vendredi 14 décembre 2012

Spiral Galaxy NGC 3627














NASA - Chandra X-ray Observatory patch / NASA - SPITZER Space Telescope patch.

Dec. 14, 2012


The spiral galaxy NGC 3627 is located about 30 million light years from Earth. This composite image includes X-ray data from NASA's Chandra X-ray Observatory (blue), infrared data from the Spitzer Space Telescope (red), and optical data from the Hubble Space Telescope and the Very Large Telescope (yellow). The inset shows the central region, which contains a bright X-ray source that is likely powered by material falling onto a supermassive black hole.

A search using archival data from previous Chandra observations of a sample of 62 nearby galaxies has shown that 37 of the galaxies, including NGC 3627, contain X-ray sources in their centers. Most of these sources are likely powered by central supermassive black holes. The survey, which also used data from the Spitzer Infrared Nearby Galaxy Survey, found that seven of the 37 sources are new supermassive black hole candidates.

Chandra X-ray Observatory

Confirming previous Chandra results, this study finds the fraction of galaxies found to be hosting supermassive black holes is much higher than found with optical searches. This shows the ability of X-ray observations to find black holes in galaxies where relatively low-level black hole activity has either been hidden by obscuring material or washed out by the bright optical light of the galaxy.

The combined X-ray and infrared data suggest that the nuclear activity in a galaxy is not necessarily related to the amount of star-formation in the galaxy, contrary to some early claims. In contrast, these new results suggest that the mass of the supermassive black hole and the rate at which the black hole accretes matter are both greater for galaxies with greater total masses.

SPITZER Space Telescope

A paper describing these results was published in the April 10, 2011 issue of The Astrophysical Journal. The authors are Catherine Grier and Smita Mathur of The Ohio State University in Columbus, OH; Himel GHosh of CNRS/CEA-Saclay in Guf-sur-Yvette, France and Laura Ferrarese from Herzberg Institute of Astrophysics in Victoria, Canada.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Read more/access all images: http://chandra.harvard.edu/photo/2012/ngc3627/

Chandra's Flickr photoset: http://www.flickr.com/photos/nasamarshall/sets/72157606205297786/

Images, Text, Credits: NASA / J.D. Harrington / Marshall Space Flight Center / Janet Anderson / Chandra X-ray Center / Megan Watzke / CXC / Ohio State Univ. / C.Grier et al.; Optical: NASA / STScI, ESO / WFI; Infrared: NASA / JPL-Caltech.

Cheers, Orbiter.ch

jeudi 13 décembre 2012

NASA Probes Prepare for Mission-Ending Moon Impact











NASA - GRAIL Mission patch.

Dec. 13, 2012

video
 Last Flight for GRAIL's Twin Spacecraft

This animation shows the final flight path for NASA’s twin Gravity Recovery and Interior Laboratory (GRAIL) mission spacecraft, which will impact the moon on Dec. 17, 2012, around 2:28 p.m. PST.

Twin lunar-orbiting NASA spacecraft that have allowed scientists to learn more about the internal structure and composition of the moon are being prepared for their controlled descent and impact on a mountain near the moon's north pole at about 2:28 p.m. PST (5:28 p.m. EST) Monday, Dec. 17.

Ebb and Flow, the Gravity Recovery and Interior Laboratory (GRAIL) mission probes, are being sent purposely into the lunar surface because their low orbit and low fuel levels preclude further scientific operations. The duo's successful prime and extended science missions generated the highest-resolution gravity field map of any celestial body. The map will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.


These maps of Earth's moon highlight the region where the twin spacecraft of NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission will impact on Dec. Image credit: NASA/GSFC.

"It is going to be difficult to say goodbye," said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "Our little robotic twins have been exemplary members of the GRAIL family, and planetary science has advanced in a major way because of their contributions."

