It’s Gonna Blow!

20 December 2014

Artist's impression of a hypernova, generating 2 gamma-ray jets. NASA/JPL-Caltech
Artist’s impression of a hypernova, generating 2 gamma-ray jets.

Eta Carinae is about 7,500 light years away, and its going to explode any time now. Mind you, “any time now” means sometime over the next ten to twenty thousand years or so. But recently the star been in the news again as an existential threat to our planet. It must be that time of year again.

Just to be perfectly clear, Eta Carinae is not a danger to Earth. Even if the star exploded as a hypernova it would simply outshine the Moon for a while. It might disrupt the sleeping and hunting habits of some terrestrial critters for a while, but it won’t mean the end of life on our planet.

What’s being hyped in the press is the possibility of a gamma ray burst from Eta Carinae. If the star produced an intense GRB in our direction, then its possible we’d be in trouble. For several seconds the sky facing Eta Carinae would appear brighter than the Sun, and we’d be exposed to intense gamma rays. If that isn’t a doomsday scenario, it would at least give us a chance to live out our post apocalyptic fantasies. But stars produce GRBs along their axis of rotation, and Eta Carinae’s axis isn’t pointed at us. The star is also shrouded by a nebula, which would dampen some of the energy of a GRB.

Of all the local stars that could become supernovae, none of them are pointed in our direction, so we have no need to worry about them. But in general, they could pose a threat to extraterrestrial civilizations (should they exist). Gamma ray bursts have been proposed as an explanation for why we haven’t seen alien civilizations in the galaxy. Perhaps they’ve all been wiped out by exploding stars.

But even that is pretty speculative. So sleep easy. Even if Eta Carinae is going to blow, it doesn’t have our name on it.