House-hunting in outer space Humor Astronomers have always struck me as impractical people. After all, spending your life studying objects you're not likely to ever touch -- or pocket -- doesn't seem to me to represent the most level-headed kind of behavior. But then again, I could be wrong. Obviously, astronomers are not seriously searching for little green men. More likely, they want to find a nice place to retire when life on Earth begins to get old. To date, intrepid "exoplanet" hunters have sighted 50 possible planets in solar systems as near as 10 and as far as 100 light years away. Now, let's see, 10 times 5.9 trillion miles (thanks Encarta!), that makes 59 trillion miles. (That isn't so far away. ) Since 1995, when planet-hunting became a fad, scientists have refined their methods. They have even begun to discover planets they can't see. This is done by looking at the spectrum of a star -- a kind of color photograph made using bottled gas, a telescope, and sheets of grating. If a star shows a blue shift, it's coming at us. If it shows a red shift, it's headed away. And if it shows a whacky shift, it probably has a planet circling around it. (All this courtesy of Alfred Doppler, the guy who gave us TV weather maps.) Once a wobble in a star has been detected, astronomers are able to calculate the orbit and mass of the invisible planet or planets that most likely cruise in round or lopsided circles around it. (Courtesy of Herr Kepler and Mr. Newton. Thanks gents!) The only problem is that, seeing you're a gazillion miles away, you're not even sure whether these are planets -- albeit, large ones like Jupiter or Saturn -- or burnt-out stars called brown dwarves. But when you're house-hunting, you can't be too fussy, or you find yourself checking into a trailer park. What with the credit card companies raising rates without warning and the price of apartments in Manhattan and Silicon Valley sky-rocketing, I'm glad astronomers are looking for real estate in the suburbs. Our own solar system seems a bit pricey. In their search for extraterrestrial worlds, they discover that smooth, regular orbits aren't the norm, and that other planetary systems have a less well groomed geometry than ours. Which, obviously, should bring the price of habitable real estate down. So what if you risk being swallowed by your sun? California has mudslides! I'm glad we've finally gotten realistic about getting a new home. August 9, 2000