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  • richardmitnick 9:35 am on April 22, 2015 Permalink | Reply
    Tags: , , Royal Astronomical Society   

    From RAS: “As bright as a hundred million Suns: the clusters of monster stars that lit up the early universe” 

    Royal Astronomical Society

    Royal Astronomical Society

    22 April 2015
    Science contact
    Dr Shantanu Basu
    University of Western Ontario
    Canada
    Tel: +1 519 661 2111 x86706
    Mob: +1 519 520 7856
    basu@uwo.ca

    Media contact
    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 x214
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    The first stars in the Universe were born several hundred million years after the Big Bang, ending a period known as the cosmological ‘dark ages’ – when atoms of hydrogen and helium had formed, but nothing shone in visible light. Now two Canadian researchers have calculated what these objects were like: they find that the first stars could have clustered together in phenomenally bright groups, with periods when they were as luminous as 100 million Suns. Alexander DeSouza and Shantanu Basu, both of the University of Western Ontario in Canada, publish their results in a paper in Monthly Notices of the Royal Astronomical Society.

    1
    An artist’s impression of some of the first stars in the early Universe. Five protostars are seen here forming in the centre of disks of gas. Credit: Shantanu Basu, University of Western Ontario.

    The two scientists modelled how the luminosity of the stars would have changed as they formed from the gravitational collapse of disks of gas. The early evolution turns out to be chaotic, with clumps of material forming and spiralling into the centre of the disks, creating bursts of luminosity a hundred times brighter than average. These first stars would have been at their brightest when they were ‘protostars‘, still forming and pulling in material.

    In a small cluster of even 10 to 20 protostars, the ongoing bursts would mean the cluster would spend large periods with enhanced brightness. According to the simulation, every so often a cluster of 16 protostars could see its luminosity increase by a factor of up to 1000, to an extraordinary 100 million times the brightness of the Sun.

    The earliest stars lived very short lives and produced the first heavy elements, like the carbon and oxygen that the chemistry of life depends upon.

    Light from these stars has travelled towards us for almost 13 billion years, so to observers on Earth they look very faint and also have their light stretched out into infrared wavelengths by the expansion of the universe. This makes these stars very hard to observe, but the next generation James Webb Space Telescope (JWST) will survey the skies to look for them.

    NASA Webb Telescope
    JWST

    Although the luminosity of an individual first star is probably too faint for JWST to spot it, the new work suggests that clusters of the first protostars could be prominent beacons in the early universe.

    Dr Basu commented: “Seeing the very first stars is a key science goal for JWST and part of astronomers’ quest to track the history of the cosmos. If we’re right, then in just a few years’ time, we could see these enigmatic and dazzlingly bright objects as they came into being, and lit up the universe around them.”

    Further information

    The new work appears in A. L. DeSouza & S. Basu, The Luminosity of Population III Star Clusters, Monthly Notices of the Royal Astronomical Society, vol. 450, pp. 295-304, 2015, published by Oxford University Press.

    See the full article here.

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  • richardmitnick 8:39 pm on March 22, 2015 Permalink | Reply
    Tags: , , Mass extinctions, Royal Astronomical Society   

    From RAS: “Does dark matter cause mass extinctions and geologic upheavals?” 

    Royal Astronomical Society

    Royal Astronomical Society

    19 February 2015

    Media contacts

    James Devitt
    Deputy Director for Media Relations
    New York University
    United States
    Tel: +1 (212) 998 6808
    Mob: +1 (914) 522 3774
    james.devitt@nyu.edu

    Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 x214
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contact

    Prof Michael Rampino
    New York University
    United States
    Tel: +1 (718) 578 1442
    mrr1@nyu.edu

    1
    NGC 4565, an edge-on spiral galaxy. The stars, dust and gas are concentrated into a thin disc, much like the one in our Milky Way galaxy. NGC 4565 and apparently smaller NGC 4562. 24-inch telescope on Mt. Lemmon, AZ. Courtesy of Joseph D. Schulman

    Mt Lemon 24 inch telescope
    Mt Lemon 24 inch telescope

    Research by New York University Biology Professor Michael Rampino concludes that Earth’s infrequent but predictable path around and through our Galaxy’s disc may have a direct and significant effect on geological and biological phenomena occurring on Earth. In a new paper in Monthly Notices of the Royal Astronomical Society, he concludes that movement through dark matter may perturb the orbits of comets and lead to additional heating in the Earth’s core, both of which could be connected with mass extinction events.