The mountain where the two spacecraft will make contact is located near a crater named Goldschmidt. Both spacecraft have been flying in formation around the moon since Jan. 1, 2012. They were named by elementary school students in Bozeman, Mont., who won a contest. The first probe to reach the moon, Ebb, also will be the first to go down, at 2:28:40 p.m. PST. Flow will follow Ebb about 20 seconds later.

Both spacecraft will hit the surface at 3,760 mph (1.7 kilometers per second). No imagery of the impact is expected because the region will be in shadow at the time.


This graphic highlights locations on the moon NASA considers "lunar heritage sites" and the path NASA's Gravity Recovery and Interior Laboratory spacecraft will take on their final flight. Image credit: NASA/JPL-Caltech.

Ebb and Flow will conduct one final experiment before their mission ends. They will fire their main engines until their propellant tanks are empty to determine precisely the amount of fuel remaining in their tanks. This will help NASA engineers validate fuel consumption computer models to improve predictions of fuel needs for future missions.

"Our lunar twins may be in the twilight of their operational lives, but one thing is for sure, they are going down swinging," said GRAIL project manager David Lehman of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Even during the last half of their last orbit, we are going to do an engineering experiment that could help future missions operate more efficiently."

Because the exact amount of fuel remaining aboard each spacecraft is unknown, mission navigators and engineers designed the depletion burn to allow the probes to descend gradually for several hours and skim the surface of the moon until the elevated terrain of the target mountain gets in their way.


These side-by-side, 3-D comparisons depict the unnamed lunar mountain targeted by the NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission for controlled impact of the Ebb and Flow spacecraft. Image credit: NASA/JPL-Caltech/MIT/GSFC.

The burn that will change the spacecrafts' orbit and ensure the impact is scheduled to take place Friday morning, Dec. 14.

"Such a unique end-of-mission scenario requires extensive and detailed mission planning and navigation," said Lehman. "We've had our share of challenges during this mission and always come through in flying colors, but nobody I know around here has ever flown into a moon mountain before. It'll be a first for us, that's for sure."

 GRAIL's Twin Spacecraft

During their prime mission, from March through May, Ebb and Flow collected data while orbiting at an average altitude of 34 miles (55 kilometers). Their altitude was lowered to 14 miles (23 kilometers) for their extended mission, which began Aug. 30 and sometimes placed them within a few miles of the moon's tallest surface features.

JPL manages the GRAIL mission for NASA's Science Mission Directorate in Washington. The mission is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems in Denver built the spacecraft. JPL is a division of the California Institute of Technology in Pasadena.

For more information about GRAIL, visit: http://www.nasa.gov/grail

Graphics (mentioned), Image, Video, Text, Credits: NASA / Dwayne Brown / JPL / DC Agle / Massachusetts Institute of Technology / Sarah McDonnell.

Greetings, Orbiter.ch

Giant Stellar Nursery











NASA - Hubble Space Telescope patch.

Dec. 13, 2012


Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33, a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 was so large, however, it could form enough stars to make a globular cluster.

Many young stars from this cloud are visible in this image from the Hubble Space Telescope, along with what is left of the initial gas cloud. Some stars were so massive they have already evolved and exploded in a supernova. The brightest stars that are left emit light so energetic that they create one of the largest clouds of ionized hydrogen gas known, comparable to the Tarantula Nebula in our Milky Way's close neighbor, the Large Magellanic Cloud.

Notes:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

ESA Hubble website: http://www.spacetelescope.org/

NASA Hubble website: http://hubblesite.org/

Image, Text, Credits: NASA / ESA.

Cheers, Orbiter.ch

mercredi 12 décembre 2012

Curiosity Rover Nearing Yellowknife Bay












NASA - Mars Science Laboratory (MSL) patch.

Dec. 12, 2012


Image above: The NASA Mars rover Curiosity used its Mast Camera (Mastcam) during the mission's 120th Martian day, or sol (Dec. 7, 2012), to record this view of a rock outcrop informally named "Shaler." Image credit: NASA/JPL-Caltech/MSSS.

