Astronomy Cmarchesin

Releases from NASA, NASA Galex, NASA's Goddard Space Flight Center, Hubble, Hinode, Spitzer, Cassini, ESO, ESA, Chandra, HiRISE, Royal Astronomical Society, NRAO, Astronomy Picture of the Day, Harvard-Smithsonian Center For Astrophysics, etc.

Friday, December 30, 2011

Subaru's Sharp Eye Confirms Signs of Unseen Planets in the Dust Ring of HR 4796 A

The SEEDS (Strategic Exploration of Exoplanets and Disks with Subaru Telescope/HiCIAO) project, a five-year international collaboration launched in 2009 and led by Motohide Tamura of NAOJ (National Astronomical Observatory of Japan) has yielded another impressive image that contributes to our understanding of the link between disks and planet formation. Researchers used Subaru's planet-finder camera, HiCIAO (High Contrast Instrument for the Subaru Next Generation Adaptive Optics), to take a crisp high-contrast image of the dust ring around HR 4796 A, a young (8-10 million years old) nearby star, only 240 light years away from Earth. The ring consists of dust grains in a wide orbit, roughly twice the size of Pluto's orbit, around the central star. The resolution of the image of the inner edge of the ring is so precise that an offset between its center and the star's position can be measured. Although data from the Hubble Space Telescope led another research group to suspect such an offset, the Subaru data not only confirm its presence but also reveal it to be larger than previously assumed.

Figure 1: Near-infrared (1.6 micron) image of the debris ring around the star HR 4796 A. An astronomical unit (AU) is a unit of length that corresponds to the average distance between the Earth and Sun, almost 92 million miles (over 149 million km).

The ring consists of dust grains in a wide orbit (roughly twice the size of Pluto's orbit) around the central star. Its edge is so precisely revealed that the researchers could confirm a previously suspected offset between the ring's center and the star's location. This "wobble" in the dust's orbit is most likely caused by the unbalancing action of – so far undetected – massive planets likely to be orbiting within the ring. Furthermore, the image of the ring appears to be smudged out at its tips and reveals the presence of finer dust extending out beyond the main body of the ring.

For high resolution versions of the above image, click on the following links: Image only or Image with labels.

What caused the wheel of dust around HR 4796 A to run off its axis? The most plausible explanation is that the gravitational force of one or more planets orbiting in the gap within the ring must be tugging at the dust, thus unbalancing their course around the star in predictable ways. Computer simulations have already shown that such gravitational tides can shape a dust ring into eccentricity, and findings from another the eccentric dust ring around the star Formalhaut may be observational evidence for the process. Since no planet candidates have been spotted near HR 4796 A yet, the planets causing the dust ring to wobble are probably simply too faint to detect with current instruments. Nevertheless, the Subaru image allows scientists to infer their presence from their influence on the circumstellar dust.

The Subaru Telescope's near-infrared image is as sharp as the Hubble Space Telescope's visible-light image, thus enabling accurate measurements of its eccentricity. While Subaru Telescope's mirror is much larger than Hubble's, light from the HR 4796 A system must first pass through the turbulent air layers of Earth's atmosphere before Subaru's instruments can measure it. Subaru's adaptive optics system (AO188) allows it to correct for most of the atmosphere's blurring effects in order to take razor-sharp images. The application of an advanced image processing technique, angular differential imaging, to the data suppressed the star's bright glare and enhanced the faint light reflected from the ring so that it was more visible.

This image gives scientists more information about the relationship between a circumstellar disk and planet formation. Planets are believed to form in the disks of gas and dust that remain around young stars as the by-products of star formation. As the material is swept up by the newborn planets or blown out of the system by the star's radiation, such (primordial) disks soon disappear in a few tens of million years. Nevertheless, some stars are surrounded by a debris or secondary disk, mainly composed of dust long after the primordial disk should have dispersed. Collisions between small solid bodies ("planetesimals") left over from planet formation may continuously replenish the dust in these disks. The dust ring around HR 4796 A is such a debris disk and provides essential information for studying planet formation and possible formed planets in such debris disk systems.

References:

Refer to the following article for the published report of the results:
Thalmann et al., The Astrophysical Journal Letters, Volume 743, Issue 1, (2011)

Articles describing other results from the SEEDS project can be found at the following locations:
Direct Images of Disks Unravel Mystery of Planet Formation, February 17, 2011. (Subaru Telescope Press release: 17 Feb. 2011)
Discovery of an Exoplanet Candidate Orbiting a Sun-Like Star, December 3, 2009. (Subaru Telescope Press release: 3 Dec. 2009)

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Little Galaxies Are Big on Dark Matter

The stellar stream in the halo of the nearby dwarf starburst galaxy NGC 4449 is resolved into its individual starry constituents in this exquisite image taken with the 8.2-meter Subaru Telescope and Suprime-Cam. Image credit: R. Jay GaBany and Aaron J. Romanowsky (UCSC) in collaboration with David Martinez-Delgado (MPIA) and NAOJ. Image processed by R. Jay GaBany

Dark matter… It came into existence at the moment of the Big Bang. Within its confines, galaxies formed and evolved. If you add up all the parts contained within any given galaxy you derive its mass, yet its gravitational effects can only be explained by the presence of this mysterious subatomic particle. It would be easy to believe that the larger the galaxy, the larger the amount of dark matter should be present, but new research shows that isn’t so. Dwarf galaxies have even higher proportions of dark matter than their larger counterparts. Although the dwarfs are the most common of all, we know very little about them – even when they consume each other. Enter the star stream…

“Several of my previous images feature the fossil remnants of these ancient mergers as faint stellar rivers called tidal streams. These stellar streams are the table crumbs from small dwarf galaxies that were gravitationally dismembered as they were devoured by the larger galaxy they orbited.” says astrophotographer, R. Jay Gabany. “The theory implies dwarf galaxies also merged and are still merging with each other. But, there has never been clear photographic evidence or a close investigation of dwarf galactic mergers until now.”

The target is NGC 4449, a small, irregular dwarf galaxy much like the the Milky Way’s Large Magellanic Cloud. What makes it interesting to astronomers is the presence of thousands of hot blue stars and massive red regions interspaced with thick dust clouds. It isn’t just forming new stars… it’s experiencing an explosion of star birth! According to current theory, dwarf galaxies such as this one could be undergoing a merger event, but there hasn’t been photographic proof until now.

