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  • richardmitnick 3:29 pm on October 20, 2014 Permalink | Reply
    Tags: , , , , , Cosmology,   

    From astrobio.net: ” Exomoons Could Be Abundant Sources Of Habitability” 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 20, 2014
    Elizabeth Howell

    With about 4,000 planet candidates from the Kepler Space Telescope data to analyze so far, astronomers are busy trying to figure out questions about habitability. What size planet could host life? How far from its star does it need to be? What would its atmosphere need to be made of?

    NASA Kepler Telescope
    NASA/Kepler

    Look at our own solar system, however, and there’s a big gap in the information we need. Most of the planets have moons, so surely at least some of the Kepler finds would have them as well. Tracking down these tiny worlds, however, is a challenge.

    europa
    Europa is one of the moons in our solar system that could host life. What about beyond the solar system? Credit: NASA/JPL/Ted Stryk

    A new paper in the journal Astrobiology, called Formation, Habitability, and Detection of Extrasolar Moons, goes over this mostly unexplored field of extrasolar research. The scientists do an extensive literature review of what is supposed about moons beyond the Solar System, and they add intriguing new results.

    A wealth of moons exist in our own solar system that could host life. Icy Europa, which is circling Jupiter, was recently discovered to have plumes of water erupting from its surface. Titan, in orbit around Saturn, is the only known moon with an atmosphere, and could have the precursor elements to life in its hydrocarbon seas that are warmed by Saturn’s heat. Other candidates for extraterrestrial hosts include Jupiter’s moons Callisto and Ganymede, as well as Saturn’s satellite Enceladus.

    Lead author René Heller, an astrophysicist at the Origins Institute at McMaster University, in Ontario, Canada, said some exomoons could be even better candidates for life than many exoplanets.

    “Moons have separate energy sources,” he said. “While the habitability of terrestrial planets is mostly determined by stellar illumination, moons also receive reflected stellar light from the planet as well as thermal emission from the planet itself.”

    Moreover, a planet like Jupiter — which hosts most of the moons in the Solar System that could support life — provides even more potential energy sources, he added. The planet is still shrinking and thereby converts gravitational energy into heat, so that it actually emits more light than it receives from the Sun, providing yet more illumination. Besides that, moons orbiting close to a gas giant are flexed by the planet’s gravity, providing potential tidal heating as an internal, geological heat source.

    tri
    Triton’s odd, melted appearance hint that the moon was captured and altered by Neptune. Credit: NASA

    Finding the first exomoon

    The first challenge in studying exomoons outside our Solar System is to actually find one. Earlier this year, NASA-funded researchers reported the possible discovery of such a moon, but this claim was ambiguous and can never be confirmed. That’s because it appeared as a one-time event, when one star passed in front of another, acting as a sort of gravitational lens that amplified the background star. Two objects popped out in the gravitational lens in the foreground — either a planet and a star, or a planet and an extremely heavy exomoon.

    For his part, Heller is convinced that exomoons are lurking in the Kepler data, but they have not been discovered yet. Only one project right now is dedicated to searching for exomoons, and is led by David Kipping at the Canadian Space Agency. His group has published several papers investigating 20 Kepler planets and candidates in total. The big restriction to their efforts is computational power, as their simulations require supercomputers.

    Another limiting factor is the number of observatories that can search for exomoons. To detect them, at least a handful of transits of the planet-moon system across their common host star would be required to absolutely make sure that the companion is a moon, Heller said. Also, the planet with the moon would have to be fairly far from its star, and decidedly not those close-in hot Jupiters that take only a few days to make an orbit. In that zone, the gravitational drag of the star would fatally perturb any moon’s orbit.

    Heller estimates that a telescope would need to stare constantly at the same patch of sky for several hundred days, minimum, to pick up an exomoon. Kepler fulfilled that obligation in spades with its four years of data gazing at the same spot in the sky, but astronomers will have to wait again for that opportunity.

    Because two of Kepler’s gyroscopes (pointing devices) have failed, Kepler’s new mission will use the pressure of the Sun to keep it steady. But it can only now point to the same region of the sky for about 80 days at at time because the telescope will periodically need to be moved so as not to risk placing its optics too close to the Sun.

    NASA’s forthcoming Transiting Exoplanet Survey Satellite [TESS} is only expected to look at a given field for 70 days. Further into the future, the European Space Agency’s PLAnetary Transits and Oscillations of stars (PLATO) will launch in 2024 for what is a planned six-year mission looking at several spots in the sky.

    NASA TESS
    NASA/TESS

    ESA PLATO
    ESA PLATO

    “PLATO is the next step, with a comparable accuracy to Kepler but a much larger field of view and hopefully a longer field of view coverage,” Heller said.

    Clues in our solar system

    pla
    Thousands of exoplanets and exoplanet candidates have been discovered, but astronomers are still searching for exomoons. Credit: ESA – C. Carreau

    Heller characterizes moons as an under-appreciated feature of extrasolar planetary systems. Just by looking around us in the Solar System, he says, astronomers have been able to make crucial explanations about how the moons must have formed and evolved together with their planets. Moons thus carry information about the substructure of planet evolution, which is not accessible by planet observations alone.

    The Earth’s moon, for example, was likely formed when a Mars-sized object collided with the proto-Earth and produced a debris disk. Over time, that debris coalesced into our moon.

    While Heller says the literature mostly focuses on collision scenarios between an Earth-sized object and a Mars-sized object, he doesn’t see any reason why crashes on a bigger scale might not happen. Perhaps an Earth-sized object crashed into an object that was five times the mass of Earth, producing an extrasolar Earth-Earth binary planet system, he suggests.

    Another collision scenario likely took place at Uranus. The gas giant’s rotation is tilted about 90 degrees in its orbit around the Sun. In other words, it is rolling on its side. More intriguing, its two dozen moons follow Uranus’ rotational equator, and they do not orbit in the same plane as Uranus’ track around the Sun. This scenario suggests that Uranus was hit multiple times by huge objects instead of just once, Heller said.

    Examining mighty Jupiter’s moons gives astronomers a sense of how high temperatures were in the disk that formed the gas giant and its satellites, Heller added. Ganymede, for example, is an icy moon. Models indicate that beyond Ganymede’s orbit (at about 15 Jupiter radii) it is sufficiently cold for water to pass from the gas to the solid (ice) stage, so the regular moons in these regions are very water-rich compared to the inner, mostly rocky moons Io and Europa.

    “It sounds a bit technical, but we couldn’t have this information about planetary accretion if we did not have the moons today to observe,” Heller said.

    Some moons could also have been captured, such as Neptune’s large moon, Triton. The moon orbits in a direction opposite to other moons in Neptune‘s system (and in fact, opposite to the direction of other large moons in the Solar System.) Plus, its odd terrain suggests that it used to be a free-floating object that was captured by Neptune’s gravity. Neptune is so huge that it raised tides within the moon, reforming its surface.

