Proxima Centauri Supernova

[ihwip]

I am curious if anybody knows just how screwed we'd be if Promixa Centauri went Type 1a. I am not familiar with its orbit around A&B but would that additional distance make a difference? Do we know at what mass white dwarves explode?

 

[yevaud]

Well, White Dwarves don't explode, so that resolves that. They have insufficient mass.

To do so, the stellar body in question must mass at least the Chandrasekhar Limit, which is 1.4 Solar masses. Less mass than that, the star will expand to a red giant as it begins to exhaust it's fuel and starts to fuse elements other than Hydrogen. Then, further down the road, it slowly shrinks down to, yes, a White Dwarf, and gradually fades away. This is the future destiny for our own sun. FYI, the Chandrasekhar Limit is actually around eight solar masses, but as the star begins to exhaust it's fuel, it also loses mass (becoming over time a Planetary Nebula), and the core remains below Chandrasekhar. Over that limit, and you get a type Ia Supernovae.

In answer to the other part of your question, were it possible for Proxima to go Supernova, we would all likely be dead - not from "blast effects," per se, but from ionizing radiation and highly energetic particles stripping away the Ozone layer. And we wouldn't get a heck of a lot of notice about it either. A burst of Neutrinos about eight hours prior to the actual optical observations (exactly what occurred with Supernovae 1987a).

Now there are circumstances in which a White Dwarf can Supernovae. If it orbits a larger companion, and accretes matter from it, it can be "pushed" over the Chandrasekhar Limit [Edit - forgot to add for Ihwip that this event is known as "Carbon Detonation."]. I'm fairly certain you've seen similar images to the following, which is an artist's representation of a White Dwarf accreting mass from it's parent.

This answer your questions?

 

[Saiph]

A type II supernova (a big star dying) is, IIRC, considered fatal to all life on earth via radiation (gamma ray basically) if it's anywhere within 50 light years...

Type II are brighter than Type I, but not by that much. The main distinguishing feature between the two types is that Type II stars have a 'plateau' in their intensity as they grow fainter. Type I just continue with a nice curve to dimmer outputs.

 

[yevaud]

I wouldn't want to witness either type from this distance.

 

[crazyeddie]

I am curious if anybody knows just how screwed we'd be if Promixa Centauri went Type 1a. I am not familiar with its orbit around A&B but would that additional distance make a difference? Do we know at what mass white dwarves explode?

Several large stars within the Milky Way have been suggested as possible supernovae within the next few thousand to hundred million years. These include Rho Cassiopeiae, Eta Carinae, RS Ophiuchi, U Scorpii, the Kitt Peak Downes star KPD1930+2752, HD 179821, IRC+10420, VY Canis Majoris, Betelgeuse, Antares, and Spica.

Many Wolf-Rayet stars, such as Gamma Velorum, WR 104, and those in the Quintuplet Cluster,are also considered possible precursor stars to a supernova explosion in the 'near' future.

The nearest supernova candidate is IK Pegasi (HR 8210), located at a distance of only 150 light-years. This closely orbiting binary star system consists of a main sequence star and a white dwarf, separated by only 31 million kilometres. The dwarf has an estimated mass equal to 1.15 times that of the Sun. It is thought that several million years will pass before the white dwarf can accrete the critical mass required to become a Type Ia supernova.

http://en.wikipedia.org/wiki/Supernova

 

[silylene]

I am most worried about Vega, as its polar axis points nearly directly at the solar system, and may one day burp a huge GRB aimed towards us. We discussed this in another thread. Here's a thread: http://www.space.com/common/forums/viewtopic.php?f=13&t=9269&hilit=vega And if you can find my old thread from the pre-Pluck days of SDC, there was a lot more information.

 

[SpaceTas]

Proxima Cen is an M dwarf main sequence star. It cannot go supernova. May every now and then send out a massive stellar flare ..... but that is only a problem if you at planetary distances.

