Posted on by Fraser Cain

Integral Solves a Gamma Ray Mystery

Image credit: ESA
ESA’s Integral gamma-ray observatory has resolved the diffuse glow of gamma rays in the centre of our Galaxy and has shown that most of it is produced by a hundred individual sources.

Integral’s high sensitivity and pointing precision have allowed it to detect these celestial objects where all other telescopes, for more than thirty years, had seen nothing but a mysterious, blurry fog of gamma rays…

During the spring and autumn of 2003, Integral observed the central regions of our Galaxy, collecting some of the perpetual glow of diffuse low-energy gamma rays that bathe the entire Galaxy.

These gamma rays were first discovered in the mid-1970s by high-flying balloon-borne experiments. Astronomers refer to them as the ‘soft’ Galactic gamma-ray background, with energies similar to those used in medical X-ray equipment.

Initially, astronomers believed that the glow was caused by interactions involving the atoms of the gas that pervades the Galaxy. Whilst this theory could explain the diffuse nature of the emission, since the gas is ubiquitous, it failed to match the observed power of the gamma rays. The gamma rays produced by the proposed mechanisms would be much weaker than those observed. The mystery has remained unanswered for decades.

Now Integral’s superb gamma-ray telescope IBIS, built for ESA by an international consortium led by Principal Investigator Pietro Ubertini (IAS/CNR, Rome, Italy), has seen clearly that, instead of a fog produced by the interstellar medium, most of the gamma-rays are coming from individual celestial objects. In the view of previous, less sensitive instruments, these objects appeared to merge together.

In a paper published today in Nature, Francois Lebrun (CEA Saclay, Gif sur Yvette, France) and his collaborators report the discovery of 91 gamma-ray sources towards the direction of the Galactic centre. Lebrun’s team includes Ubertini and seventeen other European scientists with long-standing experience in high-energy astrophysics. Much to the team’s surprise, almost half of these sources do not fall in any class of known gamma-ray objects. They probably represent a new population of gamma-ray emitters.

The first clues about a new class of gamma-ray objects came last October, when Integral discovered an intriguing gamma-ray source, known as IGRJ16318-4848. The data from Integral and ESA’s other high-energy observatory XMM-Newton suggested that this object is a binary system, probably including a black hole or neutron star, embedded in a thick cocoon of cold gas and dust. When gas from the companion star is accelerated and swallowed by the black hole, energy is released at all wavelengths, mostly in the gamma rays.

However, Lebrun is cautious to draw premature conclusions about the sources detected in the Galactic centre. Other interpretations are also possible that do not involve black holes. For instance, these objects could be the remains of exploded stars that are being energised by rapidly rotating celestial ‘powerhouses’, known as pulsars.

Observations with another Integral instrument (SPI, the Spectrometer on Integral) could provide Lebrun and his team with more information on the nature of these sources. SPI measures the energy of incoming gamma rays with extraordinary accuracy and allows scientist to gain a better understanding of the physical mechanisms that generate them.

However, regardless of the precise nature of these gamma-ray sources, Integral’s observations have convincingly shown that the energy output from these new objects accounts for almost ninety per cent of the soft gamma-ray background coming from the centre of the Galaxy. This result raises the tantalising possibility that objects of this type hide everywhere in the Galaxy, not just in its centre.

Again, Lebrun is cautious, saying, “It is tempting to think that we can simply extrapolate our results to the entire Galaxy. However, we have only looked towards its centre and that is a peculiar place compared to the rest.”

Next on Integral’s list of things to do is to extend this work to the rest of the Galaxy. Christoph Winkler, ESA’s Integral Project Scientist, says, “We now have to work on the whole disc region of the Galaxy. This will be a tough and long job for Integral. But at the end, the reward will be an exhaustive inventory of the most energetic celestial objects in the Galaxy.”

