Betelgeuse?

[The Warthog]

I took my lovely Springer bitch out for a pee last night before I turned in, and noticed that Betelgeuse looked unusually red to the naked eye. And I caught a bit on Discover's Daily Planet show that Palomar scientists are watching for the possibility that Betelgeuse may produce a supernova in anywhere from days to weeks. They say we are far enough away to not be seriously threathened, but it should produce quite a light show.

Mmmm. Betelgeuse in daytime without a telescope. Should be fun!

[Bigwings]

Dont build yer hopes up nobody will see it for clouds

[Shibby]

I know it's shrunk a lot in the last 15 years odd, apparently by 15%, but I can't find anything in the news about any potential supernova indications...

Last I heard the prediction was "any time in the next 400 years"

[brianb]

And I caught a bit on Discover's Daily Planet show that Palomar scientists are watching for the possibility that Betelgeuse may produce a supernova in anywhere from days to weeks.

Betelgeuse will almost certainly go supernova (type II core collapse) eventually but the timescale is much more likely to be in the tens of thousands of years.

The indications are that this particular supergiant hasn't even begun to produce iron yet, let alone accumulated a substantial iron core. And it certainly isn't massive enough to produce a pair production core collapse super/hypernova, which is the only type which can occur during the evolution of a massive star before a massive iron core is formed.

[James]

Funnily enough my neighbour said something similar regarding it's redness only a week or two ago... hmm. We'll, if it has to go lets get the brightest stuff over the summer and have it fade away when the dark nights return.

James

[Iris]

It has been reducing in size quite a bit in the last 15 years apparently but it is also a variable star isnt it so it's likely to puff up and settle down from time to time too no?

[iamjulian]

Trying to decide whether this is an April 1st gag? I know it is one of the stars in the "could be years from now, or in the next ten seconds" category. But would still make a good April fool. Get us all out tonight looking at it

[barkis]

What a miss it will be. Orion will not be the same. Tantamount to Richard Branson's broad smile with a tooth missing .

As a matter of Interest, when was the last Supernova in our galaxy?

Furthermore, what chance a Black Hole forming as a result?. As we apparently already have one at the galaxy centre, we may get some rivalry here.

The pair may start vieing for star munching rights.

Ron.

[The Warthog]

1987?

[barkis]

I got 1680 WH. There was one in the Large Magellanic Cloud about the time you mention I think.

Ron.

[The Warthog]

Ah, right! We couldn't see it up here.

[Ben Ritchie]

As a matter of Interest, when was the last Supernova in our galaxy?

The Cassiopeia A supernova remnant is dated to 1681 +/- 19 years, although nobody at the time observed it (Flamsteed may have done). Interestingly though we can still observe it directly via light echoes, and can even observe it from different directions. There was a paper on astro-ph about it the other day

[1003.5660] Direct Confirmation of the Asymmetry of the Cas A SN Explosion with Light Echoes

Furthermore, what chance a Black Hole forming as a result?

Very difficult question to answer. Some stars as large as 60 times the mass of the sun can certainly form neutron stars, other black holes appear to have considerably less massive progenitors. Depends on a whole host of factors.

[FraserClarke]

1987A was in the large magellanic cloud -- a satellite galaxy of the milky way. I think CasA is the most recent (we know of) in our galaxy (there may have been some on the other side that we can't see). Typical rate for a galaxy like the MW is roughly 1 every 100 years -- so we're a bit overdue...

[Demonperformer]

The indications are that this particular supergiant hasn't even begun to produce iron yet, let alone accumulated a substantial iron core.

Don't want to be controversial about this, but in November 2009 Astronomy Now, there was a question raised about using the amount of iron in a star to determine its likelihood of going supernova. Dr Alan Longstaff stated "The final stage of nucleosynthesis - the forging of iron from silicon - takes only a single day", by which I understand the chances of spotting any iron before it goes sn are next to nil.

Or have I completely misunderstood?

[barkis]

I'm afraid my understanding on this subject is woefully lacking, but a question.

I do remember a reported burst of Neutrino detection shortly after the 1987 SN. So, as I understand, Neutrinos are massless particles, so that being the case, are they not free of the laws that restrict speeds in excess of lightspeed, and that detecting sudden burst of them in the deep underground chambers purpose built for there detection might herald the demise of Betelguese. A sort of, get ready for it, it's gonna happen. Or am I in Cloud Cuckoo Land?..

Ron.

