Starship Asterisk*

http://apod.nasa.gov/apod/ap090805.html

Betelgeuse evaporating! I was just wondering what the gas is that is being given off? Looks like this star is going a different route than Eta Carinae.

Orin

What's the nearest star(s) most likely to explode and what effects would we see, hear or feel here on earth?

Betelgeuse shrinking!

http://asterisk.apod.com/vie ... =8&t=16955

bystander wrote:Betelgeuse shrinking!

http://asterisk.apod.com/vie ... =8&t=16955

Thanks bystander! I reread a lot of that. It does seem to be going a different route than Eta Carinae though. Eta Carinae seems to be giving off a lot heavier gas.http://images.google.com/images?sourcei ... e&resnum=4 The Betelgeuse must be losing hydrogen or some other light gas though. http://apod.nasa.gov/apod/ap090805.html

Orin

JuanAustin wrote:What's the nearest star(s) most likely to explode and what effects would we see, hear or feel here on earth?

http://asterisk.apod.com/vie ... 60#p107160

Does anyone 'out there' understand the structure of the image, that is, what is star and what is the gas plume? I'd assume the face of the star was the white ball in the center, but it strikes me as too large, even for a very large telescope.

C Wm Davis

cwmdavis wrote:Does anyone 'out there' understand the structure of the image, that is, what is star and what is the gas plume? I'd assume the face of the star was the white ball in the center, but it strikes me as too large, even for a very large telescope.

I think you are correct in assumming the white ball is the star. I think the green extending to the right is what they are calling the plume. The scale of the picture may be deceiving.

http://www.eso.org/public/outreach/pres ... 27-09.html
http://www.eso.org/gallery/v/ESOPIA/Sta ... s.tif.html
http://www.eso.org/gallery/v/ESOPIA/ill ... s.tif.html

More information on this giant. http://www.solstation.com/x-objects/betelgeuse.htm

Orin

Quote: (Betelgeuse is surrounded by shells of dust and gas that it has already blown off through a very strong stellar wind. There is a partial ring of dust lying out at around three times its radius, but more was found at around 650 AUs (James Kaler, 2001; and Rinehart et al, 1998). Even more dust is found around 12,000 AUs out, or 3,000 times the stellar radius. At about 36,000 AUs (or 1,000 times the stellar radius) or so, there is also abundant gas (James Kaler, 2001). In addition, there is a great, assymmetric shell of dust extending to at least 3.3 light-years or one parsec from the star (Baud et al, 1984). Although Betelgeuse is very large in diameter, astronomers believe that it contains no more than 20 Solar-masses so that the star has an average density less than air (University of Leicester Astronomy Society). )

I find it very interesting that the stars density is less than air! How can that be? It's just a giant poof ball

Orin

orin stepanek wrote:I find it very interesting that the stars density is less than air! How can that be? It's just a giant poof ball

Wikipedia: Red Supergiants wrote:These massively large stars are little more than "hot vacuums", having no distinct photosphere and simply "tailing off" into interstellar space.

orin stepanek wrote:I find it very interesting that the stars density is less than air! How can that be? It's just a giant poof ball.

But don't confuse "average" with "maximum". You can be sure that it has a nice dense core, just like any star needs to sustain fusion. It just has a very large, thin gas shell around it. Some models for our own sun suggest that when it becomes a red giant, it will be cool enough and large enough to allow the inner planets to continue on their orbits, within the star. It seems likely the outside will be low enough density; the main question is whether it will be cool enough that rocky bodies can survive without dissociation.

Chris Peterson wrote:

orin stepanek wrote:I find it very interesting that the stars density is less than air! How can that be? It's just a giant poof ball.

But don't confuse "average" with "maximum". You can be sure that it has a nice dense core, just like any star needs to sustain fusion. It just has a very large, thin gas shell around it. Some models for our own sun suggest that when it becomes a red giant, it will be cool enough and large enough to allow the inner planets to continue on their orbits, within the star. It seems likely the outside will be low enough density; the main question is whether it will be cool enough that rocky bodies can survive without dissociation.

Thanks Chris: I figured the core was denser but was really surprised that the outer layer was so rarefied. BTW are most giants similar in that the outer layers are like this?

Orin

orin stepanek wrote:I figured the core was denser but was really surprised that the outer layer was so rarefied. BTW are most giants similar in that the outer layers are like this?