Original Source: ESA News Release

Posted on by Fraser Cain

Space Adventures Seeking a Spaceport Location

Image credit: Space Adventures
Space Adventures, the world’s leading space tourism company, is currently exploring several locations around the world for construction of a space tourism spaceport. Current sites being considered are located in Australia, The Bahamas, Florida, Japan, Malaysia, Nevada, New Mexico, Oklahoma, Singapore and Dubai in the United Arab Emirates. Operations at the spaceport will include sub-orbital flights, a space flight training center and other activities.

“This is an ideal economic scenario for local communities. The building and then operation of a Space Adventures’ spaceport will undoubtedly bring tens of millions of dollars in the short-term and hundreds of millions in the long-term to the local economy through the increase of jobs and of tourists to the area and the required ancillary support,” said Tim Franta, space business consultant and former director of business development, Florida Space Authority. “It will be a win-win for both Space Adventures and the selected region.”

“Securing the location of a spaceport will be a progressive step for Space Adventures in its evolution from a space experiences provider to an actual space flight academy,” said Eric Anderson, president and CEO of Space Adventures. “We are aggressively seeking a location and enthusiastically look forward to the launch of the first Space Adventures’ sub-orbital flight from our spaceport in the coming years.”

The next generation spacecraft vehicles that will be used for the sub-orbital flights are now being tested. Space Adventures is the marketing and experience operations partner for several of the leading space vehicle manufacturing companies and has already taken over 100 seat reservations for explorers from around the world.

Space Adventures’ sub-orbital program will consist of a detailed four-day flight preparation and training experience. The highly focused and inspiring pre-flight agenda will familiarize each passenger with the flight program, critical vehicle systems, flight operations, zero gravity conditions, in-flight accelerations, and space flight safety procedures. On launch day, flight specialists will assist the passengers in suiting up and guiding each through the final checklist. Each flight will be directed by both a skilled-pilot and a precise computer controlled system. As each vehicle reaches their maximum altitude, the rocket engines will shutdown and the passengers will experience up to five minutes of continuous weightlessness, all the while gazing at the vast blackness of space set against the blue horizon of the Earth below.

Original Source: Space Adventures News Release

Posted on by Fraser Cain

More Details on Water Vapour Feedback

Image credit: NASA
A NASA-funded study found some climate models might be overestimating the amount of water vapor entering the atmosphere as the Earth warms. Since water vapor is the most important heat-trapping greenhouse gas in our atmosphere, some climate forecasts may be overestimating future temperature increases.

In response to human emissions of greenhouse gases, like carbon dioxide, the Earth warms, more water evaporates from the ocean, and the amount of water vapor in the atmosphere increases. Since water vapor is also a greenhouse gas, this leads to a further increase in the surface temperature. This effect is known as “positive water vapor feedback.” Its existence and size have been contentiously argued for several years.

Ken Minschwaner, a physicist at the New Mexico Institute of Mining and Technology, Socorro, N.M., and Andrew Dessler, a researcher with the University of Maryland, College Park, and NASA’s Goddard Space Flight Center, Greenbelt, Md, did the study. It is in the March 15 issue of the American Meteorological Society’s Journal of Climate. The researchers used data on water vapor in the upper troposphere (10-14 km or 6-9 miles altitude) from NASA’s Upper Atmosphere Research Satellite (UARS).

Their work verified water vapor is increasing in the atmosphere as the surface warms. They found the increases in water vapor were not as high as many climate-forecasting computer models have assumed. “Our study confirms the existence of a positive water vapor feedback in the atmosphere, but it may be weaker than we expected,” Minschwaner said.

“One of the responsibilities of science is making good predictions of the future climate, because that’s what policy makers use to make their decisions,” Dessler said. “This study is another incremental step toward improving those climate predictions,” he added.

According to Dessler, the size of the positive water vapor feedback is a key debate within climate science circles. Some climate scientists have claimed atmospheric water vapor will not increase in response to global warming, and may even decrease. General circulation models, the primary tool scientists use to predict the future of our climate, forecast the atmosphere will experience a significant increase in water vapor.

