Exo-planets

I was absolutely stunned yesterday when I heard the news that astronomers have found an earth-like exoplanet. Well, maybe not earth-like but a rocky planet in the habitable zone around a star. An exoplanet is a planet orbiting around a star other than our sun. When I was a kid this was purely the stuff of science fiction. We figured there were other planets but we couldn't prove it. In 1992, astronomers first detected a planet around another star.


Mind you, they didn't see the planet, they merely detected it was there by how it affected the light from the star. This was exciting news. In 1994 astronomers announced that for the first time they had imaged an exoplanet. This really blew my mind because I knew we were talking about relatively small objects that were almost unfathomable distances away.






Not life as we know it Jim
As exciting as these announcements were, the planets they discovered could not possibly contain, in the words of Dr. McCoy, "Life as we know it"." This is because the planets they discovered were what astronomers called "Hot Jupiters" We consider Jupiter to be a giant but these planets were even bigger. They were almost more failed stars than planets. The fact that they were so large is what made them detectable. These are nasty hot places. If they contain life it certainly isn't like anything we know.

All of this leads up to the announcement made recently about a planet orbiting the star Gliese 581 in the constellation Libra. Astronomers could detect it because it is big, about 5 times the size of Earth. This is certainly big but not enormous or even giant. Keep in mind that 1,400 earths can fit inside Jupiter.

The really exciting thing about it models suggest the planet may be made of rock and not of gas which makes it more like home. Also, given the distance from the star, astronomers calculate the surface temperatures could range from 32 to 104 degrees Fahrenheit. Again, sounds a lot like Earth. The news is exciting. I'm not sure how they came up with this number but if it is based purely on the size of the planet and distance from the sun I'm a little skeptical. Look at the Earth and Venus. Fairly similar size, Venus is a little closer to the sun but it also has green house gasses from hell and so the temperature there is way hotter than one would expect merely from the distance it is from the sun. the surface temperature is over 800 degrees Fahrenheit! In theory, if the atmosphere if Venus were more like Earth it might be more hospitable to life.

This comparison of rocky planets is a good thing to consider. We have four rocky worlds in our solar system. Mercury, Venus, Earth and Mars. Mercury is way too close to the sun but the other three might within the range for life. So, in our solar system we're looking at a 70% chance that life won't arise on a planet deemed suitable purely on distance. (There's still a possibility of life on some Jovian moons as well)

There's a lot we don't know and we're discovering more each day. It is an exciting time to be alive.

As a final note, this planet is 20 light years away (relatively close in the grand scheme of things) which means if there is intelligent life there they could be picking up our television and radio signals from 1987. Of course, we'd be picking up their signals from 20 years ago as well so unless they don't use broadcasting of any kind there likely isn't any intelligent life there or we would detect signals when we look at the star with radio telescopes.