Au contraire, its perfectly normal for glaxies to host more than supernova, they host hugenumbers of stars, dark and bright nebulae of allvarieties, dark matter and black holes among other things. Supernovae are what’s quite rare!

Sorry, I couldn’t resist that … I think you a word out there BA, ‘two’ or ‘one’ perhaps I’m guessing?

Incidentally – can a neutron star ever become the equivalent of a type Ia supernova? If it gathers too much mass the same way a white dwarf does a pulsar or magnetar just collapse into a black hole or can it start nuclear fusion and blow itself apart as well? & if one did, could we tell the SN apart from white dwarf ones? Anyone know?

Working on an article about the white dwarf Van Maanen’s Star at present – another neat co-incidence.

Nearby white dwarfs : Sirius B & Procyon B (F-type star a bit brighter and hotter than our Sun, 11 ly off) which are both orbiting larger main-sequence stars and could perhaps one day become nova or supernovae and then the third nearest and first single white dwarf, Van Maanen’s Star -which won’t become a supernova (SN) – at a distance of 14 light years away. Needless to say if Sirius or Procyon B do turn SN it won’t be for millions of years.

In answer to ‘ThePolynomial’ : From my recollection &/or gut-feeling I’d say we’d be in serious mass extinction territory if a supernova goes off closer than about 20-30 ly away. One closer than 50 would likely cause serious problems for us & one at about 100 ly would be getting a little close for comfort. One thats 200 or further away and its more a case of lets enjoy the show!

As for gravitat’l lensing, Glenn Becker, I very much doubt it could duplicate a single star or SN and not the entire galaxy. Not a naive question btw but a good one.

ioresult -yep. Your understanding and mine are identical on this because that’s right!

SN do occur after novae outbursts – many of them as the mass builds up. Unless the progenitor white dwarf was very close to the mass limit anyhow …

White dwarfs may vary slightly with age and mass so it makes sense that
they may not all be identical and hence not the best standard candles. Haven’t heard any news about recent doubts on their use as such, ‘jackd’ but it wouldn’t surprise me if they were a LOT less accurate as measuring
sticks than Cepheids etc ..

I’ve read an SF novel where Sirius B actually errupts into a supernova – its got some very good science and a science-versus-religion theme too so I reckon the BA and others here would enjoy it if they haven’t read it already. Its titled plainly enough, ‘Supernova’ by Roger MacBride Allen & Eric Kotani, Avon books, 1991. One slight drawback tho’ – it does feature the now-past millennnium as a minor element being mostly set in 1999-2000-2001 approx.