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News Article | December 12, 2016
Site: www.eurekalert.org

Astronomers now know that our galaxy is teeming with planets, from rocky worlds roughly the size of Earth to gas giants bigger than Jupiter. Nearly every one of these exoplanets has been discovered in orbit around a mature star with a fully evolved planetary system. New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) contain compelling evidence that two newborn planets, each about the size of Saturn, are in orbit around a young star known as HD 163296. These planets, which are not yet fully formed, revealed themselves by the dual imprint they left in both the dust and the gas portions of the star's protoplanetary disk. Previous observations of other young star systems have helped to reshape our understanding of planet formation. For example, ALMA's images of HL Tauri and TW Hydrae revealed striking gaps and prominent ring structures in the stars' dusty disks. These features may be the tantalizing first signs that planets are being born. Remarkably, these signs appeared around much younger stars than astronomers thought possible, suggesting that planet formation can begin soon after the formation of a protoplanetary disk. "ALMA has shown us amazing images and never-before-seen views of the rings and gaps around young stars that could be the hallmarks of planet formation. However, since we were only looking at the dust in the disks with sufficient detail, we couldn't be sure what created these features," said Andrea Isella, an astronomer at Rice University in Houston, Texas, and lead author on a paper published in Physical Review Letters. In studying HD 163296, the research team used ALMA to trace, for the first time, the distribution of both the dust and the carbon monoxide (CO) gas components of the disk at roughly the same level of detail. These observations revealed three distinct gaps in HD 163296's dust-filled protoplanetary disk. The first gap is located approximately 60 astronomical units from the central star, which is about twice the distance from our Sun to Neptune. (An astronomical unit - AU - is the average distance from the Earth to the Sun.) The other two gaps are 100 AU and 160 AU from the central star, well beyond the extent of our solar system's Kuiper Belt, the region of icy bodies beyond the orbit of Neptune. Using ALMA's ability to detect the faint millimeter-wavelength "glow" emitted by gas molecules, Isella and his team discovered that there was also an appreciable dip in the amount of CO in the outer two dust gaps. By seeing the same features in both the gas and the dust components of the disk, the astronomers believe they have found compelling evidence that there are two planets coalescing remarkably far from the central star. The width and depth of the two CO gaps suggest that each potential planet is roughly the same mass as Saturn, the astronomers said. In the gap nearest to the star, the team found little to no difference in the concentration of CO gas compared to the surrounding dusty disk. This means that the innermost gap could have been produced by something other than an emerging planet. "Dust and gas behave very differently around young stars," said Isella. "We know, for example, that there are certain chemical and physical process that can produce ringed structures in the dust like the ones we have seen previously. We certainly believe these structures could be the work of a nascent planet plowing through the dust, but we simply can't rule out other possible explanations. Our new observations provide intriguing evidence that planets are indeed forming around this one young star." HD 163296 is roughly 5 million years old and about twice the mass of the Sun. It is located approximately 400 light-years from Earth in the direction of the constellation Sagittarius. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA. This research is presented in a paper titled "Ringed structure of the HD 163296 disk revealed by ALMA," by Isella et al., published in Physical Review Letters.


