I have an interest in stars like the Pistol Star and Eta Carinae, but I would like to know if there are any massive ones (of supernova producing mass) within lethal distance of Earth. Of course it'll be millions of years before the next one happens period, so I'm not worried right now

Stars actually move with respect to the Sun fast enough that a million years is a pretty long time for a star to stay in 'lethal range'. To my knowledge, there are none we can see predicted to be big enough and close enough in the forseeable future.

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I'm just talking about stars that are close enough to be lethal if they were to go Supernova (or Hyper) right now. Even though it's not likely it is still a question I ponder.

There aren't any. Betelgeuse might be the closest, but we are moving away from it, and are already at a very safe distance.

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Thanks for the answer, I thought Betelgeuse might be a contender, but I guess I was a wee bit wrong.

I put even odds on Betelgeuse or Antares. Canopus is even closer, but I think it's just shy of the mass required for a SN.

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How about type Ia supernovae? There are plenty of white dwarfs around, apparently 22 within 10 parsecs (according to solstation.com). I'm not sure what the danger range for these is but we must be talking about thousands of candidates at least.

You'd need a source of material so the primary has to be very close or a red giant. I guess if you do that you can cut down the candidates to 1 or 0.

Type Ia are harder to come about, because you need a white dwarf and a companion star that the white dwarf takes energy from (mass) in order to reach the critical mass. As you said.. That really makes the possibility smaller.

There are a couple of other scenarios that might, just might, keep you awake at night*:

A GRB, either long or short - if we were unlucky enough to be in the jet of one, we'd be safe only if it were a very long way away (or, maybe, on the other side of some nice, thick ISM dust clouds). The good news is that, for reasons as yet not really known, GRBs are quite rare in the recent universe.

A magnetar, at the time of a serious starquake - same story as the GRBs, except that the safe distance is considerably smaller than for GRBs.

In both these cases, the progenitors could be, as yet, undetected by us ... they need not be within just a few pc, or even (perhaps) a few hundred pc, to be totally lethal.

There's also some other relief, in both cases: the duration of the killer blow is very short, in all the above cases, so 'only' a hemisphere would get instantly sterilised (the rest of the planet would merely have to survive the atmospheric consequences of such an instant sterilisation ... come to think of it, that may be worse). Of course, some time later there would an intense bombardment by cosmic rays, kinda like having a zillion LEPs or LHCs or Tevatrons going full-blast, straight at you, for a few hours/days ... pretty bad news, but maybe not instant sterilisation ...

*Other than doing a Messier marathon, or indulging yourself in the splendours of the sky ...

If we assume that the current models for GRBs are close to correct, we will soon be able to identify the progenitors for the short GRBs, using the LISA and later gravitational wave detectors. Concerning the long GRBs, the presumption there is that they come from low-metal giant stars, so Rho Cas and Eta Car will not qualify.

Side note: RS Oph has the potential to be a nearby type 1a (geologically) soon as far as we know.

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What do gravitiational waves have to do with gamma-ray bursts? Would we see gravitational waves earlier, the same as neutrinos?

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For the short burst GRBs we think they are from two neutron stars, or a neutron star and a stellar mass black hole, spiralling into each other. The GRB happens at the moment of actual contact, but the system will be giving off Gravitational waves that should be detectable for quite some time prior to the actual collision.

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Eta Carinae is close enough to be lethal (6,000 light years away I think?) if it went hypernova but it's current "ejections" are not pointing towards us.

IF Eta Carinae is the sort of star that can be a GRB, and was pointed at us, it would be a pretty serious event. The Earthborn extremophiles living near the deep undersea ocean vents would probably not be seriously affected.

However, new studies are indicating that Eta Carinae's metalicity is too high for it to become a GRB.

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