    The galactic disc is the region of the Milky Way galaxy where our solar system resides. It is crowded with stars and clouds of gas and dust, and also a concentration of elusive dark matter – small subatomic particles that can be detected only by their gravitational effects.

    Previous studies have shown that Earth rotates around the disc-shaped Galaxy once every 250 million years. But the Earth’s path around the Galaxy is wavy, with the Sun and planets weaving through the crowded disc approximately every 30 million years. Analysing the pattern of the Earth’s passes through the Galactic disc, Rampino notes that these disc passages seem to correlate with times of comet impacts and mass extinctions of life. The famous comet strike 66 million ago that led to the extinction of the dinosaurs is just one example.

    What causes this correlation between Earth’s passes through the Galactic disc, and the impacts and extinctions that seem to follow?

    While travelling through the disc, the dark matter concentrated there disturbs the pathways of comets typically orbiting far from the Earth in the outer Solar System, Rampino points out. This means that comets that would normally travel at great distances from the Earth instead take unusual paths, causing some of them to collide with the planet.

    But even more remarkably, with each dip through the disc, the dark matter can apparently accumulate within the Earth’s core. Eventually, the dark matter particles annihilate each other, producing considerable heat. The heat created by the annihilation of dark matter in Earth’s core could trigger events such as volcanic eruptions, mountain building, magnetic field reversals, and changes in sea level, which also show peaks every 30 million years. Rampino therefore suggests that astrophysical phenomena derived from the Earth’s winding path through the Galactic disc, and the consequent accumulation of dark matter in the planet’s interior, can result in dramatic changes in Earth’s geological and biological activity.

    His model of dark matter interactions with the Earth as it cycles through the Galaxy could have a broad impact on our understanding of the geological and biological development of Earth, as well as other planets within the Galaxy.

    Rampino said: “We are fortunate enough to live on a planet that is ideal for the development of complex life. But the history of the Earth is punctuated by large scale extinction events, some of which we struggle to explain. It may be that dark matter – the nature of which is still unclear but which makes up around a quarter of the universe – holds the answer. As well as being important on the largest scales, dark matter may have a direct influence on life on Earth.”

    In the future, he suggests, geologists might incorporate these astrophysical findings in order to better understand events that are now thought to result purely from causes inherent to the Earth. This model, Rampino adds, likewise provides new knowledge of the possible distribution and behaviour of dark matter within the Galaxy.

    See the full article here.

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  • richardmitnick 5:32 am on December 22, 2014 Permalink | Reply
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    From RAS: “The Milky Way’s new neighbour” 

    Royal Astronomical Society

    Royal Astronomical Society

    19 December 2014
    Media contact
    Robert Massey
    Royal Astronomical Society
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contact
    Prof Dimitry Makarov
    Special Astrophysical Observatory
    Nizhniy Arkhyz
    Karachai-Cherkessia
    Russia
    Tel: +7 87822 93404
    dim@sao.ru

    The Milky Way, the galaxy we live in, is part of a cluster of more than 50 galaxies that make up the ‘Local Group’, a collection that includes the famous Andromeda galaxy and many other far smaller objects. Now a Russian-American team have added to the canon, finding a tiny and isolated dwarf galaxy almost 7 million light years away. Their results appear in Monthly Notices of the Royal Astronomical Society.

    l
    Local Group

    a
    The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. The image also shows Messier Objects 32 and 110, as well as NGC 206 (a bright star cloud in the Andromeda Galaxy) and the star Nu Andromedae. This image was taken using a hydrogen-alpha filter.
    Adam Evans

    The team, led by Prof Igor Karachentsev of the Special Astrophysical Observatory in Karachai-Cherkessia, Russia, found the new galaxy, named KKs3, using the Hubble Space Telescope Advanced Camera for Surveys (ACS) in August 2014. Kks3 is located in the southern sky in the direction of the constellation of Hydrus and its stars have only one ten-thousandth of the mass of the Milky Way.

