was a student, I dreamt of having data like this,” said co-author Graham Harper of the University of Colorado, Boulder. “Knowing the actual sizes and temperatures of the atmospheric zones gives us a clue of how these huge winds start to form and how much mass is being ejected.”

    “Our innate understanding of the night sky is that stars are just points of light. The fact we can map the atmospheres of these supergiant stars in detail, is a true testament to technological advances in interferometry. These tour de force observations bring the universe close, right into our own backyard,” said Chris Carilli of the National Radio Astronomy Observatory, who was involved in the first observations of Betelgeuse at multiple radio wavelengths with the VLA in 1998.

    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 12:23 pm on February 20, 2020 Permalink | Reply
    Tags: "How Newborn Stars Prepare for the Birth of Planets", , , , , , , NRAO VLA, Planet-forming disks around very young stars in the Orion Molecular Clouds., , This survey- called VLA/ALMA Nascent Disk and Multiplicity (VANDAM)- is the largest survey of young stars and their disks to date.   

    From ALMA: “How Newborn Stars Prepare for the Birth of Planets” 

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

    From ALMA

    20 February, 2020

    Valeria Foncea
    Education and Public Outreach Officer
    Joint ALMA Observatory Santiago – Chile
    Phone: +56 2 2467 6258
    Cell phone: +56 9 7587 1963
    Email: valeria.foncea@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Bárbara Ferreira
    ESO Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: pio@eso.org

    Iris Nijman
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Cell phone: +1 (434) 249 3423
    Email: alma-pr@nrao.edu

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    VANDAM survey
    ALMA and the VLA observed more than 300 protostars and their young protoplanetary disks in Orion. This image shows a subset of stars, including a few binaries. The ALMA and VLA data compliment each other: ALMA sees the outer disk structure (visualized in blue), and the VLA observes the inner disks and star cores (orange).

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

    An international team of astronomers used two of the most powerful radio telescopes in the world to create more than three hundred images of planet-forming disks around very young stars in the Orion Clouds. These images reveal new details about the birthplaces of planets and the earliest stages of star formation.

    Most of the stars in the universe are accompanied by planets. These planets are born in rings of dust and gas, called protoplanetary disks. Even very young stars are surrounded by these disks. Astronomers want to know exactly when these disks start to form, and what they look like. But young stars are very faint, and there are dense clouds of dust and gas surrounding them in stellar nurseries. Only highly sensitive radio telescope arrays can spot the tiny disks around these infant stars amidst the densely packed material in these clouds.

    For this new research, astronomers pointed both the Atacama Large Millimeter/submillimeter Array (ALMA) and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to a region in space where many stars are born: the Orion Molecular Clouds. This survey, called VLA/ALMA Nascent Disk and Multiplicity (VANDAM), is the largest survey of young stars and their disks to date.

    Very young stars, also called protostars, form in clouds of gas and dust in space. The first step in the formation of a star is when these dense clouds collapse due to gravity. As the cloud collapses, it begins to spin – forming a flattened disk around the protostar. Material from the disk continues to feed the star and make it grow. Eventually, the left-over material in the disk is expected to form planets.

    Many aspects about these first stages of star formation, and how the disk forms, are still unclear. But this new survey provides some missing clues as the VLA and ALMA peered through the dense clouds and observed hundreds of protostars and their disks in various stages of their formation.

    Young planet-forming disks

    “This survey revealed the average mass and size of these very young protoplanetary disks,” said John Tobin of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, and leader of the survey team. “We can now compare them to older disks that have been studied intensively with ALMA as well.”

    What Tobin and his team found, is that very young disks can be similar in size, but are on average much more massive than older disks. “When a star grows, it eats away more and more material from the disk. This means that younger disks have a lot more raw material from which planets could form. Possibly bigger planets already start to form around very young stars.”

    Four special protostars

    Among hundreds of survey images, four protostars looked different than the rest and caught the scientists’ attention. “These newborn stars looked very irregular and blobby,” said team member Nicole Karnath of the University of Toledo, Ohio (now at SOFIA Science Center). “We think that they are in one of the earliest stages of star formation and some may not even have formed into protostars yet.”

    It is special that the scientists found four of these objects. “We rarely find more than one such irregular object in one observation,” added Karnath, who used these four infant stars to propose a schematic pathway for the earliest stages of star formation. “We are not entirely sure how old they are, but they are probably younger than ten thousand years.”

