An astronomy question: regarding Betelgeuse going supernova.

As our own BadAstronomer has said:

The good news is that (at around 1000 light years away) Betelgeuse going super nova would, in all likelihood, not hurt the earth:
http://www.badastronomy.com/mad/1996/sn.html

But I am concerned about the possible bad news for astronomy:

Betelgeuse going supernova (most likely not in my lifetime) will be a spectacle to behold, and good for astronomers investigating novas; but what about other astronomy disciplines? Would the light intensity obliterate a good sector of the sky to astronomy research? In other words: will astronomers lose the capacity to view objects in the vicinity of Orion? For how long? And if a big nebula is the result of the supernova, will people be able to see it with the naked eye?

I am interested in how it could affect Radio, X-ray, and Gamma ray astronomy also.

For all we know it may have already gone super nova, and the light hasn’t reached us yet.

Seems to me that the last supernova we observed a few years ago lasted 3 or 4 weeks. (To us) I understand we got a lot of information about nutrenos (SP). Detected them anyway.

Chronos?

If I am not mistaken, Betelgeuse is a red giant and therefore near the end of its evolution and could not possibly go supernova. The stars that go supernova are high mass blue giants that burn all their nuclear fuel and are too massive to support just from pressure and undergo massive and sudden collapse (time frame of collapse: one second) and the resultant heat causes an even more massive explosion at the end of which the mass is reduced so that it cannot happen again. Depending on masses and perhaps other things, it may leave behind a black hole or a neutron star. Red giants, on the other hand, are stars that are too small to go supernova but in the course of their evolution have burned essentially all the nuclear fuel they started with, and whose temperature has risen (since the last dregs of that fuel requires higher and higher temperatures to ignite) to the point of expanding the surface more and more. The surface cools even while the core heats. It is expected that in a mere 5 billion years the sun will expand till it fills the solar system out to past the earth;s orbit, swallowing Mercury, Venus, and the Earth in the process. And you thought that Earth-crossing asteroids were the only celestial objects we had to worry about!

Actually, Betelgeuse is quite likely to go supernova if its mass is high enough. It’s currently on its last steps before it runs out of fuel and collapses. cite. Google for “Betelguse and supernova” and you’ll find plenty more.

Presumably it was a blue supergiant in the past before it used up most of its fuel.

Hari Seldon, check the article by the badastronomer:

And on preview, the cite by drewbert.

In any case, my question deals mostly on what we, and astronomers, could see when the light of the explosion reaches us.

Just trying to picture it, since I don’t think we will be around to contemplate it.

Hari Seldon, Betelgeuse is a red supergiant, on a different part of the H-R diagram–same temperature as a reg giant, but more massive and therefore brighter.

It’s supposed to be as bright as the full moon, right? So it’ll be a boon for the planetary astronomers. :wink: (Galaxy people and other picky sorts who insist on observe objects with low surface brightness can only observe during “dark time” when the Moon isn’t bright.)

I guess I was wrong. I thought all red giants were going off the main sequence. But why then isn’t it blue?

While this is technically true (in our frame of reference), in astronomy it’s not uncommon to speak of an event happening when the information that it happened reaches us. Astronomers say that SN 1987A went off in 1987, and we all know what is meant by that.

Both giants and supergiants are off the main sequence. The difference is that supergiants are massive enough that their cores are hot enough to burn elements heavier than hydrogen.

The color of a star is determined by its temperature. The hotter supergiants are blue, and the cooler ones are red.

I can give you more detail tomorrow, if you like but stellar evolution isn’t really my area, and my good astrophysics text is at work.

The crab nebula supernova of 1054 was reportedly “as bright as the full moon” for nearly a week. That’s for a supernova ~6500 light-years away, so when Betelgeuse blows at 1000 ly, it should be ~42 times as bright as the full moon (6.5^2).
http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?crab+nebula

Wouldn’t this type of ‘explosion’ be a nova, Isn’t a supernova something to do with a 2 star system where one is much more massive then another and the larger star ‘feeds’ off the smaller star till such a buildup as it ‘exploads’ back to a smaller size then starts over again?