    NASA Hubble Telescope
    NASA Hubble schematic
    Hubble

    NASA Hubble ACS
    HUbble ACS

    h
    The core of the galaxy is the right hand dark object at the top centre of the image, with its stars spreading out over a large section around it. (The left hand of the two dark objects is a much nearer globular star cluster.) Credit: D. Makarov. Kks3 is a ‘dwarf spheroidal or dSph galaxy’ , lacking features like the spiral arms found in our own galaxy. These systems also have an absence of the raw materials (gas and dust) needed for new generations of stars to form, leaving behind older and fainter relics. In almost every case, this raw material seems to have been stripped out by nearby massive galaxies like Andromeda, so the vast majority of dSph objects are found near much bigger companions.

    Isolated objects must have formed in a different way, with one possibility being that they had an early burst of star formation that used up the available gas resources. Astronomers are particularly interested in finding dSph objects to understand galaxy formation in the universe in general, as even HST struggles to see them beyond the Local Group. The absence of clouds of hydrogen gas in nebulae also makes them harder to pick out in surveys, so scientists instead try to find them by picking out individual stars.

    For that reason, only one other isolated dwarf spheroidal, KKR 25, has been found in the Local Group, a discovery made by the same group back in 1999.

    Team member Prof Dimitry Makarov, also of the Special Astrophysical Observatory, commented: “Finding objects like Kks3 is painstaking work, even with observatories like the Hubble Space Telescope. But with persistence, we’re slowly building up a map of our local neighbourhood, which turns out to be less empty than we thought. It may be that are a huge number of dwarf spheroidal galaxies out there, something that would have profound consequences for our ideas about the evolution of the cosmos.”

    The team will continue to look for more dSph galaxies, a task that will become a little easier in the next few years, once instruments like the James Webb Space Telescope and the European Extremely Large Telescope begin service.

    See the full article here.

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  • richardmitnick 6:09 am on December 20, 2014 Permalink | Reply
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    From RAS: “Science and Innovation Strategy: RAS Response” 

    Royal Astronomical Society

    Royal Astronomical Society

    Friday, 19 December 2014
    No Writer Credit

    The UK government published its new Science and Innovation strategy on Wednesday 17 December. The new document, “Our Plan for Growth: science and innovation” includes a number of positive announcements and restatements of support for projects in astronomy and geophysics, such as the capital funding for the Square Kilometre Array (SKA) radio observatory and the Polar Research Ship, and the more recent support for the European Space Agency to develop the ExoMars mission.

    SKA Pathfinder Radio Telescope
    SKA Pathfinder telescope

    ESA ExoMars
    ESA/ExoMars

    The Society welcomes these, along with the statement of support for peer review in investment decisions; the importance of international collaboration, the new targets for the recruitment of maths and physics teachers, the new postgraduate loans scheme, the recognition of the success of the Gaia and Rosetta missions and the opportunities presented by Major Tim Peake’s flight to the International Space Station next year.

    ESA Gaia satellite
    ESA/Gaia

    ESA Rosetta spacecraft
    ESA/Rosetta

    More generally, one of the long-standing concerns of the scientific community has been the low level of public (and private) funding for science compared with other EU and OECD countries. The new strategy explicitly addresses this, with a pledge to examine resource spending in the 2015 Spending Review. The Society welcomes this commitment and the overarching statement that policies for science and innovation should not detract from the importance of fundamental research being carried out for its own sake.

    International collaboration, including UK leadership in European scientific programmes such as Horizon 2020, also has a high prominence. The Society endorses this view and the pledge to use the UK presidency of the EU to support this activity.

    The RAS however remains concerned about several fundamental areas, including the lack of commitment to protect the science ‘ring fence’. This flat cash budget has already been eroded significantly since 2010 and even a low inflation environment will have a serious impact on purchasing power in the years ahead. If this policy continues, the inevitable outcome will be a reduction in the resources (not least postgraduate students and postdoctoral researchers) needed to exploit scientific data. This could greatly hinder the UK’s ability to reap the full benefits of the capital investment in scientific projects. And although there is recognition of the need to recruit the most talented people from across the globe, though there seems no prospect of a loosening of the restrictions on immigration that can make such recruitment almost impossible in practice.

    President of the Royal Astronomical Society Prof Martin Barstow commented: “I am delighted to see that the Government so clearly recognises the importance of scientific research, including the ‘blue skies’ sciences that are so important to the RAS and our Fellows and which are so valued by the wider public. There has though been a hollowing out of the resource budget needed to make the most of our involvement and investment in major scientific programmes, something that will need to be tackled if the UK is to remain a world player in research. As RAS President I will be pressing the Government to tackle this in next year’s Spending Review, in order to deliver the secure environment that will allow our researchers to flourish.”

    See the full article here.

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  • richardmitnick 6:08 am on December 15, 2014 Permalink | Reply
    Tags: , , , , Royal Astronomical Society   

    From RAS: “Stretched-out solid exoplanets “ 

    Royal Astronomical Society

    Royal Astronomical Society

    Monday, 15 December 2014
    Media contact

    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 x214
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contact

    Prabal Saxena
    School of Physics, Astronomy and Computational Sciences
    George Mason University
    Virginia
    United States
    Tel: +1 516 978 2158
    psaxena2@masonlive.gmu.edu

    Astronomers could soon be able to find rocky planets stretched out by the gravity of the stars they orbit, according to a group of researchers in the United States. The team, led by Prabal Saxena of George Mason University, describe how to detect these exotic worlds in a paper in the journal Monthly Notices of the Royal Astronomical Society.

    p
    An artist’s impression of a stretched rocky planet in orbit around a red dwarf star. So close to the star, there is a difference in the strength of the gravitational field on each side of the planet, stretching it significantly. Credit: Shivam Sikroria.

    Since the first discovery in 1993, more than 1800 planets have been found in orbit around stars other than our Sun. These ‘exoplanets’ are incredibly diverse, with some gaseous like Jupiter and some mostly rocky like the Earth. The worlds also orbit their stars at very different distances, from less than a million km to nearly 100 billion km away. Planets that are very close to their stars experience harsh conditions, often with very high temperatures (>1000 degrees Celsius) and significant stretching from the tidal forces resulting from the stellar gravitational field. This is most obvious with planets with a large atmosphere (so-called ‘hot Jupiters’) but harder to see with the rockier objects.

    Prabal and his team modelled cases where the planets are in orbit close to small red dwarf stars, much fainter than our Sun, but by far the most common type of star in the Galaxy. The planets’ rotation is locked, so the worlds keep the same face towards the stars they orbit, much like the Moon does as it moves around the Earth. According to the scientists, in these circumstances the distortion of the planets should be detectable in transit events, where the planets moves in front of their stars and blocks out some of their light.

    If astronomers are able to find these extreme exoplanets, it could give them new insights into the properties of Earth-like planets as a whole. Prabal comments, “Imagine taking a planet like the Earth or Mars, placing it near a cool red star and stretching it out. Analysing the new shape alone will tell us a lot about the otherwise impossible to see internal structure of the planet and how it changes over time.”

    The subtle signals from stretched rocky planets could be found by some current telescopes, and certainly by much more powerful observatories like the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT) that are due to enter service in the next few years.

    NASA Webb Telescope
    NASA/Webb

    ESO E-ELT
    ESO E-ELT Interior
    ESO/E-ELT

    See the full article here.

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  • richardmitnick 5:43 pm on December 4, 2014 Permalink | Reply
    Tags: , , , , , , Royal Astronomical Society   

    From RAS: “Astronomers detect atomic hydrogen emission in galaxies at record breaking distances” 

    Royal Astronomical Society

    Royal Astronomical Society

    Wednesday, 03 December 2014
    Media contact (UK)

    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 x214
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contact

    Dr Barbara Catinella
    Australian Research Council Future Fellow
    Centre for Astrophysics & Supercomputing
    Swinburne University of Technology
    Australia
    Tel: +61 3 9214 4918
    bcatinella@swin.edu.au

    Using the world’s largest radio telescope, two astronomers from Swinburne University of Technology in Australia have detected the faint signal emitted by atomic hydrogen gas in galaxies three billion light years from Earth, breaking the previous record distance by 500 million light years. Their results appear in a paper published in the journal Monthly Notices of the Royal Astronomical Society.

    a
    The 305-m Arecibo radio observatory in Puerto Rico, which was used to detect the hydrogen gas in these distant galaxies. Credit: Arecibo Observatory/NAIC.

    Using the 305-m diameter Arecibo radio telescope in Puerto Rico, Dr Barbara Catinella and Dr Luca Cortese measured the hydrogen gas content of nearly 40 galaxies at distances of up to three billion light years. By doing so, the two scientists found a unique population of galaxies hosting huge reservoirs of hydrogen gas, the fuel for forming new stars like our Sun.