    Even comparing the different types of moons around planets in the Solar System reveals different timescales of formation. Jupiter includes four moons similar in size to Earth’s moon (Europa, Callisto, Ganymede and Io), while the next largest planet in our solar system, Saturn, only has one large moon called Titan. Astronomers believe Saturn has only one large moon because the gas that formed objects in our solar system was more plentiful in Jupiter’s system to provide material for the moons to form.

    The gas abundance happened as a consequence of the huge gas giant creating a void in the material surrounding our young Sun, pulling the material in for its moons. Saturn was not quite large enough to do this, resulting in fewer large moons.

    More strange situations could exist beyond our solar system’s boundaries, but it will take a dedicated search to find exomoons. Once they are discovered, however, they will allow planet formation and evolution studies on a completely new level.

    This research was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Center for Exoplanets and Habitable Worlds, which is supported by the Pennsylvania State University, the Pennsylvania Space Grant Consortium, the National Science Foundation (NSF) the NASA Astrobiology Institute.

    See the full article here.

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  • richardmitnick 2:20 pm on October 19, 2014 Permalink | Reply
    Tags: , , , , Cosmology, ,   

    From astrobio.net: “Rediscovering Venus to Find Faraway Earths “ 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 19, 2014
    fa
    Contact:
    Lyndsay Meyer
    The Optical Society
    +1.202.416.1435
    lmeyer@osa.org

    New optical device designed to measure gravitational pull of a planet should speed the search for Earth-like exoplanets.

    Astronomers Chih-Hao Li and David Phillips of the Harvard-Smithsonian Center for Astrophysics want to rediscover Venus—that familiar, nearby planet stargazers can see with the naked eye much of the year.

    Granted, humans first discovered Venus in ancient times. But Li and Phillips have something distinctly modern in mind. They plan to find the second planet again using a powerful new optical device installed on the Italian National Telescope that will measure Venus’ precise gravitational pull on the sun. If they succeed, their first-of-its-kind demonstration of this new technology will be used for finding Earth-like exoplanets orbiting distant stars.

    Italian National Telescope Galileo
    Italian National Telescope Galileo Internal
    Galileo Italian National Telescope

    “We are building a telescope that will let us see the sun the way we would see other stars,” said Phillips, who is a staff scientist at the Harvard-Smithsonian Center for Astrophysics. He and Li, a research associate at the Center for Astrophysics, will describe the device in a paper to be presented at The Optical Society’s (OSA) 98th Annual Meeting, Frontiers in Optics, being held Oct. 19-23 in Tucson, Arizona, USA. Li is the lead author of the paper, which has 12 collaborators.

    Astronomers have identified more than 1,700 exoplanets, some as far as hundreds of light years away. Most were discovered by the traditional transit method, which measures the decrease in brightness when a planet orbiting a distant star transits that luminous body, moving directly between the Earth and the star. This provides information about the planet’s size, but not its mass.

    Li and Phillips are developing a new laser-based technology known as the green astro-comb for use with the “radial velocity method,” which offers complementary information about the mass of the distant planet.

    From this information, astronomers will be able to determine whether distant exoplanets they discover are rocky worlds like Earth or less dense gas giants like Jupiter. The method is precise enough to help astronomers identify Earth-like planets in the “habitable zone,” the orbital distance “sweet-spot” where water exists as a liquid.

    Better Precision with a Laser

    The radial velocity method works by measuring how exoplanet gravity changes the light emitted from its star. As exoplanets circle a star, their gravitation tugs at the star changing the speed with which it moves toward or away from Earth by a small amount. The star speeds up slightly as it approaches Earth, with each light wave taking a fraction of a second less time to arrive than the wave before it.

    To an observer on Earth, the crests of these waves look closer together than they should, so they appear to have a higher frequency and look bluer. As the star recedes, the crests move further apart and the frequencies seem lower and redder.

    astro
    The astro-comb calibrates the Italian National Telescope’s HARPS-Nspectrograph using an observation of the asteroid Vesta. The top figure is a colorizedversion of the raw HARPS-N spectrum, showing the astro-comb calibration dottedlines and the sun’s spectrum reflected off Vesta as mostly solid vertical lines.The middle figure shows the raw data converted to a very precise standard one-dimensionalplot of spectral intensity vs. wavelength. The very regular astro-comb calibrationspectrum is below below. Credit: David Phillips

    This motion-based frequency change is known as the Doppler shift. Astronomers measure it by capturing the spectrum of a star on the pixels of a digital camera and watching how it changes over time.

    Today’s best spectrographs are only capable of measuring Doppler shifts caused by velocity changes of 1 meter per second or more. Only large gas giants or “super-earths” close to their host stars have enough gravity to cause those changes.

    The new astro-comb Li, Phillips and their colleagues are developing, however, will be able to detect Doppler shifts as small as 10 centimeters per second—small enough to find habitable zone Earth-like planets, even from hundreds of light years away.

    “The astro-comb works by injecting 8,000 lines of laser light into the spectrograph. They hit the same pixels as starlight of the same wavelength. This creates a comb-like set of lines that lets us map the spectrograph down to 1/10,000 of a pixel. So if I have light on this section of the pixel, I can tell you the precise wavelength,” Phillips explained.

    “By calibrating the spectrograph this way, we can take into account very small changes in temperature or humidity that affect the performance of the spectrograph. This way, we can compare data we take tonight with data from the same star five years from now and find those very small Doppler shifts,” he said.

    Seeing Green

    Li and his co-researchers pioneered the astro-comb several years ago, but it only worked with infrared and blue light. Their new version of the astro-comb lets astronomers measure green light—which is better for finding exoplanets.

    “The stars we look at are brightest in the green visible range, and this is the range spectrographs are built to handle,” Phillips said.

    Building the green astro-comb was a challenge, since the researchers needed to convert red laser light to green frequencies. They did it by making small fibers that convert one color of light to another.

    pla
    A slowly rotating planet is not guaranteed to be habitable, as is evident when looking at the inhospitable Venus. Credit: NASA/JPL/Caltech

    “Red light goes in and green light comes out,” Phillips said. “Even though I see it every day and understand the physics, it looks like magic.”

    The researchers plan to test the green astro-comb by pointing it at our sun, analyzing its spectrum to see if they can find Venus and rediscover its characteristic period of revolution, its size, its mass and its composition.

    “We know a lot about Venus, and we can compare our answers to what we already know, so we are more confident about our answers when we point our spectrographs at distant stars,” Li said.

    The Harvard-Smithsonian team is installing this device on the High-Accuracy Radial Velocity Planet Searcher-North (HARPS-N), a new spectrograph designed to search for exoplanets using the Italian National Telescope.

    “We will look at the thousands of potential exoplanets identified by the Kepler satellite telescope by the transit method. Together, our two methods can tell us a lot about those worlds,” Li said.

    And, because he will have already discovered Venus, he will be more certain of the answers.

    See the full article here.

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  • richardmitnick 9:43 pm on October 18, 2014 Permalink | Reply
    Tags: , , , Cosmology,   

    From SPACE.com: “Comet Siding Spring at Mars: How a Rare Celestial Event Was Discovered” 

    space-dot-com logo

    SPACE.com

    October 18, 2014
    Elizabeth Howell

    A comet that was born before the Earth formed is flying in from the edge of the solar system, bound for a dramatic date with Mars on Sunday (Oct. 19).

    Comet Siding Spring — unknown and undiscovered until 2013 — will zoom past the Red Planet Sunday afternoon in an encounter that could help scientists better understand how the solar system came to be.

    Siding Spring will fly 87,000 miles (139,500 kilometers) from Mars at 2:27 p.m. EDT (1827 GMT) Sunday, about one-third of the distance from the Earth to the moon. Researchers will observe the close encounter with the fleet of orbiters and rovers at the Red Planet.

    Siding Spring is the first comet from the Oort Cloud, a collection of icy bodies at the edge of the solar system that will be observed up close by spacecraft. All comets examined in the past came from closer in, around Jupiter’s orbit or the edge of the Kuiper Belt, a huge set of icy objects beyond Neptune.

    oort
    Artist’s conception of the Oort Cloud

    kb
    Known objects in the Kuiper belt, derived from data from the Minor Planet Center. Objects in the main belt are colored green, whereas scattered objects are colored orange. The four outer planets are blue. Neptune’s few known trojans are yellow, whereas Jupiter’s are pink. The scattered objects between Jupiter’s orbit and the Kuiper belt are known as centaurs. The scale is in astronomical units. The pronounced gap at the bottom is due to difficulties in detection against the background of the plane of the Milky Way.

    “We can’t get to an Oort Cloud comet with our current rockets,” Carey Lisse, a senior astrophysicist at the Johns Hopkins University Applied Physics Laboratory, said during a NASA news conference last week. “These orbits are very long and extended — and at very great velocities … It’s a free flyby, if you will, and that’s a very fantastic event for us to study.”

    A failed planet

    image
    In a rare celestial event, a comet will pass closer to Mars than the moon is from Earth. See how the Comet Siding Spring flyby of Mars works in this Space.com infographic.
    Credit: by Karl Tate, Infographics Artist

    Siding Spring was created in the first few million years of Earth’s solar system, Lisse said. It likely formed somewhere between the orbits of Jupiter and Neptune, where many similar objects coalesced into the giant planets. But a gravitational push kicked Siding Spring out into the Oort Cloud; it took another jolt from a passing star a million years ago or so to send it toward the inner solar system.

    Half of the comet is rocky, and the other half is made up of volatile ices, such as water and carbon dioxide. Its flight past Mars is the first time it will make it into the solar system, past Jupiter’s orbit. The comet just recently crossed the “water-ice line,” the point where water can exist as a liquid in the solar system.

    Siding Spring, which Lisse said is about the size of an Appalachian mountain, will swing by Mars in a retrograde direction, the opposite way in which the planets orbit around the sun. This means any dust that comes off the comet will be moving at about 119,000 mph (190,000 km/h) relative to Mars.

    “Anything that comes off the comet that hits either Mars or the spacecraft is going to pack a real large amount of kinetic energy — a real wallop — so that’s one of the things that we’ve been worried about,” Lisse said.

    As a result, NASA has maneuvered its three operational Mars orbiters to be on the “safe” side of the Red Planet when dust exposure is highest.

    NASA investigations

    The comet was first discovered in January 2013 by Robert McNaught at the Siding Spring Observatory in Australia. Ever since then, scientists have been studying the celestial visitor with a variety of space- and ground-based assets, in an attempt to learn more about its history.

    Siding Spring Observatory
    Siding Spring Observatory Interior
    Siding Springs Observatory

    To learn about the comet, scientists will have to get an up-close look at its nucleus, to see its shape, size and composition. If all goes according to plan, NASA’s Mars Reconnaissance Orbiter will take high-resolution pictures of the comet’s heart, making it the first time an Oort Cloud comet’s nucleus will be seen up close.

    NASA Mars Reconnaisence Orbiter
    NASA’s Mars Reconnaissance Orbiter

    NASA’s Hubble, Swift and Spitzer space telescopes have mapped out the comet’s dust, water molecules and carbon dioxide. For now, it looks like dust is coming off more slowly than researchers had expected. Little activity was seen with the water ice until June, when the comet got close enough to the sun for ice to sublimate.

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA SWIFT Telescope
    NASA/Swift

    NASA Spitzer Telescope
    NASA/Spitzer

    Some other planned observations will come from NASA’s Chandra X-Ray telescope (which will look for any material thrown in Mars’ atmosphere), and the newly arrived Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, which will see how the Red Planet’s atmosphere reacts as the comet passes by.

    NASA Chandra Telescope
    NASA/Chandra

    NASA Mars MAVEN
    NASA MAVEN

    NASA’s Curiosity and Opportunity rovers will also participate in the campaign, attempting to take the first images of a comet from the surface of another planet.

    NASA Mars Curiosity Rover
    NASA Curiosity

    NASA Mars Opportunity Rover
    NASA Opportunity

    See the full article, with video, here.

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  • richardmitnick 4:24 pm on October 17, 2014 Permalink | Reply
    Tags: , , , Cosmology, ,   

    From Daily Galaxy: “Long-Sought Source of Massive Supernovas Detected” 

    Daily Galaxy
    The Daily Galaxy

    October 17, 2014
    No Writer Credit

    For years astronomers have searched for the elusive progenitors of hydrogen-deficient stellar explosions without success. However, this changed in June 2013 with the appearance of supernova iPTF13bvn and the subsequent detection of an object at the same location in archival images obtained before the explosion using the HST. The interpretation of the observed object is controversial. The team led by [Melina] Bersten presented a self-consistent picture using models of supernova brightness and progenitor evolution. In their picture, the more massive star in a binary system explodes after transferring mass to its companion.

    A group of researchers recently presented a model that provides the first characterization of the progenitor for a hydrogen-deficient supernova. Their model predicts that a bright hot star, which is the binary companion to an exploding object, remains after the explosion. To verify their theory, the group secured observation time with the Hubble Space Telescope (HST) to search for such a remaining star. Their findings, which are reported in the October 2014 issue of The Astronomical Journal, have important implications for the evolution of massive stars.

    NASA Hubble Telescope
    NASA Hubble schematic
    NASA/ESA Hubble

    One of the challenges in astrophysics is identifying which star produces which supernova. This is particularly problematic for supernovae without hydrogen, which are called Types Ib or Ic, because the progenitors have yet to be detected directly.

    The ultimate question is: “How do progenitor stars remove their hydrogen-rich envelopes during their evolution?” Two competing mechanisms have been proposed. One hypothesizes that a strong wind produced by a very massive star blows the outer hydrogen layers, while the other suggests that a gravitationally bound binary companion star removes the outer layers. The latter case does not require a very massive star. Because these two scenarios predict vastly different progenitor stars, direct detection of the progenitor for this type of supernova can provide definitive clues about the preferred evolutionary path.

