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What happens when Betelgeuse explodes?

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Re: What happens when Betelgeuse explodes?

#31

Post by jerf »

themartorana wrote: post #15
astletron wrote: post #2

"Nighttime will be a different story. The brightness of Betelgeuse’s supernova is about the same as the quarter moon." This will last maybe a couple of weeks, but we don't expect it for 100K years.

No, but with billions of stars in our own galaxy, and more beyond, wouldn't (my misunderstanding of) the probability of witnessing a past supernova event during one's lifetime be higher than it feels like it is?

First of all, the "pastness" of looking out into space doesn't really affect probability of witnessing them.

Second, supernova occur quite frequently: http://en.wikipedia.org/wiki/List_of_supernovae That's not even a complete list, just the "important" ones. The odds of one occurring within our lifetime that is naked-eye visible are really quite good. The odds of it being spectacular much less so. It's likely to just be a point in the sky that wasn't there last week and won't be there next week.

Re: What happens when Betelgeuse explodes?

#32

Post by jjoonathan »

gunn wrote: post #8
jahnu wrote: post #7

Earlier quoted context omitted.

I feel those images are a little misleading. One might erroneously assume there is a dense surface akin to our star at the outer edge of these massive stars but.. "In the outer reaches of the photosphere the density is extremely low, yet the total mass of the star is believed to be no more than 20 M☉. Consequently, the average density is less than twelve parts per billion (1.119 × 10−8) that of the Sun. Such star mat…

Also: "estimates of its mass are poorly constrained, but range from 5 to 30 times that of the Sun". Amazing for having on the order of 16 billion times its volume.

How does that happen? Is its fuel more energetic in some sense or does the gravity-vs-pressure equilibrium simply favor lower densities for a total mass of 20M☉?

Re: What happens when Betelgeuse explodes?

#33

Post by yourad_io »

jahnu wrote: post #7
adwn wrote: post #5

To get a feel for the tremendous size of that star: https://en.wikipedia.org/wiki/File:Star-sizes.jpg

I feel those images are a little misleading. One might erroneously assume there is a dense surface akin to our star at the outer edge of these massive stars but.. "In the outer reaches of the photosphere the density is extremely low, yet the total mass of the star is believed to be no more than 20 M☉. Consequently, the average density is less than twelve parts per billion (1.119 × 10−8) that of the Sun. Such star mat…

M☉ = Solar Mass[1]. Huh.

> astronomers have the worst conventions in the world (for largely “historical reasons”)[2]

You don't say.

[1] http://en.wikipedia.org/wiki/Solar_mass

[2] article

Re: What happens when Betelgeuse explodes?

#34

Post by agrona »

Starwatcher2001 wrote: post #6

The remnents of the supernova that occurred in 1054 is known as the "Crab Nebula", AKA M1 on Messier's catalog. I remember observing this from my back garden some 10 years ago with a small telescope, but that's quite difficult now due to light polution. It's getting hard for people to see stars in many big cities, let alone fainter objects.

There's a guide (in development) at eyesonthesky.com[1] aimed at newcomers, who may be using poor telescopes in poor atmospheric and lighting conditions. I've been following it quite successfully from my back yard in Seattle. It focuses on the brightest galaxies and nebulae, interesting clusters, and binary stars.

[1] http://eyesonthesky.com/StarCharts/FirstLightGuides.aspx

Re: What happens when Betelgeuse explodes?

#36

Post by smeyer »

Filligree wrote: post #24
dghf wrote: post #10

Any risk of a gamma-ray burst affecting Earth?

Not from a supernova. Gamma-ray bursts are a wholly different phenomenon.

Not all supernovae have a GRB and not all GRBs have a supernova, but most long burst GRBs are thought to be from a supernova, no? I've been out of supernova research for a few years now, but that's what I recall.

Re: What happens when Betelgeuse explodes?

#37

Post by smeyer »

themartorana wrote: post #15
astletron wrote: post #2

"Nighttime will be a different story. The brightness of Betelgeuse’s supernova is about the same as the quarter moon." This will last maybe a couple of weeks, but we don't expect it for 100K years.

No, but with billions of stars in our own galaxy, and more beyond, wouldn't (my misunderstanding of) the probability of witnessing a past supernova event during one's lifetime be higher than it feels like it is?

It depends in part on what you mean by "witness" a supernova. We discover supernovae all the time (hundreds a year), but pretty much all of those are too faint to be seen with the naked eye. There's a decent chance of seeing a supernova visible with the naked eye in your lifetime, but a pretty small chance of one as bright as betelgeuse.

Re: What happens when Betelgeuse explodes?

#38

Post by ksmiley »

aruggirello wrote: post #18
kijin wrote: post #9

Other than slightly brighter-than-normal nights, will there be any adverse effects on Earth? The wikipedia article on near-Earth supernovae [1] suggests that Betelgeuse will be pretty safe because of its distance. But exactly how safe? What about all the delicate electronics that we've sent up to space? I suppose anything that can withstand a daily dose of solar radiation would probably be okay, but are there any spe…

Actually, a supernova would look like an impossibly tiny point source , much smaller than even your average laser pointer. I'm pretty sure the consequences of this haven't been thoroughly explored yet. I'm not sure the Betelgeuse supernova, at a brightness around that of the full moon, would ignite fires, but I certainly wouldn't want to gaze at it with naked eyes, even at that brightness. IMHO such a light, given su…

Your reasoning reminds me of the danger of retinal damage when observing a solar eclipse - a human's natural inclination to not stare at the sun is sharply reduced because the viewable area is so much smaller than usual. Looking at a thin slice of the sun is as dangerous as looking at the unobscured sun, even if it doesn't feel like it. But I don't think Betelgeuse would be dangerous in this way. It would be more like watching a lunar eclipse, which may be done without safety equipment.

Re: What happens when Betelgeuse explodes?

#39

Post by ChuckMcM »

kijin wrote: post #9

Other than slightly brighter-than-normal nights, will there be any adverse effects on Earth? The wikipedia article on near-Earth supernovae [1] suggests that Betelgeuse will be pretty safe because of its distance. But exactly how safe? What about all the delicate electronics that we've sent up to space? I suppose anything that can withstand a daily dose of solar radiation would probably be okay, but are there any spe…

Probably not unless you consider a group of self proclaimed holy men trying to follow it :-)

That said if you had some instruments closer to the heliopause you would definitely be able to detect the shock wave at that distance. It would be faint but should be well above the noise level of other particles.

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