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STS-121: The mission
Tony Ceccacci, the lead shuttle flight director for STS-121, provides a highly informative day-by-day preview of Discovery's mission using animation and other presentations. Then Rick LaBrode, the lead International Space Station flight director during STS-121, explains all of the activities occurring onboard and outside the outpost while Discovery visits.

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Detailing the EVAs
Discovery's STS-121 mission to the International Space Station will feature two scheduled spacewalks and perhaps a third if consumables permit. Spacewalkers Mike Fossum and Piers Sellers will test whether the 50-foot inspection boom carried on the shuttle could be used as a work platform for repairing the heatshield and conduct maintenance chores outside the space station. Tomas Gonzalez-Torres, the mission's lead spacewalk officer, details all the three EVAs in this pre-flight news briefing.

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STS-121 program perspective
A comprehensive series of press briefings for space shuttle Discovery's upcoming STS-121 begins with a program overview conference by Wayne Hale, NASA's manager of the shuttle program, and Kirk Shireman, the deputy program manager of the International Space Station. The two men discuss the significance of Discovery's mission to their respective programs. The briefing was held June 8 at the Johnson Space Center.

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Exploration work
NASA officials unveil the plan to distribute work in the Constellation Program for robotic and human moon and Mars exploration. This address to agency employees on June 5 was given by Administrator Mike Griffin, Associate Administrator for the Exploration Systems Mission Directorate Scott Horowitz and Constellation Program Manager Jeff Hanley.

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Exploration news briefing
Following their announcement on the Exploration work assignments to the various NASA centers, Mike Griffin, Scott Horowitz and Jeff Hanley hold this news conference to answer reporter questions.

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Scientists find reason behind black holes' light shows
UNIVERSITY OF MICHIGAN NEWS RELEASE
Posted: June 22, 2006

A team of astronomers led by the University of Michigan may know how black holes are lighting up the Universe. New data from NASA's Chandra X-ray Observatory show, for the first time, that powerful magnetic fields are the key to these brilliant and startling light shows.


This is an artist's representation of GRO J1655-40, a binary star system observed by Chandra. This binary consists of a black hole and a normal star shown in blue. Gas is being pulled away from the star and falling onto a red disk spinning around the black hole. Some of this gas spirals in towards the black hole, generating copious amounts of light along the way. This infall of matter is only possible if the gas loses some of its energy either through a wind, shown in blue, or friction in the disk. Illustration: NASA/CXC/M.Weiss
 
It is estimated that up to half of the total radiation in the universe since the Big Bang comes from material falling towards super-massive black holes, including those powering quasars, the brightest known objects. For decades, scientists have struggled to understand how black holes, the darkest objects in the Universe, can generate such prodigious amounts of radiation.

New X-ray data from Chandra give the first clear explanation for what drives this process: magnetic fields. Chandra observed a black hole system in our galaxy, known as GRO J1655-40 (J1655, for short), where a black hole was pulling material from a companion star into a disk.

"By intergalactic standards, J1655 is in our backyard so we can use it as a scale model to understand how all black holes work, including the monsters found in quasars," said Jon Miller, assistant professor at U-M, whose paper on these results appears in this week's issue of the journal Nature.

If gas in a disk around a black hole loses energy, it will swirl toward the black hole, generating light along the way. Scientists have long thought that magnetic fields may drive this energy loss by generating friction in the gas and driving a wind from the disk that carries momentum outward, in an example of conservation of momentum.

By using Chandra spectra, that is, the amount of X-rays at different energies, Miller and his team showed that the speed and density of the wind from the disk in J1655 corresponded to computer simulation predictions for winds driven by magnetic fields. The spectral fingerprint also ruled out the two other major competing theories to magnetically-driven winds.

"In 1973, theorists came up with the idea that magnetic fields could drive the generation of light by black holes," said co-author John Raymond of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. "Now, over 30 years later, we finally may have proof."

This deeper understanding of how black holes accrete matter also teaches astronomers about other properties of black holes, including how they grow.

"Just as a doctor wants to understand the causes of an illness and not merely the symptoms, astronomers try to understand what causes phenomena they see in the Universe," said co-author Danny Steeghs also of the CfA. "By understanding what makes material fall onto black holes and its energy released, we may also learn how it plunges onto other important objects."

In addition to accretion disks around black holes, magnetic fields may play an important role in disks detected around young Sun-like stars where planets are forming as well as ultra-dense objects called neutron stars.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass.