Identity Parade Clears Cosmic Collisions of the Suspicion of Promoting Black Hole Growth

ESA - Hubble Space Telescope logo.

5 January 2011

What happens when galaxies crash together? For years, these cosmic collisions have been blamed for triggering violent outbursts at the hearts of galaxies. Now, a remarkable piece of detective work has given a verdict: galactic mergers do not usually whet the appetite of the black holes that power these active galactic nuclei, meaning other, less dramatic phenomena are responsible.

Most galaxies, including our own, have a huge but well-behaved black hole at their heart, while some have messy eaters that suck in vast amounts of matter which then shines brightly as it falls towards oblivion. This causes the telltale bright spots at the centre of galaxies known as active galactic nuclei (AGN). Why are the two types so different? Until now, the leading theory has been that mergers between galaxies are instrumental in driving matter into the black holes, making them grow.

In a new study, the largest of its kind so far, astronomers set up an identity parade of galaxies to test this theory [1]. Comparing 140 active galaxies with a control group of over 1200 comparable inactive galaxies, they found that there has been no significant link between AGN activity and galactic mergers for at least the past eight billion years [2]. Therefore, other phenomena such as instabilities within galaxies, collisions of molecular clouds or tidal disruption by other galaxies flying by must instead be to blame.

The results will be published in the Astrophysical Journal on 10 January.

Zoom on the COSMOS field

The emission of radiation from active galactic nuclei is driven by the behaviour of matter such as gas clouds and even stars as it heats up and falls into the galaxy's supermassive central black hole. But an open question in the physics of active galaxies is precisely how matter crosses the final few hundreds of light-years to reach the immediate neighbourhood of the black hole before being swallowed.

Team leader Mauricio Cisternas from Germany's Max Planck Institute for Astronomy explains: "A study of this scope has become possible only recently, as the large surveys undertaken using the Hubble Space Telescope have become available. These have given us a huge sample of galaxies, both active and inactive, meaning that we can now study many distant galaxies in exquisite detail. Before these surveys, we hadn't examined many active galaxies at large cosmic distances in sufficient detail."

Cisternas and his team chose 140 active galaxies from the COSMOS survey. The COSMOS field is an area of sky roughly 10 times the area covered by the Moon, in the constellation of Sextans (the Sextant), which has been comprehensively mapped by Hubble and other telescopes at different wavelengths. It contains several hundred thousand distant galaxies of all types. The team was able to identify active galaxies from among these using X-ray observations from ESA's XMM-Newton space telescope, and they then studied the more detailed optical images of them taken by the NASA/ESA Hubble Space Telescope.

For each of the active galaxies in the study, they selected nine non-active galaxies at roughly the same distances, and thus roughly in the same stage of cosmic evolution, from the same Hubble images. This gives a grand total of just over 1400 galaxies that the team could then test for the telltale signs of mergers.

"You can usually tell when galaxies have been involved in a merger," explains Knud Jahnke, co-author of the study. "Instead of the neat, geometric spiral or smooth elliptical shapes you usually see in Hubble images, colliding galaxies typically look distorted and warped. We planned to find out whether these misshapen galaxies were more likely than regular ones to host active nuclei."

Identifying whether or not a galaxy is distorted is a matter of judgement for which the expert eye of a trained astronomer is far better than any computerised assessment. To harness this human expertise without introducing the risk of unwitting bias, Cisternas set up a kind of identity parade of galaxies, in which he had modelled and removed the bright spot that reveals the AGN. Ten galaxy experts, based at eight different institutions, independently assessed whether each of the galaxies was distorted or not, without being told which had an AGN.

None of the experts found a significant correlation between a galaxy's activity and its distortion, that is, between its black hole being well-fed and its involvement in a major merger.

