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Ship docks to station
The Russian Progress 15P resupply ship makes a fully automated rendezvous and docking with the International Space Station. An external camera on the craft provides this view of the final approach to the aft port of the Zvezda service module. (3min 49sec file)
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Hurricane Charley
A camera aboard the International Space Station captured this stunning view of the strengthening Hurricane Charley on the morning of August 12. (1min 32sec file)
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Tropical Storm Bonnie
As Tropical Storm Bonnie comes ashore in the Florida panhandle on the morning of August 12, the International Space Station provides this view as it the orbiting outpost flies overhead. (1min 40sec file)
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Reentry seen from space
An incredibly rare sight was captured by the International Space Station cameras when the discarded Progress 14P supply ship reentered Earth's atmosphere. The craft burned up during the fiery plunge, which is visible as a long streak below the station. (3min 49sec file)
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Earth as backdrop
Spectacular video of the departing Progress 14P cargo ship against the Earth backdrop is captured by the station's crew. (1min 34sec file)
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Progress undocking
The Russian Progress 14P cargo ship undocks from the International Space Station after delivering its load of supplies and fuel to the orbiting outpost. A camera mounted on the craft's nose provides this view of the Progress departing the aft port of the Zvezda service module. (2min 15sec file)
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Proton lofts Amazonas
A Russian Proton M rocket launches from Baikonur Cosmodrome carrying the Amazonas communications satellite that will serve the Americas and Europe. (2min 25sec file)
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Proton preview
This narrated animation profiles the mission of a Proton rocket launching the Amazonas communications satellite. (2min 27sec file)
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Rocket rollout
The fully assembled Proton rocket is rolled to launch pad for its flight to place the Amazonas spacecraft into orbit. (41sec file)
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MESSENGER lifts off
The Boeing Delta 2-Heavy rocket launches at 2:16 a.m. EDT carrying the NASA's MESSENGER space probe from Cape Canaveral, Florida. (5min 23sec file)
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Cocoa Beach view
The Cocoa Beach tracking camera site captured this beautiful view of the launch and separation of the ground-ignited solid rocket boosters. (1min 31sec file)
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Next station crew
Expedition 10 Commander and NASA ISS Science Officer Leroy Chiao and Soyuz Commander and Flight Engineer Salizhan Sharipov discuss their planned six-month mission on the space station. (11min 23sec file)
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Star clusters the leftovers from snacking galaxies
Posted: August 14, 2004

Globular star clusters are like spherical cathedrals of light - collections of millions of stars lumped into a space only a few dozen light-years across. If the Earth resided within a globular cluster, our night sky would be alight with thousands of stars more brilliant than Sirius.

This artist's conception shows a typical globular cluster as viewed from a hypothetical nearby planet. Research has shown that some globular clusters may be the stripped cores of former dwarf galaxies. Credit: David A. Aguilar (Harvard-Smithsonian Center for Astrophysics)
Our own Milky Way Galaxy currently holds about 200 globular clusters, but once possessed many more. According to the hierarchical theory of galaxy formation, galaxies have grown larger over time by consuming smaller dwarf galaxies and star clusters. And sometimes, it seems that the unfortunate prey is not swallowed whole but instead is munched like a peach, stripped of its outer layers to leave behind only the pit. New research by Paul Martini (Harvard-Smithsonian Center for Astrophysics) and Luis Ho (Observatories of the Carnegie Institution of Washington) shows that some globular clusters may be remnants of dwarf galaxies that were stripped of their outer stars, leaving only the galaxy's nucleus behind.

Martini and Ho reported their results in the July 20, 2004, issue of The Astrophysical Journal.

Their findings hint at an important yet puzzling connection between the largest globular clusters and the smallest dwarf galaxies. "Star clusters and galaxies are quite different from a structural standpoint - star clusters are much more centrally concentrated, for example - and so the mechanisms that form them must be quite different. Identification of star clusters in the same mass range as galaxies is a very important step toward understanding how both types of objects form," says Martini.

For their investigation, the team studied 14 globular clusters in the large elliptical galaxy Centaurus A (NGC 5128) using the 6.5-meter-diameter Magellan Clay telescope at Carnegie's Las Campanas Observatory, Chile. The clusters were selected for their brightness, and since brighter clusters tend to contain more stars and more mass, were expected to be massive. Yet their results surprised even Martini and Ho, showing that the globular clusters of Centaurus A are much more massive than most globulars in the Local Group of galaxies (which includes the Milky Way and the Andromeda Galaxy).

"The essence of our findings is that these 14 globulars are 10 times more massive than the smaller globulars in our neighborhood, and whatever process makes them can produce some really huge objects - they begin to overlap with the smallest galaxies," says Martini.

Martini also points out the recent discovery of a suspected intermediate-mass black hole in the Andromeda Galaxy globular cluster known as G1, which offers further evidence linking globular clusters to dwarf galaxies. The presence of a moderate-sized black hole is more understandable if it once occupied the center of a dwarf galaxy - a galaxy that lost its outer stars to the pull of Andromeda, leaving it only a shadow of its former self.

Ho, a co-discoverer of the intermediate-mass black hole in G1, adds, "One of the most surprising findings is that the black hole in G1 obeys the same tight correlation between black hole mass and host galaxy mass that has been well established for supermassive black holes in the centers of big galaxies. This puzzling result is more understandable if G1 was once the nucleus of a larger galaxy. A very interesting question is whether some of the massive clusters in Centaurus A also contain central black holes."

Although most of our Galaxy's globular clusters are much smaller than those of Centaurus A, the largest Milky Way globulars (such as the omega Centauri star cluster) rival those of the elliptical galaxy. The similarities between massive globulars in both galaxies may point to similar formation mechanisms. Future studies of these most massive globular clusters will explore connections between the formation processes for star clusters and galaxies.

Centaurus A is located approximately 12.5 million light-years away. It is about 65,000 light-years across and is more massive than the Milky Way and Andromeda galaxies put together. Centaurus A possesses a total of about 2000 globular clusters - more than all of the galaxies in the Local Group combined. Recent Spitzer Space Telescope observations of Centaurus A uncovered evidence that it merged with a spiral galaxy about 200 million years ago.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

The Magellan telescopes are operated by the Carnegie Institution of Washington, the University of Arizona, Harvard University, the University of Michigan, and the Massachusetts Institute of Technology.

Las Campanas Observatory is operated by the Carnegie Observatories, which was founded in 1904 by George Ellery Hale. It is one of six departments of the private, nonprofit Carnegie Institution of Washington.

The Carnegie Institution of Washington ( has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments in the U.S.: Embryology, in Baltimore, MD; the Department of Terrestrial Magnetism and the Geophysical Laboratory in Washington, DC; Plant Biology and Global Ecology in Stanford, CA.; and The Observatories in Pasadena, CA, and Chile.

Ares 1-X Patch
The official embroidered patch for the Ares 1-X rocket test flight, is available for purchase.

Apollo Collage
This beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.

Expedition 21
The official embroidered patch for the International Space Station Expedition 21 crew is now available from our stores.

Hubble Patch
The official embroidered patch for mission STS-125, the space shuttle's last planned service call to the Hubble Space Telescope, is available for purchase.



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