The 2010 Version of the Space Race
I find it quite nice that “the 2010 version of the space race”, as someone put it, seems to focus on finding extrasolar planets quite a lot. This has become much more noticeable over the past few days, when the HARPS, HATNet and Kepler teams have all announced new discoveries. The rush was apparently caused by a conference on this topic which was held this week in France.
By far the most notable is the HARPS discovery: A system with no less than five confirmed planets, which would match the record currently held by the 55 Cancri system, and two more candidate signals with a very high probability of also being planets, which would make this system the new record holder. Under these circumstances, the eight new planets (different link on each word) announced by HATNet only grant them a very distant second place, mostly thanks to HAT-P-20 b, which is a hot megajovian about two and a half times denser than Earth, therefore some ten times denser than Jupiter. The Kepler discovery of the first system with two confirmed transiting planets and another candidate signal which is very likely to be a third planet, with a radius only about 40% larger than Earth’s, seems to trail behind the rest…
I need to get back to the HARPS discovery, because it’s really interesting. The number of planets alone is enough to warrant special attention, but the distances between them tell another interesting story. The five confirmed planets, all of them with a mass roughly comparable to that of Neptune, are at about 0.06, 0.13, 0.27, 0.49 and 1.42 AU, respectively, from the star, with the two very promising candidate signals being on either end of the line, the small one, with a mass estimated to be only about 40% higher than Earth’s, a mere 0.02 AU from the star and the large one, with a mass roughly comparable to that of Saturn, orbiting at 3.4 AU. That means the distances between the planets, including the candidate signals, are about 0.04, 0.07, 0.14, 0.22, 0.93 and 1.98 AU, respectively, roughly doubling except between planets e, f and g, where it initially increases by only about 50% and then suddenly quadruples.
That may mean there could be another planet in that area, though an asteroid belt would be another possibility. To be fair, an asteroid belt seems more likely, because if there would be a planet at roughly 1 AU the distance between it and the next one would be equal to that between it and the previous one instead of doubling. But that would be possible, seeing as the distance didn’t double between planets e and f either, so I can’t rule out the possibility of a small terrestrial planet having such an orbit, seeing as its gravity shouldn’t have much of an effect on those beyond it, but could perhaps interact with the one right before it, thus explaining both anomalies. And that possibility would be of particular interest because the star in question is a G1V, so only a tenth of a class above the Sun, meaning that its habitable zone would be comparable to Sun’s, so right in that area where something appears to be missing…
But so far, with the possible exception of Gliese 581 d, we don’t have any confirmation of a planet that would fit our criteria for supporting life. Not that those criteria have to be correct, not to mention that the discovered gas giants are likely to have moons, some which could perhaps even support life as we know it. But finding a planet of just the right size and just at the right distance from its parent star remains the elusive goal of all these searches, though discovering such a small planet at such a distance from its star with our current technology would seem almost a miracle.
Yet every such discovery is interesting in itself, because it helps us paint an ever clearer picture of the galaxy we live in and better determine our place in the universe. So I’m pleased that such discoveries are getting more and more frequent and can only hope that such efforts will be encouraged even more in the future, because it’s a worthy endeavor even without discovering “another Earth, with kittens and butterflies”, as someone was saying recently.
On the other hand, I’m pleased that the Kepler team finally decided to announce something new, even if it wasn’t much. Now I’m quite sure it was just because somebody lit a fire under them because everyone else had important announcements and it would have looked really bad if they’d be the only ones with nothing meaningful to report, but a step forward is a step forward, even if it was caused by a kick in the butt.
They did recently announce that all their candidate signals have been observed with Earth-based equipment at least once and only a dozen have been ruled out as false positives, or more specifically eclipsing binaries. If you keep in mind that, according to what they said so far, they’re working on those 400 candidate signals they didn’t make public out of those found in the first 43 days of observations, that should mean that 388 are quite close to being confirmed as actual planets, or possibly 385 if the two confirmed ones and the third candidate signal noticed in that system they now announced were from that lot. So there should be one huge announcement at some point, assuming they’ll ever get to verify all of them. But I seem to remember them saying that the Earth-based observation season for the area they investigate is between March and September, so they’re unlikely to be able to do much more until next spring…
Of course, those are signals noticed in 43 days of data, though later observations have more than likely been used for confirmation. But they now have no less than 15 months of data, which should likely include thousands of candidate signals. And even that number should be extrapolated, since the transit method can only detect planets whose orbits are just at the right angle to make them pass between their parent star and us, which is in fact extremely unlikely to happen. One has to wonder how many planets would a similar mission that’d use the radial velocity method find in the same amount of time, assuming it’d get similar benefits out of gathering the data in space as opposed to from Earth.