While mergers are a common phenomenon, and are thought to play a role at least for some AGN, the study shows that they provide neither a universal nor a dominant mechanism for feeding black holes. By the study's statistics, at least 75%, and possibly all, of AGN activity over the last eight billion years must have a different explanation. Possible ways of transporting matter towards a central black hole include instabilities of structures like a spiral galaxy's bar, the collisions of giant molecular clouds within the galaxy, or the fly-by of another galaxy that does not lead to a merger (known as galactic harassment).

Could there still be a causal connection between mergers and activity in the more distant past? That is the next question the group is gearing up to address. Suitable data is bound to come from two ongoing observational programmes (Multi-Cycle Treasury Programs) with the Hubble Space Telescope, as well as from observations by its successor, the James Webb Space Telescope, which is scheduled for launch after 2014.

Notes:

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

This illustration shows the NASA-ESA Hubble Space Telescope in its high orbit 600 kilometres above Earth

[1] The international team of astronomers in this study consists of Mauricio Cisternas (Max Planck Institute for Astronomy and University of Heidelberg), Knud Jahnke (Max Planck Institute for Astronomy), Katherine J Inskip (Max Planck Institute for Astronomy), Jeyhan Kartaltepe (National Optical Astronomy Observatory), Anton M Koekemoer (Space Telescope Science Institute), Thorsten Lisker (University of Heidelberg), Aday R Robaina (Max Planck Institute for Astronomy), Marco Scodeggio (IASF-INAF), Kartik Sheth (California Institute of Technology and Spitzer Science Center), Jonathan R Trump (University of Arizona), René Andrae (Max Planck Institute for Astronomy), Takamitsu Miyaji (Universidad Nacional Autónoma de Mexico and University of California at San Diego), Elisabeta Lusso (INAF-Osservatorio Astronomico di Bologna), Marcella Brusa (Max Planck Institute for Extraterrestrial Physics), Peter Capak (California Institute of Technology), Nico Cappelluti (Max Planck Institute for Extraterrestrial Physics), Francesca Civano (Harvard Smithsonian Center for Astrophysics), Olivier Ilbert (Laboratoire d'Astrophysique de Marseille) Chris D Impey (Spitzer Science Center), Alexie Leauthaud (LBNL & Berkeley Center for Cosmological Physics), Simon J Lilly (ETH Zurich), Mara Salvato (Max Planck Institute for Plasma Physics), Nick Z Scoville (California Institute of Technology) and Yoshi Taniguchi (Ehime University).

[2] Current theories estimate that the Universe is 13.7 billion years old. The most remote galaxies (and hence the furthest back in time) that Hubble has been able to observe are seen as they were around thirteen billion years ago. The light from the galaxies used in this study has taken up to eight billion years to travel to us, which represents more than half of cosmic history.

Links:

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

    * Paper from the Astrophysical Journal (PDF): http://www.spacetelescope.org/static/archives/releases/science_papers/heic1101.pdf

    * MPIA press release: http://www.mpia.de/Public/menu_q2.php?Aktuelles/PR/2011/PR110105/PR_110105_en.html

    * Max-Planck Institute for Astronomy: http://www.mpia.de/

    * Mauricio Cisternas homepage: http://www.mpia.de/homes/cisternas/

    * Knud Jahnke homepage: http://www.mpia.de/homes/jahnke/

    * MPIA research group on coevolution of galaxies and black holes: http://www.mpia.de/coevolution/

    * COSMOS survey: http://cosmos.astro.caltech.edu/

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

Images, Video, Text, Credits: NASA / ESA /  M. Cisternas (Max-Planck Institute for Astronomy) / Video: ESA / Hubble (M. Kornmesser & L. L. Christensen).

Best regards, Orbiter.ch

Astronaut Marsha Ivins Leaves NASA

NASA logo.

Jan. 05, 2011

NASA astronaut Marsha Ivins, a veteran of five spaceflights, has retired from the agency.