    When young Type Ib supernova iPTF13bvn was discovered in nearby Spiral_galaxy NGC 5806, astronomers hoped to find its progenitor. Inspecting the available HST images did indeed reveal an object, providing optimism that the first hydrogen-free supernova progenitor would at last be identified. Due to the object’s blue hue, it was initially suggested that the object was a very hot, very massive, evolved star with a compact structure, called a “Wolf-Rayet” star. (Using models of such stars, a group based in Geneva was able to reproduce the brightness and color of the pre-explosion object with a Wolf-Rayet star that was born with over 30 times the mass of the Sun and died with 11 times the solar mass.)

    ngc5806
    NGC 5806

    burt
    Image shows spiral galaxy NGC5806 Left top: Zoomed image of supernova iPTF13bvn just after the explosion. Left bottom: HST image taken before the explosion. Progenitor of iPTF13bvn was identified. Right: Spiral galaxy NGC5806 Left top: Zoomed image of supernova iPTF13bvn just after the explosion. Left bottom: HST image taken before the explosion. Progenitor of iPTF13bvn was identified. (Image Credit: Iair Arcavi, Weizmann Institute of Science, PTF)

    “Based on such suggestions, we decided to check if such a massive star is consistent with the supernova brightness evolution,” says Melina Bersten of Kavli IPMU who led the research. However, the results are inconsistent with a Wolf-Rayet star; the exploding star must have been merely four times the mass of the Sun, which is much smaller than a Wolf-Rayet star. “If the mass was this low and the supernova lacked hydrogen, our immediate conclusion is that the progenitor was part of a binary system,” adds Bersten.

    Because the problem requires a more elaborate solution, the team set out to simulate the evolution of a binary system with mass transfer in order to determine a configuration that can explain all the observational evidence (a blue pre-explosion object with a relatively low mass devoid of hydrogen). “We tested several configurations and came up with a family of possible solutions,” explains Omar Benvenuto of IALP, Argentina. “Interestingly, the mass transfer process dictates the observational properties of the exploding star, so it allows suitable solutions to be derived even if the mass of the stars is varied,” adds Benvenuto. The team chose the case where two stars are born with 20 and 19 times the mass of the Sun. The mass transfer process causes the larger star to retain only four times the solar mass before exploding. Most importantly, the smaller star may trap part of the transferred mass, becoming a very bright and hot star.

    The existence of a hot star would provide strong evidence for the binary model presented by Bersten and collaborators. Fortunately, such a prediction can be directly tested once the supernova fades because the hot companion should become evident. “We have requested and obtained observation time with the HST to search for the companion star in 2015,” comments Gaston Folatelli of Kavli IPMU. “Until then, we must wait patiently to see if we can identify the progenitor of a hydrogen-free supernova for the first time,” Bersten adds.

    See the full article here.

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  • richardmitnick 2:26 pm on October 17, 2014 Permalink | Reply
    Tags: , , , Cosmology,   

    From ESA: “Herschel’s view of Comet Siding Spring” 

    ESASpaceForEuropeBanner
    European Space Agency

    17 October 2014

    These three images show emission from the dust in the coma surrounding the nucleus of Comet C/2013 A1 – also known as Comet Siding Spring – as observed at three different far-infrared wavelengths with ESA’s Herschel space observatory.

    three

    ESA Herschel
    ESA Herschel schematic
    ESA/Herschel

    Discovered on 3 January 2013, Comet Siding Spring is an Oort Cloud comet on its first journey into the inner Solar System. It will reach perihelion – its closest approach to the Sun – on 25 October 2014 at 1.4 AU (about 210,000,000 km). Having spent most of its life far from the Sun, this comet is much more pristine than periodic comets – those that orbit the Sun every two hundred years or less – and for that reason is particularly interesting to study.

    oort
    Artists rendering of the Kuiper Belt and Oort Cloud.

    On 31 March 2013, not long after it was discovered, astronomers observed Comet Siding Spring with Herschel. This was just one month before the observatory exhausted its supply of liquid helium coolant and ceased to collect data. When Herschel observed it, the comet was about 6.5 AU from the Sun. The observations were performed following a proposal for Director’s Discretionary Time from Peter Mattisson from the Stockholm Amateur Astronomers (STAR) in Sweden.

    The three panels show the comet at wavelengths of 70 microns (shown in blue), 100 microns (shown in green) and 160 microns (shown in red). Telescopes observing at these long wavelengths see the direct thermal emission from dust in the comet’s coma.

    The coma is resolved at the two shorter wavelengths (in the left and central panels). Close inspection of these two images reveals that the coma’s shape is slightly elongated towards the left – in the direction opposite the Sun. From these images, astronomers estimated that the coma extends some 50,000 km from the comet’s nucleus. The structure of the coma can hardly be resolved at the longest wavelength probed by Herschel (in the right panel).

    These observations were also used to calculate the total mass of dust in the coma, which amounts to about 300,000,000 kg. At the time of the Herschel observations, the comet appeared to be quite active – astronomers estimated that the activity had begun even prior to the comet’s discovery, when it was about 8 AU from the Sun. Observations performed at a later stage with space and ground-based telescopes showed that the comet’s activity has increased quite slowly over the past months, which is quite unusual for an Oort Cloud comet. There are even some hints that the comet’s activity has declined recently.

    Astronomers have been closely monitoring the activity of Comet Siding Spring because, a few days before perihelion, the comet will have an historic close approach to Mars, passing some 140,000 km from the Red Planet on 19 October 2014. The comet’s current moderate activity is good news for the fleet of spacecraft that are operated at Mars by various space agencies (including ESA’s Mars Express) because it means a low risk of dust particles hitting the instruments on board.

    Since Oort Cloud comets are discovered with an extremely short notice before perihelion – a few years at most – it is virtually impossible to plan a space mission to fly by such a comet. This is what makes Comet Siding Spring and its closest approach to Mars truly unique, as the spacecraft at Mars will have the chance to observe an Oort Cloud comet from a distance that could not possibly be achieved otherwise.

    The analysis of the Herschel images was performed by Cs. Kiss (Konkoly Observatory, Budapest, Hungary), T.G. Müller (Max-Planck-Institut für extraterrestrische Physik, Garching, Germany), M. Kidger (ESAC, European Space Agency, Madrid, Spain), P. Mattisson (STAR, Stockholm Amateur Astronomers, Sweden), and G. Marton (Konkoly Observatory, Budapest, Hungary).

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 9:33 am on October 17, 2014 Permalink | Reply
    Tags: , , , Cosmology, NASA IRIS, ,   

    From SPACE.com: “NASA Probe Finds Nanoflares and Plasma ‘Bombs’ on Sun” 

    space-dot-com logo

    SPACE.com

    October 16, 2014
    Nola Taylor Redd

    The first results from a new NASA sun-studying spacecraft are in, and they reveal a complex and intriguing picture of Earth’s star.

    NASA’s Interface Region Imaging Spectrograph probe (IRIS) has observed ‘bombs’ of plasma on the sun, nanoflares that rapidly accelerate particles, and powerful jets that may drive the solar wind, among other phenomena, five new studies report.

    iris
    The completed IRIS observatory with solar arrays destroyed prior to launch. Credit: NASA

    While spacecraft can enter planetary atmospheres, they cannot fly through the outer atmosphere of the sun, where temperatures reach 3.5 million degrees Fahrenheit (2 million degrees Celsius). Probes like IRIS instead must study the star from a safe distance. Unlike previous instruments, IRIS can take far more detailed observations of the sun, capturing observations of regions only about 150 miles (240 kilometers) wide on a time scale of just a few seconds.