    To be defined as a typical (class 0) protostar, stars should not only have a flattened rotating disk surrounding them, but also an outflow – spewing away material in opposite directions – that clears the dense cloud surrounding the stars and makes them optically visible. This outflow is important, because it prevents stars from spinning out of control while they grow. But when exactly these outflows start to happen, is an open question in astronomy.

    One of the infant stars in this study, called HOPS 404, has an outflow of only two kilometers (1.2 miles) per second (a typical protostar-outflow of 10-100 km/s or 6-62 miles/s). “It is a big puffy sun that is still gathering a lot of mass, but just started its outflow to lose angular momentum to be able to keep growing,” explained Karnath. “This is one of the smallest outflows that we have seen and it supports our theory of what the first step in forming a protostar looks like.”

    Combining ALMA and VLA

    The exquisite resolution and sensitivity provided by both ALMA and the VLA were crucial to understand both the outer and inner regions of protostars and their disks in this survey. While ALMA can examine the dense dusty material around protostars in great detail, the images from the VLA made at longer wavelengths were essential to understand the inner structures of the youngest protostars at scales smaller than our solar system.

    “The combined use of ALMA and the VLA has given us the best of both worlds,” said Tobin. “Thanks to these telescopes, we start to understand how planet formation begins.”

    The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

    More Information

    This research was presented in two papers:

    The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. A Statistical Characterization of Class 0 and I Protostellar Disks,” by J. Tobin et al., The Astrophysical Journal.

    “Detection of Irregular, Sub-mm Opaque Structures in the Orion Molecular Clouds: Protostars within 10000 years of formation?,” by N. Karnath et al., The Astrophysical Journal.

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    Observed protostars in Orion Molecular Clouds
    This image shows the Orion Molecular Clouds, the target of the VANDAM survey. Yellow dots are the locations of the observed protostars on a blue background image made by Herschel. Side panels show nine young protostars imaged by ALMA (blue) and the VLA (orange). Credit: ALMA (ESO/NAOJ/NRAO), J. Tobin; NRAO/AUI/NSF, S. Dagnello; Herschel/ESA

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    Schematic showing the formation of protostars
    This schematic shows a proposed pathway (top row) for the formation of protostars, based on four very young protostars (bottom row) observed by VLA (orange) and ALMA (blue). Step 1 represents the collapsing fragment of gas and dust. In step 2, an opaque region starts to form in the cloud. In step 3, a hydrostatic core starts to form due to an increase in pressure and temperature, surrounded by a disk-like structure and the beginning of an outflow. Step 4 depicts the formation of a class 0 protostar inside the opaque region, that may have a rotationally supported disk and more well-defined outflows. Step 5 is a typical class 0 protostar with outflows that have broken through the envelope (making it optically visible), an actively accreting, rotationally supported disk. In the bottom row, white contours are the protostar outflows as seen with ALMA.
    Credit: ALMA (ESO/NAOJ/NRAO), N. Karnath; NRAO/AUI/NSF, B. Saxton and S. Dagnello

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    Star chart of constellation Orion and observed protostars
    The Orion Molecular Clouds (blue, as seen with Herschel) are located in the constellation Orion. Red dots show the locations of the observed protostars in the VANDAM survey.
    Credit: IAU; Sky & Telescope magazine; NRAO/AUI/NSF, S. Dagnello; Herschel/ESA; ALMA (ESO/NAOJ/NRAO), J. Tobin

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The 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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    ESO 50 Large

     
  • richardmitnick 9:30 pm on October 2, 2018 Permalink | Reply
    Tags: , , , , , , NRAO VLA, ,   

    From Science: “Cosmic conundrum: The disks of gas and dust that supposedly form planets don’t seem to have the goods” 

    AAAS
    From Science Magazine

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    Artist’s illustration of the protoplanetary disk surrounding a young star. JPL-Caltech/NASA

    Astronomers have a problem on their hands: How can you make planets if you don’t have enough of the building blocks? A new study finds that protoplanetary disks—the envelopes of dust and gas around young stars that give rise to planets—seem to contain orders of magnitude too little material to produce the planets.

    “This work is telling us that we really have to rethink our planetary formation theories,” says astronomer Gijs Mulders of the University of Chicago in Illinois, who was not involved in the research.

