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News Article | April 4, 2017
Site: www.techtimes.com

Astronomers, scientists, and researchers have been questing to find new life outside Earth for a very long time. Thus, every little detail obtained, which is related to outer space, is scrutinized thoroughly. Fast and short cosmic radio bursts in space have bewildered astronomers since they were first discovered a decade ago. A previous study conducted by Harvard-Smithsonian Center for Astrophysics suggested that these Fast Radio Bursts or FRBs may have their origin in alien space probes. A new study fuels this notion and states that these FRBs indeed originate from outer space. FRBs are radio wave emissions that appear for milliseconds and occur without a specific pattern. These random occurrences not only make their detection tough, but also make it difficult for scientists to study them. The first FRB was recorded in 2007 by a radio telescope. However, the occurrence was for such a short span, that it took scientists years to decipher their origin or meaning. All astronomers could come up with were theories and suppositions, which may be far from the truth. To unravel this mystery, Manisha Caleb, a student at the Australia National University, the ARC Center of Excellence for All-sky Astrophysics, or CAASTRO, and Swinburne University of Technology undertook a study to find the origin of these FRBs. Caleb and her colleagues from Swinburne University of Technology and University of Sydney were able to identify three FRBs, which were captured by the Molonglo radio telescope. This telescope is located 25 miles from Canberra. It was earlier believed that FRBs were nothing but local interferences jutting into the line of detection. However, in 2013, CAASTRO scientists and engineers discovered that the Molonglo radio telescope was able to "place a minimum distance to the FRBs due to its enormous focal length." "Conventional single dish radio telescopes have difficulty establishing that transmissions originate beyond the Earth's atmosphere," explained Swinburne University's Chris Flynn. Owing to its enormous focal length, the radio telescope has a massive data collection and huge viewing field, which facilities optimum results for FRB searches. The researchers' main aim was to develop specific software to help sieve through the massive pile of data (1000 TB), which the telescope collected every day. During this filtering of information, the existence of three new FRBs was discovered. "Figuring out where the bursts come from is the key to understanding what makes them. Only one burst has been linked to a specific galaxy," said Caleb. The study has been published in the Monthly Notices of the Royal Astronomical Society on March 29. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


Bernardi G.,Harvard - Smithsonian Center for Astrophysics | Greenhill L.J.,Harvard - Smithsonian Center for Astrophysics | Mitchell D.A.,University of Melbourne | Ord S.M.,Curtin University Australia | And 57 more authors.
Astrophysical Journal | Year: 2013

We present a Stokes I, Q and U survey at 189 MHz with the Murchison Widefield Array 32 element prototype covering 2400 deg2. The survey has a 15.6 arcmin angular resolution and achieves a noise level of 15 mJy beam-1. We demonstrate a novel interferometric data analysis that involves calibration of drift scan data, integration through the co-addition of warped snapshot images, and deconvolution of the point-spread function through forward modeling. We present a point source catalog down to a flux limit of 4 Jy. We detect polarization from only one of the sources, PMN J0351-2744, at a level of 1.8% ± 0.4%, whereas the remaining sources have a polarization fraction below 2%. Compared to a reported average value of 7% at 1.4 GHz, the polarization fraction of compact sources significantly decreases at low frequencies. We find a wealth of diffuse polarized emission across a large area of the survey with a maximum peak of 13 K, primarily with positive rotation measure values smaller than +10 rad m-2. The small values observed indicate that the emission is likely to have a local origin (closer than a few hundred parsecs). There is a large sky area at α ≥ 2h30 m where the diffuse polarized emission rms is fainter than 1 K. Within this area of low Galactic polarization we characterize the foreground properties in a cold sky patch at (α, δ) = (4h, -27.°6) in terms of three-dimensional power spectra. © 2013. The American Astronomical Society. All rights reserved.


