Cygnus X-1: A Stellar Mass Black Hole

NASA - Chandra X-ray Observatory patch.

Nov. 18, 2011

 (Click on the image for enlarge)

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

A trio of papers with data from radio, optical and X-ray telescopes, including NASA's Chandra X-ray Observatory, has revealed new details about the birth of this famous black hole that took place millions of years ago. Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, scientists were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate. Its event horizon -- the point of no return for material falling towards a black hole -- is spinning around more than 800 times a second.

Using optical observations of the companion star and its motion around its unseen companion, the team also made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

The researchers also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory's Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.

Read more/access all images: http://chandra.harvard.edu/photo/2011/cygx1/

Image, Text, Credits: X-ray: NASA/CXC; Optical: Digitized Sky Survey / Janet Anderson / Marshall Space Flight Center / Megan Watzke.

Greetings, Orbiter.ch

NASA Orbiter Catches Mars Sand Dunes In Motion

NASA - Mars Reconnaissance Orbiter (MRO) patch.

Nov. 17, 2011

Images from NASA's Mars Reconnaissance Orbiter (MRO) show sand dunes and ripples moving across the surface of Mars at dozens of locations and shifting up to several yards. These observations reveal the planet's sandy surface is more dynamic than previously thought.

A dune in the northern polar region of Mars shows significant changes between two images taken on June 25, 2008 and May 21, 2010 by NASA's Mars Reconnaissance Orbiter. Image credit: NASA / JPL-Caltech / Univ. of Ariz. / JHUAPL.

"Mars either has more gusts of wind than we knew about before, or the winds are capable of transporting more sand," said Nathan Bridges, planetary scientist at the Johns Hopkins University's Applied Physics Laboratory in Laurel, Md., and lead author of a paper on the finding published online in the journal Geology. "We used to think of the sand on Mars as relatively immobile, so these new observations are changing our whole perspective."

While red dust is known to swirl all around Mars in storms and dust devils, the planet's dark sand grains are larger and harder to move. Less than a decade ago, scientists thought the dunes and ripples on Mars either did not budge or moved too slowly for detection.

A rippled dune front in Herschel Crater on Mars moved an average of about two meters (about two yards) between March 3, 2007 and December 1, 2010. Image credit: NASA / JPL-Caltech / Univ. of Ariz. / JHUAPL.

MRO was launched in 2005. Initial images from the spacecraft's High Resolution Imaging Science Experiment (HiRISE) camera documented only a few cases of shifting sand dunes and ripples, collectively called bedforms. Now, after years of monitoring the martian surface, the spacecraft has documented movements of a few yards or meters per year in dozens of locations across the planet.

The air on Mars is thin, so stronger gusts of wind are needed to push a grain of sand. Wind-tunnel experiments have shown that a patch of sand would take winds of about 80 mph to move on Mars compared with only 10 mph on Earth. Measurements from the meteorology experiments on NASA's Viking landers in the 1970s and early 1980s, in addition to climate models, showed such winds should be rare on Mars.

A rippled patch of sand in Becquerel Crater on Mars moved about two meters (about two yards) between November 24, 2006 and September 5, 2010. Image credit: NASA / JPL-Caltech / Univ. of Ariz. / JHUAPL.

The first hints that Martian dunes move came from NASA's Mars Global Surveyor, which operated from 1997 to 2006. But the spacecraft's cameras lacked the resolution to definitively detect the changes. NASA's Mars Exploration Rovers also detected hints of shifting sand when they touched down on the red planet's surface in 2004. The mission team was surprised to see grains of sand dotting the rovers' solar panels. They also witnessed the rovers' track marks filling in with sand.

"Sand moves by hopping from place to place," said Matthew Golombek, a co-author of the new paper and a member of the Mars Exploration Rover and MRO teams at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Before the rovers landed on Mars, we had no clear evidence of sand moving."

A rippled dune front in Herschel Crater on Mars moved an average of about one meter (about one yard) between March 3, 2007 and December 1, 2010. Image credit: NASA / JPL-Caltech / Univ. of Ariz. / JHUAPL.

