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STS-96: First ISS docking

The first shuttle mission to dock with the fledgling International Space Station came in May 1999 when Discovery linked up with the two-module orbiting outpost. The STS-96 crew tells story of the mission.

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STS-88: Building the ISS

Construction of the International Space Station commenced with Russia's Zarya module launching aboard a Proton rocket and shuttle Endeavour bringing up the American Unity connecting hub. STS-88 crew narrates highlights from the historic first steps in building the outpost.

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STS-74: Adding to Mir

The second American shuttle flight to dock with the space station Mir brought a new module to the Russian outpost. The astronauts narrate highlights from the Nov. 1995 mission.

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STS-73: Microgravity lab

The STS-73 mission in 1995 marked two weeks in space for shuttle Columbia and the second trip for the U.S. Microgravity Lab.


STS-55: German lab 2

The international crew of STS-55 narrates the highlights from the second German flight of Spacelab.


STS-43: Building TDRSS

The STS-43 crew narrates the highlights of its mission to expand NASA's Tracking and Data Relay Satellite System.


Delta 2 launches GPS

A Delta 2 rocket lifts off Dec. 20 from Cape Canaveral carrying the GPS 2R-18 navigation satellite for the Global Positioning System.

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35 years ago: Apollo 17

Apollo's final lunar voyage is relived in this movie. The film depicts the highlights of Apollo 17's journey to Taurus-Littrow and looks to the future Skylab, Apollo-Soyuz and shuttle programs.


Harmony's big move

The station's new Harmony module is detached from the Unity hub and moved to its permanent location on the Destiny lab.


Delta 4-Heavy launch

The first operational Delta 4-Heavy rocket launches the final Defense Support Program missile warning satellite for the Air Force.

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Weird object may be result of colliding protoplanets
Posted: January 10, 2008

Something bizarre orbiting a young, failed star 170 light-years from Earth may be the progeny of two protoplanets that collided and merged, astronomers announced at the American Astronomical Society meeting in Austin, Texas.

Given its hotter-than-expected temperature, dim luminosity, young age and location, the orbiting object, known as 2M1207B, should be a physical impossibility, scientists say.

"This is a strange enough object that it needs a strange explanation," Eric Mamajek of the Harvard-Smithsonian Center for Astrophysics said.

Mamajek and Michael Meyer of The University of Arizona propose that the object orbiting brown dwarf 2M1207A is small, about the size of Saturn. The "brown dwarf," or failed star, in the system is believed to be 25 times as massive as Jupiter and only about eight million years old.

The brown dwarf might be the outcome of a collision between a Saturn-sized gas giant and a planet about three times the size of Earth, Mamajek and Meyer suggest. The two smacked into each other and fused, forming one larger world still boiling from the heat generated in the titanic collision.

"Most, if not all, planets in our solar system were hit early in their history," Mamajek said. "A collision created Earth's moon and knocked Uranus on its side. It's quite likely that major collisions happen in other young planetary systems, too."

"The Earth was hit by something one-tenth its mass, and it's likely that other planets in our solar system were, too, including Venus and Uranus," Meyer said. "If that one-tenth scale holds in other planetary systems, then we could be seeing the aftermath of a collision between a 72 Earth-mass gas giant and an eight Earth-mass planet."

The collision theory is reasonable from a timescale point of view, Mamajek said. A 2400-degree Fahrenheit, Saturn-sized object would radiate its heat away over about 100,000 years. If the system were billions of years old, it is unlikely that astronomers would be looking at the right time, but because the system is only eight million years old, chances are much better that they would catch it shortly after the collision, when they could still see the hot aftermath.

The collision hypothesis makes several predictions that astronomers can test. Chief among them is a low surface gravity, which depends on a planet's mass and radius. To check this prediction, astronomers will need to get a better spectrum of 2M1207B. That's challenging because the object is very faint and very close to the brown dwarf 2M1207A.

Mamajek emphasized that while a planet collision may not be the correct explanation for the weirdness of 2M1207B, examples of colliding planets are likely to be found by the next generation of ground-based telescopes.

"Hot, post-collision planets might be a whole new class of objects we will see with the Giant Magellan Telescope."

Harvard and UA are members of an international consortium building the Giant Magellan Telescope, which is slated for completion in 2016 at a site in northern Chile. It will be composed of seven 8.4-meter primary mirrors arranged in a hexagonal pattern, giving it 4.5 times the collecting area of any current optical telescope. The UA Steward Observatory Mirror Lab cast the first GMT mirror in 2005.

"Even if we're wrong, I wouldn't be surprised if someone finds a clear-cut case in the next 10 years," Mamajek added.