Old news

May 27, 2007

A star explodes. It's the biggest and brightest stellar explosion that anyone has ever seen. It's stupendously huge. And unlike most star deaths, this one doesn't leave a little cold clinker of a black hole behind; this bang is so energetic it just blows the whole star inside-out, spewing every bit of it into the great cosmos beyond.

Astronomers were so excited about it they held a press conference this month to announce the find. Here was a supernova - or a super-dupernova - that was first spotted in September and kept on with its eruption for months. You could almost say that astronomers watched it in real time - except that it happened 240 million years ago. It took that long for the light of the explosion to reach us.

What was going on 240 million years ago? On Earth, it was the Anisian Age of the Middle Triassic period, which followed (by about 11 million years or so) the planet's greatest extinction event, in which well more than half of all species were wiped out, on land, in the air and - most especially - at sea. The earliest dinosaurs found so far appeared on Earth during the Anisian. It would be only another 238 million years until people (in the form of Homo erectus) showed up.

By that time, the light of the explosion was 99 percent of the way here.

You wouldn't have wanted to be anywhere near the bang itself when it happened. A star about 150 times as big as the sun was detonating, and the gamma radiation it let loose was about as intense as anyone might imagine. If there were any alien dinosaurs thumping around in the immediate neighborhood, they probably weren't after the radiation hit.

The star that gives new meaning to the word smithereens goes by the disappointing name of SN 2006gy. It wasn't like the sun but like the much earlier pioneer stars that probably formed much of the modern universe as they blew up and sent virtually all the elements of the periodic table outward into space. There's one star in our galaxy that shows signs of heading for the same fate. It's called Eta Carinae, and it's a hop, skip and jump away at a distance of 7,600 light-years.

That means that if we see it blowing up tomorrow, we'll be seeing something that happened as the Sahara was forming, rice was first cultivated, bricks were invented, the Black Sea was deluged with saltwater, and wine was developed. It's a meaningless coincidence, no doubt, but it's also when the Byzantine calendar says the world was created. By most forms of reckoning, that's a long time ago.

The violent death of stars is dramatic. But what wouldn't we give to be able to peer into the distant past right here at home? What secrets would our little planet divulge, if we could only get a good look at it?

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