“The picture I am sharing is of a small, dwarf galaxy known as NGC 4449 that’s located about 12.5 million light years from Earth towards the northern constellation of Canes Venatici, the Hunting Dogs. This galaxy is about the size of our Milky Way’s largest satellite galaxy, the Magellanic Cloud. But, NGC 4449 is much farther away and it is experiencing a major star burst event- an episode characterized by the production of new stars at a furious rate.” says Gabany. “This image is unique because is it captures the first dwarf galaxy known to have its own tidal stream of stars. Therefore, it represents the first closely studied example of a dwarf galaxy merging with an even smaller dwarf star system! The professional astronomers with whom I work also suspect the merger may have contributed to the ferocious production rate of new stars inside NGC 4449.”

The research done by the team led by Dr. David Martinez-Delgado has some very interesting ramifications and their paper has been accepted for publication in the Astrophysical Journal Letters.. As so well put in Jay’s photographic explanation in his webpage; “Although the cold dark matter theory predicts mergers and interactions between dwarf galaxies, there is scant observational evidence that these types of mergers are still happening in the nearby local Universe. Interactions between dwarf galaxies invoke the possibility of exploring a very different merger regime. For example, research has shown that multiple dwarf galaxies with different stellar masses may exist in similar sized dark matter halos, hence what appears as a minor merger of stars could be a major dark matter merger. Studying interactions on a small scale, such as NGC 4449, provides unique insights on the role of stars versus dark matter in galactic merger events.”

Where once amateur astrophotographers painted beautiful portraits of what lay just beyond human perception in deep space, they are now crafting images capable of true science. The eyes of their telescopes are being combined with professional instruments and producing amazing results.

“We live in an age where science has become unfettered from examining the Universe with only our physical six senses.” concludes Gabany. “This has unlocked a profound new level of understanding, resolved ancient mysteries and unlatched a Pandora’s chest filled with new questions begging for answers. We still have much to learn.”

For Further Reading: Dwarfs Gobbling Dwarfs: A Stellar Tidal Stream Around NGC 4449 and Hierarchical Galaxy Formation On Small Scales and The Big Deal About Dwarf Galaxies.

by Tammy Plotner


Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.

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Monday, December 26, 2011

Faint Galaxy with Popping Pink Features


IC 2574
Credit: ESA/Hubble & NASA

The NASA/ESA Hubble Space Telescope has imaged a region of space containing the intriguing object IC 2574. Pink bubbles blown by supernova explosions abound in this faint galaxy. The colour of these shells comes from hydrogen gas irradiated by newborn stars. The formation of the stars was triggered by shock waves from earlier supernova detonations that compressed material together.

IC 2574 is commonly known as Coddington's Nebula after the American astronomer Edwin Coddington, who discovered it in 1898. Astronomers classify IC 2574 as a dwarf irregular galaxy due to its relatively small size and lack of organisation or structure. These galaxies are thought to resemble some of the earliest that formed in the Universe. Dwarf irregular galaxies thus serve as useful "living fossils" for studying the evolution of more complex galaxy types such as our home, the Milky Way, with its central bar and spiral arms. The expanding shells in IC 2574 are of particular interest to astronomers as they reveal how supernova-driven explosions ignite round after round of star formation.

The constellation containing IC 2574 is Ursa Major (The Great Bear). IC 2574 is located about 12 million light-years away, belonging to the Messier 81 group of galaxies. This group is named after the most prominent galaxy in its midst, the big, bright and accordingly well-studied spiral galaxy Messier 81.

This picture was produced with Hubble’s Advanced Camera for Surveys, and covers a field of view of around 3.3 by 3.3 arcminutes.

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Saturday, December 24, 2011

Christmas Comet Lovejoy Captured at Paranal

PR Image eso1153a
Christmas Comet Lovejoy Captured at Paranal

PR Image eso1153b
Christmas Comet Lovejoy Seen over Santiago

PR Image eso1153c
Christmas Comet Lovejoy Captured at Paranal

The recently discovered Comet Lovejoy has been captured in stunning photos and time-lapse video taken from ESO’s Paranal Observatory in Chile. The comet graced the southern sky after it had unexpectedly survived a close encounter with the Sun.

A new time-lapse video sequence was taken by Gabriel Brammer from ESO less than two days ago on 22 December 2011. Gabriel was finishing his shift as support astronomer at the Paranal Observatory when Comet Lovejoy rose over the horizon just before dawn.

In the words of Gabriel Brammer himself: “On the last morning of my shift I tried to try catch it on camera before sunrise. The tail of the comet was easily visible with the naked eye, and the combination of the crescent Moon, comet, Milky Way and the laser guide star was nearly as impressive to the naked eye as it appears in the long-exposure photos.”

The sequence also features the pencil-thin beam of the VLT’s Laser Guide Star set against the beautiful backdrop of the Milky Way, as astronomers conduct their last observations for the night.

ESO optician Guillaume Blanchard made a marvellous wide-angle photo of Comet Lovejoy and ESO Photo Ambassador Yuri Beletsky, captured the spectacle from Santiago de Chile. Blanchard said: "For me this comet is a Christmas present to the people who will stay at Paranal over Christmas".

This bright comet was also seen from the International Space Station in another stunning time-lapse sequence on 21 December as the crew filmed lightning on the Earth’s night side.

Comet Lovejoy has been the talk of the astronomy community over the past few weeks. It was discovered on 27 November by the Australian amateur astronomer Terry Lovejoy and was classified as a Kreutz sungrazer, with its orbit taking it very close to the Sun [1]. Just last week, the comet entered the Sun’s corona, a much-anticipated event, passing a mere 140 000 kilometres from the Sun’s surface. A close shave indeed...

The comet was expected to break up and vaporise, but instead it survived its steaming hot encounter with the Sun and re-emerged a few days later, much to everyone's surprise. It is now visible from the southern hemisphere, appearing at dawn, and features a bright tail millions of kilometres long, composed of dust particles that are being blown ahead of the comet by the solar wind.

Lovejoy will now continue in its highly eccentric orbit around the Sun and once again disappear into the distant Solar System. It would be interesting to know if it will actually survive to re-appear in our skies in 314 years as predicted.

With this spectacular sequence of the 2011 Christmas Comet Lovejoy, ESO would like to wish everyone a Merry Christmas and a Happy New Year.