News Article | December 28, 2016
Site: phys.org

Here are some of the highlights of the year that was. The spectacular announcement that ripples in the very fabric of spacetime itself had been found (and from surprisingly massive black holes colliding) sent similarly massive ripples through the scientific community. The discovery was made using the Laser Interferometer Gravitational-Wave Observatory (LIGO) and represents a fundamentally new sense with which to see the universe. The gravitational waves cause one arm of the LIGO detector to stretch relative to the other by less than a thousandth of the width of a proton in the centre of the atom. Relatively speaking, that's like measuring a hair's-width change in the distance to the nearest star. This discovery was the end of a century-long quest to prove Einstein's final prediction that these gravitational waves are real. It also allows us to directly "see" that famously and fundamentally invisible entity: the black hole (as well as definitively proving its existence). The fact that the two black holes collided 1.3 billion years ago and the waves swept through Earth just days after turning the detector on only add to the incredible story of this discovery. The year started so well for SpaceX with the incredible achievement of sending a satellite into orbit, which is no mean feat itself at such low cost, before then landing that launch rocket on a barge in the ocean. A seemingly unstoppable sequence of launches and landings made it appear that a new era of vastly cheaper access to space through rockets that could be refuelled and reused was at hand. Unfortunately, with the explosion of a Falcon 9 on the launchpad, the company was grounded, but apparently hopes for a resumed launch in early January. Add to that the visionary plans to settle Mars outlined by Elon Musk, albeit not without some audacious challenges, and it's been a year of highs and lows for SpaceX. Proxima Centauri is our Sun's nearest neighbour at just over four light years away, and it appears that its solar system may contain an Earth-like world. Until this year, astronomers weren't even sure that any planets orbited the star, let alone ones that might harbour the best extrasolar candidate for life that spacecraft could visit within our lifetime. The planet, creatively named "Proxima b", was discovered by a team of astronomers at Queen Mary University in London. Using the light of Proxima Centuari, the astronomers were able to detect subtle shifts in the star's orbit (seen as a "wobble"), which is the telltale sign that another massive object is nearby. While Proxima Centuari is barely 10% the size of our Sun, Proxima b's orbit is only 11 days long, meaning it is very close to the star and lies just within the so-called habitable zone. However, follow-up with either Hubble or the upcoming James Webb Space telescope is necessary to determine if the exoplanet is as well suited for life as Earth. With a potential Earth twin identified in Proxima b, now the challenge is to reach it within a human lifetime. With the breakthrough initiative starshot, which has been funded by Russian billionaire Yuri Milner and endorsed by none other than Stephen Hawking, lightweight nanosails can be propelled by light beams to reach speeds up to millions of kilometres an hour. Such speeds would allow a spacecraft to arrive at Proxima b in about 20 years, thus enabling humans to send information to another known planet for the first time. However, there are many challenges ahead, such as the fact that the technology doesn't exist yet, and that high-speed collisions with gas and dust between stars may destroy it before it can reach its target. But humans have proven to be resourceful, and key technology is advancing at an exponential rate. Incredibly the idea of sailing to another world is no longer science fiction, but rather an outrageously ambitious science project. Perhaps, aliens are already sending out their own information in the form of radio transmissions. In another breakthrough initiative called Listen, also championed by Hawking, astronomers will be searching the habitable zones around the million closest stars to try to detect incoming radio transmissions. Involving Australia's very own Parkes telescope (as well as the Green Bank Telescope and Lick Observatory at visible wavelengths of light), observations have been running through 2016 and the search for alien signals will continue for the next decade. In 2014 the Philae lander became the first space probe to land on a comet, and even though its crash landing dictated that its science transmission would be a one-off, its recent rediscovery by Rosetta has allowed it to continue to contribute to analysis of comet 67P. Philae's crash location, as well as the orientation of the doomed probe, has allowed astronomers to accurately interpret data taken by Rosetta regarding the composition of the comet. While Philae has literally been living under (crashed on) a rock for the past two years, Rosetta has been the busy bee, taking numerous images, spectroscopy and other data of the comet. In fact, data taken from Rosetta's spectrometer has been analysed and revealed that the amino acid, glycine, is present in the comet's outgassing, which breaks away from the surface of the comet as it becomes unstable from solar heating. Glycine is one of the fundamental building blocks of life; necessary for proteins and DNA, and its confirmed extraterrestrial confirms that the ingredients for life are unique to Earth, and that we may have comets to thank for providing our microbial ancestors with those crucial ingredients. Outlook for Down Under The future for astrophysics in Australia in 2017 looks particularly bright, with two ARC Centres of Excellence: CAASTRO-3-D studying the build of atoms over cosmic time; and OzGRav exploring the universe with gravitational waves; as well as SABRE, the world's first dark matter detector in the Southern Hemisphere, installed by end of the year. If you thought 2016 was a great year in space, then you're in for a treat in 2017. Dust and gas emitted from comet 67P reveal an amino acid. Credit: ESA Explore further: LIGO discovery named Science's 2016 Breakthrough of the Year


