Star Geek: Voyager

This is cool news, although it probably doesn't mean quite what you think it means.

A scientist at N.C. State University has discovered the youngest known supernova in our galaxy.

It's only 140 years old, NCSU announced today.

Previously, the youngest supernova, or exploding star, in the Milky Way galaxy dates back to 1680 - making it more than twice as old as the latest discovery, according to NASA.

A comparison of images of the object - called G1.9+0.3 - taken in 1985 with others taken in 2007 enabled scientists to observe its rate of expansion and through that calculate when the event occurred.

"My best estimate is that it's 100 years old," said [astrophysicist Stephen] Reynolds. "140 is the upper limit."

The discovery of the supernova is significant for two reasons: One, finding it so early in its development makes it easier to learn about the original star and the effects of the blast. As one astrophysicist put it, "this is a stellar death and the corpse is still warm." And two, it helps to answer the question of the missing supernovas.

Astronomers have scoured the skies for supernovae since [the youngest previously known supernova, called Cassiopeia A,] surfaced in the 1950s. Only a half-dozen of the stellar explosions have been noted in the last millennium, but somewhere between 20 and 30 should be occurring in the Milky Way based on galactic evidence.

It's likely that a number of them have not been observed because they are obscured by clouds of gas and dust that mask their visible light - as was true in this case. Still, they can be found via the X-rays and radio waves they emit. This particular one was uncovered with help from the Chandra X-ray Observatory; some related images can be found at that link and info about Chandra (with links to other images) can be found here.

And one last thing, why this likely doesn't mean quite what you think: As the news articles tend not to make clear, the "140 years" refers to what astronomers call "Earth's time frame." That is, the energy - X-rays, etc. - from the supernova first reached the Earth no more than about 140 years ago. The star, however, is (or, if you prefer, was) about 25,000 light years away, which means the actual event occurred about 25,000 years ago, not 140.