Comet Lovejoy from the VLT, Chile from g br on Vimeo

Credit: G. Brammer/ESO

Notes

[1] Kreutz sungrazers are members of a family of comets thought to come from the break up of one single large comet in the 12th century, and which now orbit the Sun along the same path.
More information

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Links
Gabriel Brammer’s web page
Guillaume Blanchard’s web page
ESO Photo Ambassadors

Contacts

Gabriel Brammer
ESO
Vitacura, Chile
Cell: +56 9 94 89 00 75
Email: gbrammer@eso.org

Lars Lindberg Christensen
Head, ESO education and Public Outreach Department
Garching bei München, Germany
Cell: +49 173 3872 621
Email: lars@eso.org

Friday, December 23, 2011

WISE Presents a Cosmic Wreath

NASA's Wide-field Infrared Survey Explorer (WISE) mission presents the "Wreath nebula." Though this isn't the nebula's official name (it's actually called Barnard 3, or IRAS Ring G159.6-18.5), one might picture a wreath in these bright green and red dust clouds -- a ring of evergreens donned with a festive red bow, a jaunty sprig of holly, and silver bells throughout. Image credit: NASA/JPL-Caltech/UCLA. Full image and caption

Just in time for the holidays, astronomers have come across a new image from NASA's Wide-field Infrared Survey Explorer, or WISE, that some say resembles a wreath. You might even think of the red dust cloud as a cheery red bow, and the bluish-white stars as silver bells. This star-forming nebula is named Barnard 3. Baby stars are being born throughout the dusty region, while the "silver bell" stars are located both in front of, and behind, the nebula.

The bright star in the middle of the red cloud, called HD 278942, is so luminous that it is likely causing most of the surrounding clouds to glow. The red cloud is probably made of dust that is more metallic and cooler than the surrounding regions. The yellow-green region poking into the picture from the left like a sprig of holly is similar to the rest of the green "wreath" material, only more dense.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. More information is online at http://www.nasa.gov/wise , http://wise.astro.ucla.edu and http://jpl.nasa.gov/wise .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

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Hubble Captures a “Lucky” Galaxy Alignment

LRG 3-757
Credit: ESA/Hubble & NASA

An interesting galaxy has been circled in this NASA/ESA Hubble Space Telescope image. The galaxy — one of a group of galaxies called Luminous Red Galaxies — has an unusually large mass, containing about ten times the mass of the Milky Way. However, it’s actually the blue horseshoe shape that circumscribes the red galaxy that is the real prize in this image.

This blue horseshoe is a distant galaxy that has been magnified and warped into a nearly complete ring by the strong gravitational pull of the massive foreground Luminous Red Galaxy. To see such a so-called Einstein Ring required the fortunate alignment of the foreground and background galaxies, making this object’s nickname “the Cosmic Horseshoe” particularly apt.

The Cosmic Horseshoe is one of the best examples of an Einstein Ring. It also gives us a tantalising view of the early Universe: the blue galaxy’s redshift — a measure of how the wavelength of its light has been stretched by the expansion of the cosmos — is approximately 2.4. This means we see it as it was about 3 billion years after the Big Bang. The Universe is now 13.7 billion years old.

Astronomers first discovered the Cosmic Horseshoe in 2007 using data from the Sloan Digital Sky Survey. But this Hubble image, taken with the Wide Field Camera 3, offers a much more detailed view of this fascinating object.

This picture was created from images taken in visible and infrared light on Hubble’s Wide Field Camera 3. The field of view is approximately 2.6 arcminutes wide.

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Thursday, December 22, 2011

Stripped planets around a former red giant star

An artist's impression of planets orbiting close to a hot subdwarf star
Illustration courtesy S. Charpinet

An international research team, including Dr. Roy Østensen of the University of Leuven found a system of compact planets around a former red giant star. The orbits of the planets are so close to the star that they must have been engulfed in the outer layers of the star's atmosphere when it was a red giant. The red giant star's atmosphere ripped off the atmosphere and surface of the planets, leaving the planets stripped and compact. The team reports about the discovery in the journal Nature, in the issue of 21 december 2011.

Planets that orbit their parent star at less than about one astronomical unit (1 au is the Earth–Sun distance) are expected to be engulfed when the star becomes a red giant. Previous observations have revealed the existence of post-red-giant host stars with giant planets orbiting as close as 0.116 au or with brown dwarf companions in tight orbits, showing that these bodies can survive engulfment. What has remained unclear is whether planets can be dragged deeper into the red-giant envelope without being disrupted and whether the evolution of the parent star itself could be affected.

The team reports the presence of two nearly Earth-sized bodies orbiting the post-red-giant, hot B subdwarf star KIC 05807616 at distances of 0.0060 and 0.0076 au, with orbital periods of 5.7625 and 8.2293 hours, respectively. These bodies probably survived deep immersion in the former red-giant envelope. They may be the dense cores of evaporated giant planets that were transported closer to the star during the engulfment and triggered the mass loss necessary for the formation of the hot B subdwarf, which might also explain how some stars of this type did not form in binary systems.

BBC: Newly found planets are 'roasted remains'

Nature letter: A compact system of small planets around a former red-giant star
S. Charpinet, G. Fontaine, P. Brassard, E. M. Green, V. Van Grootel, S. K. Randall, R. Silvotti, A. S. Baran, R. H. Østensen, S. D. Kawaler & J. H. Telting

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Wednesday, December 21, 2011

Keck & Subaru Telescopes Find Rare Galaxy at Dawn of Time

Images showing the location of GN-108036 in Hubble and Spitzer space telescope images. Credit: NASA / JPL-Caltech / STScI-ESA / Y. Ono (Univ. of Tokyo) and B. Weiner (Univ. of Arizona)

A portion of the Keck DEIMOS spectrum of GN-108036. The red arrow points to what the researchers interpret as a Lyman Alpha emission line at 9985 Angstroms. Since hydrogen actually emits this at 1216 Angstroms, the line in the distant galaxy's spectrum has been shifted far to the red end of the spectrum due to the Doppler shift of light in an expanding universe. The "redshift" of the galaxy is calculated to be 7.2, making it one of the most distant objects ever discovered. Credit: Y. Ono, et al.

Kamuela, HI – Astronomers have spotted one of the most distant galaxies known, churning out stars at a shockingly high rate. The blob-like galaxy, called GN-108036, is located 12.9 billion light-years away from Earth, and is the most luminous galaxy known at that great distance.

The galaxy was first identified by the Subaru telescope and its extreme distance was then carefully confirmed with the Keck II telescope and its DEIMOS instrument (Deep Extragalactic Multi-Object Spectrograph). Both observatories are located on the summit of Mauna Kea, Hawaii. NASA’s Spitzer and Hubble space telescopes were used to measure the galaxy’s high star production rate, equivalent to about 100 suns per year. For comparison, our Milky Way galaxy is about five times larger and a hundred times more massive than GN-108036, but makes new stars roughly 30 times more slowly.