News Article | November 17, 2016
Site: www.eurekalert.org

A brief but brilliant burst of radiation that travelled at least a billion light years through Space to reach an Australian radio telescope last year has given scientists new insight into the fabric of the Universe. ICRAR-Curtin University's Dr Ryan Shannon, who co-led research into the sighting along with the California Institute of Technology's Dr Vikram Ravi, said the flash, known as a Fast Radio Burst (FRB), was one of the brightest seen since FRBs were first detected in 2001. The flash was captured by CSIRO's Parkes radio telescope in New South Wales. Dr Shannon, from the Curtin node of ICRAR (the International Centre for Radio Astronomy Research) and CSIRO, said all FRBs contained crucial information but this FRB, the 18th detected so far, was unique in the amount of information it contained about the cosmic web - the swirling gases and magnetic fields between galaxies. "FRBs are extremely short but intense pulses of radio waves, each only lasting about a millisecond. Some are discovered by accident and no two bursts look the same," Dr Shannon said. "This particular FRB is the first detected to date to contain detailed information about the cosmic web - regarded as the fabric of the Universe - but it is also unique because its travel path can be reconstructed to a precise line of sight and back to an area of space about a billion light years away that contains only a small number of possible home galaxies." Dr Shannon explained that the vast spaces between objects in the Universe contain nearly invisible gas and a plasma of ionised particles that used to be almost impossible to map, until this pulse was detected. "This FRB, like others detected, is thought to originate from outside of Earth's own Milky Way galaxy, which means their signal has travelled over many hundreds of millions of light years, through a medium that - while invisible to our eyes - can be turbulent and affected by magnetic fields," Dr Shannon said. "It is amazing how these very few milliseconds of data can tell how weak the magnetic field is along the travelled path and how the medium is as turbulent as predicted." This particular flash reached CSIRO's Parkes radio telescope mid-last year and was subsequently analysed by a mostly Australian team. A paper describing the FRB and the team's findings was published today in the journal Science. The Parkes telescope has been a prolific discoverer of FRBs, having detected the vast majority of the known population including the very first, the Lorimer burst, in 2001. FRBs remain one of the most mysterious processes in the Universe and likely one of the most energetic ones. To catch more FRBs, astronomers use new technology, such as Parkes' multibeam receiver, the Murchison Widefield Array (MWA) in Western Australia, and the upgraded Molonglo Observatory Synthesis Telescope near Canberra. This particular FRB was found and analysed by a system developed by the supercomputing group led by Professor Matthew Bailes at Swinburne University of Technology. Professor Bailes, who was a co-author on the Science paper, also heads The Dynamic Universe research theme in the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), which has seven Australian nodes including ICRAR-Curtin University. "Ultimately, FRBs that can be traced to their cosmic host galaxies offer a unique way to probe intergalactic space that allow us to count the bulk of the electrons that inhabit our Universe," Professor Bailes said. "To decode and further understand the information contained in this FRB is an exceptional opportunity to explore the physical forces and the extreme environment out in Space." "The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst" published November 17th 2016 in Science. CAASTRO is a collaboration of The University of Sydney, The Australian National University, The University of Melbourne, Swinburne University of Technology, The University of Queensland, The University of Western Australia and Curtin University, the latter two participating together as the International Centre for Radio Astronomy Research (ICRAR). CAASTRO is funded under the Australian Research Council (ARC) Centre of Excellence program, with additional funding from the seven participating universities and from the NSW State Government's Science Leveraging Fund. ICRAR is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia.CONTACTS


