The release of the first 43 days of Kepler data has demonstrated just how powerful a planet-hunting technology we’ve put into space. Listen to principal investigator William Borucki (NASA Ames) in a video released yesterday by NASA television:
“We’re releasing data on 156,000 stars that we’ve been monitoring with the Kepler mission for 43 days, the first dataset. In these data are some 750 planetary candidates. Some of those are actual planets, some are false positives. Our science team is looking at 400 of those candidates with ground-based telescopes, to figure out which are planets, which aren’t.”
Borucki assumes about fifty percent of the candidates will be false positives, eclipsing binary stars, starspots, or other misleading signals. Now it’s in the hands of ground-based telescopes in the Canary Islands, Texas, Arizona and Hawaii to comb through these findings to make the call. The team is also releasing the data for the remaining 350 candidates to the world community of astronomers to assist with the analysis.
Addendum: The video mentioned above has suddenly gone private. I don’t know why, but will hope to post it again when it reverts to public access.
Ponder this: The number of planet candidates here is actually greater than the number of all the planets that have been discovered in the last 15 years. We could conceivably double the list of known exoplanets with these 43 days of data alone. And, obviously, Kepler is still on the job.
…the treasure hunt for the end to cosmic loneliness continues.“The public wants to know whether there is life on other planets,” Mr. Borucki said, noting that it could take decades. The effort to get an answer, he said, reminds him of the building of the great cathedrals in Europe, in which each generation of workers had to tell themselves that “someday it will be built.”
“In a sense, we, too, are doing these things,” he said.
Well spoken. The Kepler work segues nicely into a new piece by astrobiologist and author Caleb Scharf (Columbia University), who discusses the search for habitable worlds in a guest post for Scientific American. Scharf makes the point that most stars can be described with only a few parameters. Analyze mass, age, and abundance of elements and it’s fairly easy to create the stellar taxonomy that categorizes them. Planets, however, are a different matter. With them, we consider orbit, type of primary, atmospheric composition, axial tilt, gravitational tides…
Well, you get the idea. The complete list takes in magnetic field, geology, chemistry and more. The problem this presents is that while we want to choose the right candidate planets to study for extraterrestrial life, we’re dealing with space-based observatories with finite resources. We’d like to come up with nearby stars to examine that are not so different from our Sun, but 75 percent of all stars are less than half as massive as Sol, and most nearby stars are red dwarfs like these, where planetary and stellar conditions may make life problematic.
What to do? Scharf suggests looking at the big picture by putting statistics to work:
Suppose there are biospheres scattered across many systems, perhaps driven by the same kind of microbial machinery that dominates our own. Conditions can vary tremendously among these worlds, but biospheres still persist. Environments on such planets may be held in subtly different equilibria than their sterile equivalents – seen through atmospheric composition, reflectivity, and temperature. No single world may actually present enough of a smoking gun to let us say, “there be life,” but put the data from all these planets together, and that signature might be detectable.
Could a statistical approach to astrobiology succeed? Scharf continues:
Statistics are wonderful, if finicky, things. They let us cut through the haze and see things we would otherwise never find. Suppose we accumulate crude, rudimentary data on not just a few planets, but on hundreds or thousands. No single observation of a planet may tell us if it is teeming with life, but the cumulative weight of different parts of the planetary zoo might at least tell us if there is life on some of them. By letting go of our desire to locate a single instance of life, we’d stand to answer the global question.
Interesting to keep this in mind as we learn more about Kepler’s findings. For Kepler is itself statistically based, looking at a huge number of stars with the expectation, now being borne out, that a number of these will have systems tilted just the right way so that we can observe planetary transits from our perspective here on Earth. Scharf explores the kind of signal we might dig out of the statistical noise in his Life, Unbounded blog, and it’s heartening to think that in an era when budget realities keep terrestrial planet finder spacecraft indefinitely shelved, we might still locate habitable worlds by virtue of big datasets and brute force computing.