“We’re really surprised to know that GN-108036 is quite luminous in ultraviolet and harbors a powerful star formation,” said astronomer Yoshiaki Ono of the University of Tokyo, Japan. “We had never seen such a vigorously star-forming galaxy at a comparable distance until the discovery of GN-108036.” Ono is the lead author on a paper on the results that is accepted for publication in The Astrophysical Journal. The principal investigator is Masami Ouchi, also at the University of Tokyo.

“The discovery is surprising because previous surveys had not found galaxies this bright that early in the history of the universe,” agreed Mark Dickinson of the National Optical Astronomy Observatory in Tucson. “Perhaps those surveys were just too small to find galaxies like GN-108036. It may be a special, rare object that we just happened to catch during an extreme burst of star formation.”

GN-108036 lies near the very beginning of time itself, a mere 750 million years after our universe was created in an explosive “big bang.” Its light has taken 12.9 billion years to reach us, so we are seeing it as it was in the very distant past.

Astronomers refer to the object’s distance by a number called its “redshift,” which relates to how much its light has stretched to longer, redder wavelengths due to the expansion of the universe. Objects with larger redshifts are farther away and are seen further back in time. GN-108036 has a redshift of 7.2, making it one of only a handful of galaxies have confirmed redshifts greater than 7. Only two others have been reported to be more distant than GN-108036.

During this epoch, as the universe expanded and cooled after its explosive start, hydrogen atoms permeating the cosmos formed a thick fog that was opaque to ultraviolet light. This period, before the first stars and galaxies had formed and illuminated the universe, was known as the “dark ages.” The dark ages came to an end when light from the earliest galaxies burned through, or “ionized”, the opaque gas, causing it to become transparent. Galaxies similar to GN-108036 may have played an important role in this event. The question to be answered now is how many of these galaxies existed back then.

“The high rate of star formation found for GN-108036 implies that it was rapidly building up its mass some 750 million years after the Big Bang, when the universe was only five percent of its present age,” said Bahram Mobasher, a member of the team from the University of California, Riverside. “This was therefore a likely ancestor of massive and evolved galaxies seen today.”

The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Big Island of Hawaii. The twin telescopes feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and a world-leading laser guide star adaptive optics system which cancels out much of the interference caused by Earth’s turbulent atmosphere. The 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.

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Dawn Obtains First Low Altitude Images of Vesta

NASA's Dawn spacecraft has spiraled closer and closer to the surface of the giant asteroid Vesta. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Full image and caption

This image, one of the first obtained by NASA's Dawn spacecraft in its low altitude mapping orbit, shows an area within the Rheasilvia basin in the south polar area of the giant asteroid Vesta. Image credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA. Full image and caption

This image, one of the first obtained by NASA's Dawn spacecraft in its low altitude mapping orbit, shows a part of one of the troughs at the equator of the giant asteroid Vesta. Image credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA. Full image and caption

PASADENA, Calif. – NASA's Dawn spacecraft has sent back the first images of the giant asteroid Vesta from its low-altitude mapping orbit. The images, obtained by the framing camera, show the stippled and lumpy surface in detail never seen before, piquing the curiosity of scientists who are studying Vesta for clues about the solar system's early history.

At this detailed resolution, the surface shows abundant small craters, and textures such as small grooves and lineaments that are reminiscent of the structures seen in low-resolution data from the higher-altitude orbits. Also, this fine scale highlights small outcrops of bright and dark material.

A gallery of images can be found online at: http://www.nasa.gov/mission_pages/dawn/multimedia/gallery-index.html .

The images were returned to Earth on Dec. 13. Dawn scientists plan to acquire data in the low-altitude mapping orbit for at least 10 weeks. The primary science objectives in this orbit are to learn about the elemental composition of Vesta's surface with the gamma ray and neutron detector and to probe the interior structure of the asteroid by measuring the gravity field.

The Dawn mission to the asteroids Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. The Dawn Framing Cameras have been developed and built under the leadership of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, with significant contributions by DLR German Aerospace Center, Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The framing camera project is funded by the Max Planck Society, DLR, and NASA/JPL.

More information about the Dawn mission is online at: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov .


Jia-Rui Cook
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850
jccook@jpl.nasa.gov

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Tuesday, December 20, 2011

SXP 1062: Celestial Bauble Intrigues Astronomers

Credit X-ray & Optical: NASA/CXC/Univ.Potsdam/L.Oskinova et al


With the holiday season in full swing, a new image from an assembly of telescopes has revealed an unusual cosmic ornament. Data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton have been combined to discover a young pulsar in the remains of a supernova located in the Small Magellanic Cloud, or SMC. This would be the first definite time a pulsar, a spinning, ultra-dense star, has been found in a supernova remnant in the SMC, a small satellite galaxy to the Milky Way.

In this composite image, X-rays from Chandra and XMM-Newton have been colored blue and optical data from the Cerro Tololo Inter-American Observatory in Chile are colored red and green. The pulsar, known as SXP 1062, is the bright white source located on the right-hand side of the image in the middle of the diffuse blue emission inside a red shell. The diffuse X-rays and optical shell are both evidence for a supernova remnant surrounding the pulsar. The optical data also displays spectacular formations of gas and dust in a star-forming region on the left side of the image. A comparison of the Chandra image with optical images shows that the pulsar has a hot, massive companion.

Astronomers are interested in SXP 1062 because the Chandra and XMM-Newton data show that it is rotating unusually slowly - about once every 18 minutes. (In contrast, some pulsars are found to revolve multiple times per second, including most newly born pulsars.) This relatively leisurely pace of SXP 1062 makes it one of the slowest rotating X-ray pulsars in the SMC.

Two different teams of scientists have estimated that the supernova remnant around SXP 1062 is between 10,000 and 40,000 years old, as it appears in the image. This means that the pulsar is very young, from an astronomical perspective, since it was presumably formed in the same explosion that produced the supernova remnant. Therefore, assuming that it was born with rapid spin, it is a mystery why SXP 1062 has been able to slow down by so much, so quickly. Work has already begun on theoretical models to understand the evolution of this unusual object.