News Article | December 20, 2016
Site: www.eurekalert.org

Astronomers have gotten their first look at exactly where most of today's stars were born. To do so, they used the National Science Foundation's Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) to look at distant galaxies seen as they were some 10 billion years ago. At that time, the Universe was experiencing its peak rate of star formation. Most stars in the present Universe were born then. "We knew that galaxies in that era were forming stars prolifically, but we didn't know what those galaxies looked like, because they are shrouded in so much dust that almost no visible light escapes them," said Wiphu Rujopakam, of the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo and Chulalongkorn University in Bangkok, who was lead author on the research paper. Radio waves, unlike visible light, can get through the dust. However, in order to reveal the details of such distant -- and faint -- galaxies, the astronomers had to make the most sensitive images ever made with the VLA. The new observations, using the VLA and ALMA, have answered longstanding questions about just what mechanisms were responsible for the bulk of star formation in those galaxies. They found that intense star formation in the galaxies they studied most frequently occured throughout the galaxies, as opposed to much smaller regions in present-day galaxies with similar high star-formation rates. The astronomers used the VLA and ALMA to study galaxies in the Hubble Ultra Deep Field, a small area of sky observed since 2003 with NASA's Hubble Space Telescope (HST). The HST made very long exposures of the area to detect galaxies in the far-distant Universe, and numerous observing programs with other telescopes have followed up on the HST work. "We used the VLA and ALMA to see deeply into these galaxies, beyond the dust that obscured their innards from Hubble," said Kristina Nyland, of the National Radio Astronomy Observatory (NRAO). "The VLA showed us where star formation was occurring, and ALMA revealed the cold gas that is the fuel for star formation," she added. "In this study, we made the most sensitive image ever made with the VLA," said Preshanth Jagannathan, also of NRAO. "If you took your cellphone, which transmits a weak radio signal, and put it at more than twice the distance to Pluto, near the outer edge of the solar system, its signal would be roughly as strong as what we detected from these galaxies," he added. The study of the galaxies was done by an international team of astronomers. Others involved include James Dunlop of the University of Edinburgh and Rob Ivison of the University of Edinburgh and the European Southern Observatory. The researchers reported their findings in the Dec. 1 issue of the Astrophysical Journal. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


News Article | February 24, 2017
Site: www.eurekalert.org

Three decades ago, astronomers spotted one of the brightest exploding stars in more than 400 years. The titanic supernova, called Supernova 1987A (SN 1987A), blazed with the power of 100 million suns for several months following its discovery on Feb. 23, 1987. Since that first sighting, SN 1987A has continued to fascinate astronomers with its spectacular light show. Located in the nearby Large Magellanic Cloud, it is the nearest supernova explosion observed in hundreds of years and the best opportunity yet for astronomers to study the phases before, during, and after the death of a star. To commemorate the 30th anniversary of SN 1987A, new images, time-lapse movies, a data-based animation based on work led by Salvatore Orlando at INAF-Osservatorio Astronomico di Palermo, Italy, and a three-dimensional model are being released. By combining data from NASA's Hubble Space Telescope and Chandra X-ray Observatory, as well as the international Atacama Large Millimeter/submillimeter Array (ALMA), astronomers -- and the public -- can explore SN 1987A like never before. Hubble has repeatedly observed SN 1987A since 1990, accumulating hundreds of images, and Chandra began observing SN 1987A shortly after its deployment in 1999. ALMA, a powerful array of 66 antennas, has been gathering high-resolution millimeter and submillimeter data on SN 1987A since its inception. "The 30 years' worth of observations of SN 1987A are important because they provide insight into the last stages of stellar evolution," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and the Gordon and Betty Moore Foundation in Palo Alto, California. The latest data from these powerful telescopes indicate that SN 1987A has passed an important threshold. The supernova shock wave is moving beyond the dense ring of gas produced late in the life of the pre-supernova star when a fast outflow or wind from the star collided with a slower wind generated in an earlier red giant phase of the star's evolution. What lies beyond the ring is poorly known at present, and depends on the details of the evolution of the star when it was a red giant. "The details of this transition will give astronomers a better understanding of the life of the doomed star, and how it ended," said Kari Frank of Penn State University who led the latest Chandra study of SN 1987A. Supernovas such as SN 1987A can stir up the surrounding gas and trigger the formation of new stars and planets. The gas from which these stars and planets form will be enriched with elements such as carbon, nitrogen, oxygen and iron, which are the basic components of all known life. These elements are forged inside the pre-supernova star and during the supernova explosion itself, and then dispersed into their host galaxy by expanding supernova remnants. Continued studies of SN 1987A should give unique insight into the early stages of this dispersal. Some highlights from studies involving these telescopes include: Hubble studies have revealed that the dense ring of gas around the supernova is glowing in optical light, and has a diameter of about a light-year. The ring was there at least 20,000 years before the star exploded. A flash of ultraviolet light from the explosion energized the gas in the ring, making it glow for decades. The central structure visible inside the ring in the Hubble image has now grown to roughly half a light-year across. Most noticeable are two blobs of debris in the center of the supernova remnant racing away from each other at roughly 20 million miles an hour. From 1999 until 2013, Chandra data showed an expanding ring of X-ray emission that had been steadily getting brighter. The blast wave from the original explosion has been bursting through and heating the ring of gas surrounding the supernova, producing X-ray emission. In the past few years, the ring has stopped getting brighter in X-rays. From about February 2013 until the last Chandra observation analyzed in September 2015 the total amount of low-energy X-rays has remained constant. Also, the bottom left part of the ring has started to fade. These changes provide evidence that the explosion's blast wave has moved beyond the ring into a region with less dense gas. This represents the end of an era for SN 1987A. Beginning in 2012, astronomers used ALMA to observe the glowing remains of the supernova, studying how the remnant is actually forging vast amounts of new dust from the new elements created in the progenitor star. A portion of this dust will make its way into interstellar space and may become the building blocks of future stars and planets in another system. These observations also suggest that dust in the early universe likely formed from similar supernova explosions. Astronomers also are still looking for evidence of a black hole or a neutron star left behind by the blast. They observed a flash of neutrinos from the star just as it erupted. This detection makes astronomers quite certain a compact object formed as the center of the star collapsed -- either a neutron star or a black hole -- but no telescope has uncovered any evidence for one yet. These latest visuals were made possible by combining several sources of information including simulations by Salvatore Orlando and collaborators that appear in this paper: https:/ . The Chandra study by Frank et al. can be found online at http://lanl. . Recent ALMA results on SN 87A are available at https:/ . The Chandra program is managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.