    “The combination of enhanced spatial and spectral resolution, [which are] both three to four times better than previous instruments, allows a much closer look [at the sun's atmosphere],” Hardi Peter of the Max Planck Institute for Solar System Research in Germany told Space.com by email. Peter was the lead author on a study of hot plasma ‘bombs’ on the sun.

    Nanoflare acceleration

    The surface of the sun, or photosphere, is the region visible to human eyes. Above the photosphere lie the hotter chromosphere and transition regions, which emit ultraviolet light that can only be observed from space. This is because Earth’s atmosphere absorbs most of this radiation before it reaches land-based instruments. The outer part of the solar atmosphere is called the corona.

    While much of the sun’s energy is generated in its core through hydrogen fusion, temperatures rise in the exterior layers moving out farther from the heat source. This means that something is powering that outer region, and scientists think the magnetic fields generated by the churning solar plasma provide at least part of the answer.

    In emerging active regions, magnetic fields rise through the surface into the upper atmosphere, like a string pulled upward. When the energy carried by the field lines becomes too great, they snap, disconnecting from one another and reconnecting with other broken field lines in a process known as magnetic reconnection.

    Paola Testa, of the Harvard-Smithsonian Center for Astrophysics, led a team that used IRIS to study the footprints of these loops, where he found that the intensity changed over a span of 20 to 60 seconds. Investigating possible causes, Testa determined that the variations were consistent with simulations of electrons generated from coronal nanoflares.

    “Nanoflares are short heating events releasing amounts of energy about a billion times smaller than large flares,” Testa said.

    fl
    Ultraviolet image of an active region on the sun, showing plasma at temperatures of 140,000 degrees. This image was captured by NASA’s IRIS spacecraft on Dec. 6, 2013.
    Credit: IRIS: LMSAL, NASA. Courtesy Bart De Pontieu, Lockheed Martin Solar & Astrophysics Laboratory

    Although smaller than their larger cousins, nanoflares occur more frequently, likely due to magnetic reconnection. Energy released during magnetic reconnection accelerates some particles to high energies, where they are emitted as radio waves and the highest energy X-rays. Scientists have observed these signals in medium and large flares, but for nanoflares, the rapidly moving electrons are too faint to detect directly using current instrumentation.

    “That is why our observations in the ultraviolet are particularly interesting,” Testa said. “They provide an alternative way to study these accelerated particles, although not directly observing them.”

    Hot bombs in cool regions

    In the cooler photosphere of the sun, where temperatures reach approximately 10,000 degrees F (5,500 degrees C), the magnetic fields convert a huge amount of energy from the magnetic energy stored in the field into thermal energy, heating the plasma. According to Peter, the amount of energy released would be enough to provide electric power to Germany for 8,000 years. The change creates a pocket of gas heated up to 180,000 degrees F (100,000 degrees C) in the middle of the cooler surface region.

    These pockets, or “bombs,” eject plasma. Upward-moving material probably disperses into the hot corona, Peter said, while the downward-moving plasma is quickly cooled to reach the same material as the rest of the photosphere, blending back in to the surrounding material.

    Previously, scientists spotted no indications that energy-releasing events in the photosphere would result in the high temperature spikes in pockets within the photosphere. The energy output required to heat the dense gas was thought to be too high to be obtainable.

    “With these new results that show the existence of hot pockets in cool gas, we have to either revise the amount of energy that can be supplied deep in the photosphere, or we have to think of a clever yet unknown mechanism to heat the cool, dense gas rapidly to these high temperatures,” Peter said.

    Do the twist

    In addition to disconnecting and reconnecting, the magnetic fields on the sun also twist. As the twisting field lines move away from the surface at 19 to 62 miles (30 to 100 km) per second, the nearby transition regions brighten to temperatures of up to 144,000 degrees F (80,000 C), far above the chromosphere’s average temperature of 7,800 degrees F (4,000 degrees C).

    IRIS’s detailed study of the sun revealed that the twists are far more widespread than suggested by previous studies. These twists occur in every magnetic region, both quiet and active. Observations of twists were made at IRIS’s maximum resolution, but other unresolved small-scale motions in the observations seemed to indicate the presence of even smaller twists in the field lines.

    Although the current data does not allow the scientists to determine the twists’ cause, IRIS science lead and first author Bart De Pontieu, of Lockheed Martin Solar and Astrophysics Laboratory, said that the twisting is most likely a signature of the so-called Alfven waves. These “magnetic waves [are] not unlike the waves that are generated after plucking a guitar string,” he said. The source of these waves also remains unknown.

    Another potential source could be the strong convective, or “boiling,” motions at the sun’s surface.

    “Numerical simulations of the solar convection suggest that torsional [twisting] motions can be generated, kind of like when you drain a bathtub, and you see swirling motions as the water drains out,” De Pontieu said.

    Scientists have several hypotheses for how the solar atmosphere is heated, and De Pontieu said the new observations provide constraints on these theories.

    “In particular, they provide support for models in which Alfven waves do much of the heavy lifting in the solar atmosphere,” he said.

    sun
    In its first released image of the sun, IRIS captured a view of the solar atmosphere. Credit: NASA

    As the closest and brightest star, the sun has been studied throughout history. Based on indirect evidence from Skylab and other missions in the 1970s and 1980s, astronomer Uri Feldman, of the Naval Research Laboratory, proposed the existence of “unresolved fine structures” (UFS), an important solar atmospheric component in the transition region between the chromosphere and the corona. Using IRIS’s instruments, a team lead by Viggo Hansteen, of the University of Oslo in Norway, determined that a series of low-lying magnetic loops constitute these UFS, settling a decades-long debate regarding their existence.

    The loops of the magnetic field light up for short spans of time, perhaps a minute, when the plasma in the loops are heated, either due to magnetic reconnection or the dissipation of Alfven waves. During magnetic reconnection, plasma is accelerated to 2 to 3 times the speed of sound. Sometimes the loops form in isolation; other times they are concentrated in a nest of loops.

    The debate regarding the loops’ existence stemmed in part from questions about the plasma; scientists questioned whether or not all of the plasma in the transition region was thermally connected to the corona. The presence of the low-lying loops in the transition region confirms that plasma reaching temperatures of 180,000 degrees F (100,000 degrees C) are heated by from the loops rather than the corona.

    Although the loops themselves don’t heat the corona, Hansteen said that they are probably heated with the same mechanism, though with a different response due to their higher density.

    “It is likely that these differences will allow us to focus more clearly on the nature of the unknown heating events themselves,” Hansteen said.

    Powering the solar wind

    The solar wind drives particles and plasma from the sun through the solar system. When the particles collide with Earth’s magnetic field, they produce beautiful auroras, and have the potential to interfere with satellites and communication systems. But the source of the solar wind remains a mystery.