NASA’s UARS satellite was used to measure water vapor on a global scale and with unprecedented accuracy in the upper troposphere. Humidity levels in this part of the atmosphere, especially in the tropics, are important for global climate, because this is where the water vapor has the strongest impact as a greenhouse gas.

UARS recorded both specific and relative humidity in the upper troposphere. Specific humidity refers to the actual amount of water vapor in the air. Relative humidity relates to the saturation point, the amount of water vapor in the air divided by the maximum amount of water the air is capable of holding at a given temperature. As air temperatures rise, warm air can hold more water, and the saturation point of the air also increases.

In most computer models relative humidity tends to remain fixed at current levels. Models that include water vapor feedback with constant relative humidity predict the Earth’s surface will warm nearly twice as much over the next 100 years as models that contain no water vapor feedback.

Using the UARS data to actually quantify both specific humidity and relative humidity, the researchers found, while water vapor does increase with temperature in the upper troposphere, the feedback effect is not as strong as models have predicted. “The increases in water vapor with warmer temperatures are not large enough to maintain a constant relative humidity,” Minschwaner said. These new findings will be useful for testing and improving global climate models.

NASA’s Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth system science to improve prediction of climate, weather and natural hazards using the unique vantage point of space. NASA plans to launch the Aura satellite in June 2004. Along with the Terra and Aqua satellites already in operation, Aura will monitor changes in Earth’s atmosphere.

Original Source: NASA News Release

Posted on by Fraser Cain

Ulysses is Running Out of Power

Image credit: NASA
Deep space is cold. Very cold. That’s a problem–especially if you’re flying in an old spaceship. And your power supplies are waning. And the fuel lines could freeze at any moment. Oh, and by the way, you’ve got to keep flying for thirteen more years.

It sounds like a science fiction thriller, but this is really happening to the NASA/European Space Agency spacecraft Ulysses.

Ulysses was launched in 1990 on a five-year mission to study the sun. The craft gathered new data about the speed and direction of the solar wind. It discovered the 3D shape of the sun’s magnetic field. It recorded solar flares on the sun, and super-solar flares from distant neutron stars. Ulysses even flew through the tail of comet Hyakutake, an unexpected encounter that delighted astronomers.

The mission was supposed to end in 1995, but Ulysses was too successful to quit. NASA and the ESA have granted three extensions, most recently in Feb. 2004. Ulysses is scheduled to keep going until 2008, thirteen years longer than originally planned.

Ulysses’ extended mission, as before, is to study the sun. But at the moment Ulysses is far from our star. It’s having an encounter with Jupiter, studying the giant planet and its magnetic field. Sunlight out there is 25 times less intense than what we experience on Earth, and Ulysses is getting perilously cold.

Back in the 1980’s, when Ulysses was still on Earth and being assembled, mission planners knew that the spacecraft would have to endure some low temperatures. So they put dozens of heaters onboard, all powered by a Radioisotope Thermoelectric Generator, or “RTG.” These heaters have kept Ulysses comfortably warm.

But there’s a problem: the RTG is fading.

“The power output of the RTG has been dropping since the spacecraft was launched,” says Nigel Angold, the Ulysses ESA Spacecraft Operations Manager at JPL. RTG power naturally fades as its radioactive source decays. That’s as expected. What planners didn’t expect was 13 years of extra operations.

“When Ulysses was launched in 1990 the RTG produced 285 watts. Now it’s down to 207 watts–barely enough power to run the science instruments and the heaters at the same time,” notes Angold.

Inside Ulysses the temperature varies from place to place. “Many of the science instruments are already below freezing (0 C),” says Ulysses thermal engineer Fernando Castro. “That’s OK, because they can operate at low temperature.” But the fuel lines are another matter. They’re hovering about 3 degrees above zero, “and if they freeze we’re in trouble.”

