Reasons for pessimism

Don't read this if you're easily depressed. It's the latest report from Ronald Bailey at the Global Catastrophic Risks conference:

But before becoming too complacent, keep an eye out for reports on the 210-330 meter asteroid Apophis-there's a 1 in 45,000 chance that it could hit the earth on April 13, 2036. Measurements in the next 3 to 4 years will determine just how big a chance of a collision there is.

Gamma Ray Bursts

Technion physicist Arnon Dar warned of another space hazard — gamma ray bursts (GRBs). GRBs were originally detected by U.S. military satellites that were checking to see if the Soviets were testing nuclear weapons. GRBs are beams of highly energetic photons produced when a gigantic star goes supernova. Dar described a GRB beam hitting the earth would be like a kiloton bomb per square kilometer going off at the top atmosphere. He speculated that some of the earlier mass extinctions, such as the Permian extinction in which perhaps 90 percent of all life died out might have been caused by GRBs.

So are there any stars likely to go supernova nearby? Dar pointed out that the gigantic star Eta Carinae at a distance of 7,500 light years has been extremely unstable of late. Eta Carinae is 100 times more massive than the sun and 5 million times brighter. When it goes it will be a hypernova. Dar then gave us the good news: Eta Carinae's axis is pointed away from the earth, so the GRB beam it will generate when it dies will be aimed far from us. However, don't get too complacent about GRBs. Future of Humanity Institute research fellow Anders Sandberg mentioned that some astronomers are worried that we may be looking down the barrel of gamma ray gun when the WR 104 binary located 8,000 light years away goes supernova.

Just to add to your worries . . . we'd get very little real warning that a neighbouring star had gone supernova: the GRB beam would arrive almost simultaneously with the visual or radio wave evidence of the event.