In the live chat tonight, I was asked when Betelgeuse will explode. The answer is, we don’t know. 
But that made me think about other stars that will blow, almost certainly before Betelgeuse does. I recorded my answer.
The stars I mention are Sher 25 and Eta Carinae. For the record, I said that I thought Sher 25 was 6000 light years away; it’s actually 6000 parsecs, or 20,000 light years away. I had the number right, but the unit wrong.
You can read all you want about Supernova 1987A on my Bitesize Pages, too.
February 24th, 2008 at 8:29 pm
Phil,
You sound pretty “Sher” about that.
February 24th, 2008 at 8:52 pm
Hang on. If Sher 25 has at most 10,000 years to live, and it’s 20,000 light years away, is it right to talk about it in the present tense?
I know, I know.
February 24th, 2008 at 8:54 pm
Good thing you weren’t navigating on the Kessel Run.
oh wait.
February 24th, 2008 at 9:28 pm
Phil,
Bigger isn’t always better. It would be remiss to ignore the Ia class in favor of the big ugly stars. So I’ll look at this as a David and Goliath contest, and put my money on RS Ophiuchi.
February 24th, 2008 at 9:43 pm
A Webcomic – “Schlock Mercenary” did a good joke about Eta Carinae and supernova’s back in 2001
http://www.schlockmercenary.com/d/20010202.html
Always good for a laugh.
February 24th, 2008 at 9:59 pm
Speaking of Eta Carinae, check out this article recently published in Astrobiology, which shows (rather disappointingly) that we probably won’t be fried when that big sucker goes off…
“Superluminous supernovae: No threat from Eta Carinae”
http://www.liebertonline.com/doi/abs/10.1089/ast.2007.0181
For those without a subscription to the journal, there’s a pre-print version here:
http://arxiv.org/abs/0705.4274
(and yes, this is shameless self-promotion
)
February 24th, 2008 at 10:38 pm
Pleeeeeeeeeeeeeez, BA, can you post your live chat sessions online like Chris P. does, so peeps like me with weird schedules and/or crappy connections can see them later? Pretty please, with a supernova on top?
February 24th, 2008 at 10:48 pm
Ooooooo, Brian, very cool. When I was doing all the journal searches for my chapters on SNe and GRBs, I saw a reference to blue light (or it may have been just white light) being a problem. I dallied with mentioning it but then just discussed the disruption of diurnal cycles.
I did talk with Adrian Melott quite a bit. I’m not convinced the Ordovician was from a GRB, of course, but the evidence is provocative.
February 24th, 2008 at 10:53 pm
Dear Brian,
How close would a supernova have to be to heat the kupier belt / Oort cloud enough to evaporate big bright comas off all the icy bodies out there? If it isn’t going to fry us, then lighting up the outer solar system enough to spot what is out there might be fairly useful…
February 24th, 2008 at 10:54 pm
OK – so a follow-up question. I assume no one knows for sure that the type of star SN1987A was before it blew up only shed one ring of gas before blowing up? Couldn’t there be older rings that have dissipated and remain invisible as part of a cycle that repeats itself several times before the final cataclysmic event? That would lengthen the odds of Sher blowing up any time soon.
Frankly, any new supernova in the Milky Way would be a wonder (but not too close!).
February 25th, 2008 at 7:09 am
From the title I thought this was going to be another Academy Awards article. Turns out to be an article about astronomy. Phil, you’ve got to get your priorities straight!
Oh wait… you have!
February 25th, 2008 at 7:44 am
tacitus writes:
[[I assume no one knows for sure that the type of star SN1987A was before it blew up ]]
Actually, I think they did know the type, though I don’t recall what it was. The star was catalogued as Sandoval -69 degrees, and I forget the index number, in one of the Magellanic Clouds, and I think it was a B-type blue supergiant.
February 25th, 2008 at 8:05 am
Betelgeuse will explode if you say it’s name 3 times
February 25th, 2008 at 8:37 am
tacitus: we didn’t see the three-ring system until the star blew up, and it lit up everything for many light years around it. If there had been an older ring we would have seen it. There were other structures around it, but nothing else like the rings.
Sher 25 is a little bit hotter than the star that blew up to be 87A. We know that because it is hot enough to ionize the ring around it, while the progenitor of 87A was not hot enough to do that (though just barely too cool). Hotter = more massive = shorter lifespan.
February 25th, 2008 at 9:36 am
Ok, got it. Thanks for the response.
February 25th, 2008 at 10:06 am
OOOH, goody. Exploding stars. Now, where’d I put that popcorn,,,
GAry 7
February 25th, 2008 at 10:44 am
BA — Well, none of us are 100% convinced that a GRB was responsible for the end Ordovician, but it does seem to fit well… and I got a dissertation out of it, so I’m happy!
Lab Lemming – Interesting question! Without doing any real calculations, I’d guess that the SN would have to be pretty close to strongly affect Oort cloud objects. The main threat from a SN is X- and gamma-rays (and maybe cosmic rays, over much longer time periods), and they will affect you from a much greater distance than would thermal heating or a shockwave. Past simulations show that a distance of about 10 pc is probably dangerous for a SN that’s fairly bright in gamma-rays.