Not all of the sand on Mars is blowing in the wind. The study also identifies several areas where the bedforms did not move.

"The sand dunes where we didn't see movement today could have larger grains, or perhaps their surface layers are cemented together," said Bridges, who also is a member of the HiRISE team. "These studies show the benefit of long-term monitoring at high resolution."

The eastern margin of a rippled dune in Herschel Crater on Mars moved an average distance of three meters (about three yards) between March 3, 2007 and December 1, 2010. Image credit: NASA / JPL-Caltech / Univ. of Ariz. / JHUAPL.

According to scientists, the seemingly stationary areas might move on much larger time scales, triggered by climate cycles on Mars that last tens of thousands of years. The tilt of Mars' axis relative to its orbital plane can vary dramatically. This, combined with the oval shape of Mars' orbit, can cause extreme changes in the Martian climate, much greater than those experienced on Earth. Mars may once have been warm enough that the carbon dioxide now frozen in the polar ice caps could have been free to form a thicker atmosphere, leading to stronger winds capable of transporting sand.

HiRISE is operated by the University of Arizona in Tucson. The instrument was built by Ball Aerospace & Technologies Corp. of Boulder, Colo. The Mars Exploration Rovers Opportunity and Spirit were built by JPL. JPL also manages the MRO and Mars Exploration Rover projects for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver is NASA's industry partner for the MRO Project and built the spacecraft.

MRO images and additional information is available online at: http://www.nasa.gov/mission_pages/MRO

For more information about NASA Mars missions, visit the Web at: http://www.nasa.gov/mars

Animations (mentioned), Text Credit: NASA / Dwayne Brown / JPL-Caltech / Priscilla Vega.

Best regards, Orbiter.ch

The LHC's 2011 lead-ion run gets under way

CERN - European Organization for Nuclear Research logo.

17 Nov 2011

 A lead-ion collision recorded by the ALICE experiment during the 2011 run

After several months of proton collisions, the LHC is embarking on a period of lead ion running, which will last until 7 December. This should provide large quantities of data, as the LHC's performance has been dramatically improved since the first lead-ion run in 2010.

Lead ion collisions will be studied in detail by the ALICE experiment, which is optimised for lead ions, as well as by the ATLAS and CMS experiments. By studying these collisions, physicists probe matter as it would have been in the first instants of the Universe's existence. One of their main objectives is to make tiny quantities of such matter, known as Quark Gluon Plasma, and to study how it evolved into the matter that makes up the Universe today.

Note:

The European Organization for Nuclear Research (French: Organisation européenne pour la recherche nucléaire), known as CERN, is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border. Established in 1954, the organization has twenty European member states.

The term CERN is also used to refer to the laboratory itself, which employs just under 2400 full-time employees / workers, as well as some 7931 scientists and engineers representing 608 universities and research facilities and 113 nationalities.

More information:

    CERN Bulletin: Leading lead through the LHC: http://cdsweb.cern.ch/journal/CERNBulletin/2011/43/News%20Articles/1392094?ln=en

    ALICE public website: http://aliceinfo.cern.ch/public

Follow CERN on Twitter: http://twitter.com/cern/

Image, Text, Credit: European Organization for Nuclear Research (CERN).

Cheers, Orbiter.ch

A New Map of the Moon

NASA - Lunar Reconnaissance Orbiter (LRO) patch.

Nov. 17, 2011

NASA’s Lunar Reconnaissance Orbiter science team released the highest resolution near-global topographic map of the moon ever created. This new topographic map shows the surface shape and features over nearly the entire moon with a pixel scale close to 328 feet.

Although the moon is Earth's closest neighbor, knowledge of its morphology is still limited. Due to the limitations of previous missions, a global map of the moon’s topography at high resolution has not existed until now. With LRO's Wide Angle Camera and the Lunar Orbiter Laser Altimeter instrument, scientists can now accurately portray the shape of the entire moon at high resolution.