"Marsha's incredible depth of mission experience and technical expertise has been a tremendous asset to this office," said Peggy Whitson, chief of the Astronaut Office at NASA's Johnson Space Center in Houston. "We have relied on her expertise for years in many diverse areas, including but not limited to crew provisions, optimal hardware packing, human ratings development, vehicle habitability and orbiter preflight vehicle checks. Her expertise and dedication to NASA's mission will be sorely missed."

Astronaut Marsha Ivins

Ivins joined NASA in 1974 as an engineer. She worked on space shuttle displays, controls, man-machine engineering and the development of the orbiter's head-up display. She served in Johnson's aircraft operations as a flight engineer for the Shuttle Training Aircraft and copilot of the Gulfstream I.

Ivins was selected as an astronaut in 1984. She spent more than 1,300 hours in space during five shuttle flights: STS-32 in 1990, STS-46 in 1992, STS-62 in 1994, STS-81 in 1997 and STS-98 in 2001.

Ivins most recently worked within the Astronaut Office supporting the Space Shuttle, International Space Station and Constellation Programs.

For Ivins' complete astronaut biographical information, visit: http://www.jsc.nasa.gov/Bios/htmlbios/ivins.html

For information about NASA and agency programs, visit: http://www.nasa.gov

Images, Text, Credit: NASA.

Greetings, Orbiter.ch

Andromeda’s once and future stars

ESA - HERSCHEL Mission patch / ESA - XMM-NEWTON Mission patch.

5 January 2011

Andromeda: our nearest large galactic neighbour

Two ESA observatories have combined forces to show the Andromeda Galaxy in a new light. Herschel sees rings of star formation in this, the most detailed image of the Andromeda Galaxy ever taken at infrared wavelengths, and XMM-Newton shows dying stars shining X-rays into space.

During Christmas 2010, ESA’s Herschel and XMM-Newton space observatories targeted the nearest large spiral galaxy M31. This is a galaxy similar to our own Milky Way – both contain several hundred billion stars. This is the most detailed far-infrared image of the Andromeda Galaxy ever taken and shows clearly that more stars are on their way.

Andromeda Galaxy seen in infrared

Sensitive to far-infrared light, Herschel sees clouds of cool dust and gas where stars can form. Inside these clouds are many dusty cocoons containing forming stars, each star pulling itself together in a slow gravitational process that can last for hundreds of millions of years. Once a star reaches a high enough density, it will begin to shine at optical wavelengths. It will emerge from its birth cloud and become visible to ordinary telescopes.

Many galaxies are spiral in shape but Andromeda is interesting because it shows a large ring of dust about 75 000 light-years across encircling the centre of the galaxy. Some astronomers speculate that this dust ring may have been formed in a recent collision with another galaxy. This new Herschel image reveals yet more intricate details, with at least five concentric rings of star-forming dust visible.

Andromeda Galaxy in X-rays

Superimposed on the infrared image is an X-ray view taken almost simultaneously by ESA’s XMM-Newton observatory. Whereas the infrared shows the beginnings of star formation, X-rays usually show the endpoints of stellar evolution.

XMM-Newton highlights hundreds of X-ray sources within Andromeda, many of them clustered around the centre, where the stars are naturally found to be more crowded together. Some of these are shockwaves and debris rolling through space from exploded stars, others are pairs of stars locked in a gravitational fight to the death.

In these deadly embraces, one star has already died and is pulling gas from its still-living companion. As the gas falls through space, it heats up and gives off X-rays. The living star will eventually be greatly depleted, having much of its mass torn from it by the stronger gravity of its denser partner. As the stellar corpse wraps itself in this stolen gas, it could explode.

Andromeda Galaxy in infrared and X-rays

Both the infrared and X-ray images show information that is impossible to collect from the ground because these wavelengths are absorbed by Earth’s atmosphere. The twinkling starlight seen from Earth is indeed a beautiful sight but in reality contains less than half the story. Visible light shows us the adult stars, whereas infrared gives us the youngsters and X-rays show those in their death throes.