    These very gas-rich systems each contain between 20 and 80 billion times the mass of the Sun in atomic gas. Such galaxies are rare, but astronomers believe that they were more common in the past, when the Universe was younger.

    “Atomic hydrogen gas is the fuel out of which new stars are formed, hence it is a crucial component to study if we are to understand how galaxies form and evolve,” study leader Dr Catinella said.

    “Because of the limitations of current instruments, astronomers still know very little about the gas content of galaxies beyond our local neighbourhood.”

    Local Group
    Local Group

    Co-author Dr Luca Cortese said detecting atomic hydrogen emission from distant galaxies is very challenging.

    “The signals are not only weak, but they appear at radio frequencies that are used by communication devices and radars, which generate signals billions of times stronger than the cosmic ones that we are trying to detect.”

    4
    Images of four distant galaxies observed with the Arecibo radio telescope, which have been found to host huge reservoirs of atomic hydrogen gas. Credit: Sloan Digital Sky Survey.Measuring the atomic hydrogen signal emitted by distant galaxies is one of the main scientific drivers behind the billion dollar Square Kilometre Array (SKA) project, for which technology demonstrators like the Australian SKA Pathfinder are under construction. The Arecibo observations give astronomers a glimpse into the population of gas-rich galaxies that will be routinely discovered by these instruments in coming decades.

    Sloan Digital Sky Survey Telescope
    Sloan Digital Sky Survey Telescope

    SKA Square Kilometer Array

    SKA Pathfinder Radio Telescope
    SKA Pathfinder Radio Telescope

    This project started as an experiment to see at what distances astronomers were able to detect the signal from atomic hydrogen in galaxies.

    “The outcome vastly exceeded our initial expectations,” Dr Catinella said.

    “Not only did we detect radio signals emitted by distant galaxies when the Universe was three billion years younger, but their gas reservoirs turned out to be unexpectedly large, about 10 times larger than the mass of hydrogen in our Milky Way. Such a huge amount of fuel will be able to feed star formation in these galaxies for several billion years in the future.”

    Further studies will seek to understand why these galaxies have not yet converted a great part of their gas into stars. The SKA and its pathfinders will be the key to solving this mystery.

    Further information

    The new results are published in B. Catinella & L. Cortese, HIGHz: A Survey of the Most HI-Massive Galaxies at z~0.2, Monthly Notices of the Royal Astronomical Society, in press, published by Oxford University Press (link will go live on 9 December 2014). A preprint is available on the arXiv.

    The research was supported under the Australian Research Council’s Future Fellowship and Discovery funding schemes.

    See the full article here.

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  • richardmitnick 8:26 am on November 1, 2014 Permalink | Reply
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    From RAS: “When did galaxies settle down?” 

    Royal Astronomical Society

    Royal Astronomical Society

    30 October 2014
    Media contact
    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 / 4582
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contact
    Dr Brooke Simmons
    University of Oxford
    Tel: +44 (0)1865 273637
    brooke.simmons@astro.ox.ac.uk

    Astronomers have long sought to understand exactly how the universe evolved from its earliest history to the cosmos we see around us in the present day. In particular, the way that galaxies form and develop is still a matter for debate. Now a group of researchers have used the collective efforts of the hundreds of thousands of people that volunteer for the Galaxy Zoo project to shed some light on this problem. They find that galaxies may have settled into their current form some two billion years earlier than previously thought.

    gz
    A Hubble Space Telescope image of a spiral galaxy seen when the Universe was less than a third of its current age, yet showing the same barred feature as much older, settled disk galaxies. Credit: NASA, ESA, J. Kartaltepe (NOAO), C. Lintott (Oxford), H. Ferguson (STScI), S. Faber (UCO).

    Dr Brooke Simmons of the University of Oxford and her collaborators describe the work in a paper in Monthly Notices of the Royal Astronomical Society. The team set Zoo volunteers the task of classifying the shapes of tens of thousands of galaxies observed by the Hubble Space Telescope. These objects are typically very distant, so we see them as they appeared more than 10 billion years ago, when the universe was about 3 billion years old, less than a quarter of its present age.

