Stellar Apocalypse Shows Water

Andy_Howell writes "Astronomers using the SWAS satellite found a cloud of water vapor around the aging giant star CW Leonis, and the most plausible explanation is that the star incresed in lumiosty during its giant phase and is boiling away its comets. This is the first evidence for water in another solar system. In five billion years, our sun is expected to do the same thing."

Comments

Re:Incredible discovery

[RobertFisher]

It's a pretty sad day for /. moderation when a clueless post such as this gets moderated up to "4, insightful".

It is actually very remarkable that molecules exist in space at all. Why? There are two sides to the process -- creation and destruction.

(*) Creation : Interstellar space is in general very tenuous , and so the likelihood that any two atoms combine in the gaseous phase to form a molecule is very improbable.

(*) Destruction - Once a molecule is created, it doesn't live forever. Space is a very harsh environment, and any molecules created are subjected to harsh cosmic radiation, the stellar radiation field (resulting from all stars surrounding it), as well as stellar winds and shocks. Any of these processes is cabable of disrupting molecules.

When you go ahead and do the naive estimate for the abundance of a molecule balancing creation and destruction rates, assuming only gaseous phase processes, you find that it is highly unlikely to find any substantial amounts of molecules in interstellar space. Indeed, when astronomers first invented instruments capable of detecting rotational mode transitions of molecules like CO and H_2O in interstellar space, their theoretician colleagues told them to forget the plan.

The reason why we have clouds of molecular gas in our galaxy today is a rather amazing one which no one originally anticipated. Besides gas, there are also small, solid dust grains belched out from winds from cool red giant stars in their final phases of evolution. Atoms collide and freeze out onto the surfaces of these grains, where they can remain for a very long time, migrating very slowly along the surface via Brownian processes. Every once in a while, it will bump into another or molecule frozen out in a similar fashion, thereby creating a more complex molecule. The dust grains catalyze the generation of molecules -- without them, we wouldn't have such an abundance of molecular gas in the galaxy today. Indeed, astronomers believe star formation in the early universe was substantially different from that which occurs today because such dust grains would have been completely absent.

I think this result is particularly surprising since one might expect that any winds or shocks thrown off by a star capable of boiling away a comet might also tend to powerful enough to destroy the molecules generated. If that really is the mechanism involved, it is a remarkable coincidence that the winds are just powerful enough to ablate the comets, but not so powerful as to destroy the molecules present.

Bob