Fast Facts for SXP 1062:

Credit X-ray & Optical: NASA/CXC/Univ.Potsdam/L.Oskinova et al
Scale: Image is 14 arcmin across (744 light years)
Category: Supernovas & Supernova Remnants
Coordinates: (J2000) RA 01h 29m 12.40s | Dec -73° 32' 01.70"
Constellation: Tucana
Observation Date: 11 pointings between 03/31/2010 and 04/29/2010
Observation Time: 80 hours 45 min (3 days 8 hours 45 min).
Obs. ID: 10985-10986, 11978-11979, 11988-11989, 12130-12131, 12134, 12136, 12207
Color Code: X-ray (Blue); Optical (Red, Green)
Instrument: ACIS
References: Henault-Brunet, V. et al, MNRAS 2011
Distance Estimate: 180,000 light years

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NASA Discovers First Earth-Size Planets Beyond Our Solar System

This chart compares the first Earth-size planets found around a sun-like star to planets in our own solar system, Earth and Venus. Image credit: NASA/Ames/JPL-Caltech. Full image and caption

Kepler-20e is the first planet smaller than the Earth discovered to orbit a star other than the sun. Image credit: NASA/Ames/JPL-Caltech. Full image and caption - enlarge image

Kepler-20f is the closest object to the Earth in terms of size ever discovered. With an orbital period of 20 days and a surface temperature of 800 degrees Fahrenheit (430 degrees Celsius), it is too hot to host life, as we know it. Image credit: NASA/Ames/JPL-Caltech. Full image and caption - enlarge image


An Unusual Planetary System
See animation
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PASADENA, Calif. -- NASA's Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are the smallest exoplanets ever confirmed around a star like our sun.

The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is slightly larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra.

Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit (427 degrees Celsius), is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit (760 degrees Celsius), would melt glass.

"The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. "This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them."

The Kepler-20 system includes three other planets that are larger than Earth but smaller than Neptune. Kepler-20b, the closest planet, Kepler-20c, the third planet, and Kepler-20d, the fifth planet, orbit their star every 3.7, 10.9 and 77.6 days, respectively. All five planets have orbits lying roughly within Mercury's orbit in our solar system. The host star belongs to the same G-type class as our sun, although it is slightly smaller and cooler.

The system has an unexpected arrangement. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large.

"The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system," said Jack Lissauer, planetary scientist and Kepler science team member at NASA's Ames Research Center in Moffett Field, Calif. "The analysis of Kepler data continues to reveal new insights about the diversity of planets and planetary systems within our galaxy."

Scientists are not certain how the system evolved, but they do not think the planets formed in their existing locations. They theorize the planets formed farther from their star and then migrated inward, likely through interactions with the disk of material from which they originated. This allowed the worlds to maintain their regular spacing despite alternating sizes.

The Kepler space telescope detects planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets crossing in front of, or transiting, their stars. The Kepler science team requires at least three transits to verify a signal as a planet.

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the Kepler spacecraft finds. The star field Kepler observes in the constellations Cygnus and Lyra can be seen only from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

To validate Kepler-20e and Kepler-20f, astronomers used a computer program called Blender, which runs simulations to help rule out other astrophysical phenomena masquerading as a planet.

On Dec. 5, the team announced the discovery of Kepler-22b in the habitable zone of its parent star. It is likely to be too large to have a rocky surface. While Kepler-20e and Kepler-20f are Earth-size, they are too close to their parent star to have liquid water on the surface.

"In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time," said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. "We are on the edge of our seats knowing that Kepler's most anticipated discoveries are still to come."

NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. JPL managed the Kepler mission's development.

For more information about the Kepler mission and to view the digital press kit, visit: http://www.nasa.gov/kepler .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney.b.clavin@jpl.nasa.gov

Trent Perrotto 202-358-0321
NASA Headquarters, Washington
trent.j.perrotto@nasa.gov

Michele Johnson 650-604-6982
Ames Research Center, Moffett Field, Calif.
michele.johnson@nasa.gov

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Monday, December 19, 2011

NOAO: New Insight into the Bar in the Center of the Milky Way

The BRAVA fields are shown in this image montage. For reference, the center of the Milky Way is at coordinates L= 0, B=0. The regions observed are marked with colored circles. This montage includes the southern Milky Way all the way to the horizon, as seen from CTIO. The telescope in silhouette is the CTIO Blanco 4-m. (Just peaking over the horizon on the left is the Large Magellanic Cloud, the nearest external galaxy to our own.). Image Credit: D. Talent, K. Don, P. Marenfeld & NOAO/AURA/NSF and the BRAVA Project

BRAVA Data

It sounds like the start of a bad joke: do you know about the bar in the center of the Milky Way Galaxy? Astronomers first recognized almost 80 years ago that the Milky Way Galaxy, around which the sun and its planets orbit, is a huge spiral galaxy. This isn’t obvious when you look at the band of starlight across the sky, because we are inside the galaxy: it’s as if the sun and solar system is a bug on the spoke of a bicycle wheel. But in recent decades astronomers have suspected that the center of our galaxy has an elongated stellar structure, or bar, that is hidden by dust and gas from easy view. Many spiral galaxies in the universe are known to exhibit such a bar through the center bulge, while other spiral galaxies are simple spirals. And astronomers ask, why? In a recent paper Dr. Andrea Kunder, of Cerro Tololo Inter-American Observatory (CTIO) in northern Chile, and a team of colleagues have presented data that demonstrates how this bar is rotating.

As part of a larger study dubbed BRAVA, for Bulge Radial Velocity Assay, a team assembled by Dr. R. Michael Rich at UCLA, measured the velocity of a large sample of old, red stars towards the galactic center. (See image) They did this by observing the spectra of these stars, called M giants, which allows the velocity of the star along our line of sight to be determined. Over a period of 4 years almost 10,000 spectra were acquired with the CTIO Blanco 4-meter telescope, located in the Chilean Atacama desert, resulting in the largest homogeneous sample of radial velocities with which to study the core of the Milky Way. Analyzing the stellar motions confirms that the bulge in the center of our galaxy appears to consist of a massive bar, with one end pointed almost in the direction of the sun, which is rotating like a solid object. Although our galaxy rotates much like a pinwheel, with the stars in the arms of the galaxy orbiting the center, the BRAVA study found that the rotation of the inner bar is cylindrical, like a toilet roll holder. This result is a large step forward in explaining the formation of the complicated central region of the Milky Way.

