Big space boom soon?

[Alondro]

Uh-oh...  It's the Beetlejuice star!

Say the name 3 times, and it'll asplode

Hmm, that's quite a huge contraction, and it's been gradual.  I wonder if this means the star has at last run out of net-energy gain fusion at the core and is now starting to lose energy by generating iron.  We may be witnessing the first stages of the star losing the battle with its own gravity as the outflow of energy begins to slow.  A gradual shrinking is what you'd expect as the star's fusion reactor begins to sputter.  It might resurge a bit if convection brings in some lighter elements during the contraction phase, but this could be the beginning of the end for it.

If it shrinks much further, say down to 70% of its normal diameter, a supernova is imminent... though that could still mean at least 100 years.

[Sofox]

Ford Prefect's going to be so pissed.

[superluser]

Ford Prefect's going to be so pissed.

Why?  He's not near Betelgeuse now, and no one on his planet survived the Great Collapsing Hrung Disaster (except his father).

[Turnsky]

it's prolly gone already, the light just hasn't reached us yet.

[Valynth]

Lets just hope the energy is not concentrated enough to seriously affect earth when it gets here.

Or that by the time it hits, we'll have evacuated this star system.

in any case, this is some very disturbing news.

[Lysander]

Still 100 years until it might explode? Dang, seeing the sky at night just as bright as daytime for a few days would be awesome.   

[Corgatha Taldorthar]

According to the article, over 15 years it's  brightness has remained more or less the same, but it's diameter has shrunk quite a bit. That indicates that it's getting hotter, and putting out more heat and radiation pressure.


I'm not an astronomer (About the best credentials I casn claim is an A in an astrophysics class a few years ago), but I seem to recall the core bounce (that brief period between the fusion of iron and the star's collapse) to last seconds or at most minutes.  Iron fusion loses energy, and the start starts falling apart at an ever increasing rate.


My guess is more along the lines of it's moving from helium fusion to Carbon/Oxygen fusion. (or some other step along the way) and is in the current stage of contraction collapse. If I'm right, (Hit or miss there, really) then Betelgeuse will continue contracting and heating up for a little bit (probably less than 100 years) and then become even bigger in volume but cooler, becoming further red but with a larger disc.


Further information. Betelgeuse is approximately 650 light years from earth,reasonably close on a steller scale. Fortunately, it's axis of rotation does not point towards the solar system, so a gamma ray burst from the supernova would not hit us. Which means that Earth is probably safe, barring perhaps a slight rise in background radiation hitting earth. A supernova out of Betelgeuse would probably outshine the moon in the night sky however, and might be visible during the day for months......

Which would be awesome to watch.

[Tapewolf]

My guess is more along the lines of it's moving from helium fusion to Carbon/Oxygen fusion. (or some other step along the way) and is in the current stage of contraction collapse. If I'm right, (Hit or miss there, really) then Betelgeuse will continue contracting and heating up for a little bit (probably less than 100 years) and then become even bigger in volume but cooler, becoming further red but with a larger disc.

I did a quick google search for Carbon-Oxygen fusion and came up with some fascinating stuff, the timescales involved in particular.  I never realised it went quite that quickly.

Firstly, I've read a couple of places saying that Betelgeuse is already in its Carbon/Oxygen stage.
But secondly, Betelgeuse is supposedly about 20 solar masses.  The figures for a 25 solar mass star are given, but they're interesting.  I'm not entirely sure whether a 20 solar mass star would burn up faster because there's less fuel or slower because there's less gravitational force....

Anyway, supposedly for a 25M star, the C-O fusion only lasts for about 600 years.
After that the fusion rates get very, very fast, e.g. it could hit iron and 'crash' within two years of leaving the C-O cycle.

IMHO this one is worth reading:
http://www.opencourse.info/astronomy/introduction/19.stars_death_high-mass/

This one is more dry but points out what the above didn't quite say, that after it reaches its 1-day Silicon cycle, it runs straight into Iron:

http://www.astronomy.ohio-state.edu/~ryden/ast162_4/notes15.html


EDIT:
Too bad my father's in the US and out of contact.  I'd love to talk to him about this.

[Corgatha Taldorthar]

Firstly, I've read a couple of places saying that Betelgeuse is already in its Carbon/Oxygen stage.

But secondly, Betelgeuse is supposedly about 20 solar masses.  The figures for a 25 solar mass star are given, but they're interesting.  I'm not entirely sure whether a 20 solar mass star would burn up faster because there's less fuel or slower because there's less gravitational force....

Anyway, supposedly for a 25M star, the C-O fusion only lasts for about 600 years.

Oh, did not realize that about Betelgeuse. In that case, if it's Carbon/oxygen is collapsing, it doesn't have too long. As for the second point.... *caughs and puts on lab coat*

The fundamental force driving all stellar mechanics is gravitation of the star in respect to it's own molecules. That much mass starts to collapse on itself into a little dot. The more mass, the harder gravity "squeezes" the star's gas. As gas gets drawn to the core, it heats up, and the atoms start colliding harder and harder, eventually hard enough to overcome the strong nuclear force and to fuse.

It's the energy from fusion that powers the star, and that energy pushes things back outward, keeping the stars radius more or less constant. But you need more fuel per second to keep that equilibrium going, because of the greater mass of the star. So bigger stars invariably burn out faster than smaller ones, barring bizarro events. (Like stellar collisions that merge the two gas bodies)

[Alondro]

I've always assumed there's plenty of wiggle room in those theories, simply because at this point they are just theories.  No one has ever seen a red supergiant in its final century, so it's impossible to be sure what the clues to last throes will be.  

The models do not include the complex convection system within stars that can bring material from the outer layers in contact with the core, perhaps buying just a tad more time for the star, but weakening the output of energy just enough to cause the star to begin to implode.  Remember, the big ballooned size of a supergiant is due entirely to the massive amounts of energy being thrown out from the core.  As that energy diminishes, gravity starts to win.  Thus, we are seeing the beginning of the end as the star moves off the C/O stage.  It could still take a century, but the star is nearly doomed.  Then the final cataclysmic implosion occurs once the iron stage is reached.

At any rate, this will be a very useful star to study to either confirm or refute the supernova theories.   It's also a plus that we likely won't get fried in the process.  

[Tapewolf]

I've always assumed there's plenty of wiggle room in those theories, simply because at this point they are just theories.  No one has ever seen a red supergiant in its final century, so it's impossible to be sure what the clues to last throes will be.  

Yeah.  Most of the lectures and suchlike present it as if it goes from one fuel to another in a clean and distinct fashion - that may be true, but IMHO it seems more likely that it will be a fuzzy transition.

It's the energy from fusion that powers the star, and that energy pushes things back outward, keeping the stars radius more or less constant. But you need more fuel per second to keep that equilibrium going, because of the greater mass of the star. So bigger stars invariably burn out faster than smaller ones, barring bizarro events. (Like stellar collisions that merge the two gas bodies)

Thanks for clarifying that.