    Stars are born from colossal clouds of gas and dust and, in their earliest stages, are surrounded by a thin disk of material. Dust grains within this halo collide, sometimes sticking together. The clumps build up into planetary cores, which are big enough to gravitationally attract additional dust and gas, eventually forming planets.

    But many details about this process remain unknown, such as just how quickly planets arise from the disk, and how efficient they are in capturing material. The disks, surrounded by an obscuring haze of gas and dust, are difficult to observe. But radio telescopes can penetrate the haze and investigate young stars. The brightness of radio waves emitted by dust in the disk can be used to give a reasonable estimate of its overall mass.

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

    The Atacama Large Millimeter Array (ALMA), a radio observatory in the Atacama Desert in Chile, has made it far easier to study protoplanetary disks. In the new study, astronomers led by Carlo Manara of the European Southern Observatory in Munich, Germany, used ALMA to compare the masses of protoplanetary disks around young stars between 1 million and 3 million years old to the masses of confirmed exoplanets and exoplanetary systems around older stars of equivalent size. The disk masses were often much less than the total exoplanet mass—sometimes 10 or 100 times lower, the team will report in an upcoming paper in Astronomy & Astrophysics.

    Although such findings have been reported before for a few star systems, the study is the first to point out the mismatch over several hundred different systems. “I think what this work does is really set this as a fact,” Manara says.

    It is possible that astronomers are simply looking at the disks too late. Perhaps some planets form in the first million years, sucking up much of the gas and dust, Manara says. ALMA has found that some extremely young stars, such as the approximately 100,000-year-old HL Tauri, already have ringlike gaps in their disks, potentially indicating that protoplanets are sweeping up material inside of them.

    “But if you solve one problem, you end up with another,” says astronomer Jonathan Williams of the University of Hawaii Institute for Astronomy in Honolulu, who was also not involved in the work. If planetary cores form early, when so much material remains in the disk, nothing would stop them from ballooning into Jupiter-size behemoths. Yet the emerging census of exoplanets shows that most are Earth- or Neptune-size worlds.

    Williams favors the idea that current telescopes are simply missing some of the material. ALMA’s wavelengths are tuned to best see the smallest bits of dust. But a great deal of mass, perhaps as much as 10 times what’s been observed, could be hidden in the form of pebbles, which are slightly too big to show up in such investigations. A proposed upgrade to the Very Large Array, a radio telescope in New Mexico, should be able to spot such hidden debris, perhaps accounting for some of the missing material.

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

    One final possibility is that protoplanetary disks are somehow sucking in additional material from the surrounding interstellar medium. Manara says some recent simulations show young stars drawing in fresh material for much longer periods of time than previously believed. He hopes that observations of the earliest stages of star formation from the upcoming Square Kilometer Array or James Webb Space Telescope will help researchers decide between these different hypotheses.

    NASA/ESA/CSA Webb Telescope annotated

    See the full article here .


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    Please help promote STEM in your local schools.

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  • richardmitnick 1:51 pm on December 19, 2017 Permalink | Reply
    Tags: A specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster, , In 2014 astronomers reported the detection of an unusual emission line in X-ray light from the Perseus and other galaxy clusters, , , NRAO VLA, Perseus Cluster: A New Twist in the Dark Matter Tale   

    From Chandra: “Perseus Cluster: A New Twist in the Dark Matter Tale” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    December 19, 2017

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    Composite

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    X-ray

    3
    Optical/Radio
    Credit X-ray: NASA/CXO/Oxford University/J. Conlon et al. Radio: NRAO/AUI/NSF/Univ. of Montreal/Gendron-Marsolais et al. Optical: NASA/ESA/IoA/A. Fabian et al.; DSS

    Dark matter is a mysterious invisible substance that makes up about 85% of matter in the Universe.

    In 2014, astronomers reported the detection of an unusual emission line in X-ray light from the Perseus and other galaxy clusters.

    A new interpretation of this detection and follow up observations may provide an explanation of this signal.

    If confirmed with future observations, this result could help resolve the nature of dark matter.

    An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter, as described in our latest press release [written by Megan Watzke, Chandra X-ray Center, Cambridge, Mass. 617-496-7998 mwatzke@cfa.harvard.edu]. The finding involves a new explanation for a set of results made with NASA’s Chandra X-ray Observatory, ESA’s XMM-Newton and Hitomi, a Japanese-led X-ray telescope.

