Debra Fischer (Yale University) takes a brief look at the next thirty years as part of a Discover Magazine 30th anniversary section, an appearance notable more for what Fischer doesn’t say than what she does. Any hint of how her radial velocity studies of the Alpha Centauri system are proceeding? I wouldn’t have expected any, I’ll admit, and Fischer says nothing about it, but the betting here is that we’ll have an announcement within the next year either by Fischer or Michel Mayor’s team either giving us a planetary discovery or sharply constraining the alternatives.
What Fischer does speculate on beyond the notion that we’ll detect life in exoplanetary atmospheres is that interstellar probes will eventually fly. You may recall Robert Freitas’ notion of interstellar probes loaded with artificial intelligence and as tiny as sewing needles, scattered into the galaxy in their hordes to investigate potentially habitable worlds. Fischer, too, likes miniaturization, which does so much to mitigate the huge propulsion issues:
Outside the gravitational field of Earth, we could launch robotic spacecraft to other destinations in our solar system. Further ahead I’d like to see tiny spacebots – smaller than your cell phone—travel outside our solar system to the nearest star system, Alpha Centauri. By keeping the mass of those spacebots low, we could more easily accelerate them. We could launch an army of these tiny bots and have them do what your cell phone does: take pictures and phone home.
Yes, and just maybe we could use them to create the kind of communications station at the Alpha Centauri gravitational lensing distance that Claudio Maccone envisages, using it to communicate at extremely low power with a comparable robotic relay at our Sun’s gravitational focus. That would set up tremendous bandwidth opportunities for tiny transmitters and allow valuable scientific studies to flourish.
Meanwhile, we’ll all keep speculating on the big question for the immediate future — when will the first habitable extraterrestrial planet be discovered? Greg Laughlin (UC-Santa Cruz) and Samuel Arbesman (Harvard University) have a go at this with a new paper that attempts a sociometric analysis of the question. The researchers create a metric of habitability that can be applied to already discovered planets and use a boostrap analysis to extrapolate discoveries into the immediate future. The prediction that emerges from this is near-term: The first Earth-like planet will be discovered (with high probability) by mid-year 2011. The method will likely be planetary transit or radial velocity (Debra Fischer’s Alpha Centauri work again comes to mind).
Will Kepler find the first habitable planet? Don’t count on it. For one thing, the next Kepler results we get will be of planets that are probably too hot to sustain life:
While the initial results of Kepler were released on June 15, 2010, the Kepler team has delayed publication of 400 of the most promising extrasolar planetary candidates until February 2011. Within this large pool of withheld candidates, it is virtually certain that some have radii that are observationally indistinguishable from Earth’s radius. It is likely, however, that because of the limited time base line of the mission to date, the Kepler planet candidates to published in February 2011 may be too hot to support significant values for H [habitability].
Laughlin and Arbesman re-ran their analysis using only those planets discovered via the transit method, learning that the method cannot determine a likely date of discovery because we have relatively few planets found by transits, and all rank very low on the habitability scale. But the authors’ habitability metric curve deployed on a larger population of 370 well-characterized known exoplanets continues to point to as early as May of 2011 and very likely by the end of 2013 for that first habitable planet. The method, fully described in the paper, is fascinating. What’s more, with target dates this close, we’ll have an early read on how prescient its authors really are.
Interestingly enough, the authors note that the habitability factor for most of the 370 planets in their study is zero, but of course Gliese 581d is an exception, recently examined by other authors and found to be potentially habitable. Laughlin and Arbesman disagree with the assessment, pointing out that the planet’s mass should be close to ten Earth masses. The paper describes Gl 581d’s ‘…possibly water-dominated composition more akin to an ice giant planet such as Uranus or Neptune than to a terrestrial planet like the Earth.’
The paper is Arbesman and Laughlin, “A Scientometric Prediction of the Discovery of the First Potentially Habitable Planet with a Mass Similar to Earth,” accepted by PLoS ONE (preprint). Re Gliese 581d, the paper is Wordsworth et al., “Is Gliese 581d Habitable? Some Constraints from Radiative-Convective Climate Modeling” (preprint).