News Article | November 4, 2016
Site: www.eurekalert.org

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a tsunami of stars and gas that is crashing midway through the disk of a spiral galaxy known as IC 2163. This colossal wave of material - which was triggered when IC 2163 recently sideswiped another spiral galaxy dubbed NGC 2207 - produced dazzling arcs of intense star formation that resemble a pair of eyelids. "Although galaxy collisions of this type are not uncommon, only a few galaxies with eye-like, or ocular, structures are known to exist," said Michele Kaufman, an astronomer formerly with The Ohio State University in Columbus and lead author on a paper published today in the Astrophysical Journal. Kaufman and her colleagues note that the paucity of similar features in the observable universe is likely due to their ephemeral nature. "Galactic eyelids last only a few tens of millions of years, which is incredibly brief in the lifespan of a galaxy. Finding one in such a newly formed state gives us an exceptional opportunity to study what happens when one galaxy grazes another," said Kaufman. The interacting pair of galaxies resides approximately 114 million light-years from Earth in the direction of the constellation Canis Major. These galaxies brushed past each other - scraping the edges of their outer spiral arms - in what is likely the first encounter of an eventual merger. Using ALMA's remarkable sensitivity and resolution, the astronomers made the most detailed measurements ever of the motion of carbon monoxide gas in the galaxy's narrow eyelid features. Carbon monoxide is a tracer of molecular gas, which is the fuel for star formation. The data reveal that the gas in the outer portion of IC 2163's eyelids is racing inward at speeds in excess of 100 kilometers a second. This gas, however, quickly decelerates and its motion becomes more chaotic, eventually changing trajectory and aligning itself with the rotation of the galaxy rather than continuing its pell-mell rush toward the center. "What we observe in this galaxy is very much like a massive ocean wave barreling toward shore until it interacts with the shallows, causing it to lose momentum and dump all of its water and sand on the beach," said Bruce Elmegreen, a scientist with IBM's T.J. Watson Research Center in Yorktown Heights, New York, and co-author on the paper. "Not only do we find a rapid deceleration of the gas as it moves from the outer to the inner edge of the eyelids, but we also measure that the more rapidly it decelerates, the denser the molecular gas becomes," said Kaufman. "This direct measurement of compression shows how the encounter between the two galaxies drives gas to pile up, spawn new star clusters and form these dazzling eyelid features." Computer models predict that such eyelid-like features could evolve if galaxies interacted in a very specific manner. "This evidence for a strong shock in the eyelids is terrific. It's all very well to have a theory and simulations suggesting it should be true, but real observational evidence is great," said Curtis Struck, a professor of astrophysics at Iowa State University in Ames and co-author on the paper. "ALMA showed us that the velocities of the molecular gas in the eyelids are on the right track with the predictions we get from computer models," said Kaufman. "This critical test of encounter simulations was not possible before." Astronomers believe that such collisions between galaxies were common in the early universe when galaxies were closer together. At that time, however, galactic disks were generally clumpy and irregular, so other processes likely overwhelmed the formation of similar eyelid features. The authors continue to study this galaxy pair and currently are comparing the properties (e.g., locations, ages, and masses) of the star clusters previously observed with NASA's Hubble Space Telescope with the properties of the molecular clouds observed with ALMA. They hope to better understand the differences between molecular clouds and star clusters in the eyelids and those elsewhere in the galaxy pair. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