    The fast-moving solar wind travels hundreds of kilometers per second, carrying low-density materials. Previous instruments lacked the ability to study the small-scale regions thought to be responsible for the wind with the precision necessary to understand it.

    Scientists suspect that the solar wind originates from the bright network structures on the sun, appearing as bright lanes enclosing dark cells. These lanes flow outward from the sun, funneled by the magnetic structure, and eventually merge together into a single solar wind stream that flows steadily from the sun.

    A team lead by Hui Tian, of the Harvard-Smithsonian Center for Astrophysics, identified high-speed, intermittent jets in what scientists think is the solar wind source region, making these jets likely candidates for the initial stage of the solar wind. Rather than producing a steady outflow, the jets are sporadic, accelerating particles to speeds up of to 155 miles per second (250 km/s).

    “If these jets really are the nascent solar wind, then solar wind models must be updated to produce these intermittent, high-speed and small-scale outflows in the interface region,” Tian said.

    “If the answer is no, at least the impact of these jets on the still-not-observed nascent solar wind outflow should be carefully evaluated, because these jets are the most prominent dynamic feature in the believed solar wind source region,” he said.

    All five papers, along with a perspective piece by Louise Harra of the University College London, were published online today (Oct. 16) in the journal Science.

    See the full article, with video, here.

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  • richardmitnick 9:58 pm on October 16, 2014 Permalink | Reply
    Tags: , , , , Cosmology   

    From Caltech: “A Newborn Supernova Every Night” 

    Caltech Logo
    Caltech

    10/16/2014
    Douglas Smith

    Thanks to a $9 million grant from the National Science Foundation and matching funds from the Zwicky Transient Facility (ZTF) collaboration, a new camera is being built at Caltech’s Palomar Observatory that will be able to survey the entire Northern Hemisphere sky in a single night, searching for supernovas, black holes, near-Earth asteroids, and other objects. The digital camera will be mounted on the Samuel Oschin Telescope, a wide-field Schmidt telescope that began its first all-sky survey in 1949. That survey, done on glass plates, took nearly a decade to complete.

    Caltech Palomar Samuel Ochin Telescope
    Caltech Palomar Samuel Ochin Telescope Interior
    Samuel Ochin Telescope

    The ZTF camera’s field of view will encompass 47 square degrees, larger than 200 full moons. By contrast, the field of view of the Hubble Space Telescope is so small that a mosaic of 130 of its images of the moon would be needed to see it in its entirety. “The Hubble Space Telescope and the big ground-based telescopes see really deep but have small fields of view,” says astrophysicist Eric Bellm, a postdoctoral scholar at Caltech and ZTF’s project scientist. With its field of view, ZTF will be able to identify supernovas less than 24 hours old every single night. This quick response is critical, as the light emitted in the first few hours after a supernova explodes contains a wealth of information that cannot be retrieved later.

    “Discovery is only the first step,” says Shrinivas Kulkarni, ZTF’s principal investigator and Caltech’s John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science. “When something unusual is found, we will rapidly respond with some of the world’s most powerful telescopes,” including the Palomar Observatory’s 200-inch Hale.

    Caltech Palomar Hale Telescope
    Caltech Palomar Hale Telescope
    Caltech Palomar Hale Telescope

    In time, researchers hope, ZTF itself will be pointed at targets identified by the Laser Interferometer Gravitational-wave Observatory (LIGO), an NSF-funded project run by Caltech and MIT that is searching for gravitational waves. These ripples in the fabric of space and time are predicted to occur when neutron stars, black holes, or other massive objects collide. Currently, LIGO is offline undergoing a technical upgrade to Advanced LIGO, which is slated to begin operations in 2016. If and when Advanced LIGO registers a gravitational wave, it will command ZTF to scan the ribbon of sky from which the signal emanated, searching for any visible change that might mark the point of origin.

    ZTF—the successor to the intermediate Palomar Transient Factory (iPTF) survey and its predecessor, the Palomar Transient Factory—is a fully automated wide-field survey that uses the Oschin telescope to collect data that are then sent to the Infrared Processing and Analysis Center (IPAC) on the Caltech campus. At IPAC, software developed for PTF looks for anything that has changed between frames. ZTF will shoot one frame per minute at 18 gigabits per frame—the rough equivalent of watching eight hours of high-definition movies on Netflix every 60 seconds.

    “ZTF is really about celestial cinematography,” says Mansi Kasliwal (PhD ’11), currently a visiting associate in astronomy who will start as an assistant professor of astronomy at Caltech in September 2015. “Our new camera can make a movie of the entire sky. Moving solar-system bodies such as asteroids will just pop out at us, and we’ll be able to study catastrophic explosive transients such as supernovas and stars being torn apart by black holes.”

    “Processing so many images in real time is a huge challenge,” says IPAC’s executive director, George Helou. “It takes imaginative programming and powerful computers.” ZTF will visit every corner of the sky some 900 times over the course of its three-year observing program; IPAC will compile the data into atlases of variable stars, active galactic nuclei, and other astronomically interesting objects.

    Part of the NSF grant will fund an annual summer institute, coordinated by Pomona College in Claremont, California, to train students from across the United States in the latest astronomy instrumentation skills, large sky surveys, and data-analysis software.

    “These undergraduates will be controlling some of the largest telescopes in the world and getting a taste of the excitement of the scientific process,” explains Bryan Penprase, a professor at Pomona College and a co-principal investigator on the project, and the organizer of the summer institute. “The technology is so advanced that discoveries will be common. In just one night, the ZTF can discover hundreds of new sources. It’s an incredible thing for a student to be able to say, ‘I discovered that thing in the sky that no one else has ever seen before.'”

    The Zwicky Transient Facility is named in memory of Caltech astronomer Fritz Zwicky, who pioneered the use of wide-field Schmidt-type telescopes for sky surveys. Zwicky was the prime mover behind the Oschin’s construction, using its survey plates to hunt for supernovas—a term that Zwicky and Walter Baade coined in 1931. Zwicky also predicted the existence of neutron stars, dark matter, and gravitational lensing.

    ZTF is a public-private partnership supported by the National Science Foundation, Caltech, IPAC, the Weizmann Institute of Science (Israel), the Oskar Klein Centre (Sweden), Humboldt University (Germany), Los Alamos National Laboratory, Lawrence Berkeley National Laboratory, the Jet Propulsion Laboratory, the TANGO consortium (Taiwan), the University of Wisconsin–Milwaukee, and Pomona College. The survey will begin in 2017

    See the full article here.

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 9:23 pm on October 16, 2014 Permalink | Reply
    Tags: , , , Cosmology, ,   

    From NRAO: “Milky Way Ransacks Nearby Dwarf Galaxies, Stripping All Traces of Star-Forming Gas” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    October 15, 2014
    Contact: Charles E. Blue, Public Information Officer
    (434) 296-0314; cblue@nrao.edu

    Astronomers using the National Science Foundation’s Green Bank Telescope (GBT) in West Virginia, along with data from other large radio telescopes, have discovered that our nearest galactic neighbors, the dwarf spheroidal galaxies, are devoid of star-forming gas, and that our Milky Way Galaxy is to blame.

    mw

    These new radio observations, which are the highest sensitivity of their kind ever undertaken, reveal that within a well-defined boundary around our Galaxy, dwarf galaxies are completely devoid of hydrogen gas; beyond this point, dwarf galaxies are teeming with star-forming material.