Fuel lines are critical to the mission. They deliver hydrazine propellant to the ship’s eight thrusters. Every week or so, ground controllers fire the thrusters to keep Ulysses’ radio antenna pointing toward Earth. The thrusters won’t work if the hydrazine freezes. No thrusters means no communication. The mission would be lost.

About eight meters of fuel line snake through the spaceship. Every twist and turn is a possible cold spot, a place where the hydrazine can begin to solidify. “If the hydrazine freezes anywhere, I don’t know if we can safely thaw it again,” worries Castro. When hydrazine thaws, it expands, possibly enough to rupture the fuel lines. Ulysses’ propellant would fizzle uselessly into space.

The temperature at any given point along the fuel lines is bewilderingly sensitive to what’s going on elsewhere in the spacecraft. Turning on a scientific instrument “here” might cause a chill “over there,” because it takes power away from one of the heaters. Firing a thruster, playing back or recording data: almost anything could upset Ulysses’ delicate thermal balance.

Above: The complicated interior of Ulysses. Dark blocks are science instruments and other devices. Fuel lines, denoted by red, blue and green, lead from a central hydrazine tank to the thrusters. Click here to view areas most vulnerable to freezing.

Even the simple act of sending the spacecraft a message can cause problems. Systems engineer Andy McGarry recalls, “last month we were sending some new commands to Ulysses when the temperature began to drop, as much as 0.8 degrees C near the fuel lines. We were less than a degree from the freezing point of hydrazine–too close for comfort.”

Engineers quickly figured out the problem. “All of Ulysses’ science instruments had been activated to study Jupiter,” explains McGarry, “and this was straining the RTG to its limit.” Ulysses would have trouble supporting even one more device. But when a signal arrived from Earth, another device did turn on, automatically: the decoder, which translates radio signals into a stream of binary ones and zeros understood by Ulysses’ computers. “The decoder was stealing power from the heaters.”

Since then ground controllers have learned to keep their transmissions to Ulysses brief, so the temperature can’t fall very far.

Ulysses is about to turn away from Jupiter and head back to the sun. Eventually solar heating will keep the hydrazine warm, and onboard heaters can be turned off, “but that won’t happen until 2007,” says Angold. Meanwhile, engineers at JPL keep a constant watch on the spacecraft.

Mission scientist Steve Suess at the NASA Marshall Space Flight Center believes it’s worth the effort. “The extended mission gives us a chance to learn a lot more about the sun.” Of special interest is the Solar Minimum. Solar activity waxes and wanes every 11 years, he explains. Ulysses studied the sun’s quiet phase, Solar Minimum, between 1994 and 1995. Now Ulysses gets to do it again. “The next Solar Minimum is due around 2006,” says Suess, “but it won’t be the same as before.” In 2001 the sun’s magnetic field flipped. The north pole shifted south, and vice versa. Magnetically speaking, the sun is now upside down. How will that affect Solar Minimum?

Perhaps Ulysses will find out ? if it doesn’t freeze to death first.

Original Source: NASA Science Story

Posted on by Fraser Cain

The Origins of Oxygen on Earth

Image credit: NASA
Christopher Chyba is the principal investigator for The SETI Institute lead team of the NASA Astrobiology Institute. Chyba formerly headed the SETI Institute’s Center for the Study of Life in the Universe. His NAI team is pursuing a wide range of research activities, looking at both life’s beginnings on Earth and the possibility of life on other worlds. Astrobiology Magazine’s managing editor, Henry Bortman, spoke recently with Chyba about several of his team’s projects that will explore the origin and significance of oxygen in Earth’s atmosphere.

Astrobiology Magazine: Many of the projects that members of your team will be working on have to do with oxygen in Earth’s atmosphere. Today oxygen is a significant component of the air we breathe. But on early Earth, there was very little oxygen in the atmosphere. There is a great deal of debate about just how and when the planet’s atmosphere became oxygenated. Can you explain how your team’s research will approach this question?