    ESA/XMM Newton X-ray telescope

    JAXA/Hitomi telescope lost

    If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the Universe.

    The image shown here contains X-ray data from Chandra (blue) of the Perseus galaxy cluster, which has been combined with optical data from the Hubble Space Telescope (pink) and radio emission from the Very Large Array (red).

    NASA/ESA Hubble Telescope

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

    In 2014, researchers detected an unusual spike of intensity, known as an emission line, at a specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster. They also reported the presence of this same emission line in a study of 73 other galaxy clusters.

    In the subsequent months and years, astronomers have tried to confirm the existence of this 3.5 keV line. They are eager to do so because it may give us important clues about the nature of dark matter. However, it has been debated in the astronomical community exactly what the original and follow-up observations have revealed.

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    Credit: NASA/CXC/M. Weiss

    A new analysis of Chandra data by a team from Oxford University, however, is providing a fresh take on this debate. The latest work shows that absorption of X-rays at an energy of 3.5 keV is detected when observing the region surrounding the supermassive black hole at the center of Perseus. This suggests that dark matter particles in the cluster are both absorbing and emitting X-rays (see our artist’s impression above for a diagram helping to explain this behavior, where 3.5 keV X-rays are shown). If the new model turns out to be correct, it could provide a path for scientists to one day identify the true nature of dark matter. For next steps, astronomers will need further observations of the Perseus cluster and others like it with current X-ray telescopes and those being planned for the next decade and beyond.

    A paper describing these results was published in Physical Review D on December 19, 2017 and a preprint is available online. The authors of the paper are Joseph Conlon, Francesca Day, Nicolas Jennings, Sven Krippendorf and Markus Rummel, all from Oxford University in the UK. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

    From the Press Release

    Other materials about the findings are available at:
    http://chandra.si.edu/photo/2017/dark/

    For more Chandra images, multimedia and related materials, visit:
    http://www.nasa.gov/chandra

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

     
  • richardmitnick 11:53 am on April 21, 2017 Permalink | Reply
    Tags: , An Exploration of Dusty Galaxies, , , , , NRAO VLA, Submillimeter Common-User Bolometer Array (SCUBA-2), UKIDSS Ultra Deep Survey field   

    From AAS NOVA: ” An Exploration of Dusty Galaxies” 

    AASNOVA

    American Astronomical Society

    21 April 2017
    Susanna Kohler

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    A small section of the UKIDSS Ultra Deep Survey field. A new study of 53 submillimeter galaxies in this field reveals more about galaxies in our early universe. [University of Nottingham/Omar Almaini]

    Submillimeter galaxies — i.e., galaxies that we detect in the submillimeter wavelength range — are mysterious creatures. It’s only within the last couple decades that we’ve had telescope technology capable of observing them, and we’re only now getting to the point where angular resolution limits allow us to examine them closely. A new study has taken advantage of new capabilities to explore the properties of a sample of 52 of these galaxies.

    Dusty Star Formation

    Submillimeter galaxies are generally observed in the early universe. Though they’re faint in other wavebands, they’re extremely luminous in infrared and submillimeter — their infrared luminosities are typically trillions of times the Sun’s luminosity. This is thought to be because these galaxies are very actively forming stars at rates of hundreds of times that of the Milky Way!

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    Example 10” × 10” true-color images of ten submillimeter galaxies in the authors’ ALMA-identified sample. [Simpson et al. 2017]

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

    Submillimeter galaxies are also extremely dusty, so we don’t see their star formation directly in optical wavelengths. Instead, we see the stellar light after it’s been absorbed and reemitted by interstellar dust lanes — we’re indirectly observing heavily obscured star formation.

    Why look for submillimeter galaxies? Studying them can help us to learn about galaxy and star formation early in our universe’s history, and help us to understand how the universe has evolved into what we see locally today.

    Submillimeter Struggles

    Due to angular resolution limitations in the past, we often couldn’t pin down the exact locations of submillimeter galaxies, preventing us from examining them properly. But now a team of scientists has used the Atacama Large Millimeter/submillimeter array (ALMA) to precisely locate 52 submillimeter galaxies identified by the Submillimeter Common-User Bolometer Array (SCUBA-2) in the UKIDSS Ultra Deep Survey field.

