The universe is a dangerous place. There are lots of ways humans could be eradicated, or nearly so. Apart from the terrestrial threats (some hideous disease being the strongest candidate; our own stupidity doesn't reach this sort of threat level), we also face threats from our stellar neighbourhood. An impact with a large, very fast-moving body could make the Earth effectively uninhabitable. A nearby supernova could flash off the atmosphere and burn the planet to a cinder (highly unlikely; there don't seem to be any candidate stars close enough). Or we could be hit by a gamma-ray burst, an intense pulse of short wavelength radiation from a collapsing star that could fry us at a thousand light years, and cause mass-extinction from substantially further. Fortunately, the latter event is staggeringly rare - it requires just the right type of star, and its rotational pole must be pointed in the right direction.
Unfortunately, a Sydney astronomer has found just such a star, and its pointed right at us. WR104 is a Wolf-Rayet star, a massive hot star which is rapidly ejecting its outer layers. Its rotational axis is aligned within 16° of Earth. And its only 8,000 light years away. When it blows (and it will blow; the estimated lifetime of Wolf-Rayet stars is on the order of half a million years, but we have no idea how long this one has been ticking for), it may give rise to a gamma-ray burst, which might be broad enough to hit us. If it does, it would probably burn off most of the ozone layer, causing interesting climatic effects and a mass-extinction. Or we could get lucky (and if we do, any astrophysicists around at the time will no doubt get some excellent data to refine their models of such events).
This is not something we can predict, let alone do anything about. Bruce Willis with a nuclear bomb would not be able to save us. It's just bad luck, the cosmic equivalent of being run over by a bus. Shit happens, so wear clean underpants.