Christopher Chyba: The usual story, with which you’re probably familiar, is that after oxygenic photosynthesis evolved, there was then a huge biological source of oxygen on early Earth. That’s the usual view. It may be right, and what’s usually the case in these kinds of arguments is not whether one effect is right or not. Probably many effects were active. It’s a question of what was the dominant effect, or whether there were several effects of comparable importance.

SETI Institute researcher Friedemann Freund has a completely non-biological hypothesis about the rise of oxygen, which has some experimental support from laboratory work that he’s done. The hypothesis is that, when rocks solidify from magma, they incorporate small amounts of water. Cooling and subsequent reactions leads to the production of peroxy links (consisting of oxygen and silicon atoms) and molecular hydrogen in the rocks.

Then, when the igneous rock is subsequently weathered, the peroxy links produce hydrogen peroxide, which decomposes into water and oxygen. So, if this is right, simply weathering igneous rocks is going to be a source of free oxygen into the atmosphere. And if you look at some of the quantities of oxygen that Friedemann is able to release from rocks in well-controlled situations in his initial experiments, it might be that this was a substantial and significant source of oxygen on early Earth.

So even apart from photosynthesis, there might be a kind of natural source of oxygen on any Earth-like world that had igneous activity and liquid water available. This would suggest that the oxidation of the surface might be something that you expect to occur, whether photosynthesis happens early or late. (Of course, the timing of this depends on oxygen sinks as well.) I emphasize that’s all a hypothesis at this point, for much more careful investigation. Friedemann’s done only pilot experiments so far.

One of the interesting things about Friedemann’s idea is that it suggests there might be an important source of oxygen on planets completely independent of biological evolution. So there might be a natural driver towards the oxidation of the surface of a world, with all the ensuing consequences for evolution. Or maybe not. The point is to do the work and find out.

Another component of his work, which Friedemann will do with the microbiolologist Lynn Rothschild of NASA Ames Research Center, has to do with this question of whether in environments associated with weathered igneous rocks and the production of oxygen, you could have created micro-environments that would have allowed certain microorganisms living in those environments to have pre-adapted to an oxygen-rich environment. They’ll be doing work with microorganisms to try to address that question.

AM: Emma Banks will be looking at chemical interactions in the atmosphere of Saturn’s moon Titan. How does that tie into understanding oxygen on early Earth?

CC: Emma’s looking at another abiotic way that might be important in oxidizing a world’s surface. Emma does chemical computational models, all the way down to the quantum mechanical level. She does them in a number of contexts, but what’s relevant to this proposal has to do with haze formation.

On Titan – and possibly on the early Earth as well, depending on your model for the atmosphere of the early Earth – there’s a polymerization of methane [the combination of methane molecules into larger hydrocarbon-chain molecules] in the upper atmosphere. Titan’s atmosphere is several percent methane; almost all the rest of it is molecular nitrogen. It’s bombarded with ultraviolet light from the sun. It’s also bombarded with charged particles from Saturn’s magnetosphere. The effect of that, acting on the methane, CH4 , is to break the methane up and polymerize it into longer-chain hydrocarbons.

If you start polymerizing methane into longer and longer carbon chains, each time you add another carbon onto the chain, you’ve got to get rid of some hydrogen. For example, to go from CH4 (methane) to C2H6, (ethane) you have to get rid of two hydrogens. Hydrogen is an extremely light atom. Even if it makes H2, that’s an extremely light molecule, and that molecule’s lost off the top of Titan’s atmosphere, just as it’s lost off the top of the Earth’s atmosphere. If you bleed hydrogen off the top of your atmosphere, the net effect is to oxidize the surface. So it’s another way that gives you a net oxidation of a world’s surface.

