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Phoenix update

Scientists report on the progress of the Phoenix lander exploring the northern plains of Mars during this Sept. 29 update.

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Two shuttles sighted

Stunning aerial views of shuttles Atlantis and Endeavour perched atop launch pads 39A and 39B on Sept. 20.

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Endeavour to pad 39B

Space shuttle Endeavour made the journey from Kennedy Space Center to pad 39B in the predawn hours of Sept. 19.

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MAVEN to Mars

NASA has selected the Mars Atmosphere and Volatile Evolution spacecraft, or MAVEN, for launch to the Red Planet.

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Endeavour to the VAB

For its role as a rescue craft during the Hubble servicing mission and the scheduled November logistics run to the space station, Endeavour is moved to the Vehicle Assembly Building.

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STS-125: The mission

A detailed step-by-step preview of space shuttle Atlantis' STS-125 mission to extend the life and vision of the Hubble Space Telescope.

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STS-125: The EVAs

The lead spacewalk officer provides indepth explanations of the five EVAs to service Hubble during Atlantis' flight.

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STS-125: The crew

The seven shuttle Atlantis astronauts hold a press conference one month before their planned launch to Hubble.

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Stars stop forming when big galaxies collide
YALE UNIVERSITY NEWS RELEASE
Posted: October 7, 2008

NEW HAVEN, Conn. - Astronomers studying new images of a nearby galaxy cluster have found evidence that high-speed collisions between large elliptical galaxies may prevent new stars from forming, according to a paper to be published in a November 2008 issue of The Astrophysical Journal Letters.


A deep image of part of the Virgo cluster revealing tendrils of ionized hydrogen gas 400,000 light-years long that connect the elliptical galaxy M86 (right) and the disturbed spiral galaxy NGC 4438 (left). Credit: Tomer Tal and Jeffrey Kenney/Yale University and NOAO/AURA/NSF
 
Led by Jeffrey Kenney, professor and chair of astronomy at Yale, the team saw a spectacular complex of warm gas filaments 400,000 light-years-long connecting the elliptical galaxy M86 and the spiral galaxy NGC 4438 in the Virgo galaxy cluster, providing striking evidence for a previously unsuspected high-speed collision between the galaxies. The view was constructed using the wide-field Mosaic imager on the National Science Foundation telescope at Kitt Peak National Observatory near Tucson, Arizona.

"Our data show that this system represents the nearest recent collision between a large elliptical galaxy and a large spiral galaxy," said Kenney, who is lead author of the paper. "This discovery provides some of the clearest evidence yet for high-speed collisions between large galaxies, and it suggests a plausible alternative to black holes as an explanation of what turns off star formation in the biggest galaxies."

Previously, scientists had seen the filaments of gas around both galaxies, but had not seen or inferred any connection between the two galaxies located approximately 50 million light-years from Earth. The new image shows extended and faint emissions that directly connect the two galaxies - and there are no obvious stars in the filaments.

As in most elliptical galaxies, gas within M86 is extremely hot, and radiates X-rays in a long plume, which had previously been interpreted as a tail of gas being stripped as M86 falls into the Virgo cluster. The new image suggests that most of the disturbances in M86 are instead due to the collision with NGC 4438.

"Like with a panoramic camera, the view from the telescope using the wide-field imager at Kitt Peak let us see the bigger picture," said Kenney. "We needed to look deep and wide to see the M86 complex."

A current mystery in astronomy is what causes the biggest galaxies in the universe -primarily elliptical galaxies like M86 - to stop forming stars. "Something needs to heat up the gas so it doesn't cool and form stars," Kenney says. "Our new study shows that gravitational interactions may do the trick."

According to the authors, low-velocity collisions between small- or medium-sized galaxies often produce an increase in the local star formation rate, but in high-velocity collisions that happen naturally between large galaxies, the energy of the collision can cause the gas to heat up so much that it cannot easily cool and form stars.

"The same physical processes occur in both strong and weak encounters, and by studying the observable effects in extreme cases like M86 we can learn about the role of gravity in the heating of galaxy gas, which appears to be quite significant," Kenney adds.

Co-authors of the study include Yale graduate student Tomer Tal, former Yale student Hugh Crowl, now at the University of Massachusetts, WIYN Observatory Director George Jacoby, and John Feldmeier of Youngstown State University.

Kitt Peak National Observatory is part of the National Optical Astronomy Observatory (NOAO), which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The founding members of the WIYN Observatory partnership are the University of Wisconsin, Indiana University, Yale University, and NOAO.

STS-134 Patch

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The final planned flight of space shuttle Endeavour is symbolized in the official embroidered crew patch for STS-134. Available in our store!
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Final Shuttle Mission Patch

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The crew emblem for the final space shuttle mission is now available in our store. Get this piece of history!
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Apollo Collage
This beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.
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STS-133 Patch

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The final planned flight of space shuttle Discovery is symbolized in the official embroidered crew patch for STS-133. Available in our store!
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Anniversary Shuttle Patch

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This embroidered patch commemorates the 30th anniversary of the Space Shuttle Program. The design features the space shuttle Columbia's historic maiden flight of April 12, 1981.
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Mercury anniversary

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Celebrate the 50th anniversary of Alan Shephard's historic Mercury mission with this collectors' item, the official commemorative embroidered patch.
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