The NASA Mars rover Curiosity drove 63 feet (19 meters) northeastward early Monday, Dec. 10, approaching a step down into a slightly lower area called "Yellowknife Bay," where researchers intend to choose a rock to drill.

The drive was Curiosity's fourth consecutive driving day since leaving a site near an outcrop called "Point Lake," where it arrived last month. These drives totaled 260 feet (79 meters) and brought the mission's total odometry to 0.37 mile (598 meters).

The route took the rover close to an outcrop called "Shaler," where scientists used Curiosity's Chemistry and Camera (ChemCam) instrument and Mast Camera (Mastcam) to assess the rock's composition and observe its layering. Before departure from Point Lake, a fourth sample of dusty sand that the rover had been carrying from the "Rocknest" drift was ingested and analyzed by Curiosity's Sample Analysis at Mars (SAM) instrument.


This map traces where NASA's Mars rover Curiosity drove between landing at a site subsequently named "Bradbury Landing," and the position reached during the mission's 123rd Martian day, or sol, (Aug. 10, 2012). Image credit: NASA/JPL-Caltech/Univ. of Arizona.

Curiosity ended Monday's drive about 30 percent shorter than planned for the day when it detected a slight difference between two calculations of its tilt, not an immediate risk, but a trigger for software to halt the drive as a precaution. "The rover is traversing across terrain different from where it has driven earlier, and responding differently," said Rick Welch, mission manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We're making progress, though we're still in the learning phase with this rover, going a little slower on this terrain than we might wish we could."

Curiosity is approaching a lip where it will descend about 20 inches (half a meter) to Yellowknife Bay. The rover team is checking carefully for a safe way down. Yellowknife Bay is the temporary destination for first use of Curiosity's rock-powdering drill, before the mission turns southwestward for driving to its main destination on the slope of Mount Sharp.

(Click on the image for enlarge)

Image above: The NASA Mars rover Curiosity used its Navigation Camera (Navcam) during the mission's 120th Martian day, or sol (Dec. 7, 2012), to record the seven images combined into this panoramic view. Image credit: NASA/JPL-Caltech.

JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Science Laboratory Project and the mission's Curiosity rover for NASA's Science Mission Directorate, Washington. JPL designed and built the rover.

More information about Curiosity is online at http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/ . You can follow the mission on Facebook at: http://www.facebook.com/marscuriosity and on Twitter at: http://www.twitter.com/marscuriosity

Curiosity gallery: http://www.nasa.gov/mission_pages/msl/multimedia/gallery-indexEvents.html

Images (mentioned), Text, Credit: NASA / JPL / Guy Webster.

Greetings, Orbiter.ch

Greedy black hole discovered in Andromeda












ESA - XMM-Newton Mission patch.

Dec. 12, 2012

Studying the Andromeda galaxy with ESA's XMM-Newton X-ray space observatory, astronomers have discovered a new bright X-ray source that hosts a stellar-mass black hole accreting mass at a very high rate. The source's location in an external galaxy allowed the astronomers to probe the emission both from the black hole's accretion disc, at X-ray wavelengths, and from its jets, in radio waves. These observations revealed, for the first time in an extragalactic stellar-mass black hole, the link between the source's X-ray brightening and the ejection of radio-bright material from the vicinity of the black hole into the jets, indicating an accretion rate close to the black hole's Eddington limit, or even above it.

Black holes are the densest objects in the Universe and, even though they do not emit light, astronomers can detect them indirectly because of their effect on the surrounding matter. A black hole's intense gravity attracts nearby matter, which falls onto the dense compact object via an accretion disc. As it is accreted onto the black hole, the matter emits large amounts of X-rays.

A new ultra-luminous X-ray source in Andromeda. Credit: ESA/XMM-Newton/MPE

 Both in stellar-mass black holes – which derive from the collapse of very massive stars – and in the supermassive black holes that sit at the centre of massive galaxies, the accretion of matter is accompanied by the release of powerful jets. These outflows of energetic particles can be observed across the electromagnetic spectrum, and are especially bright at radio wavelengths. Accretion discs and jets are two aspects of the same phenomenon, and by studying their connection astronomers can investigate the physical mechanisms that take place close to a black hole.