The full set of 10,000 spectra were compared with a computer simulation of how the bar formed from a pre-existing disk of stars. Dr. Juntai Shen of the Shanghai Observatory developed the model. The data fits the model extremely well, and suggests that before our bar existed, there was a massive disk of stars. This is in contrast to the standard picture in which our galaxy’s central region formed from the chaotic merger of gas clouds, very early in the history of the Universe. The implication is that gas played a role, but appears to have largely organized into a massive rotating disk, that then turned into a bar due to the gravitational interactions of the stars.

The stellar spectra also allow the team to analyze the chemical composition of the stars. While all stars are composed primarily of hydrogen, with some helium, it is the trace of all the other elements in the periodic table, called “metals” by astronomers, that allow us to say something about the conditions under which the star formed. The BRAVA team found that stars closest to the plane of the Galaxy have a lower ratio of metals than stars further from the plane. While this trend confirms standard views, the BRAVA data cover a significant area of the bulge that can be chemically fingerprinted. By mapping how the metal content of stars varies throughout the Milky Way, star formation and evolution is deciphered, just as mapping carbon dioxide concentrations in different layers of Antarctic ice reveal ancient weather patterns.

The international team of astronomy on this project has made all of their data available to other astronomers so that additional analysis will be possible. They note that in the future it will be possible to measure more precise motions of these stars so that they can determine the true motion in space, not just the motion along our line of sight.

A preprint version of the research paper accepted for publication is available on the Web at http://arxiv.org/abs/1112.1955

NOAO, which manages CTIO, is operated by the Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.

Media Contact:

Dr. Katy Garmany
Deputy Press Officer
National Optical Astronomy Observatory
950 N Cherry Ave
Tucson AZ 85719 USA
+1 520-318-8526
E-mail:kgarmany@noao.edu

Science Contact

Dr. Andrea Kunder
Cerro Tololo Inter-American Observatory
La Serena, Chile
akunder@ctio.noao.edu

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Saturday, December 17, 2011

Standing out from the Crowd

NGC 6642
Credit: ESA/Hubble & NASA

The compact nature of globular clusters is a double-edged sword. On the one hand, having so many stars of a similar age in one bundle gives astronomers insights into the chemical makeup of our galaxy in its early history. But, at the same time, the high density of stars in the cores of globulars also makes it difficult for astronomers to resolve individual stars.

The core of NGC 6642, shown here in this Hubble Space Telescope image, is particularly dense, making this globular a difficult observational target for most telescopes. Furthermore, it occupies a very central position in our galaxy, which means that images inadvertently capture many stars that don’t belong to the cluster — these “field stars” just get in the way.

However, using Hubble’s powerful Advanced Camera for Surveys (ACS), astronomers can identify and remove such distracting field stars, and resolve the cluster’s dense core in unprecedented detail. Using Hubble’s ACS, astronomers have already made many interesting finds about NGC 6642. For example, many “blue stragglers” (stars which seemingly lag behind in their rate of aging) have been spotted in this globular, and it is known to be lacking in low-mass stars.

This picture was created from visible and infrared images taken with the Wide Field Channel of the Advanced Camera for Surveys. The field of view is approximately 1.6 by 1.6 arcminutes.

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Thursday, December 15, 2011

Young star rebels against its parent cloud

PR Image heic1118a
Hubble view of star-forming region S106

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Hubble/Subaru composite of star-forming region S 106

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Ground-based view of the area around star-forming region S 106

Videos

PR Video heic1118a
Hubblecast 51: Star-forming region S 106

PR Video heic1118b
Animation of S 106

PR Video heic1118c
Zooming in on S 106

PR Video heic1118d
Pan over S 106

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Artist’s impression of S 106

Hubble’s Wide Field Camera 3 has captured this image of a giant cloud of hydrogen gas illuminated by a bright young star. The image shows how violent the end stages of the star-formation process can be, with the young object shaking up its stellar nursery.

Despite the celestial colours of this picture, there is nothing peaceful about star forming region Sh 2-106, or S106 for short. A devilish young star, named S106 IR, lies in it and ejects material at high speed, which disrupts the gas and dust around it. The star has a mass about 15 times that of the Sun and is in the final stages of its formation. It will soon quieten down by entering the main sequence, the adult stage of stellar life.

For now, S106 IR remains embedded in its parent cloud, but it is rebelling against it. The material spewing off the star not only gives the cloud its hourglass shape but also makes the hydrogen gas in it very hot and turbulent. The resulting intricate patterns are clearly visible in this Hubble image.

The young star also heats up the surrounding gas, making it reach temperatures of 10 000 degrees Celsius. The star’s radiation ionises the hydrogen lobes, making them glow. The light from this glowing gas is coloured blue in this image.

Separating these regions of glowing gas is a cooler, thick lane of dust, appearing red in the image. This dark material almost completely hides the ionising star from view, but the young object can still be seen peeking through the widest part of the dust lane.

S106 was the 106th object to be catalogued by the astronomer Stewart Sharpless in the 1950s. It is a few thousand light-years distant in the direction of Cygnus (The Swan). The cloud itself is relatively small by the standards of star-forming regions, around 2 light-years along its longest axis. This is about half the distance between the Sun and Proxima Centauri, our nearest stellar neighbour.

This composite picture was obtained with the Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope. It results from the combination of two images taken in infrared light and one which is tuned to a specific wavelength of visible light emitted by excited hydrogen gas, known as H-alpha. This choice of wavelengths is ideal for targetting star-forming regions. The H-alpha filter isolates the light emitted from hydrogen in gas clouds while the infrared light can shine through the dust that often obscures these regions.

Notes

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Image credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

Links
Images of Hubble
NASA press release

Contacts

Oli Usher
Hubble/ESA
Garching, Germany
Tel: +49-89-3200-6855
Email: ousher@eso.org

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NASA's RXTE Detects 'Heartbeat' of Smallest Black Hole Candidate

This animation compares the X-ray 'heartbeats' of GRS 1915 and IGR J17091, two black holes that ingest gas from companion stars. GRS 1915 has nearly five times the mass of IGR J17091, which at three solar masses may be the smallest black hole known. A fly-through relates the heartbeats to hypothesized changes in the black hole's jet and disk. Credit: NASA/Goddard Space Flight Center/CI Lab. Download this video and related content from NASA Goddard's Scientific Visualization Studio

An international team of astronomers has identified a candidate for the smallest-known black hole using data from NASA's Rossi X-ray Timing Explorer (RXTE). The evidence comes from a specific type of X-ray pattern, nicknamed a "heartbeat" because of its resemblance to an electrocardiogram. The pattern until now has been recorded in only one other black hole system.

