Thursday, November 5, 2009

Space Aliens, Stars, Scientists, and This is Where I Came In

"Stars May be Cosmic Road Signs to Intelligent Aliens" (November 5, 2009)

"When scientists search the heavens for habitable worlds beyond Earth, they don't necessarily know what to look for. A new study has found that the most probable place to find intelligent life in the galaxy is around stars with roughly the mass of the sun, and surface temperatures between 5,300 and 6,000 Kelvin (9,100 and 10,300 degrees Fahrenheit) - in fact, stars very similar to our own sun.

"Learning that sun-like stars are good candidates for life may not sound surprising, but it isn't always what scientists have thought.

" 'The principle of mediocrity says that, barring any evidence to the contrary, our observations should be typical among those of all intelligent observers,' said researcher Daniel Whitmire, a physicist at the University of Louisiana at Lafayette. 'But the typical star is not like the sun - the typical star is a low mass star. We don't find ourselves around a typical star and we show the reason why in this paper. Our results confirm the principle of mediocrity as applied to the sun.'

"Sun-like stars are actually a minority in the galaxy - 93 percent of stars in the Milky Way are less massive, less luminous and cooler than the sun...."

"...To make their calculation, Whitmire and colleague John Matese combined models of how planets form with data on the distribution of stars in the galaxy as a function of mass. The planet models show when worlds are most likely to form in the habitable zone - a Goldilocks region around a star in which a planet would be just right for life - not too close that its surface would be boiling, and not too far that it would be frigid either. Planets in the habitable zone are the best candidates for having liquid water, which is thought to be a prerequisite of life.

"In general, the planet-formation theories predict that more massive stars are the most likely to have planets in the habitable zone. So the larger a parent star is, the more likely its planets will have environments conducive to life...."

Flying-saucer enthusiasts and made-for-television 'documentaries' notwithstanding, the only planet that we know of which hosts intelligent life is Earth - and we're the intelligent life.

Scary, isn't it?

Anyway, this article discusses a more-than-usually-serious look at where to look for planets that are big enough to keep an atmosphere but not too big, not too hot and not too cold, and circling a star that stays on the main sequence long enough for sludge to develop into something interesting.

I don't 'believe in' space aliens - or life on other planets. On the other hand, the presence of organic molecules in (some) clouds of interstellar debris, mathematical models of star formation suggesting that the planet we're standing on isn't a statistical freak, and the sheer size of the cosmos - all suggest to me that we might not be the only place with creatures like pond scum, mosquitoes, mushrooms - and us.

About the title to this post: When I was growing up, about a half-century back, the default assumption for most people who thought seriously about the possibility of life elsewhere in the universe was that it would almost certainly be found around a star quite a lot like the sun. Later, the idea was that smaller stars, because of their greater number, offered better odds.

Like the title said: this is where I came in.

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