    East Asia Observatory James Clerk Maxwell telescope, Mauna Kea, Hawaii, USA

    The precise locations made possible by ALMA allowed the team — led by James Simpson (University of Edinburgh and Durham University) — to identify the multi-wavelength properties of these galaxies in a pilot study that they hope to extend to many more similar galaxies in the future.

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    Photometric redshift distribution of the ALMA-identified submillimeter galaxies in the authors’ sample (grey). [Simpson et al. 2017]

    Lessons from Distant Galaxies

    What did Simpson and collaborators learn in this study?

    1. For the set of galaxies for which the team could measure photometric redshifts, the median redshift was z ~ 2.65 (though redshifts ranged up to z ~ 5).
    2. Submillimeter galaxies are cooler and larger than local far-infrared galaxies (known as ULIRGs). The authors therefore argue that it’s unlikely that ULIRGs are evolved versions of submillimeter galaxies.
    3. Estimates of dust mass in these galaxies suggest that effectively all of the optical-to-near-infrared light from colocated stars is obscured by dust.
    4. Estimates of the future stellar mass of these galaxies suggest that they cannot evolve into lenticular or spiral galaxies. Instead, the authors conclude, submillimeter galaxies must be the progenitors of local elliptical galaxies.

    Citation

    J. M. Simpson et al 2017 ApJ 839 58. doi:10.3847/1538-4357/aa65d0

    Related Journal Articles

    The scuba-2 cosmology legacy survey: alma resolves the rest-frame far-infrared emission of sub-millimeter galaxies doi: 10.1088/0004-637X/799/1/81
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    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    See the full article here .

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  • richardmitnick 2:36 pm on October 26, 2016 Permalink | Reply
    Tags: , , , L1448 IRS3B system, , NRAO VLA, , Young Stellar System Caught in Act of Forming Close Multiples   

    From ALMA: “Young Stellar System Caught in Act of Forming Close Multiples” 

    ALMA Array

    ALMA

    26 October 2016
    Dave Finley
    Public Information Officer
    Karl G. Jansky Very Large Array (VLA)
    Tel: 1 575.835-7302
    Email: dfinley@nrao.edu

    Nicolás Lira T.
    Education and Public Outreach Coordinator
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 24 67 65 19
    Cell: +56 9 94 45 77 26
    Email: nicolas.lira@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 202 236 6324
    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 image of the L1448 IRS3B system, with two young stars at the center and a third distant from them. Spiral structure in the dusty disk surrounding them indicates instability in the disk, astronomers said. Credit: Bill Saxton, ALMA (ESO/NAOJ/NRAO), NRAO/AUI/NSF.

    For the first time, astronomers have seen a dusty disk of material around a young star fragmenting into a multiple-star system. Scientists had suspected such a process, caused by gravitational instability, was at work, but new observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA) revealed the process in action.

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

    “This new work directly supports the conclusion that there are two mechanisms that produce multiple star systems — fragmentation of circumstellar disks, such as we see here, and fragmentation of the larger cloud of gas and dust from which young stars are formed,” said John Tobin, of the University of Oklahoma and Leiden Observatory in the Netherlands.

    Stars form in giant clouds of gas and dust, when the tenuous material in the clouds collapses gravitationally into denser cores that begin to draw additional material inward. The infalling material forms a rotating disk around the young star. Eventually, the young star gathers enough mass to create the temperatures and pressures at its center that will trigger thermonuclear reactions.

    Previous studies had indicated that multiple star systems tend to have companion stars either relatively close, within about 500 times the Earth-Sun distance, or significantly farther apart, more than 1,000 times that distance. Astronomers concluded that the differences in distance result from different formation mechanisms. The more widely-separated systems, they said, are formed when the larger cloud fragments through turbulence, and recent observations have supported that idea.

    The closer systems were thought to result from fragmentation of the smaller disk surrounding a young protostar, but that conclusion was based principally on the relative proximity of the companion stars.

    2
    Combined ALMA and VLA image of L1448 IRS3B system. Credit: Bill Saxton, ALMA (ESO/NAOJ/NRAO), NRAO/AUI/NSF.

    “Now, we’ve seen this disk fragmentation at work,” Tobin said.

