Betelgeuse's stunning rainbow nebula uncovered

[Judi Lynn]

June 23, 2011 2:42 PM
Betelgeuse's stunning rainbow nebula uncovered
ByPhil Plait .



Infra-red image of Betelgeuse. The inner black
circle is the 2009 shot of the star and its
surrounding gas. (ESO/P. Kervella)

(Discover)
For one of the brightest stars in the sky, Betelgeuse still has some surprises up its sleeve. We’ve known for a couple of years it’s surrounded by a cloud of gas, but new observations show that nebula is far larger than previously thought!

This new image is care of the Very Large Telescope, and shows a very deep and very high-resolution shot of Betelgeuse in the infrared. The inner black circle is the 2009 shot of the star and its surrounding gas -- what we knew about before -- and the big image shows all the gas around it just discovered. At the very center is a red circle indicating the actual size of Betelgeuse on this scale -- it's a red supergiant, and nearly two billion kilometers in diameter.

This structure is actually a wind of material blown off of the star itself. The exact mechanism behind this is unclear, though. Red supergiants are so big that gravity on their "surface" (they don’t really have a surface; they just kinda fade away into space) is very weak, and they can barely hold on to the material there. They are also incredibly luminous — Betelgeuse is 6000 trillion kilometers away, yet one of the brightest stars in the sky — so much so that the pressure of light is very strong. This pressure can lift material off the surface and blow it into space. It’s also known that Betelgeuse has gigantic convection cells bringing hot material from deep below up to the surface, and that’s part of this process as well.

Once the material is ejected it forms into dust grains: complex molecules including hydrocarbons. The astronomers doing this observation detected oxygen-rich dust in this nebula (PDF), which given the environment is most likely silica or alumina. Silica, also known as silicon dioxide, is the main constituent of sand and quartz! That’s the most common constituent in the Earth’s crust — over 60% by mass — and we think that a lot of the materials in the Earth’s crust actually formed in the winds of red giants and supergiants.

More:
http://www.cbsnews.com/stories/2011/06/23/scitech/main20073751.shtml