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

In 2015, the All Sky Automated Survey for SuperNovae (ASAS-SN) detected an event, named ASASSN-15lh, that was recorded as the brightest supernova ever -- and categorised as a superluminous supernova, the explosion of an extremely massive star at the end of its life. It was twice as bright as the previous record holder, and at its peak was 20 times brighter than the total light output of the entire Milky Way. An international team, led by Giorgos Leloudas at the Weizmann Institute of Science, Israel, and the Dark Cosmology Centre, Denmark, has now made additional observations of the distant galaxy, about 4 billion light-years from Earth, where the explosion took place and they have proposed a new explanation for this extraordinary event. "We observed the source for 10 months following the event and have concluded that the explanation is unlikely to lie with an extraordinarily bright supernova. Our results indicate that the event was probably caused by a rapidly spinning supermassive black hole as it destroyed a low-mass star," explains Leloudas. In this scenario, the extreme gravitational forces of a supermassive black hole, located in the centre of the host galaxy, ripped apart a Sun-like star that wandered too close -- a so-called tidal disruption event, something so far only observed about 10 times. In the process, the star was "spaghettified" and shocks in the colliding debris as well as heat generated in accretion led to a burst of light. This gave the event the appearance of a very bright supernova explosion, even though the star would not have become a supernova on its own as it did not have enough mass. The team based their new conclusions on observations from a selection of telescopes, both on the ground and in space. Among them was the Very Large Telescope at ESO's Paranal Observatory, the New Technology Telescope at ESO's La Silla Observatory and the NASA/ESA Hubble Space Telescope [1]. The observations with the NTT were made as part of the Public ESO Spectroscopic Survey of Transient Objects (PESSTO). "There are several independent aspects to the observations that suggest that this event was indeed a tidal disruption and not a superluminous supernova," explains coauthor Morgan Fraser from the University of Cambridge, UK (now at University College Dublin, Ireland). In particular, the data revealed that the event went through three distinct phases over the 10 months of follow-up observations. These data overall more closely resemble what is expected for a tidal disruption than a superluminous supernova. An observed re-brightening in ultraviolet light as well as a temperature increase further reduce the likelihood of a supernova event. Furthermore, the location of the event -- a red, massive and passive galaxy -- is not the usual home for a superluminous supernova explosion, which normally occur in blue, star-forming dwarf galaxies. Although the team say a supernova source is therefore very unlikely, they accept that a classical tidal disruption event would not be an adequate explanation for the event either. Team member Nicholas Stone from Columbia University, USA, elaborates: "The tidal disruption event we propose cannot be explained with a non-spinning supermassive black hole. We argue that ASASSN-15lh was a tidal disruption event arising from a very particular kind of black hole." The mass of the host galaxy implies that the supermassive black hole at its centre has a mass of at least 100 million times that of the Sun. A black hole of this mass would normally be unable to disrupt stars outside of its event horizon -- the boundary within which nothing is able to escape its gravitational pull. However, if the black hole is a particular kind that happens to be rapidly spinning -- a so-called Kerr black hole -- the situation changes and this limit no longer applies. "Even with all the collected data we cannot say with 100% certainty that the ASASSN-15lh event was a tidal disruption event," concludes Leloudas. "But it is by far the most likely explanation." [1] As well as the data from ESO's Very Large Telescope, the New Technology Telescope and the NASA/ESA Hubble Space Telescope the team used observations from NASA's Swift telescope, the Las Cumbres Observatory Global Telescope (LCOGT), the Australia Telescope Compact Array, ESA's XMM-Newton, the Wide-Field Spectrograph (WiFeS and the Magellan Telescope. This research was presented in a paper entitled "The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole", by G. Leloudas et al. to appear in the new Nature Astronomy magazine. The team is composed of G. Leloudas (Weizmann Institute of Science, Rehovot, Israel; Niels Bohr Institute, Copenhagen, Denmark), M. Fraser (University of Cambridge, Cambridge, UK), N. C. Stone (Columbia University, New York, USA), S. van Velzen (The Johns Hopkins University, Baltimore, USA), P. G. Jonker (Netherlands Institute for Space Research, Utrecht, the Netherlands; Radboud University Nijmegen, Nijmegen, the Netherlands), I. Arcavi (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California, Santa Barbara, USA), C. Fremling (Stockholm University, Stockholm, Sweden), J. R. Maund (University of Sheffield, Sheffield, UK), S. J. Smartt (Queen's University Belfast, Belfast, UK), T. Krühler (Max-Planck-Institut für extraterrestrische Physik, Garching b. München, Germany), J. C. A. Miller-Jones (ICRAR - Curtin University, Perth, Australia), P. M. Vreeswijk (Weizmann Institute of Science, Rehovot, Israel), A. Gal-Yam (Weizmann Institute of Science, Rehovot, Israel), P. A. Mazzali (Liverpool John Moores University, Liverpool, UK; Max-Planck-Institut für Astrophysik, Garching b. München, Germany), A. De Cia (European Southern Observatory, Garching b. München, Germany), D. A. Howell (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California Santa Barbara, Santa Barbara, USA), C. Inserra (Queen's University Belfast, Belfast, UK), F. Patat (European Southern Observatory, Garching b. München, Germany), A. de Ugarte Postigo (Instituto de Astrofisica de Andalucia, Granada, Spain; Niels Bohr Institute, Copenhagen, Denmark), O. Yaron (Weizmann Institute of Science, Rehovot, Israel), C. Ashall (Liverpool John Moores University, Liverpool, UK), I. Bar (Weizmann Institute of Science, Rehovot, Israel), H. Campbell (University of Cambridge, Cambridge, UK; University of Surrey, Guildford, UK), T.-W. Chen (Max-Planck-Institut für extraterrestrische Physik, Garching b. München, Germany), M. Childress (University of Southampton, Southampton, UK), N. Elias-Rosa (Osservatoria Astronomico di Padova, Padova, Italy), J. Harmanen (University of Turku, Piikkiö, Finland), G. Hosseinzadeh (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California Santa Barbara, Santa Barbara, USA), J. Johansson (Weizmann Institute of Science, Rehovot, Israel), T. Kangas (University of Turku, Piikkiö, Finland), E. Kankare (Queen's University Belfast, Belfast, UK), S. Kim (Pontificia Universidad Católica de Chile, Santiago, Chile), H. Kuncarayakti (Millennium Institute of Astrophysics, Santiago, Chile; Universidad de Chile, Santiago, Chile), J. Lyman (University of Warwick, Coventry, UK), M. R. Magee (Queen's University Belfast, Belfast, UK), K. Maguire (Queen's University Belfast, Belfast, UK), D. Malesani (University of Copenhagen, Copenhagen, Denmark; DTU Space, Denmark), S. Mattila (University of Turku, Piikkiö, Finland; Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Piikkiö, Finland; University of Cambridge, Cambridge, UK), C. V. McCully (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California Santa Barbara, Santa Barbara, USA), M. Nicholl (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), S. Prentice (Liverpool John Moores University, Liverpool, UK), C. Romero-Ca[ñ] - https:/ izales (Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute of Astrophysics, Santiago, Chile), S. Schulze (Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute of Astrophysics, Santiago, Chile), K. W. Smith (Queen's University Belfast, Belfast, UK), J. Sollerman (Stockholm University, Stockholm, Sweden), M. Sullivan (University of Southampton, Southampton, UK), B. E. Tucker (Australian National University, Canberra, Australia; ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia), S. Valenti (University of California, Davis, USA), J. C. Wheeler (University of Texas at Austin, Austin, USA), and D. R. Young (Queen's University Belfast, Belfast, UK). 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 | September 14, 2016
Site: www.rdmag.com