To chart the lives of stars, we need to see it all and that is where Herschel and XMM-Newton contribute so much.

More information:

Herschel overview: http://www.esa.int/esaSC/SEMM4AKPO8G_index_0_ov.html

Online Showcase of Herschel Images OSHI: http://oshi.esa.int/

Images, Text, Credits: infrared: ESA / Herschel / PACS / SPIRE / J. Fritz, U. Gent; X-ray: ESA / XMM-Newton / EPIC / W. Pietsch, MPE; optical: R. Gendler.

Cheers, Orbiter.ch

VISTA Stares Deeply into the Blue Lagoon

ESO - European Southern Observatory logo.

5 January 2011

This new infrared image of the Lagoon Nebula was captured as part of a five-year study of the Milky Way using ESO’s VISTA telescope at the Paranal Observatory in Chile. This is a small piece of a much larger image of the region surrounding the nebula, which is, in turn, only one part of a huge survey.

Infrared-visible light comparison of views of the Lagoon Nebula (Messier 8)

Astronomers are currently using ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) to scour the Milky Way’s central regions for variable objects and map its structure in greater detail than ever before. This huge survey is called VISTA Variables in the Via Lactea (VVV) [1]. The new infrared image presented here was taken as part of this survey. It shows the stellar nursery called the Lagoon Nebula (also known as Messier 8, see eso0936), which lies about 4000–5000 light-years away in the constellation of Sagittarius (the Archer).

The star formation region Messier 8 in the constellation of Sagittarius

Infrared observations allow astronomers to peer behind the veil of dust that prevents them from seeing celestial objects in visible light. This is because visible light, which has a wavelength that is about the same size as the dust particles, is strongly scattered, but the longer wavelength infrared light can pass through the dust largely unscathed. VISTA, with its 4.1-metre diameter mirror — the largest survey telescope in the world — is dedicated to surveying large areas of the sky at near-infrared wavelengths deeply and quickly. It is therefore ideally suited to studying star birth.

Zooming in on the VISTA view of the Lagoon Nebula (Messier 8)

Stars typically form in large molecular clouds of gas and dust, which collapse under their own weight. The Lagoon Nebula, however, is also home to a number of much more compact regions of collapsing gas and dust, called Bok globules [2]. These dark clouds are so dense that, even in the infrared, they can block the starlight from background stars. But the most famous dark feature in the nebula, for which it is named, is the lagoon-shaped dust lane that winds its way through the glowing cloud of gas.

VISTA’s infrared view of the Lagoon Nebula (Messier 8)

Hot, young stars, which give off intense ultraviolet light, are responsible for making the nebula glow brightly. But the Lagoon Nebula is also home to much younger stellar infants. Newborn stars have been detected in the nebula that are so young that they are still surrounded by their natal accretion discs. Such new born stars occasionally eject jets of matter from their poles. When this ejected material ploughs into the surrounding gas short-lived bright streaks called Herbig–Haro objects [3] are formed, making the new-borns easy to spot. In the last five years, several Herbig–Haro objects have been detected in the Lagoon Nebula, so the baby boom is clearly still in progress here.

IR-visible crossfade of the Lagoon Nebula (Messier 8)

Notes:

[1] This survey, one of six VISTA surveys currently in progress, will image the central parts of the Milky Way many times over a period of five years and will detect huge numbers of new variable objects.

The VISTA telescope

[2] Bart Bok was a Dutch-American astronomer who spent most of his long career in the United States and Australia. He first noticed the dark spots that now bear his name, in star formation regions and speculated that they may be associated with the earliest stages of star formation. The hidden baby stars were only observed directly when infrared imaging was possible several decades later.