Emma’s interested in this primarily with respect to what takes place on Titan. But it’s also potentially relevant as a kind of global oxidizing mechanism for the early Earth. And, bringing nitrogen into the picture, she’s interested in the potential production of amino acids out of these conditions.

AM: One of the mysteries about early life on Earth is how it survived the damaging effects of ultraviolet (UV) radiation before there was enough oxygen in the atmosphere to provide an ozone shield. Janice Bishop, Nathalie Cabrol and Edmond Grin, all of whom are with the SETI Institute, are exploring some of these strategies.

CC: And there are a lot of potential strategies there. One is just being deep enough below the surface, whether you’re talking about the land or the sea, to be completely shielded. Another is to be shielded by minerals within the water itself. Janice and Lynn Rothschild are working on a project that is examining the role of ferric oxide minerals in water as a kind of UV shield.

In the absence of oxygen the iron in water would be present as ferric oxide. (When you have more oxygen, the iron oxidizes further; it becomes ferrous and drops out.) Ferric oxide could potentially have played the role of an ultraviolet shield in the early oceans, or in early ponds or lakes. To investigate how good it is as a potential UV shield, there are some measurements you might want to make, including measurements in natural environments, such as in Yellowstone. And once again there’s a microbiological component to the work, with Lynn’s involvement.

This is related to the project that Nathalie Cabrol and Edmond Grin are pursuing, from a different perspective. Nathalie and Edmond are very interested in Mars. They are both on the Mars Exploration Rover science team. In addition to their Mars work, Nathalie and Edmond explore environments on Earth as Mars analog sites. One of their topics of investigation is strategies for survival in high-UV environments. There’s a lake six kilometers high on Licancabur (a dormant volcano in the Andes). We now know there’s microscopic life in that lake. And we’d like to know what are its strategies for surviving in the high-UV environment there? And that’s a different, very empirical way of getting at this question of how life survived in the high-UV environment that existed on early Earth.

These four projects are all coupled, because they have to do with the rise of oxygen on early Earth, how organisms survived before there was substantial oxygen in the atmosphere, and then, how all this relates to Mars.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Universe Today Maintenance Thursday

If you had problems accessing Universe Today yesterday, don’t worry, you weren’t alone. I was “lucky” enough to end up on the homepage of Google News for the Sedna story. The resulting traffic brought my webserver to its knees. I had a chat with my service provider and they’ve recommended some upgrades to the server to better handle future traffic spikes. They’ll be installing the new hardware on Thursday at 1500 UTC (10 am EST), so the website will be down for 1-2 hours. Okay, Google… bring it on.

Thanks to everyone who donated over the weekend… it was good timing. 🙂

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Wallpaper: Bonneville Crater

Image credit: NASA/JPL
NASA’s Spirit rover has taken a beautiful panoramic image of the Bonneville crater. Here’s a 1024×768 wallpaper of the crater. The original image was quite wide, covering 180-degrees, so it doesn’t quite fit a computer screen normally – this image has been cropped a bit. Spirit recorded this photo on March 12, 2004, using its panoramic camera. By taking such a detailed image, scientists can get a good idea about the surface material at the crater.

Posted on by Fraser Cain

Proton Launches W3A Satellite

Image credit: ILS
A Russian Proton rocket successfully placed the Eutelsat W3A satellite into orbit this morning, marking the second mission in three days for International Launch Services (ILS).

This was the first flight of the year for the Khrunichev-built Proton vehicle, which has carried out more than 300 missions for the Russian government and commercial customers over nearly 40 years.

This also was the third mission of the year for ILS. The company?s other vehicle, the Lockheed Martin (NYSE: LMT) Atlas rocket, successfully launched a satellite Saturday morning from Cape Canaveral, Fla.

?We celebrate another success for Proton, and thank our customer, Eutelsat, for again placing its confidence in us,? said ILS President Mark Albrecht. ?This marks the seventh mission on an ILS vehicle for Eutelsat, and we?re proud to say they have all been flawless.?

