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Sky survey accomplished in satellite's spare time EUROPEAN SPACE AGENCY NEWS RELEASE Posted: May 7, 2006 For the past four years, while ESA's XMM-Newton X-ray observatory has been slewing between different targets ready for the next observation, it has kept its cameras open and used this spare time to quietly look at the heavens. The result is a "free-of-charge" mission spin-off" - a survey that has now covered an impressive 25 percent of the sky. The rapid slewing of the satellite across the sky means that a star or a galaxy passes in the field of view of the telescope for ten seconds only. However, the great collecting area of the XMM-Newton mirrors, coupled with the efficiency of its image sensors, is allowing thousands of sources to be detected. Furthermore, XMM-Newton can pinpoint the position of X-rays coming from the sky with a resolution far superior to that available for most previous all-sky surveys. This is sufficient to allow the source of these X-rays to be found in many cases. By comparing XMM-Newton survey's data with those obtained over a decade ago by the international ROSAT mission, which also performed an all-sky survey, scientists can now check the long-term stability, or the evolution, of about two thousand objects in the sky. An initial look shows that some sources have changed their brightness level by an incredible amount. The most extreme of these are variable stars and more surprisingly galaxies, whose unusual volatility may be due to large quantities of matter being consumed by an otherwise dormant central black hole. The slew survey is particularly sensitive to active galactic nuclei (AGN) - galaxies with an unusually bright nucleus - which can be traced out to a distance of ten thousand million light years. While most stars and galaxies look like points in the sky, about 15 percent of the sources catalogued by XMM-Newton have an extended X-ray emission. Most of these are clusters of galaxies - gigantic conglomerations of galaxies which trap hot gas that emit X-rays over scales of a million light years. Eighty-one of these clusters are already famous from earlier work but many other clusters, previously unknown, appear in this new XMM-Newton sky catalogue. Scientists hope that the newly detected sources of this kind also include very distant clusters which are highly luminous in X-rays, as these objects are invaluable for investigating the evolution of the Universe. Follow-up observations by large optical telescopes are now needed to determine the distances of the individual galaxies in the newly discovered clusters. Using traditional pointed observations, it takes huge amounts of telescope-time to image very large sky features, such as old supernova remnants, in their entirety. The slewing mechanism provides a very efficient method of mapping these objects, and several have been imaged including the 20 000 year-old Vela supernova remnant, which occupies a sky area 150 times larger than the full moon. Extraordinarily bright, low-mass X-ray binary systems of stars (called "LMXB") - either powered by matter pulled from a normal star, or exploding onto the surface of a neutron star, or being consumed by a black hole - are observed with sufficient sensitivity to record their detailed light spectrum. Passes across these intense X-ray sources can help astronomers to understand the long-term physics of the interaction between the two stars of the binary system. Many areas of astronomy are expected to be influenced by the XMM-Newton sky survey. Today, 3 May 2006, the XMM-Newton scientist have released a part of the catalogue resulting from the initial processing of the highest quality data obtained so far. Such data correspond to a sky coverage of about 15 percent, and include more than 2700 very bright sources and a further 2000 sources of lower significance. Currently, about 55 percent of the catalogue entries have been identified with known stars, galaxies, quasars and clusters of galaxies. A faster turn-around of slew-data processing is now planned to catch interesting transient (or temporary) targets in the act, before they have a chance to fade. This will give access to rare, energetic events, which only a sensitive wide-angle survey such as XMM-Newton's can achieve. It is planned to continually update the catalogue as XMM-Newton charts its way through the stars. This will cover at least 80 percent of the sky, leaving a tremendous legacy for the future. |
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A seven-person crew featuring payload specialists from France and Saudi Arabia flew aboard the June 1985 mission of space shuttle Discovery. They narrate the highlights of STS-51G in this post-flight film. Three communications satellites -- for Mexico, the Arab countries and the U.S. -- were launched from the payload bay. And the SPARTAN 1 astrophysics spacecraft was deployed from the shuttle's robot arm for a two-day freeflight to make its science observations before being retrieved and returned to Earth.
The flight of Spacelab 3 aboard Challenger in April/May 1985 was a week-long scientific research mission using a laboratory tucked in the shuttle's payload bay. Experiments focused on material and fluid behaviors in weightlessness, plus observations of monkeys in the lab. The crew also watched amazing auroral displays over Earth. This post-flight crew film shows the highlights of STS-51B and includes remarkable views out the shuttle cockpit window during launch showing the Chesapeake Bay, New York City and Cape Cod as Challenger soared up the eastern seaboard.
Discovery launched April 12, 1985 on the STS-51D mission. A U.S. military communications satellite, known as Leasat 3, failed to activate after its deployment from the payload bay. That set the stage for a spacewalk -- the shuttle program's first unplanned EVA -- to attach handcrafted "Flyswatter" objects on the shuttle robotic arm to hit a timing switch on the satellite. The rescue attempt did not succeed. Upon landing at Kennedy Space Center, Discovery blew a tire. The crew, including Senator Jake Garn of Utah, narrate this post-flight film of highlights from the week-long mission.
NASA managers hold this news conference April 28 to give an update on plans for the next space shuttle mission, the ongoing external fuel tank testing and debates over further modifications.
The Boeing Delta 2 rocket carrying the CALIPSO and CloudSat atmospheric research spacecraft lifts off at 3:02 a.m. local time April 28 from Vandenberg Air Force Base, California.
Inside the Vehicle Assembly Building, the external fuel tank for the STS-121 space shuttle mission is hoisted into position for attachment with the twin solid rocket boosters atop a mobile launch platform. The tank, ET-119, will carry the liquid oxygen and liquid hydrogen to feed Discovery's three main engines during launch.
In preparation for space shuttle Discovery's departure from its Orbiter Processing Facility hangar for rollover to the Vehicle Assembly Building and mating with the tank and boosters, the ship's 60-foot long payload bay doors are swung shut.