News Article | February 15, 2017
Site: www.eurekalert.org

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a surprising connection between a supermassive black hole and the galaxy where it resides. Powerful radio jets from the black hole - which normally suppress star formation - are stimulating the production of cold gas in the galaxy's extended halo of hot gas. This newly identified supply of cold, dense gas could eventually fuel future star birth as well as feed the black hole itself. The researchers used ALMA to study a galaxy at the heart of the Phoenix Cluster, an uncommonly crowded collection of galaxies about 5.7 billion light-years from Earth. The central galaxy in this cluster harbors a supermassive black hole that is in the process of devouring star-forming gas, which fuels a pair of powerful jets that erupt from the black hole in opposite directions into intergalactic space. Astronomers refer to this type of black-hole powered system as an active galactic nucleus (AGN). Earlier research with NASA's Chandra X-ray observatory revealed that the jets from this AGN are carving out a pair of giant "radio bubbles," huge cavities in the hot, diffuse plasma that surrounds the galaxy. These expanding bubbles should create conditions that are too inhospitable for the surrounding hot gas to cool and condense, which are essential steps for future star formation. The latest ALMA observations, however, reveal long filaments of cold molecular gas condensing around the outer edges of the radio bubbles. These filaments extend up to 82,000 light-years from either side of the AGN. They collectively contain enough material to make about 10 billion suns. "With ALMA we can see that there's a direct link between these radio bubbles inflated by the supermassive black hole and the future fuel for galaxy growth," said Helen Russell, an astronomer with the University of Cambridge, UK, and lead author on a paper appearing in the Astrophysical Journal. "This gives us new insights into how a black hole can regulate future star birth and how a galaxy can acquire additional material to fuel an active black hole." The new ALMA observations reveal previously unknown connections between an AGN and the abundance of cold molecular gas that fuels star birth. "To produce powerful jets, black holes must feed on the same material that the galaxy uses to make new stars," said Michael McDonald, an astrophysicist at the Massachusetts Institute of Technology in Cambridge and coauthor on the paper. "This material powers the jets that disrupt the region and quenches star formation. This illustrates how black holes can slow the growth of their host galaxies." Without a significant source of heat, the most massive galaxies in the universe would be forming stars at extreme rates that far exceed observations. Astronomers believe that the heat, in the form of radiation and jets from an actively feeding supermassive black hole, prevents overcooling of the cluster's hot gas atmosphere, suppressing star formation. This story, however, now appears more complex. In the Phoenix Cluster, Russell and her team found an additional process that ties the galaxy and its black hole together. The radio jets that heat the core of the cluster's hot atmosphere also appear to stimulate the production of the cold gas required to sustain the AGN. "That's what makes this result so surprising," said Brian McNamara, an astronomer at the University of Waterloo, Ontario, and co-author on the paper. "This supermassive black hole is regulating the growth of the galaxy by blowing bubbles and heating the gases around it. Remarkably, it also is cooling enough gas to feed itself." This result helps astronomers understand the workings of the cosmic "thermostat" that controls the launching of radio jets from the supermassive black hole. "This could also explain how the most massive black holes were able to both suppress run-away starbursts and regulate the growth of their host galaxies over the past six billion years or so of cosmic history," noted Russell. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