    The Milky Way Galaxy is actually the largest member of a compact clutch of galaxies that are bound together by gravity. Swarming around our home Galaxy is a menagerie of smaller dwarf galaxies, the smallest of which are the relatively nearby dwarf spheroidals, which may be the leftover building blocks of galaxy formation. Further out are a number of similarly sized and slightly misshaped dwarf irregular galaxies, which are not gravitationally bound to the Milky Way and may be relative newcomers to our galactic neighborhood.

    “Astronomers wondered if, after billions of years of interaction, the nearby dwarf spheroidal galaxies have all the same star-forming ‘stuff’ that we find in more distant dwarf galaxies,” said astronomer Kristine Spekkens, assistant professor at the Royal Military College of Canada and lead author on a paper published in the Astrophysical Journal Letters.

    Previous studies have shown that the more distant dwarf irregular galaxies have large reservoirs of neutral hydrogen gas, the fuel for star formation. These past observations, however, were not sensitive enough to rule out the presence of this gas in the smallest dwarf spheroidal galaxies.

    By bringing to bear the combined power of the GBT (the world’s largest fully steerable radio telescope) and other giant telescopes from around the world, Spekkens and her team were able to probe the dwarf galaxies that have been swarming around the Milky Way for billions of years for tiny amounts of atomic hydrogen.

    “What we found is that there is a clear break, a point near our home Galaxy where dwarf galaxies are completely devoid of any traces of neutral atomic hydrogen,” noted Spekkens. Beyond this point, which extends approximately 1,000 light-years from the edge of the Milky Way’s star-filled disk to a point that is thought to coincide with the edge of its dark matter distribution, dwarf spheroidals become vanishingly rare while their gas-rich, dwarf irregular counterparts flourish.

    There are many ways that larger, mature galaxies can lose their star-forming material, but this is mostly tied to furious star formation or powerful jets of material driven by supermassive black holes. The dwarf galaxies that orbit the Milky Way contain neither of these energetic processes. They are, however, susceptible to the broader influences of the Milky Way, which itself resides within an extended, diffuse halo of hot hydrogen plasma.

    The researchers believe that, up to a certain distance from the galactic disk, this halo is dense enough to affect the composition of dwarf galaxies. Within this “danger zone,” the pressure created by the million-mile-per-hour orbital velocities of the dwarf spheroidals can actually strip away any detectable traces of neutral hydrogen. The Milky Way thus shuts down star formation in its smallest neighbors.

    “These observations therefore reveal a great deal about size of the hot halo and about how companions orbit the Milky Way,” concludes Spekkens.

    See the full article here.

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

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

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

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

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  • richardmitnick 3:28 pm on October 16, 2014 Permalink | Reply
    Tags: , , , Cosmology,   

    From Hubble: ” NASA’s Hubble Finds Extremely Distant Galaxy through Cosmic Magnifying Glass” 

    NASA Hubble Telescope

    Hubble

    October 16, 2014
    Felicia Chou
    Headquarters, Washington
    202-358-0257

    Peering through a giant cosmic magnifying glass, NASA’s Hubble Space Telescope has spotted a tiny, faint galaxy — one of the farthest galaxies ever seen. The diminutive object is estimated to be more than 13 billion light-years away.

    aabel
    The mammoth galaxy cluster Abell 2744 is so massive that its powerful gravity bends the light from galaxies far behind it, making these otherwise unseen background objects appear larger and brighter than they would normally.
    Image Credit:
    NASA, J. Lotz, (STScI)

    This galaxy offers a peek back to the very early formative years of the universe and may just be the tip of the iceberg.

    “This galaxy is an example of what is suspected to be an abundant, underlying population of extremely small, faint objects that existed about 500 million years after the big bang, the beginning of the universe,” explained study leader Adi Zitrin of the California Institute of Technology in Pasadena, California. “The discovery is telling us galaxies as faint as this one exist, and we should continue looking for them and even fainter objects, so that we can understand how galaxies and the universe have evolved over time.”

    The galaxy was detected by the Frontier Fields program, an ambitious three-year effort that teams Hubble with NASA’s other great observatories — the Spitzer Space Telescope and Chandra X-ray Observatory — to probe the early universe by studying large galaxy clusters. These clusters are so massive their gravity deflects light passing through them, magnifying, brightening, and distorting background objects in a phenomenon called gravitational lensing. These powerful lenses allow astronomers to find many dim, distant structures that otherwise might be too faint to see.

    NASA Spitzer Telescope
    NASA Spitzer schematic
    NASA/Spitzer

    NASA Chandra Telescope
    NASA Chandra schematic
    NASA/Chandra

    The discovery was made using the lensing power of the mammoth galaxy cluster Abell 2744, nicknamed Pandora’s Cluster, which produced three magnified images of the same, faint galaxy. Each magnified image makes the galaxy appear 10 times larger and brighter than it would look without the zooming qualities of the cluster.

    The galaxy measures merely 850 light-years across — 500 times smaller than our Milky Way galaxy– and is estimated to have a mass of only 40 million suns. The Milky Way, in comparison, has a stellar mass of a few hundred billion suns. And the galaxy forms about one star every three years, whereas the Milky Way galaxy forms roughly one star per year. However, given its small size and low mass, Zitrin said the tiny galaxy actually is rapidly evolving and efficiently forming stars.

    The astronomers believe galaxies such as this one are probably small clumps of matter that started to form stars and shine, but do not yet have a defined structure. It is possible Hubble is only detecting one bright clump magnified due to the lensing. This would explain why the object is smaller than typical field galaxies of that time.

    Zitrin’s team spotted the galaxy’s gravitationally multiplied images using near-infrared and visible-light photos of the galaxy cluster taken by Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys. But they needed to measure how far away it was from Earth.

    NASA Hubble WFC3
    WFC3 on Hubble

    NASA Hubble ACS
    ACS on Hubble

    Usually, astronomers can determine an object’s distance based on how far its light has been stretched as the universe slowly expands. Astronomers can precisely measure this effect through spectroscopy, which characterizes an object’s light. But the gravitationally-lensed galaxy and other objects found at this early time period are too far away and too dim for spectroscopy, so astronomers use an object’s color to estimate its distance. The universe’s expansion reddens an object’s color in predictable ways, which scientists can measure.

    Zitrin’s team performed the color-analysis technique and took advantage of the multiple images produced by the gravitational lens to independently confirm the group’s distance estimate. The astronomers measured the angular separation between the three magnified images of the galaxy in the Hubble photos. The greater the angular separation due to lensing, the farther away the object is from Earth.

    To test this concept, the astronomers compared the three magnified images with the locations of several other closer, multiply-imaged background objects captured in Hubble images of Pandora’s cluster. The angular distance between the magnified images of the closer galaxies was smaller.