    NASA Hubble Telescope
    NASA Hubble schematic
    NASA/ESA Hubble

    The newly classified galaxies are striking in that they look a lot like those in today’s universe, with disks, bars and spiral arms. But theorists predict that these should have taken another 2 billion years to begin to form, so things seem to have been settling down a lot earlier than expected.

    ngc
    A European Southern Observatory image of the barred spiral galaxy NGC 1365, rotated to match the orientation of the first image. NGC 1365 is about 56 million light years away, so we see it as it appears 56 million years ago, or 10 billion years later than the galaxy in the HST image. Credit: ESO/IDA/Danish 1.5 m/ R. Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron. Brooke comments: “When we started looking for these galaxies, we didn’t really know what we’d find. We had predictions from galaxy simulations that we shouldn’t find any of the barred features that we see in nearby, evolved galaxies, because very young galaxies might be too agitated for them to form.”

    ‘But we now know that isn’t the case. With the public helping us search through many thousands of images of distant galaxies, we discovered that some galaxies settle very early on in the Universe.”

    See the full article here.

    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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  • richardmitnick 4:45 pm on September 22, 2014 Permalink | Reply
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    From RAS: “Finding hints of gravitational waves in the stars” 

    Royal Astronomical Society

    Royal Astronomical Society

    September 22, 2014

    Media contact

    Kendra Snyder
    Manager of Science Communication
    Department of Communications
    American Museum of Natural History
    New York
    USA
    Tel: +1 212 496 3419
    ksnyder@amnh.org

    Science contacts

    Prof Barry L McKernan
    Department of Astrophysics
    American Museum of Natural History
    New York
    USA
    bmckernan@amnh.org

    Saavik K Ford
    Associate Professor
    American Museum of Natural History
    New York
    USA
    sford@amnh.org
    Scientists have shown how gravitational waves—invisible ripples in the fabric of space and time that propagate through the universe—might be “seen” by looking at the stars. The new model proposes that a star that oscillates at the same frequency as a gravitational wave will absorb energy from that wave and brighten, an overlooked prediction of [Albert] Einstein’s 1916 theory of general relativity. The study, which was published today in the journal Monthly Notices of the Royal Astronomical Society: Letters, contradicts previous assumptions about the behaviour of gravitational waves.

    “It’s pretty cool that a hundred years after Einstein proposed this theory, we’re still finding hidden gems,” said Barry McKernan, a research associate in the American Museum of Natural History’s Department of Astrophysics, who is also a professor at CUNY’s Borough of Manhattan Community College; a faculty member at CUNY’s Graduate Center; and a Kavli Scholar at the Kavli Institute for Theoretical Physics.

    Gravitational waves can be thought of like the sound waves emitted after an earthquake, but the source of the “tremors” in space are energetic events like supernovae (exploding stars), binary neutron stars (pairs of burned-out cores left behind when stars explode), or the mergers of black holes and neutron stars. Although scientists have long known about the existence of gravitational waves, they’ve never made direct observations but are attempting to do so through experiments on the ground and in space.

    gw
    An illustration of the gravitational waves generated by two black holes in orbit around one other. Credit: NASA. Part of the reason why detection is difficult is because the waves interact so weakly with matter. But McKernan and his colleagues from CUNY, the Harvard-Smithsonian Center for Astrophysics, the Institute for Advanced Study, and Columbia University, suggest that gravitational waves could have more of an effect on matter than previously thought.

    The new model shows that stars with oscillations—vibrations—that match the frequency of gravitational waves passing through them can resonate and absorb a large amount of energy from the ripples.

    “It’s like if you have a spring that’s vibrating at a particular frequency and you hit it at the same frequency, you’ll make the oscillation stronger,” McKernan said. “The same thing applies with gravitational waves.”

    If these stars absorb a large pulse of energy, they can be “pumped up” temporarily and made brighter than normal while they discharge the energy over time. This could provide scientists with another way to detect gravitational waves indirectly.

    “You can think of stars as bars on a xylophone—they all have a different natural oscillation frequency,” said co-author Saavik Ford, who is a research associate in the Museum’s Department of Astrophysics as well as a professor at the Borough of Manhattan Community College, CUNY; a faculty member at CUNY’s Graduate Center; and a Kavli Scholar at the Kavli Institute for Theoretical Physics.