News Article | December 21, 2016
Site: www.eurekalert.org

ALMA observes radio waves from the Universe, at the low-energy end of the electromagnetic spectrum. With the newly installed Band 5 receivers, ALMA has now opened its eyes to a whole new section of this radio spectrum, creating exciting new observational possibilities. The European ALMA Programme Scientist, Leonardo Testi, explains the significance: "The new receivers will make it much easier to detect water, a prerequisite for life as we know it, in our Solar System and in more distant regions of our galaxy and beyond. They will also allow ALMA to search for ionised carbon in the primordial Universe." It is ALMA's unique location, 5000 metres up on the barren Chajnantor plateau in Chile, that makes such an observation possible in the first place. As water is also present in Earth's atmosphere, observatories in less elevated and less arid environments have much more difficulty identifying the origin of the emission coming from space. ALMA's great sensitivity and high angular resolution mean that even faint signals of water in the local Universe can now be imaged at this wavelength [1]. The Band 5 receiver, which was developed by the Group for Advanced Receiver Development (GARD at Onsala Space Observatory, Chalmers University of Technology, Sweden, has already been tested at the APEX telescope in the SEPIA instrument. These observations were also vital to help select suitable targets for the first receiver tests with ALMA. The first production receivers were built and delivered to ALMA in the first half of 2015 by a consortium consisting of the Netherlands Research School for Astronomy (NOVA) and GARD in partnership with the National Radio Astronomy Observatory (NRAO, which contributed the local oscillator to the project. The receivers are now installed and being prepared for use by the community of astronomers. To test the newly installed receivers observations were made of several objects including the colliding galaxies Arp 220, a massive region of star formation close to the centre of the Milky Way, and also a dusty red supergiant star approaching the supernova explosion that will end its life [2]. To process the data and check its quality, astronomers, along with technical specialists from ESO and the European ALMA Regional Centre (ARC) network, gathered at the Onsala Space Observatory in Sweden, for a "Band 5 Busy Week" hosted by the Nordic ARC node [3] (http://www. ). The final results have just been made freely available to the astronomical community worldwide. Team member Robert Laing at ESO is optimistic about the prospects for ALMA Band 5 observations: "It's very exciting to see these first results from ALMA Band 5 using a limited set of antennas. In the future, the high sensitivity and angular resolution of the full ALMA array will allow us to make detailed studies of water in a wide range of objects including forming and evolved stars, the interstellar medium and regions close to supermassive black holes." [1] A key spectral signature of water lies in this expanded range -- at a wavelength of 1.64 millimetres. [2] The observations were performed and made possible by the ALMA Extension of Capabilities team in Chile. [3] The ESO Band 5 Science Verification team includes: Elizabeth Humphreys, Tony Mroczkowski, Robert Laing, Katharina Immer, Hau-Yu (Baobab) Liu, Andy Biggs, Gianni Marconi and Leonardo Testi. The team working on processing the data included: Tobia Carozzi, Simon Casey, Sabine König, Ana Lopez-Sepulcre, Matthias Maercker, Iván Martí-Vidal, Lydia Moser, Sebastien Muller, Anita Richards, Daniel Tafoya and Wouter Vlemmings. The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA. ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become "the world's biggest eye on the sky".


News Article | October 26, 2016
Site: www.eurekalert.org

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. "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. "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. 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. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