In research published today, Australian scientists have taken a critical step towards understanding why different types of galaxies exist throughout the Universe. The research, made possible by cutting-edge AAO instrumentation, means that astronomers can now classify galaxies according to their physical properties rather than human interpretation of a galaxy’s appearance. For the past 200 years, telescopes have been capable of observing galaxies beyond our own galaxy, the Milky Way. Only a few were visible to begin with but as telescopes became more powerful, more galaxies were discovered, making it crucial for astronomers to come up with a way to consistently group different types of galaxies together. In 1926, the famous American astronomer Edwin Hubble refined a system that classified galaxies into categories of spiral, elliptical, lenticular or irregular shape. This system, known as the Hubble sequence, is the most common way of classifying galaxies to this day. Despite its success, the criteria on which the Hubble scheme is based are subjective, and only indirectly related to the physical properties of galaxies. This has significantly hampered attempts to identify the evolutionary pathways followed by different types of galaxies as they slowly change over billions of years. Dr Luca Cortese, from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said the world’s premier astronomical facilities are now producing surveys consisting of hundreds of thousands of galaxies rather than the hundreds that Hubble and his contemporaries were working with. “We really need a way to classify galaxies consistently using instruments that measure physical properties rather than a time consuming and subjective technique involving human interpretation,” he said. In a study led by Dr Cortese, a team of astronomers has used a technique known as Integral Field Spectroscopy to quantify how gas and stars move within galaxies and reinterpret the Hubble sequence as a physically based two-dimensional classification system. “Thanks to the development of new technologies, we can map in great detail the distribution and velocity of different components of galaxies. Then, using this information we’re able to determine the overall angular momentum of a galaxy, which is the key physical quantity affecting how the galaxy will evolve over billions of years. “Remarkably, the galaxy types described by the Hubble scheme appear to be determined by two primary properties of galaxies–mass and angular momentum. This provides us with a physical interpretation for the well known Hubble sequence whilst removing the subjectiveness and bias of a visual classification based on human perception rather than actual measurement.” The new study involved 488 galaxies observed by the 3.9m Anglo Australian Telescope in New South Wales and an instrument attached to the telescope called the Sydney-AAO Multi-object Integral-field spectrograph or ‘SAMI’. The SAMI project, led by the University of Sydney and the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), aims to create one of the first large-scale resolved survey of galaxies, measuring the velocity and distribution of gas and stars of different ages in thousands of systems. “Australia has a lot of expertise with this type of astronomy and is really at the forefront of what’s being done,” said Professor Warrick Couch, Director of the Australian Astronomical Observatory and CAASTRO Partner Investigator. “For the SAMI instrument we succeeded in putting 61 optical fibres within a distance that’s less than half the width of a human hair. “That’s no small feat, it’s making this type of work possible and attracting interest from astronomers and observatories from around the world.” Future upgrades of the instrument are planned that will allow astronomers to obtain even sharper maps of galaxies and further their understanding of the physical processes shaping the Hubble sequence. “As we get better at doing this and the instruments we’re using are upgraded, we should be able to look for the physical triggers that cause one type of galaxy to evolve into another—that’s really exciting stuff,” Dr Cortese said.