    ‘If you have two black holes merging with each other and emitting gravitational waves at a certain frequency, you’re only going to hit one of the bars on the xylophone at a time. But because the black holes decay as they come closer together, the frequency of the gravitational waves changes and you’ll hit a sequence of notes. So you’ll likely see the big stars lighting up first followed by smaller and smaller ones.”

    The work also presents a different way to indirectly detect gravitational waves. From the perspective of a gravitational wave detector on Earth or in space, when a star at the right frequency passes in front of an energetic source such as merging black holes, the detector will see a drop in the intensity of gravitational waves measured. In other words, stars—including our own Sun—can eclipse background sources of gravitational waves.

    “You usually think of stars as being eclipsed by something, not the other way around,” McKernan said.

    The researchers will continue to study these predictions and try to determine how long it would take to observe these effects from a telescope or detector.

    See the full article here.

    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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  • richardmitnick 8:22 am on September 19, 2014 Permalink | Reply
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    From RAS: “Monster galaxies gain weight by eating smaller neighbours” 

    Royal Astronomical Society

    Royal Astronomical Society

    Friday, 19 September 2014
    Media contact

    Kirsten Gottschalk
    Media Contact, ICRAR (Perth, GMT +8:00)
    Tel: +61 8 6488 7771
    Mob: +61 438 361 876
    kirsten.gottschalk@icrar.org

    University of Western Australia Media Office
    Tel: +61 8 6488 7977

    Science contacts

    Dr Aaron Robotham
    ICRAR – UWA (Currently travelling in South Africa, GMT +2:00)
    aaron.robotham@icrar.org

    Professor Simon Driver
    Principal Investigator of the GAMA project
    ICRAR – UWA (Perth, GMT +8:00)
    Tel: +61 8 6488 7747
    simon.driver@icrar.org

    Massive galaxies in the Universe have stopped making their own stars and are instead snacking on nearby galaxies, according to research by Australian scientists. They publish their results in the journal Monthly Notices of the Royal Astronomical Society.

    Astronomers looked at more than 22,000 galaxies and found that while smaller galaxies are very efficient at creating stars from gas, the most massive galaxies are much less efficient at star formation, producing hardly any new stars themselves, and instead grow by eating other galaxies.

    Dr Aaron Robotham, who is based at the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said smaller ‘dwarf’ galaxies were being eaten by their larger counterparts.

    “All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” he said.

    “Then every now and then they get completely cannibalised by some much larger galaxy.”

    many
    Some of the many thousands of merging galaxies identified within the GAMA survey. Credit: Professor Simon Driver and Dr Aaron Robotham, ICRAR. Dr Robotham, who led the research, said our own Milky Way is at a tipping point and is expected to now grow mainly by eating smaller galaxies, rather than by collecting gas.

    “The Milky Way hasn’t merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we’ve cannibalised” he said.

    “We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.”

    smc
    The two-color image shows an overview of the full Small Magellanic Cloud (SMC) and was composed from two images from the Digitized Sky Survey 2. The field of view is slightly larger than 3.5 × 3.6 degrees. N66 with the open star cluster NGC 346 is the largest of the star-forming regions seen below the center of the SMC.
    Date 10 November 2005
    Source http://www.spacetelescope.org/images/html/heic0514c.html (direct link)
    Author NASA/ESA Hubble and Digitized Sky Survey 2

    lmc
    Large Magellanic Cloud
    No text

    NASA Hubble Telescope
    NASA/ESA Hubble

    Sloan Digital Sky Survey Telescope
    Sloan Digital Sky Survey Telescope at Apache Point

    But Dr Robotham said the Milky Way is eventually going to get its comeuppance when it merges with the nearby Andromeda Galaxy in about five billion years.

    andro
    Andromeda Galaxy
    The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. The image also shows Messier Objects 32 and 110, as well as NGC 206 (a bright star cloud in the Andromeda Galaxy) and the star Nu Andromedae. This image was taken using a hydrogen-alpha filter.
    18 September 2010, Adam Evans

    “Technically, Andromeda will eat us because it’s the more massive one” he said.

    Almost all of the data for the research was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy And Mass Assembly (GAMA) survey, which is led by Professor Simon Driver at ICRAR.

    aat
    aai
    Anglo-Australian Telescope

    The GAMA survey involves more than 90 scientists and took seven years to complete. This study is one of over 60 publications to have come from the work, with another 180 currently in progress.