The Proton vehicle lifted off at 4:06 a.m. local time (6:06 p.m. Monday EST, 23:06 GMT). In less than 10 minutes, the three-stage Proton vehicle finished its climb into space, leaving the Breeze M upper stage to continue the mission for the next nine hours. The Breeze M?s engine underwent five burns to place the W3A satellite into a geosynchronous transfer orbit at 1:16 p.m. Baikonur time (3:16 a.m. Tuesday EST, 08:16 GMT).

?Our congratulations to ILS for another flawless launch for Eutelsat, which follows six successful launches on the Atlas rocket from Cape Canaveral,? said Giuliano Berretta, CEO of Eutelsat. ?W3A is the heaviest and most complex satellite yet launched for our company. Its ride into geostationary transfer orbit on the Proton/Breeze M will enable us to optimize the operational lifetime of W3A and take us to new levels of efficiency.?

When it enters service later this year, the W3A satellite will provide broadband, direct-to-home and other communications services to Eutelsat customers in Europe, the Middle East and Africa. It is an EADS Astrium Eurostar E3000 model satellite, the largest spacecraft launched to date for Eutelsat.

?Congratulations to ILS for the successful launch of the Proton, which put W3A in geostationary orbit this morning,? said Antoine Bouvier, CEO of EADS Astrium. ?It is a major event for us as it is the maiden launch of a Eurostar E3000 and the first to be launched by Proton.?

ILS is a joint venture of Lockheed Martin Corp. and Khrunichev State Research and Production Space Center. ILS, based in McLean, Va., markets and manages all missions for Atlas and commercial missions on Proton.

Original Source: ILS News Release

Posted on by Fraser Cain

SOHO Sees a Huge Prominence on the Sun

Image credit: SOHO
On Friday, 12 March 2004, the Sun ejected a spectacular ‘eruptive prominence’ into the heliosphere. SOHO, the ESA/NASA solar watchdog observatory, faithfully recorded the event.

This ‘eruptive prominence’ is a mass of relatively cool plasma, or ionised gas. We say ‘relatively’ cool, because the plasma observed by the Extreme-ultraviolet Imaging Telescope (EIT) on board SOHO was only about 80 000 degrees Celsius, compared to the plasma at one or two million degrees Celsius surrounding it in the Sun’s tenuous outer atmosphere, or ‘corona’.

At the time of this snapshot, the eruptive prominence seen at top right was over 700 000 kilometres across – over fifty times Earth’s diameter – and was moving at a speed of over 75 000 kilometres per hour.

Eruptive prominences of this size are associated with coronal mass ejections (CMEs), and the combination of CMEs and prominences can affect Earth’s magnetosphere when directed toward our planet. In this case, the eruptive prominence and associated CME were directed away from Earth.

SOHO is a mission of international co-operation between ESA and NASA, launched in December 1995. Every day SOHO sends thrilling images from which research scientists learn about the Sun’s nature and behaviour. Experts around the world use SOHO images and data to help them predict ‘space weather’ events affecting our planet.

Original Source: ESA News Release

Posted on by Fraser Cain

Mountain of Sky Survey Data Released

Image credit: SDSS
One of the largest astronomy catalogs ever compiled was released to the public today by the Sloan Digital Sky Survey (SDSS).

With photometric and spectroscopic observations of the sky gathered during the last two years, this second data release (DR2) offers six terabytes of images and catalogs, including two terabytes in an easy to use searchable database.

This public data release provides digital images and measured properties of more than 88 million celestial objects, as well as spectra and redshifts of over 350,000 objects. The data are available from the SDSS Web site (http://www.sdss.org/DR2) or from the SkyServer Web site more attuned to the general public (http://skyserver.sdss.org/).

The SDSS is the most ambitious astronomical survey ever undertaken. A consortium of more than 200 astronomers at 13 institutions around the world, the SDSS will map in detail one-quarter of the entire sky, determining the positions and brightnesses of several hundred million celestial objects. It will also measure the distances to approximately one million galaxies and quasars.