"We have now found a black hole that allows us to see the coupling between accretion disc and jets 'in action'," comments Matthew Middleton from the University of Durham, UK, and the Astronomical Institute 'Anton Pannekoek' at the University of Amsterdam, in the Netherlands.

Middleton led a study of XMMU J004243.6+412519, an X-ray binary in the Andromeda galaxy which consists of a stellar-mass black hole that is accreting matter from a low-mass companion star. The source was discovered using ESA's XMM-Newton X-ray space observatory. The results of the study are published online on 12 December 2012 in the journal Nature.

"When we observe an accreting black hole in our Galaxy, the Milky Way, we look at it through the interstellar material in the Galactic Plane, which absorbs most of the X-rays from the black hole's accretion disc. When we observe other galaxies, instead, our line of sight goes through much smaller amounts of interstellar material in the Galactic Plane, so the X-ray emission from the disc is clearer," explains Middleton.

video

 Video above: Discovery of a new ultra-luminous X-ray source in Andromeda. Credit: ESA/XMM-Newton/MPE.

The source was discovered in January 2012 by an X-ray monitoring programme of the Andromeda galaxy led by Wolfgang Pietsch from the Max-Planck Institut für Extraterrestrische Physik in Garching, Germany.

"Andromeda is the closest large galaxy to the Milky Way and hosts a rich variety of stellar populations, ranging from very young stars to the compact remnants of stars that have already concluded their life cycle," says Pietsch.

The programme has been observing Andromeda's population of novae – binary systems where a white dwarf is accreting mass from a companion star – with XMM-Newton and NASA's Chandra X-ray Observatory.

"If they are part of a binary system, stellar remnants such as white dwarfs, neutron stars and black holes may accrete matter from their companion and, in the process, shine brightly in X-rays. Our programme was designed specifically to monitor novae, which emit mainly soft X-rays below 1 keV. However, an interesting by-product is the detection of X-ray binaries, which host neutron stars or black holes and emit well beyond 1 keV," Pietsch adds.

About ten days after its discovery, XMMU J004243.6+412519 underwent a dramatic brightness boost. With a luminosity in excess of 1039 erg/s, it was classified as an ultra-luminous X-ray source, or ULX. This is only the second ULX known in the Andromeda galaxy.

"After this exceptional brightening, the X-ray spectrum of the source changed too, revealing a stronger contribution from the accretion disc," says Middleton.

"These changes reflect the transition to a new regime of mass accretion: by then, the black hole was accreting matter at a rate that was very close to its Eddington limit, or even above it."


Image above: Artist's impression of 'ballistic' jets ejected by a stellar-mass black hole. Credit: ESA/AOES Medialab.

 The Eddington limit identifies the maximum luminosity that can be radiated by matter as it falls onto a black hole, and depends on the black hole's mass. This key value is defined for a spherical accretion process, so can be exceeded in the context of disc accretion. However, the theoretical understanding of mass accretion breaks down at the Eddington limit. Data from black holes that are accreting beyond this limit can help astronomers understand how the structure of the disc changes at such high accretion rates and, possibly, also what triggers the outflow of material from the vicinity of the black hole.

"We suspected that the transition to a higher mass accretion rate might be linked to the onset of radio jets, so we used radio telescopes to monitor the outflowing material," says Middleton.

"The radio data exhibit multiple flares on timescales of just a few days, suggesting that the increase in the mass accretion rate might have triggered a 'ballistic' jet – a series of consecutive ejections of material," he adds.

In the Milky Way, there are only four black holes known to accrete at a high enough rate to create these jets. But by extending the search to other galaxies, many more may be found – the astronomers already know about a hundred candidates. Like the one discovered in Andromeda, these are valuable as they allow astronomers to study the connection between the accretion disc and jets without the interference of interstellar absorption.

