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STS-51D: Flyswatter spacewalk
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.

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Fuel tank update
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.

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CALIPSO and CloudSat
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.

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Tank meets SRBs
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.

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Discovery payload bay
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.

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Progress docking
Take a virtual ride aboard the Russian Progress 21P cargo freighter as it docks with the International Space Station. This movie captures the final approach and successful linkup from a camera on the Progress craft's nose.

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First view of monstrous stars being born
Posted: May 2, 2006

Scientists have secured their first look at the birth of monstrous stars that shine 100,000 times more brightly than the Sun, thanks to ESA's Infrared Space Observatory (ISO).

The discovery allows astronomers to begin investigating why only some regions of space promote the growth of these massive stars.

Space is littered with giant clouds of gas. Occasionally, regions within these clouds collapse to form stars. "One of the major questions in the field of study is why do some clouds produce high- and low-mass stars, whilst others form only low-mass stars?" asks Oliver Krause, Max-Planck-Institut fuer Astronomie, Heidelberg and Steward Observatory, Arizona.

The conditions necessary to form high-mass stars are difficult to deduce because such stellar monsters form far away and are shrouded behind curtains of dust. Only long wavelengths of infrared radiation can escape from these obscuring cocoons and reveal the low temperature dust cores that mark the sites of star formation. This radiation is exactly what ISO's ISOPHOT far-infrared camera has collected.

Stephan Birkmann, Oliver Krause and Dietrich Lemke, all of the Max-Planck-Institut fuer Astronomie, Heidelberg, used ISOPHOT's data to zero-in on two intensely cold and dense cores, each containing enough matter to form at least one massive star. "This opens up a new era for the observations of the early details of high-mass star formation," says Krause.

The data was collected in the ISOPHOT Serendipity Survey (ISOSS), a clever study pioneered by Lemke. He realised that when ISO was turning from one celestial object to another, valuable observing time was being lost. He organised for ISOPHOT's far-infrared camera to continuously record during such slews and beam this data to Earth.

During the ISO mission, which lasted for two and a half years during 1995-98, the spacecraft made around 10 000 slews, providing a web of data across the sky for the previously unexplored window of infrared emission at 170 micrometres. This wavelength is 310 times longer than optical radiation and reveals cold dust down to just 10K (-263 deg Celsius). A catalogue was produced of the cold sites in the survey.

Birkmann and his colleagues investigated this catalogue and found fifty potential places of high-mass stellar birth. A campaign of follow-up observations using ground-based telescopes revealed that object ISOSS J18364-0221 was in fact two cold dense cores that looked suspiciously like those associated with the birth of low-mass stars, but containing much more mass.

The first core is at 16.5 Kelvin (-256.5 deg Celsius). It contains seventy-five times the mass of the Sun and shows signs of gravitational collapse. The second one is around 12K (-261 deg Celsius) and contains 280 solar masses. The team are currently studying the other potential sites.

Although ISO is no longer operational, ESA is currently participating in the Japanese Aerospace Exploration Agency's infrared mission, Akari (former ASTRO-F). It will fill in the blanks in the ISOSS data by surveying the whole sky at six infrared wavebands. Beyond Akari, ESA will continue to pioneer infrared astronomy with its space telescope, Herschel, due to launch in 2008. Birkmann says, "With its 3.5 metre mirror and its far-infrared detectors, Herschel will unveil the earliest phases of massive star birth in unprecedented detail."

This work could also help make sense of the most distant objects in the Universe. "When astronomers look billions of light years into space, all they can see are the bright, high-mass stars in very distant galaxies. If we can understand how these stars form, we may be able to apply that knowledge to understand how galaxies evolve," says Krause.

The findings appear on the 20 January 2006 issue of The Astrophysical Journal (637:380-383). The original article, titled "Very cold and massive cores near ISOSS J18364_0221: implications for the initial conditions of high-mass star formation," is by S. M. Birkmann and D. Lemke (Max-Planck-Institut fuer Astronomie, Heidelberg, Germany), and O. Krause (Max-Planck-Institut fuer Astronomie, Heidelberg, Germany, and Steward Observatory, University of Arizona, Tucson, AZ, US)