    Dr Robotham said as galaxies grow, they have a stronger gravitational field and can therefore more easily pull in their neighbours. He said the reason star formation slows down in really massive galaxies is thought to be because of extreme feedback events in a very bright region at the centre of a galaxy known as an active galactic nucleus.

    “The topic is much debated, but a popular mechanism is where the active galactic nucleus basically cooks the gas and prevents it from cooling down to form stars,” Dr Robotham said.

    Ultimately, gravity is expected to cause all the galaxies in bound groups and clusters to merge into a few super-giant galaxies, although we will have to wait many billions of years before that happens.

    “If you waited a really, really, really long time that would eventually happen, but by really long I mean many times the age of the Universe so far,” Dr Robotham explained.

    See the full article here.

    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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  • richardmitnick 11:14 am on September 16, 2014 Permalink | Reply
    Tags: , , , , , Royal Astronomical Society   

    From RAS: “219 million stars: a detailed catalogue of the visible Milky Way” 

    Royal Astronomical Society

    Royal Astronomical Society

    16 September 2014
    Media contact

    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contacts

    Dr Geert Barentsen
    University of Hertfordshire
    Tel: +44 (0)1707 284603
    g.barentsen@herts.ac.uk

    Prof. Janet Drew
    University of Hertfordshire
    Tel: +44 (0)1707 286576
    j.drew@herts.ac.uk

    A new catalogue of the visible part of the northern part of our home Galaxy, the Milky Way, includes no fewer than 219 million stars. Geert Barentsen of the University of Hertfordshire led a team who assembled the catalogue in a ten year programme using the Isaac Newton Telescope (INT) on La Palma in the Canary Islands. Their work appears today in the journal Monthly Notices of the Royal Astronomical Society.

    Isaac Newton 2.5m telescope
    Isaac Newton 2.5m telescope interior
    Isaac Newton Telescope

    dense
    A density map of part of the Milky Way disk, constructed from IPHAS data. The axes show galactic latitude and longitude, coordinates that relate to the position of the centre of the galaxy. The mapped data are the counts of stars detected in i, the longer (redder) wavelength broad band of the survey, down to a faint limit of 19th magnitude. Although this is just a small section of the full map, it portrays in exquisite detail the complex patterns of obscuration due to interstellar dust. Credit: Hywel Farnhill, University of Hertfordshire.

    From dark sky sites on Earth, the Milky Way appears as a glowing band stretching across the sky. To astronomers, it is the disk of our own galaxy, a system stretching across 100,000 light-years, seen edge-on from our vantage point orbiting the Sun. The disk contains the majority of the stars in the galaxy, including the Sun, and the densest concentrations of dust and gas.

    The unaided human eye struggles to distinguish individual objects in this crowded region of the sky, but the 2.5-metre mirror of the INT enabled the scientists to resolve and chart 219 million separate stars. The INT programme charted all the stars brighter than 20th magnitude – or 1 million times fainter than can be seen with the human eye.

    Using the catalogue, the scientists have put together an extraordinarily detailed map of the disk of the Galaxy that shows how the density of stars varies, giving them a new and vivid insight into the structure of this vast system of stars, gas and dust.

    The image included here, a cut-out from a stellar density map mined directly from the released catalogue, illustrates the new view obtained. The Turner-like brush strokes of dust shadows would grace the wall of any art gallery. Maps like these also stand as useful tests of new-generation models for the Milky Way.

    The production of the catalogue, IPHAS DR2 (the second data release from the survey programme The INT Photometric H-alpha Survey of the Northern Galactic Plane, IPHAS), is an example of modern astronomy’s exploitation of ‘big data’. It contains information on 219 million detected objects, each of which is summarised in 99 different attributes.

    With this catalogue release, the team are offering the world community free access to measurements taken through two broad band filters capturing light at the red end of the visible spectrum, and in a narrow band capturing the brightest hydrogen emission line, H-alpha. The inclusion of H-alpha also enables exquisite imaging of the nebulae (glowing clouds of gas) found in greatest number within the disk of the Milky Way. The stellar density map illustrated here is derived from the longest (reddest) wavelength band in which the darkening effect of the dust is moderated in a way that brings out more of its structural detail, compared to maps built at shorter (bluer) wavelengths.

    See the full article here.

    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

    ScienceSprings relies on technology from

    MAINGEAR computers

    Lenovo
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    Dell
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