I have question that's been nagging at me for the past hour.

General physics and astronomy discussions not directly related to Celestia
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Draconiator

I have question that's been nagging at me for the past hour.

Post #1by Draconiator » 01.04.2004, 04:28

If Proxima Centauri (any of them, a or b) was a Sun-sized star, would Earth be affected when it finally went supernova? I was thinking about this since I came to the site here to look around.

Evil Dr Ganymede
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Post #2by Evil Dr Ganymede » 01.04.2004, 08:46

No, because it wouldn't go supernova if it was a sun-like star - they're not massive enough. sun-like stars become planetary nebulae/white dwarfs, which is a considerably less explosive process!

If it was massive enough to turn into a supernova, then beforehand it'd be bloody bright in the sky since it'd be a massive red supergiant like Antares or Betelgeuse, just over a parsec away (it'd be apparent magnitude about -10, if I've figured that out properly).

The supernova itself would be... stupidly bright. it'd probably turn night into day. And flood us all with horribly lethal radiation and kill everything on the planet probably. And then the ejecta would hit the solar system eventually (I'd guess after a decade or two?), and I have no idea would that would do, but that wouldn't matter since we'd all be dead by then I think :).

So it wouldn't be fun either way. But it would be very pretty :D

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Post #3by Don. Edwards » 01.04.2004, 11:03

Evil Dr Ganymede,
Hmmm, what about Sirius? It is only 8 light years away and it is a type A0. Would we see and or get any effect from it as it goes through its midlife crisis and death?

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Post #4by Ynjevi » 01.04.2004, 13:33

Don. Edwards wrote:Hmmm, what about Sirius? It is only 8 light years away and it is a type A0. Would we see and or get any effect from it as it goes through its midlife crisis and death?


I don't know how long it takes Sirius A to change to red giant (under 1 Gyr anyway), but it's well enough to travel far away from the Sun. And even if it was dying red giant now, it would hardly hurt us, as it will just create a planetary nebula.

I'm remembering that Sirius was about 8 times more distant when Sirius B blew out its outer parts and transformed into a white dwarf. That must have been quite a sight! (Edit: Later studies indicate that Sirius B became a white dwarf well over 100 Myr ago, so this seems not be the case...)

Sirius was once part of the Ursa Major cluster, and has thus the same age as the stars in the Big Dipper except for Dubhe (Alpha UMa) and Alkaid (Eta UMa). Sirius B evolved quicker than them (they're still in the main sequence or just becoming giants) and thus it was a more massive and brighter star.

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Post #5by Evil Dr Ganymede » 01.04.2004, 18:49

I don't think Sirius is massive enough to die as a supernova either. Though I don't know what is the nearest star that could... There don't seem to be any supergiants within about 30 pc of Sol - I think epsilon aquilae might be the closest (an F0 Ia supergiant).

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Post #6by Ynjevi » 01.04.2004, 20:49

Evil Dr Ganymede wrote:I don't think Sirius is massive enough to die as a supernova either. Though I don't know what is the nearest star that could... There don't seem to be any supergiants within about 30 pc of Sol - I think epsilon aquilae might be the closest (an F0 Ia supergiant).


Epsilon Aquilae a supergiant? Well, Jim Kaler's Stars site says Epsilon Aql is an ordinary K1 giant about 154 lys distant. The closest supergiant to us is Canopus, but with a mass of 8-9 times solar even it is too small to explode as supernova. The closest supernova progenitor is probably Betelgeuse.

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Post #7by Evil Dr Ganymede » 01.04.2004, 23:09

D'oh! Eps AUR (Maaz) is the F0Ia supergiant. It got muddled up there, sorry. You're right. Eps AQL is the K2 III giant.

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Post #8by Mikeydude750 » 05.04.2004, 00:12

Of course, if Betelgeuse exploded, we'd still be in a world of hurt, from the radiation and all...

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Post #9by Evil Dr Ganymede » 05.04.2004, 00:56

Mikeydude750 wrote:Of course, if Betelgeuse exploded, we'd still be in a world of hurt, from the radiation and all...


Would we? It's almost 430 lightyears away...

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Post #10by Don. Edwards » 05.04.2004, 04:49

Yes and if Betelgeuse went nova tomorrow we won't know about it for at least that length of time. So what would we care? It would be the worry of our very late descendants to worry about. And here is hopping that our descendants have the forethought to spread throughout the stars and not stay home on our little planet. I am sure that at nearly 430 LY away Betelgeuse would mean us no harm but there are other reasons to get our collective arses out there into space. The more of humanity spread around the better chance of us surviving as a species than to sit here at home on our hands doing nothing.
just my thoughts.

Don. Edwards
I am officially a retired member.
I might answer a PM or a post if its relevant to something.

Ah, never say never!!
Past texture releases, Hmm let me think about it

Thanks for your understanding.

Evil Dr Ganymede
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Post #11by Evil Dr Ganymede » 05.04.2004, 05:11

Yeah... but it might have gone supernova 425 years ago, in which case we'd find out pretty soon :).

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Post #12by revent » 05.04.2004, 06:32

Out of curiousity, I actually sat down and tried to handwave my way through this. I just used simple geometry, so don't nitpick. :)

Given the surface area of a 430 ly sphere, and the cross sectional area of the Earth, about 1.6x10^-24th of the released energy would pass through the Earth.

Now, type I supernovea are normally described as being brighter than a galaxy, and there are about 1x10^8 stars in the Milky Way, so it's fair to say that we'd be seeing something on the order of 1.6x10^-16th of the TOTAL power output of a typical star from the supernova (though /very/ little of this energy would actually be coupled to the Earth, and I'm totally disregarding attenuation).

For comparison, about 4.5x10^-10th of the total energy output of the sun is incident of the Earth, so the supernova would deliver about a million times less energy to the Earth than the Sun. I think we're safe. :)

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Post #13by Ynjevi » 05.04.2004, 10:53

Indeed, Betelgeuse is way too distant to harm us in any way.

Betelgeuse's mass is thought to lie between 12 and 17 solar masses (although I've seen higher estimates). If its mass is near the lower end (or under) of the range, it may even not explode as supernova.

~ Jyri


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