Named IGR J17091-3624 after the astronomical coordinates of its sky position, the binary system combines a normal star with a black hole that may weigh less than three times the sun's mass. That is near the theoretical mass boundary where black holes become possible.

Gas from the normal star streams toward the black hole and forms a disk around it. Friction within the disk heats the gas to millions of degrees, which is hot enough to emit X-rays. Cyclical variations in the intensity of the X-rays observed reflect processes taking place within the gas disk. Scientists think that the most rapid changes occur near the black hole's event horizon, the point beyond which nothing, not even light, can escape.

Astronomers first became aware of the binary system during an outburst in 2003. Archival data from various space missions show it becomes active every few years. Its most recent outburst started in February and is ongoing. The system is located in the direction of the constellation Scorpius, but its distance is not well established. It could be as close as 16,000 light-years or more than 65,000 light-years away.

The record-holder for wide-ranging X-ray variability is another black hole binary system named GRS 1915+105. This system is unique in displaying more than a dozen highly structured patterns, typically lasting between seconds and hours.

"We think that most of these patterns represent cycles of accumulation and ejection in an unstable disk, and we now see seven of them in IGR J17091," said Tomaso Belloni at Brera Observatory in Merate, Italy. "Identifying these signatures in a second black hole system is very exciting."

In GRS 1915, strong magnetic fields near the black hole's event horizon eject some of the gas into dual, oppositely directed jets that blast outward at about 98 percent the speed of light. The peak of its heartbeat emission corresponds to the emergence of the jet.

Changes in the X-ray spectrum observed by RXTE during each beat reveal that the innermost region of the disk emits enough radiation to push back the gas, creating a strong outward wind that stops the inward flow, briefly starving the black hole and shutting down the jet. This corresponds to the faintest emission. Eventually, the inner disk gets so bright and hot it essentially disintegrates and plunges toward the black hole, re-establishing the jet and beginning the cycle anew. This entire process happens in as little as 40 seconds.

While there is no direct evidence IGR J17091 possesses a particle jet, its heartbeat signature suggests that similar processes are at work. Researchers say that this system's heartbeat emission can be 20 times fainter than GRS 1915 and can cycle some eight times faster, in as little as five seconds.

Astronomers estimate that GRS 1915 is about 14 times the sun's mass, placing it among the most-massive-known black holes that have formed because of the collapse of a single star. The research team analyzed six months of RXTE observations to compare the two systems, concluding that IGR J17091 must possess a minuscule black hole.

"Just as the heart rate of a mouse is faster than an elephant's, the heartbeat signals from these black holes scale according to their masses," said Diego Altamirano, an astrophysicist at the University of Amsterdam in The Netherlands and lead author of a paper describing the findings in the Nov. 4 issue of The Astrophysical Journal Letters.

The researchers say this analysis is just the start of a larger program to compare both of these black holes in detail using data from RXTE, NASA's Swift satellite and the European XMM-Newton observatory.

"Until this study, GRS 1915 was essentially a one-off, and there's only so much we can understand from a single example," said Tod Strohmayer, the project scientist for RXTE at NASA's Goddard Space Flight Center in Greenbelt, Md. "Now, with a second system exhibiting similar types of variability, we really can begin to test how well we understand what happens at the brink of a black hole."

Launched in late 1995, RXTE is second only to Hubble as the longest serving of NASA's operating astrophysics missions. RXTE provides a unique observing window into the extreme environments of neutron stars and black holes.

Related links

Dutch press release

Italian press release
http://www.media.inaf.it/2011/12/12/batticuore-buco-nero/

GRS 1915+105: Taking the Pulse of a Black Hole System
http://chandra.harvard.edu/photo/2011/g1915/

RXTE Homes in on a Black Hole's Jets
http://www.nasa.gov/topics/universe/features/black-hole-jets.html


Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Md.

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A Galaxy Blooming with New Stars

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Wide-field view of NGC 253 from the VLT Survey Telescope

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The galaxy NGC 253 in the constellation of Sculptor

PR Image eso1152c
Wide-field view of the sky around NGC 253

PR Video eso1152a
Zooming in on NGC 253

VLT Survey Telescope snaps wide-field view of NGC 253

The VLT Survey Telescope (VST) has captured the beauty of the nearby spiral galaxy NGC 253. The new portrait is probably the most detailed wide-field view of this object and its surroundings ever taken. It demonstrates that the VST, the newest telescope at ESO's Paranal Observatory, provides broad views of the sky while also offering impressive image sharpness.

NGC 253 gleams about eleven and a half million light-years away in the southern constellation of Sculptor. It is often just called the Sculptor Galaxy, although other descriptive names include the Silver Coin or Silver Dollar Galaxy. It is easy to get a good look at NGC 253 through binoculars as it is one of the brightest galaxies in the sky after the Milky Way's closest, big galactic neighbour, the Andromeda Galaxy.

Astronomers have noted the widespread active star formation in NGC 253 and labelled it a "starburst" galaxy [1]. The many bright clumps dotting the galaxy are stellar nurseries where hot young stars have just ignited. The radiation streaming from these giant blue-white babies makes the surrounding hydrogen gas clouds glow brightly (green in this image).

This nearby spiral galaxy was discovered by the German–British astronomer Caroline Herschel, the sister of the famed astronomer William Herschel, as she searched for comets in 1783. The Herschels would have been delighted by the crisp, richly detailed view of NGC 253 that the VST can provide.

This latest image of NGC 253 was taken during VST’s science verification phase — when the telescope’s scientific performance is assessed before it enters operations. The VST data are being combined with infrared images from VISTA (eso0949) to identify the younger generations of stars in NGC 253. This picture is more than 12 000 pixels across and the superb sky conditions at ESO’s Paranal Observatory, combined with the fine telescope optics, result in sharp star images over the entire image.

The VST is a 2.6-metre wide-field survey telescope with a one-degree field of view — twice as broad as the full Moon [2]. The VST programme is a joint venture between the INAF–Osservatorio Astronomico di Capodimonte, Naples, Italy and ESO (eso1119). The 268-megapixel camera OmegaCAM at its heart is designed to map the sky both quickly and with very fine image quality. VST is the largest telescope in the world designed to exclusively survey the sky in visible light, complementing ESO's VISTA infrared survey telescope, also located at Paranal.

Zooming into this new picture not only allows a very detailed inspection of the star-forming spiral arms of the galaxy to be made, but also reveals a very rich tapestry of much more distant galaxies far beyond NGC 253.