[3] Although not the first to see such objects, the astronomers George Herbig and Guillermo Haro were the first to study the spectra of these strange objects in detail and realise that they were not just clumps of gas and dust that reflected light, or glowed under the influence of the ultraviolet light from young stars, but were a new class of objects associated with star formation.
More information

The science team for VVV includes Dante Minniti (Universidad Catolica, Chile), Phil Lucas (University of Hertfordshire, UK), Ignacio Toledo  (Universidad Catolica) and Maren Hempel  (Universidad Catolica).

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 VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

    * Photos of VISTA: http://www.eso.org/public/images/archive/category/surveytelescopes/

    * VVV survey main page: http://mwm.astro.puc.cl/mw/index.php/Main_Page


Images, Videos, Text, Credits: ESO / VVV / Acknowledgment: Cambridge Astronomical Survey Unit / IAU and Sky & Telescope / Videos: S. Brunier / S. Guisard / Music: John Dyson (from the album "Darklight").

Greetings, Orbiter.ch

NASA Mars Exploration Rovers - The Road Less Traveled

NASA - Mars Exploration Rover "Spirit" (MER-A) patch / NASA - Mars Exploration Rover "Opportunity" (MER-B) patch.

Jan. 3, 2011

 This image, acquired on sol 127 (May 12, 2004), shows the path the rover traveled on its way to the base of the "Columbia Hills."

On Jan. 4, 2004, Spirit--the first of two NASA Mars Exploration Rovers--landed on the Red Planet for what was to be a 90-day mission. This image, acquired on sol 127 (May 12, 2004), shows the path the rover traveled on its way to the base of the "Columbia Hills." The hills can be seen silhouetted against the horizon on the far left side.

Since sol 2210 (March 22, 2010), Spirit has been silent, and the project's scientists continue to listen for Spirit with the Deep Space Network and Mars Odyssey orbiter. The project is also conducting a paging technique called "Sweep & Beep" to stimulate the rover. Since the period of peak solar activity occurs in mid-March 2011, leaving Spirit plenty of occasion to respond. Spirit's sister spacecraft Opportunity continues to explore Mars, arriving in December 2010 at the 80-meter (262-foot) diameter Santa Maria crater on its journey to Endeavour crater.

NASA Spacecraft Provides Travel Tips for Mars Rover

NASA's Mars Opportunity rover is getting important tips from an orbiting spacecraft as it explores areas that might hold clues about past Martian environments.

Opportunity's traverse on Mars from landing day to Santa Maria crater

Researchers are using a mineral-mapping instrument aboard NASA's Mars Reconnaissance Orbiter to help the rover investigate a large ancient crater called Endeavour. The orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is providing maps of minerals at Endeavour's rim that are helping the team choose which area to explore first and where to go from there. As Mars Reconnaissance Orbiter orbits more than 241 kilometers high (150 miles), the CRISM instrument provides mapping information for mineral exposures on the surface as small as a tennis court.

Image above: NASA's Mars Exploration Rover Opportunity used its navigation camera to record this view of Santa Maria crater at the end of a drive during the 2,450th Martian day, or sol, of the rover's work on Mars (Dec. 15, 2010). Image credit: NASA / JPL-Caltech.

"This is the first time mineral detections from orbit are being used in tactical decisions about where to drive on Mars," said Ray Arvidson of Washington University in St. Louis. Arvidson is the deputy principal investigator for the Spirit and Opportunity rovers and a co-investigator for CRISM.

Opportunity's science team chose to begin driving the rover toward the 22.5-kilometer-wide (14-mile-wide) crater in 2008, after four years studying other sites in what initially was planned as a three-month mission. The rover has traveled approximately nine miles since setting out for Endeavour crater. It will take several months to reach it.

Navigation camera movie of Opportunity's view towards Endeavour crater

The team plans for Opportunity's exploration of Endeavour to begin at a rim fragment called Cape York. That feature is too low to be visible by the rover, but appears from orbit to be nearly surrounded by water-bearing minerals. The planned route then turns southward toward a higher rim fragment called Cape Tribulation, where CRISM has detected a class of clay minerals not investigated yet by a ground mission. Spacecraft orbiting Mars found these minerals to be widespread on the planet. The presence of clay minerals at Endeavour suggests an earlier and milder wet environment than the very acidic, wet one indicated by previous evidence found by Opportunity.