News Article | December 6, 2016
Site: spaceref.com

Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) have, for the first time, achieved a precise size measurement of small dust particles around a young star through radio-wave polarization. ALMA's high sensitivity for detecting polarized radio waves made possible this important step in tracing the formation of planets around young stars. Astronomers have believed that planets are formed from gas and dust particles, although the details of the process have been veiled. One of the major enigmas is how dust particles as small as 1 micrometer aggregate to form a rocky planet with a diameter of 10 thousand kilometers. Difficulty in measuring the size of dust particles has prevented astronomers from tracing the process of dust growth. Akimasa Kataoka, a Humboldt Research Fellow stationed at Heidelberg University and the National Astronomical Observatory of Japan, tackled this problem. He and his collaborators have theoretically predicted that, around a young star, radio waves scattered by the dust particles should carry unique polarization features. He also noticed that the intensity of polarized emissions allows us to estimate the size of dust particles far better than other methods. To test their prediction, the team led by Kataoka observed the young star HD 142527 with ALMA and discovered, for the first time, the unique polarization pattern in the dust disk around the star. As predicted, the polarization has a radial direction in most parts of the disk, but at the edge of the disk, the direction is flipped perpendicular to the radial direction. Comparing the observed intensity of the polarized emissions with the theoretical prediction, they determined that the size of the dust particles is at most 150 micrometers. This is the first estimation of the dust size based on polarization. Surprisingly, this estimated size is more than 10 times smaller than previously thought. "In the previous studies, astronomers have estimated the size based on radio emissions assuming hypothetical spherical dust particles," explains Kataoka. "In our study, we observed the scattered radio waves through polarization, which carries independent information from the thermal dust emission. Such a big difference in the estimated size of dust particles implies that the previous assumption might be wrong." The team's idea to solve this inconsistency is to consider fluffy, complex-shaped dust particles, not simple spherical dust. In the macroscopic view, such particles are indeed large, but in the microscopic view, each small part of a large dust particle scatters radio waves and produces unique polarization features. According to the present study, astronomers obtain these "microscopic" features through polarization observations. This idea might prompt astronomers to reconsider the previous interpretation of observational data. "The polarization fraction of radio waves from the dust disk around HD 142527 is only a few percent. Thanks to ALMA's high sensitivity, we have detected such a tiny signal to derive information about the size and shape of the dust particles," said Kataoka. "This is the very first step in the research on dust evolution with polarimetry, and I believe the future progress will be full of excitement." Reference: "Millimeter Polarization Observation of the Protoplanetary Disk around HD 142527," A. Kataoka et al., 2016 Nov. 10, Astrophysical Journal Letters [http://iopscience.iop.org/article/10.3847/2041-8205/831/2/L12, preprint: https://arxiv.org/abs/1610.06318]. The research team members are Akimasa Kataoka (Humboldt Research Fellowship for Postdoctoral Researchers / Heidelberg University / National Astronomical Observatory of Japan / former Postdoctoral Fellowship for Research Abroad at Japan Society for Promoting Science), Takashi Tsukagoshi (Ibaraki University), Munetake Momose (Ibaraki University), Hiroshi Nagai (National Astronomical Observatory of Japan), Takayuki Muto (Kogakuin University), Cornelis P. Dullemond (Heidelberg University), Adriana Pohl (Heidelberg University / Max Planck Institute for Astronomy), Misato Fukagawa (Nagoya University), Hiroshi Shibai (Osaka University), Tomoyuki Hanawa (Chiba University), Koji Murakawa (Osaka Sangyo University) This research was supported by a Grant-in-Aid from the Japan Society for the Promotion of Science and the Ministry of Education, Culture, Sports, Science and Technology, Japan (No. 23103004, 15K17606, 26800106). The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA. Please follow SpaceRef on Twitter and Like us on Facebook.


Kino M.,KASI | Ito H.,RIKEN | Kawakatu N.,Hiroshima Institute of Technology | Orienti M.,National institute for astrophysics | And 3 more authors.
Astronomische Nachrichten | Year: 2016

We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolution of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock, while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in the radio band while it is bright in the TeV γ -ray band and can be detectable by CTA. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Nagai H.,Japan National Astronomical Observatory | Chida H.,Japan National Astronomical Observatory | Kino M.,KASI | Orienti M.,National institute for astrophysics | And 3 more authors.
Astronomische Nachrichten | Year: 2016

Re-started jet activity occurred in the bright nearby radio source 3C 84 in about 2005. The re-started jet is forming a prominent component (namely C3) at the tip of jet. The component has showed an increase in radio flux density for more than 7 years while the radio spectrum remains optically thin. This suggests that the component is the head of a radio lobe including a hotspot where the particle acceleration occurs. Thus, 3C 84 is a unique laboratory to study the physical properties at the very early stage of radio source evolution. Another important aspect is that high energy and very high energy γ -ray emissions are detected from this source. The quest for the site of γ -ray emission is quite important to obtain a better understanding of γ -ray emission mechanisms in radio galaxies. In this paper, we review the observational results from very long baseline interferometry (VLBI) monitoring of 3C 84 reported in series of our previous papers. We argue the nature of re-started jet/radio lobe and its relation with high-energy emission. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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