There is a possibility that white dwarfs can go supernova. But this requires special circumstances.
It has to be in a close binary where it accrets hydrogen from its companion, not to slow or not to fast. The extra hydrogen must accumulate. Too fast you get continuous nuclear burning (a soft soft x-ray source), and a strong stellar wind too slow you get nova or recurrent nova explosions. You need to have the star pass the Chandrashakar limit 1.4 solar mass. Then you get compression leading to collapse toward a neutron star plus run-away nuclear reactions (not just hydrogen burning) with complete destruction of the white dwarf. It is easier to get the critical mass if accreting mostly He (ex core of giant, or another white dwarf).

No body is quiet sure what is the minimum safe distance. It's the UV/gamma-ray flux that is the killer

 

[ihwip]

Now there are circumstances in which a White Dwarf can Supernovae. If it orbits a larger companion, and accretes matter from it, it can be "pushed" over the Chandrasekhar Limit [Edit - forgot to add for Ihwip that this event is known as "Carbon Detonation."]. I'm fairly certain you've seen similar images to the following, which is an artist's representation of a White Dwarf accreting mass from it's parent.

This answer your questions?

OK, this almost answers my questions. My remaining question is, say Proxima IS collecting mass from Alpha and Beta. At what point will it detonate? Would this perhaps vary? I recall being told that they gauge various distances due to the believed identical brightness when a white dwarf blows. If a white dwarf was almost at the edge and we knew how fast it was accreting mass, could we predict roughly when it will blow?

 

[crazyeddie]

OK, this almost answers my questions. My remaining question is, say Proxima IS collecting mass from Alpha and Beta. At what point will it detonate? Would this perhaps vary? I recall being told that they gauge various distances due to the believed identical brightness when a white dwarf blows. If a white dwarf was almost at the edge and we knew how fast it was accreting mass, could we predict roughly when it will blow?

First of all, Proxima Centauri is in a distant orbit of Alpha Centauri A and B, and is not close enough to draw gases from either star....in fact, there is some doubt regarding whether or not Proxima Centauri is actually gravitationally bound to Alpha Centauri at all. Secondly, even if it were in a close orbit, I don't think it has the gravitational gradient it would need to pull material from it's companion star, because it's just not massive enough. Rather, I think the opposite would occur: the larger, more massive companion star would pull gases off of Proxima Centauri, ultimately reducing it's mass to the point where it could no longer sustain hydrogen fusion at it's core.....in effect, turning it into a brown dwarf. Does this sound correct to you more physics-minded members out there?

 

[dragon04]

Via prior explanation, he knows that. What he's asking is that IF Proxima was a white dwarf, and IF Proxima had a higher mass than A or B, and IF it was in an orbit close enough to draw off mass to eventually become a Type 1A.......

The best thing would have been to ask if there's a predictable time frame of a White Dwarf of Mass (x) in a sufficiently proximal orbit to a lower-mass companion going supernova in a Type 1A detonation. That's really what he's asking.

 

[Saiph]

In an answer to that hypothetical: Yeah, I'm sure we could estimate it's final detonation. To within a few hundred thousand years no less.

For instance, we see Betelguese could go anytime now...within the next what? 100,000 years?

One of the first signs of trouble for such a star though is the repeated Nova events that must occur. The gas stolen by the white dwarf will compact and undergo fusion on the surface of the star. Since it isn't insulate and diffused by a stellar atmosphere this will be very intense, and short lived. And periodic.

The star will only go Supernova when enough ash from these repeated Nova events builds up to push it over the Chandrasekhar limit.

 

[yevaud]

One of the first signs of trouble for such a star though is the repeated Nova events that must occur. The gas stolen by the white dwarf will compact and undergo fusion on the surface of the star. Since it isn't insulate and diffused by a stellar atmosphere this will be very intense, and short lived. And periodic.

For the reading audience, this is known as "Helium Flash."

 

[eburacum45]

I am most worried about Vega, as its polar axis points nearly directly at the solar system, and may one day burp a huge GRB aimed towards us. We discussed this in another thread. Here's a thread: http://www.space.com/common/forums/viewtopic.php?f=13&t=9269&hilit=vega And if you can find my old thread from the pre-Pluck days of SDC, there was a lot more information.

I am certain that in the old threads we determined that there is absolutely no threat from Vega.

Vega is a perfectly normal. main sequence A class star; A class stars are far too small to become gamma ray bursters.