Notes

[1] Further details about NGC 253 have been revealed by ESO's Very Large Telescope (VLT) along with the NASA/ESA Hubble Space Telescope. These instruments showed in 2009 that, at its centre, NGC 253 harbours a supermassive black hole with very similar properties to those of the black hole lurking in the Milky Way's core (see ESO Press Release eso0902).

[2] The image presented here has been cropped and is slightly smaller than the full VST field of view.

More information

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links
Photos of the VST
VST public web pages

Contacts

Massimo Capaccioli
University of Naples Federico II and INAF-Capodimonte Astronomical Observatory
Naples, Italy
Tel: +39 081 557 5601
Cell: +39 335 677 6940
Email: capaccioli@na.infn.it

Richard Hook
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

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Wednesday, December 14, 2011

A Black Hole's Dinner is Fast Approaching

PR Image eso1151a
Simulation of gas cloud after close approach to the black hole at the centre of the Milky Way

PR Image eso1151b
Simulation of gas cloud approaching the black hole at the centre of the Milky Way

PR Image eso1151c
The centre of the Milky Way showing a newly discovered and rapidly moving cloud

Videos

PR Video eso1151a
ESOcast 39: A Black Hole’s Dinner is Fast Approaching

PR Video eso1151b
Video News Release 36: A Black Hole’s Dinner is Fast Approaching (eso1151b)

PR Video eso1151c
Simulation of gas cloud approaching the black hole at the centre of the Milky Way

PR Video eso1151d
Zooming in on the centre of the Milky Way

PR Video eso1151e
Animation of objects orbiting the centre of the Milky Way

PR Video eso1151f
A gas cloud falling towards the supermassive black hole at the centre of the Milky Way

PR Video eso1151g
Video News Release: A Black Hole’s Dinner is Fast Approaching – B-roll

Astronomers using ESO’s Very Large Telescope have discovered a gas cloud with several times the mass of the Earth accelerating fast towards the black hole at the centre of the Milky Way. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed. The results will be published in the 5 January 2012 issue of the journal Nature.

During a 20-year programme using ESO telescopes to monitor the movement of stars around the supermassive black hole at the centre of our galaxy (eso0846) [1], a team of astronomers led by Reinhard Genzel at the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, has discovered a unique new object fast approaching the black hole.

Over the last seven years, the speed of this object has nearly doubled, reaching more than 8 million km/h. It is on a very elongated orbit [2] and in mid-2013 it will pass at a distance of only about 40 billion kilometres from the event horizon of the black hole, a distance of about 36 light-hours [3]. This is an extremely close encounter with a supermassive black hole in astronomical terms.

This object is much cooler than the surrounding stars (only about 280 degrees Celsius), and is composed mostly of hydrogen and helium. It is a dusty, ionised gas cloud with a mass roughly three times that of the Earth. The cloud is glowing under the strong ultraviolet radiation from the hot stars around it in the crowded heart of the Milky Way.

The current density of the cloud is much higher than the hot gas surrounding the black hole. But as the cloud gets ever closer to the hungry beast, increasing external pressure will compress the cloud. At the same time the huge gravitational pull from the black hole, which has a mass four million times that of the Sun, will continue to accelerate the inward motion and stretch the cloud out along its orbit.

“The idea of an astronaut close to a black hole being stretched out to resemble spaghetti is familiar from science fiction. But we can now see this happening for real to the newly discovered cloud. It is not going to survive the experience,” explains Stefan Gillessen (MPE) the lead author of the paper.

The cloud’s edges are already starting to shred and disrupt and it is expected to break up completely over the next few years [4]. The astronomers can already see clear signs of increasing disruption of the cloud over the period between 2008 and 2011.

The material is also expected to get much hotter as it nears the black hole in 2013 and it will probably start to give off X-rays. There is currently little material close to the black hole so the newly-arrived meal will be the dominant fuel for the black hole over the next few years.

One explanation for the formation of the cloud is that its material may have come from nearby young massive stars that are rapidly losing mass due to strong stellar winds. Such stars literally blow their gas away. Colliding stellar winds from a known double star in orbit around the central black hole may have led to the formation of the cloud.

“The next two years will be very interesting and should provide us with extremely valuable information on the behaviour of matter around such remarkable massive objects,” concludes Reinhard Genzel.

Notes

[1] The black hole at the centre of the Milky Way is formally known as Sgr A* (pronounced Sagittarius A star). It is the closest supermassive black hole known by far and hence is the best place to study black holes in detail.

[2] The observations were made using the NACO infrared adaptive optics camera and the SINFONI infrared spectrograph, both attached to the ESO Very Large Telescope in Chile. The centre of the Milky Way lies behind thick dust clouds that scatter and absorb visible light and must be observed at infrared wavelengths where the clouds are more transparent.

[3] A light-hour is the distance that light travels in one hour. It is a little more than the distance from the Sun to the planet Jupiter in the Solar System. For comparison the distance between the Sun and the nearest star is more than four light-years. The cloud will pass at less than ten times the distance from the Sun to Neptune from the black hole

[4] This effect well known from the physics of fluids and can be seen when for example pouring syrup in a glass of water. The flow of syrup downwards through the water will be disrupted and the droplet will break apart — effectively diluting the syrup in the water.

More information

This research was presented in a paper “A gas cloud on its way towards the super-massive black hole in the Galactic Centre”, by S. Gillessen et al., to appear in the 5 January 2012 issue of the journal Nature.

The team is composed of S. Gillessen (Max-Planck-Institut für extraterrestrische Physik [MPE], Germany), R. Genzel (MPE; Department of Physics, University of California [UC], USA), T. Fritz (MPE, Germany), E. Quataert (Department of Astronomy, UC, USA), C. Alig (Universitätssternwarte der Ludwig-Maximilians-Universität [LMU], Germany), A. Burkert (MPE; LMU), J. Cuadra (Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Chile), F. Eisenhauer (MPE), O. Pfuhl (MPE), K. Dodds-Eden (MPE), C. Gammie (Center for Theoretical Astrophysics, University of Illinois, USA), T. Ott (MPE).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Research paper in Nature
MPE web page on the Galactic Centre
Images of Paranal

Contacts

Stefan Gillessen
Max-Planck Institute for Extraterrestrial Physics
Garching, Germany
Tel: +49 89 30000 3839
Email: ste@mpe.mpg.de

Reinhard Genzel
Max-Planck Institute for Extraterrestrial Physics
Garching, Germany
Tel: +49 89 30000 3281
Email: genzel@mpe.mpg.de

Richard Hook
ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

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