Beyond the stars, things are much more complicated than you might think


Kepler’s search region

NASA has been characteristically cautious about declaring what recent findings from the Kepler’s “search for habitable” planets project mean. Unfortunately for NASA, they have someone working for them who is probably either an extrovert, or just excessively enthusiastic, astronomer Dimitri Sasselov,  and he has declared that there are hundreds of potential new Earths out there (a statement that got him into some trouble with his bosses, apparently). Except that he was right, as it turns out, and now whenever someone interviews him, he’s been Pavlovian-trained to be cautious and not say too much, even if he’s right.


Although when this earlier interview was conducted (unrelated to Dimitri Sasselov), scientists (who are notoriously cautious) were still asking “if” there were other worlds out there, Kepler has begun to prove that OF COURSE THERE ARE, as has been speculated for thousands of years. Humans are not simply making this stuff up! The problem right now is that we won’t know how dense these planets are, since Kepler’s telescope and equipment can only gauge size, not weight of matter:

By watching the light from some 150,000 stars for the dimming that could signal a planet crossing in front of them, Kepler is extraordinarily efficient at finding possible planets. But Kepler has yet to find another Earth — a small, rocky planet with an orbit of a few hundred days and well inside the habitable zone in which water can exist and life can arise. That is for a fundamental reason; the blips that Kepler detects show only the radius, and not the mass, of an observed planet, which means that the density and composition generally remain unknown.

Moreover, the scientific objective of the Kepler mission is not to discover Earth-like planets. Instead, it is to estimate the fraction of Sun-like stars that have Earth-like planets — statistics that could greatly enhance astronomers’ understanding of how planetary systems form. Determining which of the blips correspond to planets — rather than systems of stars in which one is eclipsed, causing a similar dimming — is what the researchers spend most of their time on, says William Borucki, a space scientist and Kepler principal investigator at NASA Ames. The only way to do that, he says, is the hard way: painstakingly sorting the real signals from the false positives. —Nature News

More recent Stardate podcasts discuss how many stars have been discovered. Producers of this show aren’t ready to make the claim that Kepler’s observational lens has discovered any new Earths, in spite of what Dimitar Sassolov says, of course. Finding another Earth is not happening quickly, largely because there do not seem to be any copies of our planet. Our planet might just be as unique as we think it is.

Or it might not, since literally thousands of potential Earths might exist, but we do not yet have the data we need to assess what it is we are looking at. I’m kind of bummed, to be honest, because by this time, the Jetsons’ promise, made back in 1962, ought to be coming true, that we could all be living on other planets, some of them just like Earth. Obviously, though, the Jetsons was ahead of its time.

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