News Article | September 14, 2016
Site: phys.org

The research, made possible by cutting-edge AAO instrumentation, means that astronomers can now classify galaxies according to their physical properties rather than human interpretation of a galaxy's appearance. For the past 200 years, telescopes have been capable of observing galaxies beyond our own galaxy, the Milky Way. Only a few were visible to begin with but as telescopes became more powerful, more galaxies were discovered, making it crucial for astronomers to come up with a way to consistently group different types of galaxies together. In 1926, the famous American astronomer Edwin Hubble refined a system that classified galaxies into categories of spiral, elliptical, lenticular or irregular shape. This system, known as the Hubble sequence, is the most common way of classifying galaxies to this day. Despite its success, the criteria on which the Hubble scheme is based are subjective, and only indirectly related to the physical properties of galaxies. This has significantly hampered attempts to identify the evolutionary pathways followed by different types of galaxies as they slowly change over billions of years. Dr Luca Cortese, from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said the world's premier astronomical facilities are now producing surveys consisting of hundreds of thousands of galaxies rather than the hundreds that Hubble and his contemporaries were working with. "We really need a way to classify galaxies consistently using instruments that measure physical properties rather than a time consuming and subjective technique involving human interpretation," he said. In a study led by Dr Cortese, a team of astronomers has used a technique known as Integral Field Spectroscopy to quantify how gas and stars move within galaxies and reinterpret the Hubble sequence as a physically based two-dimensional classification system. "Thanks to the development of new technologies, we can map in great detail the distribution and velocity of different components of galaxies. Then, using this information we're able to determine the overall angular momentum of a galaxy, which is the key physical quantity affecting how the galaxy will evolve over billions of years. "Remarkably, the galaxy types described by the Hubble scheme appear to be determined by two primary properties of galaxies–mass and angular momentum. This provides us with a physical interpretation for the well known Hubble sequence whilst removing the subjectiveness and bias of a visual classification based on human perception rather than actual measurement." The new study involved 488 galaxies observed by the 3.9m Anglo Australian Telescope in New South Wales and an instrument attached to the telescope called the Sydney-AAO Multi-object Integral-field spectrograph or 'SAMI'. The SAMI project, led by the University of Sydney and the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), aims to create one of the first large-scale resolved survey of galaxies, measuring the velocity and distribution of gas and stars of different ages in thousands of systems. "Australia has a lot of expertise with this type of astronomy and is really at the forefront of what's being done," said Professor Warrick Couch, Director of the Australian Astronomical Observatory and CAASTRO Partner Investigator. "For the SAMI instrument we succeeded in putting 61 optical fibres within a distance that's less than half the width of a human hair. "That's no small feat, it's making this type of work possible and attracting interest from astronomers and observatories from around the world." Future upgrades of the instrument are planned that will allow astronomers to obtain even sharper maps of galaxies and further their understanding of the physical processes shaping the Hubble sequence. "As we get better at doing this and the instruments we're using are upgraded, we should be able to look for the physical triggers that cause one type of galaxy to evolve into another—that's really exciting stuff," Dr Cortese said. More information: The SAMI Galaxy Survey: the link between angular momentum and optical morphology. arxiv.org/abs/1608.00291