XMM-Newton spacecraft

"The discovery of a black hole in Andromeda accreting close to its Eddington limit extends the study of stellar-mass black hole accretion beyond the Milky Way," comments Norbert Schartel, XMM-Newton Project Scientist at ESA.

Stellar-mass black holes allow astronomers to study the dynamics of accretion in great detail as the process happens on much shorter temporal scales than in supermassive black holes.

"Further observations of similar sources in other galaxies will deepen our understanding of the nature and origin of the powerful jets that stem from stellar-mass black holes as well as from the supermassive black holes that are hosted in active galaxies," he concludes.

Notes for editors:

The study presented here is based on X-ray data from ESA's XMM-Newton and NASA's Swift and Chandra X-ray observatories. The X-ray data were complemented by observations at radio wavelengths performed with the Karl G. Jansky Very Large Array (VLA), the Very Long Baseline Array (VLBA) and the Arcminute Microkelvin Imager Large Array (AMI-LA).

The source, XMMU J004243.6+412519, was discovered within an XMM-Newton survey of the Andromeda galaxy, designed to study the X-ray source population of this galaxy with particular emphasis on novae. About ten days after the discovery, new data from XMM-Newton revealed a significant brightening of this source; astronomers kept observing the source using Swift and Chandra. Radio observations started about 40 days after the discovery. The source was observed again with XMM-Newton about 6 months after the discovery, when the source had become fainter.

The European Space Agency's X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. It is the biggest scientific satellite to have been built in Europe and uses over 170 wafer-thin cylindrical mirrors spread over three high throughput X-ray telescopes. Its mirrors are among the most powerful ever developed. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects. The scientific community can apply for observing time on XMM-Newton on a competitive basis.

Related publications:

M. J. Middleton, et al., "Bright radio emission from an ultraluminous stellar-mass microquasar in M31", Nature, 2012. DOI: 10.1038/nature11697.

Related Links:

Related multimedia from NASA Goddard's Scientific Visualization Studio:
http://svs.gsfc.nasa.gov/vis/a010000/a011100/a011162/

NRAO press release: http://www.nrao.edu/pr/2012/microquasar/

"Andromeda Galaxy Pops Up Ultraluminous X-ray Sources" (02.24.12): http://www.nasa.gov/mission_pages/swift/bursts/Ultraluminous-Xrays.html

"Swift, XMM-Newton Satellites Tune Into a Middleweight Black Hole" (11.10.09): http://www.nasa.gov/topics/universe/features/middle_blackhole.html

Images, Video, Text, Credits: ESA / XMM-Newton / MPE / AOES Medialab.

Cheers, Orbiter.ch

Hubble census finds galaxies at redshifts 9 to 12












ESA - Hubble Space Telescope logo.

12 December 2012

 High-redshift galaxy candidates in the Hubble Ultra Deep Field 2012

Astronomers using the NASA/ESA Hubble Space Telescope have uncovered seven primitive galaxies from a distant population that formed more than 13 billion years ago. In the process, their observations have put forward a candidate for the record for the most distant galaxy found to date (at redshift 11.9), and have shed new light on the earliest years of cosmic history. The galaxies are seen as they were when the Universe was less than 4 percent of its present age.

A team of scientists using the Hubble Space Telescope has made new observations of the Hubble Ultra Deep Field (see heic0406, heic0916), as part of a project to improve our understanding of the early years of the Universe.

The resulting images offer the deepest ever view of the Universe at near-infrared wavelengths, which capture the redshifted [1] light of early galaxies. Because light takes so long to travel from these remote objects, astronomers are looking back in time, seeing these galaxies as they appeared 600 million years after the Big Bang (the Universe is now 13.7 billion years old). One object spotted by the team may be the most distant ever observed.

The Hubble Ultra Deep Field 2012

The new data have allowed the team, co-led by Richard Ellis (Caltech, USA) and Ross McLure (University of Edinburgh, UK), to uncover six previously-unknown galaxies in this era, and to rule out a number of tentative identifications of distant galaxies made by other scientists in previous research. This is the first statistically robust census of galaxies at such an early time in cosmic history, and shows that the number of galaxies steadily increased with time, supporting the idea that the first galaxies didn’t form in a sudden burst but gradually assembled their stars.

