Saturday, November 28, 2009


Galaxies collision

A pileup on an intergalactic freeway
There are freeway pileups, and then there are pileups such as the one shown in this composite image from the Chandra X-Ray Observatory,
Hubble Space Telescope and Hawaii's Keck Observatory. The picture reveals a massive collision of four separate clusters of galaxies along a 13 million light-year-long stretch of intergalactic highway known as a filament, filled with galaxies, gas and dark matter. As the clusters plow into each other, they release heat, giving the pileup in the filament one of the highest temperatures ever seen in such a system, scientists noted.

Galactic collision reveals dark matter
Evidence for the existence of dark matter, a mysterious and invisible substance that is thought to make up most of the mass in the universe, was revealed when astronomers watched two giant galaxy clusters collide. The observation, made with the Chandra X-Ray Observatory and other
telescopes, shows how the collision separated the dark matter from ordinary matter. In the image, the pink color represents ordinary matter from the collided galaxies. The blue is the dark matter, which passed right through the galactic wreckage and is inferred by the effect its gravity has on light from more distant galaxies.

Jets blast from galactic black hole
This composite radio, X-ray and visible-light image shows lobes and jets of electrons screaming out from a supermassive black hole at the center of Centaurus A, a giant elliptical galaxy about 13 million light years from Earth. The black hole has a mass equal to 100 million suns. The jets are emitted as matter is sucked into the massive black hole, and they travel at about half the
speed of light. When the jets slam into the surrounding gas, they create a shock wave – the bluish x-ray emissions seen most prominently in the lower right lobe.

Black hole rips apart a star
For some black holes, star gas apparently isn't enough sustenance: They go for the whole thing. This artist's rendering shows how a supermassive black hole at the center of a galaxy called RX J1242-11, located about 700 million light years away, likely ripped apart a star the size of our sun. The gravitational tug of the black hole stretched the star apart. Only about 1 percent of the star was actually consumed by the black hole, scientists told reporters in a news briefing. The rest was flung off into the galaxy by the momentum of the interaction.

Stellar explosion sends out jet of gamma rays
A stellar explosion in a galaxy 7.5 billion light years away was powerful and bright enough to be seen with the naked eye on Earth. Astronomers picked up more detailed observations of the explosion, called a gamma ray burst, with NASA's Swift satellite. Then they conducted follow-up observations with ground- and space-based
telescopes around the world. The pile of data drew the best picture yet of the poorly understood gamma ray bursts and showed that Earth was in the near direct path of a jet that shot out of the star. Had the explosion happened in our galaxy, astronomers said, it would have spelled big trouble for life on Earth. The illustration here shows how the gamma ray burst may have appeared up close.

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