    Tobin, Kaitlin Kratter of the University of Arizona, and their colleagues used ALMA and the VLA to study a young triple-star system called L1448 IRS3B, located in a cloud of gas in the constellation Perseus, some 750 light-years from Earth. The most central of the young stars is separated from the other two by 61 and 183 times the Earth-Sun distance. All three are surrounded by a disk of material that ALMA revealed to have spiral structure, a feature that, the astronomers said, indicates instability in the disk.

    “This whole system probably is less than 150,000 years old.” Kratter said. “Our analysis indicates that the disk is unstable, and the most widely separated of the three protostars may have formed only in the past 10,000 to 20,000 years,” she added.

    3
    Artist’s conception of how the triple-star system develops. Left, disk of material fragments into separate protostars. Right, the resulting stellar system. Credit: Bill Saxton, NRAO/AUI/NSF.

    The L1448 IRS3B system, the astronomers conclude, provides direct observational evidence that fragmentation in the disk can produce young multiple-star systems very early in their development.

    “We now expect to find other examples of this process and hope to learn just how much it contributes to the population of multiple stars,” Tobin said.

    The scientists presented their findings in the October 27 edition of the journal Nature.

    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 2:30 pm on June 9, 2016 Permalink | Reply
    Tags: , , NRAO VLA, , VLASS begins   

    From NRAO: “The VLA Sky Survey Pilot Begins” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    6.9.16

    1
    Claire Chandler, VLASS Project Director

    1

    The Very Large Array Sky Survey (VLASS) will be a three-epoch (32-month cadence), all-sky, S-band (2-4 GHz) continuum polarimetry survey with 2.5-arcsecond spatial resolution. The survey will span seven years and six VLA configuration cycles, and will begin in 2017, pending successful achievement of the design phase milestones. The total VLA telescope time required for the survey is ~5400 hours, or ~900 hours per configuration cycle.

    With the decision to proceed with the VLASS (see 17 Dec 2015 e-News), a 200-hr pilot in the recently commenced VLA B-configuration of semester 2016A has been approved, with the first observations starting June 2016. This pilot survey will inform VLASS implementation and operational issues associated with the full survey as input to design reviews, while at the same time providing the community with early VLASS-type data products. The pilot will be observed in as similar a mode to the full VLASS as possible, including:

    S-band (2-4 GHz), 1024 x 2 MHz channels
    VLA B-configuration, 2.5-arcsec resolution
    On-The-Fly (OTF) mosaics scanning at 3.31 arcmin/sec in right ascension, at constant declination
    Net mapping speed ~20 deg2/hr, 4-hr scheduling blocks covering 80 deg2 (10o x 8o tiles)

    Some areas will be covered with three passes to provide a similar sensitivity as that expected from three epochs of the full VLASS (70 microJy/beam), while others will be observed with a single pass (120 microJy/beam) to maximize sky coverage. The pilot will cover key galactic and extragalactic fields that have good multi-wavelength ancillary data, as well as covering areas of sky with good prior radio observations for technical validation of the OTF mosaicking observing mode. The total area to be covered will be ~2500 deg2, and will include:

    VLASS Pilot Fields, 3 passes (70 microJy/beam):

    Galactic Plane fields: Galactic Center, Cygnus, Cepheus
    Extragalactic fields: Cosmological Evolution Survey, Sloane Digital Sky Survey (SDSS) Stripe 82, Chandra Deep Field South

    VLASS Pilot Fields, 1 pass (120 microJy/beam):

    SDSS South Galactic Cap / FIRST southern sky for declination > 0 deg
    SDSS North Galactic Cap fields: Great Observatories Origins Deep Survey – North, Elais-N1, Lockman Hole, H-ATLAS North, Bootes

    Raw visibility data will be immediately available through the NRAO archive under project code TVPILOT. Data products (calibrated visibility data, images) will be made available after undergoing quality assurance.

    At this time, we encourage community participation in various Science Working Groups as we define and refine the operational aspects of the pilot survey:

    Extragalactic Working Group
    Galactic Working Group
    Transients Working Group
    Polarization Working Group
    EPO Working Group
    Survey Implementation Working Group
    NRAO Data Products, Archiving and Enhanced Data Products Working Group

    A Google Group has been set up to facilitate discussion and communication within the working groups, please visit to sign up.

    See the full article here .