For more information about LRO, visit: http://www.nasa.gov/mission_pages/LRO/main/index.html and http://lunar.gsfc.nasa.gov/

Image, Text, Credit: NASA / Goddard Space Flight Center / DLR / ASU.

Greetings, Orbiter.ch

New LHC results announced in Paris

CERN - European Organization for Nuclear Research logo.

16 Nov 2011

This week's Hadron Collider Physics Symposium (HCP2011) in Paris is the first opportunity for the LHC experiments, ATLAS, CMS and LHCb to present new results following the end of the LHC's 2011 proton run. For the fourth large LHC collaboration, ALICE, 2011 is just getting underway with the LHC embarking on a four-week lead-ion run.

Hadron Collider Physics Symposium (HCP2011)

Highlights presented at HCP2011 include the first Higgs search result that combines data from ATLAS and CMS. This analysis includes data collected up to August, and it underlines the conclusions that were presented that month: the Standard Model Higgs boson is running out of places to hide. If it exists, it will either be found or definitively ruled out during the course of next year's LHC run. Finding this long sought particle would be a triumph for the LHC, ruling it out would herald major change in the way we view our universe at the microscopic level.

Large Hadron Collider (LHC)

Another highlight comes from LHCb, which has compared the decays of charm particles with those of their antimatter counterparts. LHCb can measure these decays to greater precision than any previous experiment.

Note:

The European Organization for Nuclear Research (French: Organisation européenne pour la recherche nucléaire), known as CERN, is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border. Established in 1954, the organization has twenty European member states.

The term CERN is also used to refer to the laboratory itself, which employs just under 2400 full-time employees/workers, as well as some 7931 scientists and engineers representing 608 universities and research facilities and 113 nationalities.

More information:

    Bulletin: Charming surprise: http://cdsweb.cern.ch/journal/CERNBulletin/2011/46/News%20Articles/1398216?ln=de

    LHCb public web page: http://lhcb-public.web.cern.ch/lhcb-public/

    Hadron Collider Physics Symposium: http://hcp2011.lpnhe.in2p3.fr/

Images, Text, Credit: CERN / HCP2011.

Greetings, Orbiter.ch

NASA Probe Data Show Evidence of Liquid Water on Icy Europa

NASA - Galileo Mission patch.

11.16.11

Data from a NASA planetary mission have provided scientists evidence of what appears to be a body of liquid water, equal in volume to the North American Great Lakes, beneath the icy surface of Jupiter's moon, Europa.

The data suggest there is significant exchange between Europa's icy shell and the ocean beneath. This information could bolster arguments that Europa's global subsurface ocean represents a potential habitat for life elsewhere in our solar system. The findings are published in the scientific journal Nature.

Image above: Europa's "Great Lake." Scientists speculate many more exist throughout the shallow regions of the moon's icy shell. Image Credit: Britney Schmidt / Dead Pixel FX / Univ. of Texas at Austin.

"The data opens up some compelling possibilities," said Mary Voytek, director of NASA's Astrobiology Program at agency headquarters in Washington. "However, scientists worldwide will want to take a close look at this analysis and review the data before we can fully appreciate the implication of these results."

NASA's Galileo spacecraft, launched by the space shuttle Atlantis in 1989 to Jupiter, produced numerous discoveries and provided scientists decades of data to analyze. Galileo studied Jupiter, which is the most massive planet in the solar system, and some of its many moons.

One of the most significant discoveries was the inference of a global salt water ocean below the surface of Europa. This ocean is deep enough to cover the whole surface of Europa and contains more liquid water than all of Earth's oceans combined. However, being far from the sun, the ocean surface is completely frozen. Most scientists think this ice crust is tens of miles thick.

"One opinion in the scientific community has been if the ice shell is thick, that's bad for biology. That might mean the surface isn't communicating with the underlying ocean," said Britney Schmidt, lead author of the paper and postdoctoral fellow at the Institute for Geophysics, University of Texas at Austin. "Now, we see evidence that it's a thick ice shell that can mix vigorously and new evidence for giant shallow lakes. That could make Europa and its ocean more habitable."