This map indicates geological units in the region of Mars around a smaller area where NASA's Mars Exploration Rover Opportunity has driven from early 2004 through late 2010. Image credit: NASA / JPL-Caltech / JHU-APL / WUSTL.

"We used to have a disconnect between the scale of identifying minerals from orbit and what missions on the surface could examine," said CRISM team member Janice Bishop of NASA's Ames Research Center in Moffett Field, Calif., and the SETI Institute of Mountain View, Calif. "Now, rovers are driving farther and orbital footprints are getting smaller."

Ten years ago, an imaging spectrometer on NASA's Mars Global Surveyor orbiter found an Oklahoma-sized area with a type of the mineral hematite exposed. This discovery motivated selection of the area as Opportunity's 2004 landing site. Each pixel footprint for that spectrometer was 3.2 kilometers (2 miles) across. CRISM resolves areas about 18 meters (60 feet) across. Last fall, the instrument began using a pixel-overlap technique that provided even better resolution.

Opportunity view of Endeavour crater from panorama camera

Opportunity has just reached a 90-meter-diameter crater (300-foot) called Santa Maria, where CRISM detected a patch of ground with indications of water bound into the mineral. Opportunity will conduct a science campaign at the crater for the next several weeks to compare the ground results to the orbital indications.

"Opportunity has driven farther in the past Martian year than in any previous one," said John Callas, Mars Exploration Rover project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

A Martian year lasts approximately 23 months. During the past Martian year, Opportunity covered more than 12 kilometers (7.5 miles) of the mission's 26 total kilometers (16 miles) traveled since it landed in January 2004. The rover has returned more than 141,000 images.

Image above: NASA's Mars Exploration Rover Opportunity approached Santa Maria Crater in December 2010. With a diameter of about 90 meters (295 feet), this crater is slightly smaller than Endurance Crater, which Opportunity explored for about half a year in 2004. Image credit: NASA / JPL-Caltech / Univ. of Arizona.

Mars Reconnaissance Orbiter reached the Red Planet in 2006 to begin a two-year primary science mission. Its data show Mars had diverse wet environments at many locations for differing durations during the planet's history, and climate-change cycles persist into the present era. The mission has returned more planetary data than all other Mars missions combined.

JPL manages the Mars Exploration Rovers and the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., manages CRISM.

See news conference images: http://www.nasa.gov/mission_pages/mer/telecon/20101216/index.html

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

Images, Videos, Text,  Credit: NASA / JPL-Caltech / Univ. of Arizona / JHU-APL / WUSTL.

Best regards, Orbiter.ch

SOHO Spots 2,000th Comet

NASA - ESA SOHO Mission patch.

January 2, 2011

As people on Earth celebrate the holidays and prepare to ring in the New Year, an ESA/NASA spacecraft has quietly reached its own milestone: on December 26, the Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet.

Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet

Drawing on help from citizen scientists around the world, SOHO has become the single greatest comet finder of all time. This is all the more impressive since SOHO was not specifically designed to find comets, but to monitor the sun.

"Since it launched on December 2, 1995 to observe the sun, SOHO has more than doubled the number of comets for which orbits have been determined over the last three hundred years," says Joe Gurman, the U.S. project scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Md.

Of course, it is not SOHO itself that discovers the comets -- that is the province of the dozens of amateur astronomer volunteers who daily pore over the fuzzy lights dancing across the pictures produced by SOHO's LASCO (or Large Angle and Spectrometric Coronagraph) cameras. Over 70 people representing 18 different countries have helped spot comets over the last 15 years by searching through the publicly available SOHO images online.

