How many planets? is an interactive feature from New Scientist detailing the late Kepler exoplanet-hunting spacecraft’s planetary haul.
Kepler focused its gaze on a tiny piece of the sky near the constellation Cygnus, about 150,000 stars. By looking for small dips in a star’s intensity caused by a planet orbiting in front of it, the Kepler team tallied 3,588 possible exoplanets.
By then throwing out all the big boys that are nothing like Earth (down to 1,696) and then focusing on the planets that are in their star’s habitable zone (where the conditions could allow for liquid water on its surface), they narrowed it down to 51 possible Earth-like exoplanets.
Not that many, eh? Well, keep in mind that Kepler would miss planets who weren’t in the right orientation or orbited dim stars. A few calculation corrections tick that number up to 22,500…
Finally, Kepler was only looking at 0.28% of the sky. Expand it to the whole of the Milky Way, and you get something like 15-30 billion possible Earth-like planets. (I want to emphasize the possible there, because really, who knows?)
Kepler may be gone, but I can’t wait to see what future planet-hunting missions, using different detection strategies like gravitational distortion and newer imaging equipment, can find. Earth is definitely not alone. The real question for our time is this: Are we alone?
Explore the full interactive at New Scientist. For more exoplanet explorations, check out Lee Billings’ new book Five Billion Years of Solitude: The Search For Life Among The Stars