One previously-claimed candidate extreme redshift galaxy in the Hubble Ultra Deep Field was confirmed by the team. This is UDFj-39546284, for a while claimed to be the most distant known galaxy, at redshift 10 (heic1103). However, the improved and extended dataset has allowed the scientists to shed unexpected new light on this object, showing that it either lies at an even greater distance than previously thought (at a redshift of 11.9, handing it back the distance record), or must otherwise be a previously unknown type of extreme emission-line galaxy at much lower redshift [2].

“Our study has taken the subject forward in two ways,” says Ellis. “First, we have used Hubble to make longer exposures than previously. The added depth is essential to reliably probe the early period of cosmic history. Second, we have used Hubble’s available colour filters very effectively to measure galaxy distances more precisely.”

Studying galaxies in the early years of the Universe is fraught with difficulties. Scientists are working at the very limits of what Hubble is capable of, and must grapple with sometimes ambiguous data. A number of tentative identifications of distant galaxies have been disproved in the past, and this project is designed in part to improve the quality of data available [3].

Part of this involves taking additional data through filters which have already been used to take deep images of the Hubble Ultra Deep Field, but the team has also added new imaging through previously unexploited filters. “We added an additional filter, and undertook much deeper exposures in some filters than in earlier work in order to convincingly reject the possibility that some of our galaxies might be foreground objects,” said team member James Dunlop (University of Edinburgh, UK).

The observations, part of a project called Hubble Ultra Deep Field 2012 (UDF 2012), were made over a period of six weeks during August and September 2012, and the first results are now appearing in a series of scientific papers. The UDF 2012 team is publicly releasing these unique data before the end of the year, after preparing them for other research groups to use.

Hubble in orbit

A major goal of the new program was to determine how rapidly the number of galaxies increased over time in the early Universe. This measure is the key evidence for how quickly galaxies build up their constituent stars.

“This discovery of a significant population of galaxies at redshifts greater than 8, coupled with our new analysis of the number and properties of galaxies at redshift 7 and 8, support the idea that galaxies assembled progressively over time,” said the project co-leader Ross McLure (University of Edinburgh, UK).

The results from the UDF 2012 campaign suggest there will be many undiscovered galaxies even deeper in space waiting to be revealed by the forthcoming James Webb Space Telescope, which will be launched in 2018.

The team’s finding on the distant galaxy census has been accepted for publication in The Astrophysical Journal Letters.

Notes:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The research is presented in a paper entitled “The abundance of star-forming galaxies in the redshift range 8.5 to 12: new results from the 2012 Hubble Ultra Deep Field campaign,” accepted for publication in the the Astrophysical Journal Letters.

The international team of astronomers in this study was led by Richard Ellis (Caltech, USA), Ross McLure (University of Edinburgh, UK), James Dunlop (University of Edinburgh, UK) and Brant Robertson (University of Arizona, USA).

[1] Astronomers plumb the depths of the Universe, and probe its history, by measuring how much the light from an object has been stretched by the expansion of space. This is called the redshift value or z. The greater the observed z value for a galaxy, the more distant it is in time and space, as observed from our position in the Milky Way. Before Hubble was launched, astronomers could only see galaxies out to a z of approximately 1, corresponding to an era halfway through the history of the Universe. The original Hubble Deep Field, taken in 1995, leapfrogged to z = 4, or roughly 90 percent of the way back to the beginning of time. The Advanced Camera for Surveys (ACS) produced the Hubble Ultra Deep Field of 2004, pushing back the limit to z ~ 6. ACS was installed on Hubble during Servicing Mission 3B in 2002. Hubble’s first infrared camera, the Near Infrared Camera and Multi-Object Spectrometer reached out to z = 7. The Wide Field Camera 3 (WFC3) first took us back to z ~ 8, and has now plausibly penetrated back for the first time to z ~ 12. The James Webb Space Telescope is expected to extend this back to a z of approximately 15, 275 million years after the Big Bang, and possibly beyond. The very first stars may have formed between redshifts 30 and 15.

