New Homes for ET?

OK, we've known since 1995 that there are hordes of planets out there, unseen worlds lying far beyond the dark pickets of our solar system. In fact, astronomers have uncovered about 500 of these worlds, panning them out of their data at the rate of roughly one a week. That's pretty impressive when you consider that it took Homo sapiens 150,000 years to find the first planet not visible to the naked eye (Uranus), and a further 65 years to find a second (Neptune).

With the tally of exoplanets (as they're called by cognescenti) so high, few of the finds draw the attention of mainstream media. Another planet? Been there, done that. But in the last few days, researchers have announced two discoveries that are distinguished by being systems of planets. One was found with NASA's Kepler telescope, and the other by a group of European astronomers using the 3.6 meter telescope at La Silla, in Chile.

All of which is interesting, because the vast majority of the exoplanets discovered so far have been singletons.

Check that. They might not really be the only kid on their stellar block. It may just seem that way. The techniques used to find exoplanets are strongly biased towards big guys in tight orbits. Smaller worlds that pirouette farther from their sun -- the type of planet that ET might want to phone -- are much tougher to find.

So the new discoveries represent an experimental triumph, at least. But beyond the technical kudos, they're also giving credence to something we've suspected forever but still haven't proven: namely, that the type of multiple-planet solar system we live in isn't oddball at all, but is as humdrum as hairpins.

That would, of course, be good news for those who hope to find extraterrestrial life.

But there's something else of interest in these fresh finds: Two of the newly discovered worlds are barely bigger than Earth, with circumferences only about 15 percent larger than that of our own world. That's the good news, since Earth-size planets have been elusive.

The bad news, at least in this case, is that the small planets in these systems are in star-hugging orbits that guarantee they'll be hotter than broiled jalapenos.

The long-term news is this: it sounds like a pretty safe wager that within two years, you're going to be reading about the discovery of worlds that really are comparable to Earth in size and temperature. That story will be above the fold.

So wouldn't we immediately pivot our antennas in the directions of such planets, to see if they're leaking signals that would indicate intelligent beings? Well, of course we would. But I beg you to be realistic. Inquisitive extraterrestrials could have aimed their antennas at Earth for four-and-a-half billion years without detecting any signals. If technological societies last, on average, even as long as ten thousand years before they either self-destruct or decide to abandon technology and spend their days in navel contemplation, we're going to require hundreds of thousands of Earth-like worlds to feel confident that at least one or two might be transmitting. It's like winning the lottery.

But that's all OK. Finding a few cousins of Earth would tell us, unequivocally, that those myriad lottery tickets are out there. After that, it's just a matter of continuing to play.

And Ireland's largest bookmaker -- Paddy Power seems to agree. They just cut the odds on extraterrestrial life being discovered in the next decade from 33-to-1 to 10-to-1.