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Scientists ID our youngest supernova (age 140)

May 17, 2008|From the Associated Press

Astronomers have discovered the youngest known supernova in the Milky Way galaxy, still just a baby at 140 years old.

The scientists, who announced their findings Wednesday, used a radio observatory in New Mexico and NASA's Chandra X-ray Observatory in space to determine when the supernova occurred. They dated the event to around 1868.

Before this, the youngest supernova in the Milky Way was thought to have occurred around 1680.

A supernova is the catastrophic explosion of a star that releases an extraordinary amount of energy, enough to outshine an entire galaxy.

This new baby supernova is located near the center of the Milky Way and is obscured by dense gas and dust.

Two or three supernovae are thought to occur every century in the Milky Way. That means there are probably even younger ones out there waiting to be identified, said David Green of the University of Cambridge in Britain, who led the radio observatory study.

Green and others have been tracking the remnant of this supernova since 1985 via the National Science Foundation's Very Large Array, a radio astronomy observatory. But it wasn't until last year that a team led by North Carolina State University physicist Stephen Reynolds found, with help from Chandra, how much the remnant had expanded. That indicated the supernova was much younger than initial estimates, which had ranged from 400 to 1,000 years old.

The Very Large Array made new observations in March and helped pinpoint the age at 140 years, possibly younger if the expansion has been slowing.

"It's the combination of the radio and the X-ray, the older technique and the new one, that tells us what this object really is. So you get a lot more when you put all of these clues together," said Robert Kirsh- ner, a Harvard University astronomer who is not affiliated with the study.

"It's a little like one of those shows on TV where they investigate a death. This is a stellar death, all right, and the corpse is still warm," Kirshner said in a teleconference call with reporters.

Astronomers typically observe supernova remnants that are 10,000 or so years old. Getting the total picture, from the start, is important in figuring out how often supernovae explode in the Milky Way.

In this case, "you're actually getting to see the rock that made the splash, not the wave that's going out into the pond," Kirshner said.

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