[2] The observations taken through the 1400nm filter, in which UDFj-39546284 was not visible, showed that the galaxy may be more distant than previously thought (as it only appears in the redder 1600nm filter). The additional observations through the 1600nm filter, in which the galaxy is visible, gave additional confidence that the galaxy is indeed real. There remains a small possibility that the object could be an extreme emission-line galaxy at much more modest distances (between redshift 2 and 3), but if this is the case then the object would have to be a previously undiscovered type of extreme emission-line galaxy. This hypothesis cannot be fully excluded until the object’s spectrum has been studied. This will not be possible until the the James Webb Space Telescope comes online in 2018. However, the balance of the available evidence favours the interpretation that this is the most distant object seen to date.

[3] Because the distance to faraway galaxies is measured by the extent to which their light is reddened by the expansion of the cosmos, accurate and comprehensive measurements of brightnesses at different wavelengths (i.e. different colours of light) is essential for studying the Universe’s early years. The only way to make unambiguous measurements of redshift (and hence distance) is using spectroscopy, in which the light of a galaxy is dispersed into a rainbow, much like a prism does with white light. This gives a full profile of the colours of a galaxy, allowing astronomers to identify key features in the spectrum produced by known chemical elements at specific wavelengths. The way these features are shifted can be used to make very precise measurements of redshift. In particular, the position of these features let scientists distinguish whether a galaxy has indeed been reddened by the expansion of the cosmos (and so is very distant) or whether it is simply intrinsically red (in which case it could be much closer), because the method does not rely on the overall redness of the object, but on specific identifiable spectral features.

However, spectroscopy of objects as faint as those uncovered in this study is not feasible with current facilities. Instead, the astronomers have used what is, in effect, a crude version of spectroscopy, based on making images through ten different filters which cover the optical-to-near-infrared spectral region. This enables the broad spectral shape — but not the detailed features — of the light from a galaxy to be established. In this case, the method enabled the scientists to search for a characteristic sharp “step” in the galaxy spectrum, produced by the absorption of all very blue ultraviolet light by the neutral hydrogen gas which pervaded the Universe during most of the first billion years of cosmic history. The carefully chosen near-infrared filters exploited in this new study enabled this technique to be extended up to redshifts as high as 12 for the first time.

Links:

Research paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1219.pdf

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

NASA release: http://hubblesite.org/newscenter/archive/releases/2012/48

UDF 2012 project: http://udf12.arizona.edu/

Images, Text, Credits: ESA / NASA / R. Ellis (Caltech), and the HUDF 2012 Team.

Greetings, Orbiter.ch

Cassini Spots Mini Nile River on Saturn Moon










ESA / NASA - Cassini International patch.

12 December 2012

The international Cassini mission has spotted what appears to be a miniature extraterrestrial version of the Nile River: a river valley on Saturn’s moon Titan that stretches more than 400 km from its ‘headwaters’ to a large sea.

It is the first time images have revealed a river system this vast and in such high resolution anywhere beyond Earth.

Titan’s Nile River

Scientists deduce that the river is filled with liquid because it appears dark along its entire extent in the high-resolution radar image, indicating a smooth surface.

“Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of this same Titan sea,” says Jani Radebaugh, a Cassini radar team associate at Brigham Young University, USA.

“Such faults – fractures in Titan’s bedrock – may not imply plate tectonics, like on Earth, but still lead to the opening of basins and perhaps to the formation of the giant seas themselves.”

Titan’s Nile River (click on the image for enlarge)

Titan is the only other world we know of that has stable liquid on its surface. While Earth’s hydrologic cycle relies on water, Titan’s equivalent cycle involves hydrocarbons such as ethane and methane.

Images from Cassini’s visible-light cameras in late 2010 revealed regions that darkened after recent rainfall.