News Article | September 15, 2016
Site: www.rdmag.com

The mystery of a rare change in the behaviour of a supermassive black hole at the centre of a distant galaxy has been solved by an international team of astronomers using ESO's Very Large Telescope along with the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory. It seems that the black hole has fallen on hard times and is no longer being fed enough fuel to make its surroundings shine. Many galaxies are found to have an extremely bright core powered by a supermassive black hole. These cores make "active galaxies" some of the brightest objects in the Universe. They are thought to shine so brightly because hot material is glowing fiercely as it falls into the black hole, a process known as accretion. This brilliant light can vary hugely between different active galaxies, so astronomers classify them into several types based on the properties of the light they emit. Some of these galaxies have been observed to change dramatically over the course of only 10 years; a blink of an eye in astronomical terms. However, the active galaxy in this new study, Markarian 1018 stands out by having changed type a second time, reverting back to its initial classification within the last five years. A handful of galaxies have been observed to make this full-cycle change, but never before has one been studied in such detail. The discovery of Markarian 1018's fickle nature was a chance by-product of the Close AGN Reference Survey (CARS), a collaborative project between ESO and other organisations to gather information on 40 nearby galaxies with active cores. Routine observations of Markarian 1018 with the Multi-Unit Spectroscopic Explorer (MUSE) installed on ESO's Very Large Telescope revealed the surprising change in the light output of the galaxy. "We were stunned to see such a rare and dramatic change in Markarian 1018", said Rebecca McElroy, lead author of the discovery paper and a PhD student at the University of Sydney and the ARC Centre of Excellence for All Sky Astrophysics (CAASTRO). The chance observation of the galaxy so soon after it began to fade was an unexpected opportunity to learn what makes these galaxies tick, as Bernd Husemann, CARS project leader and lead author of one of two papers associated with the discovery, explained: "We were lucky that we detected the event just 3-4 years after the decline started so we could begin monitoring campaigns to study details of the accretion physics of active galaxies that cannot be studied otherwise." The research team made the most of this opportunity, making it their first priority to pinpoint the process causing Markarian 1018's brightness to change so wildly. This could have been caused by any one of a number of astrophysical events, but they could rule out the black hole pulling in and consuming a single star and cast doubt on the possibility of obscuration by intervening gas. But the true mechanism responsible for Markarian 1018's surprising variation remained a mystery after the first round of observations. However, the team were able to gather extra data after they were awarded observing time to use the NASA/ESA Hubble Space Telescope, and NASA's Chandra X-ray Observatory. With the new data from this suite of instruments they were able to solve the mystery—the black hole was slowly fading because it was being starved of accretion material. "It's possible that this starvation is because the inflow of fuel is being disrupted", said Rebecca McElroy. "An intriguing possibility is that this could be due to interactions with a second supermassive black hole". Such a black hole binary system is a distinct possibility in Markarian 1018, as the galaxy is the product of a major merger of two galaxies—each of which likely contained a supermassive black hole in its centre. Research continues into the mechanisms at work in active galaxies such as Markarian 1018 that change their appearance. "The team had to work fast to determine what was causing Markarian 1018's return to the shadows," comments Bernd Husemann. "Ongoing monitoring campaigns with ESO telescopes and other facilities will allow us to explore the exciting world of starving black holes and changing active galaxies in more detail." This research was presented in two papers entitled "Mrk 1018 returns to the shadows after 30 years as a Seyfert 1", and "What is causing Mrk 1018's return to the shadows after 30 years?", both to appear as Letters in the journal Astronomy & Astrophysics.

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