Image above: Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain. Image Credit: Paul Schenk / NASA.

Schmidt and her team focused on Galileo images of two roughly circular, bumpy features on Europa's surface called chaos terrains. Based on similar processes seen on Earth -- on ice shelves and under glaciers overlaying volcanoes -- they developed a four-step model to explain how the features form. The model resolves several conflicting observations. Some seemed to suggest the ice shell is thick. Others suggest it is thin.

This recent analysis shows the chaos features on Europa's surface may be formed by mechanisms that involve significant exchange between the icy shell and the underlying lake. This provides a mechanism or model for transferring nutrients and energy between the surface and the vast global ocean already inferred to exist below the thick ice shell. This is thought to increase the potential for life there.

Image above: Europa, as viewed from NASA’s Galileo spacecraft. Visible are plains of bright ice, cracks that run to the horizon, and dark patches that likely contain both ice and dirt. Image Credit: NASA.

The study authors have good reason to believe their model is correct, based on observations of Europa from Galileo and of Earth. Still, because the inferred lakes are several miles below the surface, the only true confirmation of their presence would come from a future spacecraft mission designed to probe the ice shell. Such a mission was rated as the second highest priority flagship mission by the National Research Council's recent Planetary Science Decadal Survey and is being studied by NASA.

Four step process for building "chaos terrains" on Europa

"This new understanding of processes on Europa would not have been possible without the foundation of the last 20 years of observations over Earth's ice sheets and floating ice shelves," said Don Blankenship, a co-author and senior research scientist at the Institute for Geophysics, where he leads airborne radar studies of the planet's ice sheets.

Galileo was the first spacecraft to directly measure Jupiter's atmosphere with a probe and conduct long-term observations of the Jovian system. The probe was the first to fly by an asteroid and discover the moon of an asteroid. NASA extended the mission three times to take advantage of Galileo's unique science capabilities, and it was put on a collision course into Jupiter's atmosphere in September 2003 to eliminate any chance of impacting Europa.

The Galileo mission was managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., for the agency's Science Mission Directorate.

For images and a video animation of the findings, visit the University of Texas at Austin: http://www.jsg.utexas.edu/news/2011/11/scientists-find-evidence-for-great-lake-on-europa/

Images (mentioned), Video, Text, Credits: NASA / Dwayne Brown / Marc Airhart, University of Texas at Austin.

Greetings, Orbiter.ch

The Cool Clouds of Carina

ESO - European Southern Observatory logo.

16 November 2011

APEX gives us a new view of star formation in the Carina Nebula

The Cool Clouds of Carina

Observations made with the APEX telescope in submillimetre-wavelength light reveal the cold dusty clouds from which stars form in the Carina Nebula. This site of violent star formation, which plays host to some of the highest-mass stars in our galaxy, is an ideal arena in which to study the interactions between these young stars and their parent molecular clouds.

Using the LABOCA camera on the Atacama Pathfinder Experiment (APEX) telescope on the plateau of Chajnantor in the Chilean Andes, a team of astronomers led by Thomas Preibisch (Universitäts–Sternwarte München, Ludwig-Maximilians-Universität, Germany), in close cooperation with Karl Menten and Frederic Schuller (Max-Planck-Institut für Radioastronomie, Bonn, Germany), imaged the region in submillimetre light. At this wavelength, most of the light seen is the weak heat glow from cosmic dust grains. The image therefore reveals the clouds of dust and molecular gas — mostly hydrogen — from which stars may form. At -250ºC, the dust grains are very cold, and the faint glow emanating from them can only be seen at submillimetre wavelengths, significantly longer than those of visible light. Submillimetre light is, therefore, key to studying how stars form and how they interact with their parent clouds.