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    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO/GBT radio telescope
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 11:49 am on March 14, 2016 Permalink | Reply
    Tags: , , NRAO VLA, Our Galactic Center   

    From AAS NOVA: “Imaging the Heart of Our Galaxy” 

    AASNOVA

    Amercan Astronomical Society

    14 March 2016
    Susanna Kohler

    Galactic Center NRAO VLA
    Galactic Center. NRAO/VLA

    New radio images of the center of the Milky Way are providing an unprecedented view of the structure and processes occurring in the Galactic center.

    Improved Radio View

    A recent study led by Jun-Hui Zhao (Harvard-Smithsonian Center for Astrophysics) presents new images of the Galactic center using the Jansky Very Large Array (JVLA) at 5.5 GHz.

    NRAO VLA
    NRAO/VLA

    The images center on the radio-bright zone at the core of our galaxy, with the field of view covering the central 13’ of the Milky Way — equivalent to a physical size of ~100 light-years.

    Due to recent hardware and software improvements in the VLA, these images are much deeper than any previously obtained of the Galactic center, reaching an unprecedented 100,000:1 dynamic range. Not only do these observations provide a detailed view of previously known structures within the Sagittarius A radio complex in the Milky Way’s heart, but they also reveal new features that can help us understand the processes that formed this bright complex.

    Features in Sagittarius A

    Sgr A consists of three main components nested within each other: the supernova remnant Sgr A East, the mini-spiral structure Sgr A West (located off-center within the Sgr A East structure), and the compact radio source Sgr A* (located near the center of the mini-spiral). Sgr A* is the supermassive black hole that resides at the very center of the Milky Way.

    SGR A
    SGR A*

    The newest JVLA images reveal numerous filamentary sources that trace out two radio lobes, oriented nearly perpendicular to the Galactic plane and ~50 light-years in size. These are smaller radio counterparts to the enormous (on the scale of 30,000 light-years!) gamma-ray Fermi bubbles that have been observed to extend from the Galactic center. The bipolar radio structures appear to be due to winds emanating from Sgr A* itself, from a central cluster of massive stars, or from a combination of the two.

    Supernova Structures

    The outermost shape of Sgr A East — which looks like an elliptical ring — is thought to be an expanding spherical shell from a past supernova explosion, appearing as an ellipse because of our angle of view. In the newest JVLA images, Zhao and collaborators identify a new structure inside of the ring that they term the “Sigma Front”.

    The authors argue that this emission front — which is shaped like the capital Greek letter sigma — may be the reflection of the supernova blast wave bouncing off of the dense, clumpy circumnuclear molecular disk around Sgr A* (which encircles the mini-spiral, but isn’t visible in radio wavelengths). Under this assumption, they use the Sigma Front to constrain the geometry of the supernova explosion.

    These new JVLA images contain a wealth of information in their detail, and analysis is only just beginning. Further examination of these images will continue to help us learn about the activity at the heart of our galaxy.
    Citation

    Jun-Hui Zhao et al 2016 ApJ 817 171. doi:10.3847/0004-637X/817/2/171

    See the full article here .

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  • richardmitnick 8:31 am on December 29, 2015 Permalink | Reply
    Tags: , , Magnetic Fields and Star Formation, NRAO VLA,   

    From NRAO: “Twisted Magnetic Fields Give New Insights on Star Formation” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    1
    Magnetic field lines (purple) are twisted as they are dragged inward toward a swirling, dusty disk surrounding a young star in this artist’s conception. CREDIT: Bill Saxton, NRAO/AUI/NSF.

    21 December 2015
    Media Contact:
    Dave Finley, Public Information Officer
    (575) 835-7302
    dfinley@nrao.edu

    Using new images that show unprecedented detail, scientists have found that material rotating around a very young protostar probably has dragged in and twisted magnetic fields from the larger area surrounding the star. The discovery, made with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) radio telescope, has important implications for how dusty disks — the raw material for planet formation — grow around young stars.

    NRAO VLA
    VLA

    The scientists studied a young protostar about 750 light-years from Earth in the constellation Perseus. Their observations, made in 2013 and 2014, measured the alignment, or polarization, of radio waves emitted by material, mostly dust, falling into a burgeoning disk orbiting the young star. The polarization information revealed the configuration of magnetic fields in this region near the star.