Also there was some talk on space.com a while back about a massive star fairly close to earth that might hypernova (or might already have hypernova’d - just didn’t get here yet). Because of the close proximity it could knock out satalites.

k2dave: What you’re calling a supernova is a “supernova Type Ia”. Betelgeuse has the potential to become a “supernova Type II”. The terminology is an unfortunate artifact: the two types of supernovae do not have enough to do with each other to justify calling them the same thing, but c’est l’Astronomie.

Betelgeuse is 426ly from Sol from what I’ve read not 1000ly. Searching google has shown some disparity in the distances giving measurements of 400-600ly but this is the only place where I saw 1000ly mentioned.
Why does there seem to be different estimates?

Parallax measurements (from the ground) are only really accurate up to about 100 parsecs (about 300 ly). Distances further than that have large error bars (technogeekese for ‘closer to a guess than a measurement’).

Hipparcos (satellite that measured parallaxes) extended this limit, but I’m not sure by how much. It’s result for Betelgeuse is 131 parsecs or about 427 ly.

As for temperatures, I asked how come supergiants span the spectrum some time ago, and the answer was rather complex, but in summary, IIRC, star color depends on surface temperature. The most massive supergiants are hot enough at the surface to be blue, but other and still extremely massive stars are sufficiently distended to have cooled down to red at the surface (while still at fusion-of-complex-element temperatures at the core).

Hipparcos got a parallax of 0.00763 arcsec for betelgeuse (alpha_Ori). As already stated that puts it at a distance of 426 ly (3.26/0.000763), not 1000 ly.
Recalculating the brightness of a betelgeuse nova with that figure gives a factor of 231 times as bright as the crab nebula explosion, or the full moon. That’s about 6 units of magnitude.
Pretty bright:
Full Moon -12.5
Betelgeuse Nova -18.5
Sun -26

Before 1987, it was assumed that all Type II supernovae were red supergiants. The progenitor of SN1987A shocked everyone by exploding when it was blue.

Stars expand and become red, then contract and become blue. Some do this more than once, some get to blue and blow up. It depends on many factors, including, of all things, the chemical composition of the atmosphere of the star (different amounts of elements like magnesium can maker a huge difference in the life cycle of the star because some absorb photons better than others, changing how the star dumps its excess heat). A companion star might change this as well; if it is close enough, mass can be exchanged between the two stars, messing up the nice, neat order of things.

SN1987A was definitely a red supergiant before it turned blue and exploded; the rings around it tell us that. I wrote about this on my website in a series of essays about 87A.

As to the OP, a very bright supernova would make some observations near it difficult. As someone else pointed out, it could make the sky bright around it like the full Moon does, making things difficult for deep sky astronomy (except from space). On the other hand, most astronomers would gladly give up a few months observing time to see a supernova up close… at least, safely up close.

Before any comment I have to say this first: Welcome back Policarp! :cool:

Sorry for forgetting how to write your name The Bad Astronomer! I am honored to get a reply from you.

It looks like the star is closer than I thought. While it will look brighter than the full moon, the area that the star will cover on the sky will be smaller no? Since this would be an explosion, would it not follow then a quick expansion of the object in the sky and then a very gradual fade out? Or will future generations look at the direction of Orion and see something like a crab nebula with the naked eye?

I definitely agree. And every telescope on earth will be pointed at the supernova anyway, so it doesn’t matter if you can see other objects or not.

However I think many instruments will have problems observing such a bright target. Bad Astronomer, since you’re familiar with the Hubble, do you think it’ll be able to see the SN?

As for X-rays, I won’t take the time to do a detailed calculation but the Ginga satellite observed about 10 counts/sec of X-ray emission from SN 1987a. Since Betelgeuse is 400 times closer, the same instrument will detect over a million counts per second. Or rather, it’d receive that much flux and be completely overwhelmed. It’s not enough to cause any damage to satellites, and there should be no danger to our health, but you can’t point Chandra at it and take an image either. I suspect the only way to observe the supernova X-rays is to use a solar X-ray telescope. (This is easier said than done because solar satellites aren’t designed to look away from the sun. You can’t point the telescope and solar panels in different directions, for one thing.)