The Carina Nebula in the constellation of Carina

The APEX LABOCA observations are shown here in orange tones, combined with a visible light image from the Curtis Schmidt telescope at the Cerro Tololo Interamerican Observatory. The result is a dramatic, wide-field picture that provides a spectacular view of Carina’s star formation sites. The nebula contains stars with a total mass equivalent to over 25 000 Suns, while the mass of the gas and dust clouds is that of about 140 000 Suns.

However, only a fraction of the gas in the Carina Nebula is in sufficiently dense clouds to collapse and form new stars in the immediate future (in astronomical terms, meaning within the next million years). In the longer term, the dramatic effects of the massive stars already in the region on their surrounding clouds may accelerate the star formation rate.

High-mass stars live for only a few million years at most (a very short lifespan compared to the ten billion years of the Sun), but they profoundly influence their environments throughout their lives. As youngsters, these stars emit strong winds and radiation that shape the clouds around them, perhaps compressing them enough to form new stars. At the ends of their lives, they are highly unstable, being prone to outbursts of stellar material until their deaths in violent supernova explosions.

Digitized Sky Survey Image of Eta Carinae Nebula

A prime example of these violent stars is Eta Carinae, the bright yellowish star just to the upper left of the centre of the image. It has over 100 times the mass of our Sun, and is among the most luminous stars known. Within the next million years or so, Eta Carinae will explode as a supernova, followed by yet more supernovae from other massive stars in the region.

These violent explosions rip through the molecular gas clouds in their immediate surroundings, but after the shockwaves have travelled more than about ten light-years they are weaker, and may instead compress clouds that are a little further away, triggering the formation of new generations of stars. The supernovae may also produce short-lived radioactive atoms that are picked up by the collapsing clouds. There is strong evidence that similar radioactive atoms were incorporated into the cloud that collapsed to form our Sun and planets, so the Carina Nebula may provide additional insights into the creation of our own Solar System.

The Cool Clouds of Carina

The Carina Nebula is some 7500 light-years distant in the constellation of the same name (Carina, or The Keel). It is among the brightest nebulae in the sky because of its large population of high-mass stars. At about 150 light-years across, it is several times larger than the well-known Orion Nebula. Even though it is several times further away than the Orion Nebula, its apparent size on the sky is therefore about the same, making it also one of the largest nebulae in the sky.

The 12-metre-diameter APEX telescope is a pathfinder for ALMA, the Atacama Large Millimeter/submillimeter Array, a revolutionary new telescope that ESO, together with its international partners, is building and operating, also on the Chajnantor plateau. APEX is itself based on a single prototype antenna constructed for the ALMA project, while ALMA will be an array of 54 antennas with 12-metre diameters, and an additional 12 antennas with 7-metre diameters. While ALMA will have far higher angular resolution than APEX, its field of view will be much smaller. The two telescopes are complementary: for example, APEX will find many targets across wide areas of sky, which ALMA will be able to study in great detail.

APEX is a collaboration between the Max-Planck-Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. The operation of APEX is entrusted to ESO.

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

More information:

These LABOCA observations are described in the paper “A deep wide-field sub-mm survey of the Carina Nebula complex” by Preibisch et al., A&A, 525, A92 (2011): http://adsabs.harvard.edu/abs/2011A%26A...525A..92P

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”.

Link:

More information about the work of Thomas Preibisch’s team on the Carina Nebula: A panchromatic  view of massive star feedback and triggered star formation in the Carina Nebula: http://www.usm.lmu.de/people/preibisch/carina_project.html

Images, Text, Credits: ESO / APEX / T. Preibisch et al. (Submillimetre); N. Smith, University of Minnesota / NOAO / AURA / NSF (Optical) / IAU and Sky & Telescope / Digitized Sky Survey 2. Acknowledgment: Davide De Martin / Video: ESO / APEX / T. Preibisch et al.; N. Smith, University of Minnesota / NOAO / AURA / NSF; Nick Risinger (skysurvey.org); Digitized Sky Survey 2. Music: John Dyson (from the album Moonwind) / Douglas Pierce-Price (ALMA / APEX).

Cheers, Orbiter.ch