    “The alignment of magnetic fields in this region near young stars is very important to the development of the disks that orbit them. Depending on its alignment, the magnetic field can either hinder the growth of the disk or help funnel material onto the disk, allowing it to grow,” said Leslie Looney, of the University of Illinois at Urbana-Champaign.

    As material from the envelope of dust and gas surrounding the young star falls inward toward the rotating disk, it is likely to drag magnetic field lines with it. Because of this, the structure of the magnetic field near the star will become different from the field’s structure farther away.

    “Our VLA observations are showing us this region, where the change in shape of the magnetic field is taking place,” said Erin Cox, also of the University of Illinois Urbana-Champaign. The observations, she added, produced the first images at wavelengths of 8 and 10 millimeters to show the polarization near a protostar.

    The observations also indicated that millimeter- to centimeter-sized particles are numerous in the disk surrounding the young star. Since the protostar is only about 10,000 years old — very short in astronomical timescales — this may mean that such grains form and grow quickly in the environment of a still-forming star.

    The star, dubbed NGC1333 IRAS 4A, is one of two young stars forming within a common envelope of dust and gas. The disk around it contains material with a total mass more than twice that of our Sun.

    Cox and Looney are part of an international team of astronomers studying the protostar. The scientists are reporting their results in the Astrophysical Journal Letters.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 10:41 am on November 18, 2015 Permalink | Reply
    Tags: , , , NRAO VLA   

    From Hubble: “A Multi-Wavelength View of Radio Galaxy Hercules A” 

    NASA Hubble Telescope

    Hubble

    November 29, 2012
    Reposted by ESA 16/11/2015

    Ray Villard
    Space Telescope Science Institute, Baltimore, Md.
    410-338-4514
    villard@stsci.edu

    John Stoke
    National Radio Astronomy Observatory, Charlottesville, Va.
    434-244-6896
    jstoke@nrao.edu

    Dave Finley
    National Radio Astronomy Observatory, Socorro, N.M.
    575-835-7302
    dfinley@nrao.edu

    1
    NASA, ESA, S. Baum, C. O’Dea (RIT), R. Perley, W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

    [ESA] Scientists often use the combined power of multiple telescopes to reveal the secrets of the Universe – and this image is a prime example of when this technique is strikingly effective.

    [HubbleSite]Spectacular jets powered by the gravitational energy of a supermassive black hole in the core of the elliptical galaxy Hercules A illustrate the combined imaging power of two of astronomy’s cutting-edge tools, the Hubble Space Telescope’s Wide Field Camera 3 [WFC3], and the recently upgraded Karl G. Jansky Very Large Array (VLA) radio telescope in New Mexico.

    NASA Hubble WFC3
    WFC3

    NRAO VLA
    VLA

    Some two billion light-years away, the yellowish elliptical galaxy in the center of the image appears quite ordinary as seen by Hubble in visible wavelengths of light. The elliptical galaxy is roughly 1,000 times more massive than the bulge of our Milky Way and harbors a 2.5-billion-solar-mass central black hole that is 1,000 times more massive than the black hole in the Milky Way. But the innocuous-looking galaxy, also known as 3C 348, has long been known as the brightest radio-emitting object in the constellation Hercules. Emitting nearly a billion times more power in radio wavelengths than our Sun, the galaxy is one of the brightest extragalactic radio sources in the entire sky.

    The VLA radio data reveal enormous, optically invisible jets that, at one-and-a-half million light-years wide, dwarf the visible galaxy from which they emerge. The jets are very-high-energy plasma beams, subatomic particles and magnetic fields shot at nearly the speed of light from the vicinity of the black hole. The outer portions of both jets show unusual ring-like structures suggesting a history of multiple outbursts from the supermassive black hole at the center of the galaxy.

    The innermost parts of the jets are not visible because of the extreme velocity of the material; relativistic effects confine all of the light to a narrow cone aligned with the jets, and so that light is not seen by us. Far from the galaxy, the jets become unstable and break up into the rings and wisps.

    The entire radio source is surrounded by a very hot, X-ray-emitting cloud of gas, not seen in this optical-radio composite.

    Hubble’s view of the field also shows a companion elliptical galaxy very close to the center of the optical-radio source, which may be merging with the central galaxy. Several other elliptical and spiral galaxies that are visible in the Hubble data may be members of a cluster of galaxies. Hercules A is by far the brightest and most massive galaxy in the cluster.

    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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