    “These measurements imply that, given the large angular separation between the three images of our background galaxy, the object must lie very far away,” Zitrin explained. “It also matches the distance estimate we calculated, based on the color-analysis technique. So we are about 95 percent confident this object is at a remote distance, at redshift 10, a measure of the stretching of space since the big bang. The lensing takes away any doubt that this might be a heavily reddened, nearby object masquerading as a far more distant object.”

    Astronomers have long debated whether such early galaxies could have provided enough radiation to warm the hydrogen that cooled soon after the big bang. This process, called reionization, is thought to have occurred 200 million to 1 billion years after the birth of the universe. Reionization made the universe transparent to light, allowing astronomers to look far back into time without running into a “fog” of cold hydrogen.

    The team’s results appeared in the September online edition of The Astrophysical Journal Letters.

    For images and more information about Hubble, visit:

    http://www.nasa.gov/hubble

    See the full article here.

    Another view of Abell 2744 from Hubble

    abel 2744
    Description: Abell 2744, nicknamed Pandora’s Cluster. The galaxies in the cluster make up less than five percent of its mass. The gas (around 20 percent) is so hot that it shines only in X-rays (coloured red in this image). The distribution of invisible dark matter (making up around 75 percent of the cluster’s mass) is coloured here in blue.
    Date:22 June 2011

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

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  • richardmitnick 2:06 pm on October 16, 2014 Permalink | Reply
    Tags: , , , Cosmology, , Max Planck Institute for Astronomy   

    From Keck: “Scientists Build First Map of Hidden Universe” 

    Keck Observatory

    Keck Observatory

    Keck Observatory

    October 15, 2014
    Khee-Gan Lee
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Phone: (+49|0) 6221 –528 467
    email: lee@mpia.de

    Joe Hennawi
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Phone: (+49|0) 6221 –528 263
    email: joe@mpia.de

    MEDIA CONTACTS:
    Steve Jefferson
    Communications Officer
    W. M. Keck Observatory
    Phone: (808)881-3827
    email: sjefferson@keck.hawaii.edu

    Dr. Markus Pössel
    Public Information Officer
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Phone: (+49|0) 6221 –528 261
    email: pr@mpia.de

    A team led by astronomers from the Max Planck Institute for Astronomy has created the first three-dimensional map of the ‘adolescent’ Universe, just 3 billion years after the Big Bang. This map, built from data collected from the W. M. Keck Observatory, is millions of light-years across and provides a tantalizing glimpse of large structures in the ‘cosmic web’ – the backbone of cosmic structure.

    map
    3D map of the cosmic web at a distance of 10.8 billion light years from Earth. The map was generated from imprints of hydrogen gas observed in the spectrum of 24 background galaxies, which are located behind the volume being mapped. This is the first time that large-scale structures in such a distant part of the Universe have been mapped directly. The coloring represents the density of hydrogen gas tracing the cosmic web, with brighter colors representing higher density. Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA)

    more

    On the largest scales, matter in the Universe is arranged in a vast network of filamentary structures known as the ‘cosmic web’, its tangled strands spanning hundreds of millions of light-years. Dark matter, which emits no light, forms the backbone of this web, which is also suffused with primordial hydrogen gas left over from the Big Bang. Galaxies like our own Milky Way are embedded inside this web, but fill only a tiny fraction of its volume.

    Now a team of astronomers led by Khee-Gan Lee, a post-doc at the Max Planck Institute for Astronomy, has created a map of hydrogen absorption revealing a three-dimensional section of the universe 11 billions light years away – the first time the cosmic web has been mapped at such a vast distance. Since observing to such immense distances is also looking back in time, the map reveals the early stages of cosmic structure formation when the Universe was only a quarter of its current age, during an era when the galaxies were undergoing a major ‘growth spurt’.

    The map was created by using faint background galaxies as light sources, against which gas could be seen by the characteristic absorption features of hydrogen. The wavelengths of each hydrogen feature showed the presence of gas at a specific distance from us. Combining all of the measurements across the entire field of view allowed the team a tantalizing glimpse of giant filamentary structures extending across millions of light-years, and paves the way for more extensive studies that will reveal not only the structure of the cosmic web, but also details of its function – the ways that pristine gas is funneled along the web into galaxies, providing the raw material for the formation of galaxies, stars, and planets.

    Using the light from faint background galaxies for this purpose had been thought impossible with current telescopes – until Lee carried out calculations that suggested otherwise. To ensure success, Lee and his colleagues obtained observing time at Keck Observatory, home of the two largest and most scientifically productive telescopes in the world.

    Although bad weather limited the astronomers to observing for only 4 hours, the data they collected with the LRIS instrument was completely unprecedented. “We were pretty disappointed as the weather was terrible and we only managed to collect a few hours of good data. But judging by the data quality as it came off the telescope, it was clear to me that the experiment was going to work,” said Max Plank’s Joseph Hennawi, who was part of the observing team.

    Keck LRIS
    Keck’s LRIS

    “The data were obtained using the LRIS spectrograph on the Keck I telescope,” Lee said. “With its gargantuan 10m-diameter mirror, this telescope effectively collected enough light from our targeted galaxies that are more than 15 billion times fainter than the faintest stars visible to the naked eye. Since we were measuring the dimming of blue light from these distant galaxies caused by the foreground gas, the thin atmosphere at the summit of Mauna Kea allowed more of this blue light to reach the telescope and be measured by the highly sensitive detectors of the LRIS spectrograph. The data we collected would have taken at least several times longer to obtain on any other telescope.”

    Their absorption measurements using 24 faint background galaxies provided sufficient coverage of a small patch of the sky to be combined into a 3D map of the foreground cosmic web. A crucial element was the computer algorithm used to create the 3D map: due to the large amount of data, a naïve implementation of the map-making procedure would require an inordinate amount of computing time. Fortunately, team members Casey Stark and Martin White (UC Berkeley and Lawrence Berkeley National Lab) devised a new fast algorithm that could create the map within minutes. “We realized we could simplify the computations by tailoring it to this particular problem, and thus use much less memory. A calculation that previously required a supercomputer now runs on a laptop”, says Stark.

    The resulting map of hydrogen absorption reveals a three-dimensional section of the universe 11 billions light years away – this is first time the cosmic web has been mapped at such a vast distance. Since observing to such immense distances is also looking back in time, the map reveals the early stages of cosmic structure formation when the Universe was only a quarter of its current age, during an era when the galaxies were undergoing a major ‘growth spurt’. The map provides a tantalizing glimpse of giant filamentary structures extending across millions of light-years, and paves the way for more extensive studies that will reveal not only the structure of the cosmic web, but also details of its function – the ways that pristine gas is funneled along the web into galaxies, providing the raw material for the formation of galaxies, stars, and planets.

    The Low Resolution Imaging Spectrometer (LRIS) is a very versatile visible-wavelength imaging and spectroscopy instrument commissioned in 1993 and operating at the Cassegrain focus of Keck I. Since it has been commissioned it has seen two major upgrades to further enhance its capabilities: addition of a second, blue arm optimized for shorter wavelengths of light; and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe.

    See the full article here.

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

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

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
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