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Senate hearing
The Senate Commerce Committee holds a confirmation hearing on President Bush's nomination of Shana Dale to be the new NASA deputy administrator, replacing former astronaut Fred Gregory.

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Astronaut Q&A
As NASA celebrates five years of continuous human presence aboard the International Space Station, former resident astronauts from Expedition crews who lived aboard the outpost held this recent question and answer session at the Johnson Space Center.

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Shuttle engine test
For the first time since Hurricane Katrina, NASA's Stennis Space Center in Mississippi conducts a test-firing of a space shuttle main engine. The engine was run as part of a certification series on the Advanced Health Management System, which monitors engine performance.

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Edwards air show
Edwards Air Force Base hosted an open house and air show this past weekend. NASA's Dryden Flight Research Center demonstrated some of its specialized aircraft -- a highly modified NF-15B, a high-altitude ER-2, and F/A-18 and T-34. On the ground, a variety of specialized air and space vehicles were on display in the NASA exhibit, ranging from the Mars rovers to the 747 space shuttle carrier aircraft.

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ISS science 'suitcases'
Scientists eagerly examine suitcase-like packages, called the Materials International Space Station Experiments, or MISSEs, after return to Earth. The MISSE packages were flown outside the orbiting station to expose different materials to the space environments for study.

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Tracking hurricanes
This 2005 Atlantic hurricane season has a been a record-breaker. Satellite imagery since June 1 has been compiled into this movie to track the 21 named storms as they formed and traveled, many making landfall.

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Neutron star found where a black hole was expected
Posted: November 2, 2005

A very massive star collapsed to form a neutron star and not a black hole as anticipated, according to new results from NASA's Chandra X-ray Observatory. This discovery shows that nature has a harder time making black holes than previously thought.

The optical image (left) of Westerlund 1 shows a dense cluster of young stars, several with masses of about 40 suns. Some astronomers speculated that repeated collisions between such massive stars in the cluster might have led to formation of an intermediate-mass black hole, more massive than 100 suns. A search of the cluster with Chandra (right) found no evidence for this type of black hole. Instead they found a neutron star (CXO J164710.2-455216), a discovery which may severely limit the range of stellar masses that lead to the formation of stellar black holes. Credit: NASA/CXC/UCLA/M.Muno et al.
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Scientists found this neutron star - a dense whirling ball of neutrons about 12 miles in diameter - in an extremely young star cluster. Astronomers were able to use well-determined properties of other stars in the cluster to deduce that the parent star of this neutron star was at least 40 times the mass of the sun.

"Our discovery shows that some of the most massive stars do not collapse to form black holes as predicted, but instead form neutron stars, said Michael Muno, a University of California, Los Angeles, postdoctoral Hubble fellow. He is lead author of a paper to be published in an upcoming edition of The Astrophysical Journal Letters.

When very massive stars make neutron stars and not black holes, they will have a greater influence on the composition of future generations of stars. When the star collapses to form the neutron star, more than 95 percent of its mass, much of which is metal-rich material from its core, is returned to the space around it.

"This means that enormous amounts of heavy elements are put back into circulation and can form other stars and planets," said J. Simon Clark of the Open University in the United Kingdom.

Astronomers do not completely understand how massive a star must be to form a black hole rather than a neutron star. The most reliable method for estimating the mass of the parent star is to show that the neutron star or black hole is a member of a cluster of stars, all of which are close to the same age.

Because more massive stars evolve faster than less massive ones, the mass of a star can be estimated if its evolutionary stage is known. Neutron stars and black holes are the end stages in the evolution of a star, so their parent stars must have been among the most massive stars in the cluster.

The work described by Muno was based on two Chandra observations on May 22 and June 18, 2005. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.