The 1999th and 2000th comet were both discovered on December 26 by Michal Kusiak, an astronomy student at Jagiellonian University in Krakow, Poland. Kusiak found his first SOHO comet in November 2007 and has since found more than 100.

 SOHO spacecraft (Artist's view)

"There are a lot of people who do it," says Karl Battams who has been in charge of running the SOHO comet-sighting website since 2003 for the Naval Research Lab in Washington, where he also does computer processing for LASCO. "They do it for free, they're extremely thorough, and if it wasn't for these people, most of this stuff would never see the light of day."

Battams receives reports from people who think that one of the spots in SOHO's LASCO images looks to be the correct size and brightness and headed for the sun – characteristics typical of the comets SOHO finds. He confirms the finding, gives each comet an unofficial number, and then sends the information off to the Minor Planet Center in Cambridge, Mass, which categorizes small astronomical bodies and their orbits.

It took SOHO ten years to spot its first thousand comets, but only five more to find the next thousand. That's due partly to increased participation from comet hunters and work done to optimize the images for comet-sighting, but also due to an unexplained systematic increase in the number of comets around the sun. Indeed, December alone has seen an unprecedented 37 new comets spotted so far, a number high enough to qualify as a "comet storm."

LASCO was not designed primarily to spot comets. The LASCO camera blocks out the brightest part of the sun in order to better watch emissions in the sun's much fainter outer atmosphere, or corona. LASCO's comet finding skills are a natural side effect -- with the sun blocked, it's also much easier to see dimmer objects such as comets.

"But there is definitely a lot of science that comes with these comets," says Battams. "First, now we know there are far more comets in the inner solar system than we were previously aware of, and that can tell us a lot about where such things come from and how they're formed originally and break up. We can tell that a lot of these comets all have a common origin." Indeed, says Battams, a full 85% of the comets discovered with LASCO are thought to come from a single group known as the Kreutz family, believed to be the remnants of a single large comet that broke up several hundred years ago.

A "sungrazing" comet with prominent tail, as seen by SOHO

The Kreutz family comets are "sungrazers" – bodies whose orbits approach so near the Sun that most are vaporized within hours of discovery – but many of the other LASCO comets boomerang around the sun and return periodically. One frequent visitor is comet 96P Machholz. Orbiting the sun approximately every six years, this comet has now been seen by SOHO three times.

SOHO is a cooperative project between the European Space Agency (ESA) and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA.

Solar and Heliospheric Observatory Homepage: http://sohowww.nascom.nasa.gov/

Images, Text, Credits: NASA / ESA / ROSCOSMOS.

Greetings, Orbiter.ch

Kepler Mission Manager Update of 12.30.10

NASA - Kepler Mission logo labeled.

January 1, 2011


In response to the Dec. 22, 2010 Safe Mode event on the Kepler spacecraft, the mission team has brought in several experts and begun a detailed anomaly investigation.

The team's initial results are that the Kepler spacecraft appears to be in good condition, and that the on-board fault protection is working as designed. During an initial assessment of the likely source of the anomaly, the team has been able to highlight the circuits most likely to have been involved in causing the safe mode. The team also has performed a failure analysis, which has not yet revealed any part that would have produced the behavior seen on the spacecraft, and has identified no part failures that would put the spacecraft at undue risk.

Kepler spacecraft (Artist's view)

With this assessment, the team commanded the spacecraft to gather more data on both the primary and back-up electronics. Those data were gathered on Dec. 29, 2010 and on Dec. 30, 2010, and are being analyzed. The results appear to show that the back-up electronics are not suffering from the same problem seen on the primary unit.

Science operations will not resume until the first week in Jan. 2011, at the earliest, while the team assesses whether or not to switch to the back-up hardware.

Meanwhile, the team is assessing delaying the next science data download, currently scheduled for late Jan. 2011, to minimize future data disruptions.

Images, Text, Credit: NASA.

Happy New Year 2011, greetings, Orbiter.ch