You may find this interesting, orin


http://www.space.com/scienceastronomy/a ... 01018.html

Mark

orin stepanek wrote:BTW are most giants similar in that the outer layers are like this?

Not sure, but I assume so. You can get some sense of things by realizing that the mass range of stars is about 0.1 solar masses to 150 solar masses, so 1500 to 1. The diameter range (for stars still undergoing fusion) is around 0.15 solar diameters to about 650 solar diameters, which corresponds to a volume range of about 1e10 to 1. Clearly there is a huge density range.

Zeta Orionis appears to be nestled in the Horsehead Nebula, a region of intense starbirth. Actually, Zeta Orionis is only 135 light-years from Earth, while the nebula is 1,600 light-years distant.

I read your link Mark. 8) I did find it interesting; still, seems it doesn't help to add years to Alnitak's life. According to the article it's life span isn't long enough for life as we know it to evolve on a planet that may be orbiting it. The above quote shows how close it is from here. I found that interesting also. When you look at the Orion constellation; it's hard to imagine that some of it's stars are a lot farther than others. BTW Another link has it at a greater distance.http://www.daviddarling.info/encycloped ... nitak.html

Orin

orin stepanek wrote:The above quote shows how close it is from here. I found that interesting also. When you look at the Orion constellation; it's hard to imagine that some of it's stars are a lot farther than others.

Optical illusion ....

Related link here... :

http://books.google.co.uk/books?id=bmlI ... an&f=false

You may find the rest of that link interesting as well..

enjoy

Mark

cwmdavis wrote:... it strikes me as too large, even for a very large telescope.

I had to do the calculations to believe it myself. I was raised in a world where stars were just points of light even with maximum telescopic resolution. But it's true. The angular resolution of the ESO VLT is 2 ten-thousandths of an arc second (250 times as fine as the HST) in certain wavelengths, and the angular size of Betelgeuse is a few hundredths of an arc second. The resolution and size of the image in the photo are well within specs. Very impressive.

I'm a little confused by a couple things. The APOD commentary says that Betelgeuse, a red giant, may go supernova in the next few thousand years. But my limited understanding of red giants is that when the star 'blows' it produces a planetary nebula and the core of the star collapses to a white dwarf. The same sort of fate is forecasted for our sun - swelling to a red giant, thence to a planetary nebula and a white dwarf. This scenario is substantially more benign than a supernova where the final outcome is either a neutron star or a black hole. Perhaps Betelgeuse is a special case?

Also, at a distance of just 640 light years, I can imagine that when Betelgeuse goes nova we may have a 'new star' rivaling in brightness the full moon. Any chance that radiation from the event may pose a threat to Earth?

AZJames wrote:I'm a little confused by a couple things. The APOD commentary says that Betelgeuse, a red giant, may go supernova in the next few thousand years. But my limited understanding of red giants is that when the star 'blows' it produces a planetary nebula and the core of the star collapses to a white dwarf.

Betelgeuse isn't a red giant, nor does the commentary say this. It is a red supergiant, which lies on an entirely different branch of stellar evolution than red giants. Red supergiants normally end up going supernova (Type II).

Also, at a distance of just 640 light years, I can imagine that when Betelgeuse goes nova we may have a 'new star' rivaling in brightness the full moon. Any chance that radiation from the event may pose a threat to Earth?

A supernova further than 100 ly from Earth is unlikely to pose any threat.

When Betelgeuse goes it will brighten the night sky for quite a while! I found a small viedo that may be interesting. http://www.youtube.com/watch?v=pl-oR7hTTYY

Orin

This clip does not represent actual time does it?

http://www.youtube.com/watch?v=pl-oR7hTTYY

How long does this clips time represent?

Mark

mark swain wrote:This clip does not represent actual time does it?

http://www.youtube.com/watch?v=pl-oR7hTTYY

How long does this clips time represent?

Mark

I haven't the foggiest about the time; but I imagine it will be spectacular! 8) I'd like to see it; but I'll bet it'll be long past my time. Then again; could be tomorrow.

Orin

Thanks Chris. Guess I read the commentary a little too quickly.

orin stepanek wrote: http://apod.nasa.gov/apod/ap090805.html

Betelgeuse evaporating! I was just wondering what the gas is that is being given off?
Looks like this star is going a different route than Eta Carinae.

http://adsabs.harvard.edu/abs/1984ApJ...284..223L After finding this link; I presume that the ejecta must be oxygen, nitrogen, and carbon. I don't know what else it might be.

Orin