An artist's rendition of Kepler-11, a newly announced system of 6 confirmed transiting exoplanets that will be a laboratory for planet-formation theories for years to come. If these 6 worlds were somehow transplanted into our own solar system, all of them would lie within the orbit of Venus, and 5 would lie within the orbit of Mercury. How this "packed" planetary system was formed is a puzzle for astronomers. NASA/Tim Pyle
The Kepler teleconference ended a couple of hours ago. I tried my best to live-tweet salient details, so you can get your fill on my Twitter page. Here's the very compressed big picture: Kepler is working nearly flawlessly, and it's finding oodles of *candidate* transiting exoplanets, some of which appear to be rocky worlds orbiting in the habitable zones of their stars.
The Kepler team has announced more than 1200 new candidates.
Of those, 68 are approximately Earth-sized (equal to or less than 1.25 Earth radii). More than 50 candidates of all sizes are located in the habitable zone of their host stars, including 5 that are less than twice the size of Earth. The evidence suggests that smaller planets occur more frequently around smaller, cooler stars than hotter, larger stars, of which our Sun is one example. Nearly 15 percent of the stars with candidate planets harbor more than one candidate, suggesting that multi-planet systems are fairly common.
Much more work remains to be done, and indeed the follow-up observations required to confirm that all these candidates are actually planets will likely take many years. We still don't know if life exists elsewhere in the universe, but we've now taken another major step into the asymptotic frontier, and life's cosmic abundance appears more inevitable than it did yesterday.
This moment has been coming for a long, long time.
Most commentators will point to Kepler's immediate origins in a 1992 mission proposal called FRESIP from Kepler's eventual Principal Investigator, William Borucki. But I prefer to trace the defining moment back forty years more, in the overlooked musings of a brilliant Russian-American astronomer, Otto Struve.
In this paper, first published in The Observatory in 1952, Struve lays out the basic case for hunting for planets using both high-precision radial-velocity spectroscopy as well as transit photometry. He was a remarkably prescient man, and his story is worth telling, but that will be for another time. Suffice to say, I think Struve deserves far more credit than he has received for his early contributions to the wildly successful modern era of planet-hunting.
Of course, the trail goes back further still. Some 2,500 years ago, in Ionian Greece, a man named Leucippus, of the town of Miletus, first theorized that everything in the universe was made of tiny, indivisible atoms.
His disciple, Democritus, extended these ideas to state that endless configurations of atoms and void created infinite worlds that exist apart from our own, and that the Milky Way's soft glow emerges from countless faraway suns. Two centuries later, the philosopher Epicurus best summarized these ideas in a letter to a certain Herodotus (not to be confused with the historian of the same name): "There are infinite worlds both like and unlike this world of ours ... We must believe that in all worlds there are living creatures and plants and other things we see in this world."
It's not a stretch to say that, with today's announcement, the Kepler team has, in one swift stroke, made more progress toward solving this ancient mystery than has been made in the entirety of previous human history on Earth.
Think about that, and then realize that the most exciting steps—confirming these planets, finding ones even more Earth-like around nearby stars, and studying them for signs of life—still lie in our future. With any luck, and a hefty helping of public engagement, these things will happen before you, me, and everyone we know are only memories like Struve and Democritus.
Read More: Here's a nice round-up of coverage from Emily Lakdawalla of the Planetary Society. Nature has an excellent overview of the new discoveries, including a smashing Kepler feature story by Eugenie Samuel Reich, and an accompanying piece from yours truly discussing cost-effective technical and technological developments that are poised to deliver potentially habitable worlds for prices even a rabid deficit-hawk could love. I'll probably discuss some of those developments in more detail in coming blog posts.