Cassini’s visual and infrared mapping spectrometer confirmed liquid ethane at a lake in Titan’s southern hemisphere known as Ontario Lacus in 2008.

Mosaic of river channel and ridge area on Titan

“This radar-imaged river by Cassini provides another fantastic snapshot of a world in motion, which was first hinted at from the images of channels and gullies seen by ESA’s Huygens probe as it descended to the moon’s surface in 2005,” says Nicolas Altobelli, ESA’s Cassini Project Scientist.

The Cassini–Huygens mission is a cooperative project of NASA, ESA and ASI, the Italian space agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and ASI, working with team members from the US and several European countries.

Related links:

At Saturn and Titan: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Cassini-Huygens in depth: http://sci.esa.int/huygens

NASA JPL Cassini site: http://saturn.jpl.nasa.gov/

Italian Space Agency: http://www.asi.it/en

Images, Text, Credits: ESA / NASA / JPL–Caltech / ASI / University of Arizona.

Best regards, Orbiter.ch

North Korea rocket launch: satellite successfully sent into orbit










North Korea Rocket.

Dec. 12, 2012

 North Korea rocket launch satellite successfully sent into orbit

North Korea successfully launched a long-range rocket on Wednesday, defying international warnings and risking possible sanctions. The White House described the move as a "highly provocative act that threatens regional security".

North Korea successfully fired a long-range rocket on Wednesday, defying international warnings as Kim Jong Un’s regime took a big step towards potentially developing a nuclear missile.

video
North Korea rocket launch

While the rocket launch will enhance the credentials of young leader Kim, who took power after his father Kim Jong Il’s death a year ago, it is also likely to bring fresh sanctions against the country and further complicate ties between North Korea, its neighbours, and the West.

The United States, South Korea and Japan quickly condemned the morning launch, which they see as a test of the technology needed to mount a nuclear warhead on a missile that could one day be used as a threat against the US. Pyongyang claims the rocket was fired to see if the country had the capability to put a satellite into orbit.

Image, Video, Text, Credits: FRANCE 24 / Katerina VITTOZZI / AP.

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mardi 11 décembre 2012

Atlas 5 rocket lofts mini-shuttle into space for secret mission












USAF - OTV-3 Mission patch.

Dec. 11, 2012

An Atlas 5 rocket sent the Air Force's X-37B mini-shuttle on its first repeat flight on Tuesday, kicking off a months-long classified mission reportedly aimed at testing advanced spy satellite sensors.


Image above: A United Launch Alliance Atlas 5 rocket lifts off from Cape Canaveral Air Force Station's Launch Complex 41 on Tuesday, carrying the U.S. military's X-37B mini-shuttle into space.

Despite earlier concerns about the weather at Cape Canaveral Air Force Station, the launch went off on time, just after 1 p.m. ET.

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Launch of X-37B Mini Space Shuttle on OTV-3 Mission

One-fourth the size of the real space shuttle, the X-37B has captured the imaginations of everyone from amateur satellite trackers to potential military rivals. The X-37B can orbit Earth for months, then re-enter the atmosphere and land autonomously.

Each of the first two X-37B missions ended with the mini-shuttle landing on a runway at Vandenberg Air Force Base in California. Two different X-37Bs were flown for those missions, but this marks the first time that the 29-foot-long, Boeing-built craft has been reflown in space. The X-37B's reusability is one of its big selling points.

The X-37B, also known as the Orbital Test Vehicle 3 (on the image OTV-1)

Although the Air Force has not publicly discussed what the space plane will be doing, experts have surmised that the sensors tested by the X-37B will be used on smaller satellites, including low-cost, 4-inch-wide (10-centimeter-wide) CubeSats that can be tracked from the field using little more than a laptop.

The Air Force says there's a chance this mission will end with a landing on the space shuttle runway here at Florida's Kennedy Space Center.

Images, Video, Text, Credits: USAF / ULA / Reuters / Scott Audette.

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