February 25th, 2008 at 1:05 pm
If it is 20000 lightyears away, doesnt that mean its likely already blown up?(and we havent seen it yet) Is there any way to measure these things before the light reaches us?
February 25th, 2008 at 1:29 pm
The short answer to for BicycleRepairMan is: effectively no. The one exception is that the neutrinos arrive a little earlier (seconds to minutes) because they get out of the star before the shock wave hits the surface. Otherwise, the information simply can’t get here any faster than the light.
February 25th, 2008 at 3:11 pm
Considering how your book is (almost) done, and how you seem to be making some videos lately, have you considered bringing back Q&BA anytime soon?
*Crosses fingers*
February 25th, 2008 at 6:20 pm
I thought the yellow hypergiants like Rho Cassiopeiae were the best candidates for supernovae. I agree that the ring is a suspicious sign after what we see with 1987A.
February 25th, 2008 at 6:40 pm
Brian: from your paper:
“With a luminosity of about 3 × 10[^]37 J s-1, about 0.5 mW m-2 could irradiate the
Earth’s surface for several months over much of the southern hemisphere.”
Insolation at 1 AU is about 1500W m-2
So your supernova is about 3 million times dimmer that the sun here on Earth. However, if we assume that insolation in the solar system obeys the inverse square law, while supernova illumination is constant, then at a distance of 3E6^.5 AU, they should be equal.
That’s about 1732 AU, which is pretty far out in the Oort cloud.
So, pretty dim. Oh well.
p.s. The first time I read the paper, I read W instead of mW, which would have made the crossover 55AU- or just beyond Pluto’s aphelion. Foiled by a prefix!
p.p.s. BA, do you allow LaTeX?
February 25th, 2008 at 7:50 pm
It is taking every single bit of willpower I have to refrain…
February 25th, 2008 at 10:38 pm
Oh, I just looked up eta Carinae and Sher 25, and they are both in the end of Carina near to the Southern Cross, around 60 deg south. So it would be great if either went off- from down here they would never set.
February 26th, 2008 at 2:52 am
How about Procyon B and Sirius B – the white dwarf companions to theDogtsar &little Dogstar?
Are they likely to result in supernova – esp. given Procyon A is already evolving towards gianthood?
(BTW. There was, incidentally, an SF novel based on this for Sirius’es “Pup” blowing up – ‘Supernova’ by Roger MacBride Allen & Eric Kotani, Avon books, 1991.)
February 26th, 2008 at 3:04 am
Said # Barton Paul Levenson on 25 Feb 2008 at 7:44 am
“tacitus writes:
[[I assume no one knows for sure that the type of star SN1987A was before it blew up ]]
Actually, I think they did know the type, though I don’t recall what it was. The star was catalogued as Sandoval -69 degrees, and I forget the index number, in one of the Magellanic Clouds, and I think it was a B-type blue supergiant.”
Yeah – blue supergiant.
The precursor star that exploded as SN 1987 A was catalogued as Sanduleak (or Sk) – 69 202.
(See in ‘End in Fire’ by Paul Murdin,Cambridge Uni. Press, 1990.)
February 26th, 2008 at 3:17 am
Woilf-Rayet stars (like Luminous Blue Variables eg. Eta Carinae) asre also meant theoretically to end up going supernova – but does anyone know if any supernova have been confirmed as coming from Wolf-Rayet (class W or WR) stars?
Incidentally, the name Sanduleak comes from the star catalogue by Nicholas Sanduleak (pron. “Sand-you-lee-ak) of 1,272 hot blue stars in the Large Magellanic Cloud & the stars observed spectral type – pre-Supernova – was B3 Ia or bright supergiant of spectral type B3.
February 26th, 2008 at 4:39 am
Procyon and Sirius B both have fairly large orbital radii- more than 9 AU- so they won’t get engulfed when their companions become giants. And neither is close to the critical mass.
February 26th, 2008 at 6:33 am
BicycleRepairMan writes:
[[If it is 20000 lightyears away, doesnt that mean its likely already blown up?(and we havent seen it yet) Is there any way to measure these things before the light reaches us?]]
Yes, it probably has blown up already, and we’re just not seeing it yet. No, there’s no way to measure it before the light reaches us. As far as present-day physics can tell, there is no easy way to send a signal faster than the speed of light. (Technically you can do it by warping space or with a “wormhole,” but creating or using either takes enormous amounts of power and requires something called “negative energy density matter” which may not exist.)
February 26th, 2008 at 6:36 am
StevoR writes:
[[How about Procyon B and Sirius B - the white dwarf companions to theDogtsar &little Dogstar?
Are they likely to result in supernova - esp. given Procyon A is already evolving towards gianthood? ]]
No. There is something called a “type I supernova” which involves matter from a red giant star falling onto a white dwarf, but the two stars have to be very close together — Sirius A and B, and Procyon A and B, are separated by several AUs — they are “visual binaries.” A close binary of the type required would only be visible from Earth as a “spectroscopic” or “eclipsing” binary.
February 26th, 2008 at 6:37 am
Incidentally, you were right about the SN1987A progenitor. I got the name wrong. (I probably got “Sandoval” from a Star Trek episode with a colonist leader of that name.) The correct designation was Sanduleak -69 degrees 202.