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ISS command change
The Expedition 10 crew hands command of the International Space Station to the Expedition 11 crew in this ceremony staged in the Destiny module on April 22. (1min 49sec file)
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Griffin goes before press
Michael Griffin, NASA's new administrator, holds his first news conference from agency headquarters to discuss shuttle return to flight, exploration plans and Hubble servicing. (46min 44sec file)
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NASA's new boss
During his first day on the job, Michael Griffin, NASA's new administrator, addresses agency employees and answers questions on a variety of topics on April 14. (28min 50sec file)
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Griffin in his own words
Nominated to become the new administrator of NASA, Michael Griffin gives an opening statement to a Senate committee about his thoughts on the agency. (6min 38sec file)
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Senators quiz Griffin
Senators ask a wide range of questions to NASA administrator nominee Michael Griffin concerning the future exploration, the space shuttle and space station programs, Hubble servicing options and aeronautics funding. (27min 06sec file)
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Soyuz docking
The Russian Soyuz TMA-6 capsule docks to the space station's Pirs module, delivering the Expedition 11 to the outpost for a half-year mission. (4min 15sec file)
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Launch of Expedition 11
The Russian Soyuz TMA-6 spacecraft is launched to put the International Space Station's Expedition 11 crew in Earth orbit.
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Shuttle external tank
Highlights of pre-flight work involving the redesigned external fuel tank for the space shuttle return to flight mission is packaged into this movie with narration. (6min 32sec file)
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Silhouette reveals hidden shape of star's envelope
Posted: April 22, 2005

Detailed new images of the starbirth nursery in the Omega Nebula (M17) have revealed a multi component structure in the envelope of dust and gas surrounding a very young star. The stellar newborn, called M17-SO1, has a flaring torus of gas and dust, and thin conical shells of material above and below the torus.

Every step is carefully planned and thoroughly documented in the Genesis lab at Johnson Space Center as scientists extract solar wind collectors from the Genesis spacecraft's "concentrator" and prepare them for analysis. Credit: NASA/JSC
Shigeyuki Sako from University of Tokyo and a team of astronomers from the National Astronomical Observatory of Japan, the Japan Aeorospace Exploration Agency, Ibaraki University, the Purple Mountain Observatory of the Chinese Academy of Sciences, and Chiba University obtained these images and analyzed them in infrared wavelengths in order to understand the mechanics of protoplanetary disk formation around young stars. Their work is described in a detailed article in the April 21, 2005 edition of Nature.

The research team wanted to find a young star located in front of a bright background nebula and use near-infrared observations to image the surrounding envelope in silhouette, in a way comparable to how dentists use X-rays to take images of teeth. Using the Infrared Camera and Spectrograph with Adaptive Optics on the Subaru telescope, the astronomers looked for candidates in and around the Omega Nebula, which lies about 5,000 light-years away in the constellation Sagittarius.

They found a large butterfly-shaped near-infrared silhouette of an envelope about 150 times the size of our solar system surrounding a very young star. They made follow-up observations of the region using the Cooled Mid-Infrared Camera and Spectrograph on the Subaru telescope and the Nobeyama Millimeter Array at the Nobeyama Radio Observatory. By combining the results from the near-infrared, mid-infrared, and millimeter wave radio observations, the researchers determined that the M17-SO1 is a protostar about 2.5 to 8 times the mass of the Sun, and that the butterfly-like silhouette reveals an edge-on view of the envelope.

The near-infrared observations reveal the structure of the surrounding envelope with unprecedented levels of detail. In particular, observations using the 2.166 emission line of hydrogen (called the Brackett gamma (Br $B&C (B) line) show that the envelope has multiple components instead of one simple structure. Around the equator of the protostar, the torus of dust and gas increases in thickness farther way from the star. Thin cone-shaped shells of material extend away from both poles of the star.

The discovery of the multi-component structure puts new constraints on how an envelope feeds material to a protostellar disk forming within its boundaries. "It's quite likely that our own solar system looked like M17-SO1 when it was beginning to form," said Sako. "We hope to confirm the relevance of our discovery for understanding the mechanism of protoplanetary disk formation by using the Subaru telescope to take infrared images with high resolution and high sensitivity of many more young stars.