“Getting DR2 out to the broader astronomical community and to the general public will allow these data to be analyzed for projects limited only by the imagination and ingenuity of the user,” said Michael Strauss of Princeton University, scientific spokesperson for the SDSS.

Strauss explained that while members of the SDSS international collaboration have written more than 200 scientific papers with SDSS data, “we feel we’ve barely started. There is far more interesting science to be done and discoveries to be made with these data than we have time or people to do. This is why this data release is so important.” Public searchable data in the survey have doubled from June 2003 to today.

“Many external researchers are already using the data from earlier public releases”, explained Alex Szalay of the Johns Hopkins University, an architect of the SDSS’s data mining tools. In fact, researchers from outside of the consortium wrote roughly half of the SDSS-related papers presented at recent American Astronomical Society meetings. “This is a clear indication that we’ve kept our promise to the scientific community of getting them uniformly high quality data in a timely manner and in a searchable format.”

The first public data release from the SDSS in 2003 contained information on 50 million objects, including spectra and redshifts for almost 200,000 of these objects. The SDSS is an ongoing survey that recorded its first observations in May 1998 and is funded for operations through Summer 2005.

The 2.5-meter SDSS telescope is located at Apache Point Observatory in New Mexico and is operated by the Astrophysical Research Consortium. The telescope has two main instruments: an imaging camera, one of the largest ever built, and a spectrograph capable of recording data from 640 objects at a time. The camera creates images from digital scans through five filters: ultraviolet, green, red, and two infrared bands.

CATALOG OF RESULTS
Scientific findings and ground-breaking discoveries already achieved with the DR2 data from the most distant quasars, to the coolest stars, the properties of galaxies to the sizes of asteroids, the structure of the halo of our Milky Way and the large-scale structure of the universe.

DR2 consists of images from 3,324 square degrees of the Northern sky and more than 88 million galaxies, stars, and quasars. The survey is complete for objects as faint as 22.2 magnitude, three million times fainter than the faintest star that can be seen with the naked eye on a dark night.

In addition to images from the SDSS telescope, the DR2 includes the spectra, and therefore redshifts, of 260,000 galaxies, 36,000 quasars, and 48,000 stars, according to consortium member Mark Subbarao of the University of Chicago. The galaxy and quasar catalogs are the largest ever produced.

SEARCH REFINEMENTS
Jim Gray of Microsoft Corp. was part of the team working to make the observations accessible to the astronomical community and the public. The team developed several algorithms to efficiently search the complicated database.

“The SDSS is a BIG database with researchers making very complicated queries for spatial, color and space parameters,” explained Gray, a distinguished engineer in Microsoft’s Scaleable Servers Research Group and manager of Microsoft’s Bay Area Research Center.

“It has been very rewarding working with the SDSS. The people are very creative, enthusiastic, and bright. The SDSS has shown that we database folks need to do a better job in many ways,” Gray said. “For Microsoft, the SkyServer and Catalog Archive Server are an information-at-your-fingertips project we’ve helped develop for astronomers. I see them as archetypes of what all the sciences need.”

Ani Thakar, an SDSS astronomer from the Johns Hopkins University’s Center for Astrophysical Sciences, who has worked closely with Szalay and Gray on the SkyServer, said the DR2 database has a form-based Web page for imaging and spectroscopic queries.

“This gives astronomers the ability to extract detailed information from the database without having to learn a query language. We’ve also added a batch service that lets users submit queries that are likely to take a long time. They can come back later and pick up the results,” Thakar explained.

DR2 also offers enhanced querying and filtering options like image cutout and finding chart services. Users can cross-identify objects by uploading lists of object positions on the sky.

The SDSS anticipates releasing more data in its ongoing celestial census late this year.

Original Source: SDSS News Release