[Demonperformer]

I believe the 1987A neutrino burst occurred about 30 min before the light of the sn reached us, in which case the answer would be yes, but not a lot.

[barkis]

I believe the 1987A neutrino burst occurred about 30 min before the light of the sn reached us, in which case the answer would be yes, but not a lot.

Enough time to shield your eyes though:D:D.

I gather the light output from a SN can vastly outshine the parent galaxies combined light. So are we looking at a brighter than the full moon scenario here?

Ron.

[Ben Ritchie]

Or have I completely misunderstood?

We've never watched a red supergiant age and die, so there's a lot of uncertainty as to what happens to a star like Betelgeuse. Indeed, it's not even clear if it will end it's life while a red supergiant - depending on the metallicity and main sequence rotational velocity it may loop back to the hot side of the HR diagram and become a Wolf-Rayet or Ofpe star before it goes bang. There are clues to how evolved it is though, because RSGs are highly convective and 'dredge up' the products of nuclear burning, so more evolved stars have higher abundances of heavier elements (especially alpha-process elements).

That's a convoluted answer, but these are very complex objects and their evolutionary behaviour is still far from understood. I'm currently doing some work on this cluster

Largest swarm of giant stars is a 'supernova factory' - space - 09 August 2007 - New Scientist

and getting quite interested in RSGs, fascinating things

[The Warthog]

Don't want to be controversial about this, but in November 2009 Astronomy Now, there was a question raised about using the amount of iron in a star to determine its likelihood of going supernova. Dr Alan Longstaff stated "The final stage of nucleosynthesis - the forging of iron from silicon - takes only a single day", by which I understand the chances of spotting any iron before it goes sn are next to nil.

Or have I completely misunderstood?

Interestingly, that's exactly what the Palomar scientist, a Finnish astronomer named Loof Lirpa, was saying about it.

[TheThing]

Loof Lirpa! Excellent, love it!

Rumour has it, if you read the entire thread backwards it contains Satanic verses!

Nice one Warthog.

[Neil English]

Betelgeuse is like Vesuvius: nobody knows when it's gonna go boom but it could happen anytime soon!

Neil.

[George]

Lets hope it happens on the first night of SGL5

[brianb]

Dr Alan Longstaff stated "The final stage of nucleosynthesis - the forging of iron from silicon - takes only a single day"

Well this obviously depends on density & temperature of the core, which depends heavily on the star's mass. But - though the silicon burning reaction releases much less energy than hydrogen, helium or carbon burning - the energy release from silicon burning is still of the order of 1% of the star's total lifetime output, and I doubt that's going to happen in a day - if it did then the luminosity would be great enough to blow away all the star's atmosphere & outer layers, resulting in something quite similar to a SN explosion ... and leaving behind a silicon / iron white dwarf, something which may exist but is not a common supernova remnant.

The silicon core can only "ignite" when it is massive enough to overcome degeneracy pressure... don't forget that, so long as it remains inert, it will be essentially isothermal but the density will be greatest at the centre, so that's where the reaction will start, proceeding outwards in a shell ... and the iron disintegration core collapse (Type II SN) will occur only when its mass is sufficient for the central pressure to overcome degeneracy.

Silicon "burning" is actually rather different to earlier types of nuclear fission. The temperature has become so high that some of the photons released are energetic enough to tear apart heavy nuclei; the process is more of a statistical equilibrium process where silicon group nuclei are broken up, some of the light nuclei are captured by heavier ones & there is a leakage towards the iron group (Fe, Co, Ni) which resist photodisintegration until much higher temperatures are reached. This process is not susceptible to the sort of "detonation" which can happen with e.g. a helium core. There is simply no reason to suppose that the transition from silicon core to iron core with silicon burning shell is anything other than quasistable.

[Ben Ritchie]

and leaving behind a silicon / iron white dwarf, something which may exist but is not a common supernova remnant.

I'm not a WD expert, but I think the borderline is the Oxygen-Neon WD, believed to be the accretor in so-called "neon novae" (i.e. novae unusually rich in magnesium and neon). These are the remnants of stars that were massive enough to burn carbon to neon, but not to start neon burning in the core. I think (but may be wrong!) that Neon burning marks the point at which the core mass becomes too massive to form a WD.

Worth remembering too that there are other important processes apart from the fiducial 'onion' model of core burning - you see elements more massive than iron in RSGs and asymptotic giant branch stars, so they don't just form during late-stage core burning and core-collapse SNe

[TheThing]

Ok, don't people get that it was an April Fool?!?