The Kepler Five

Or at least the first five. The Kepler Space Telescope today announced its first five extrasolar planet discoveries at the American Astronomical Society meeting in Washington, DC. Kepler was launched March 6th, 2009 with the goal of finding Earth like planets orbiting other stars.

These first five planets, named 4b, 5b. 6b. 7b, and 8b (they skipped 1-3 since the first three detections were previously known planets that happened to be in Kepler's field of view) are not very Earth like. The smallest is about the size of Neptune and the largest are bigger than Jupiter. They all orbit very close to their stars with periods on the order of days. Their temperatures can be as high as a couple of thousand degrees Fahrenheit.

Since these planets pass in front of the stars, we can measure their diameters. Follow up measurements can give us their masses so we can find the densities of these planets. The most extreme world, Kepler 7b, has the density of styrofoam...for the entire planet!

It shouldn't surprise us that these are the types of planets Kepler finds first. It is easy to find big planets that orbit close to their stars. Finding planets that orbit farther from the star takes longer simply because they don't pass in front of the star nearly as often. As time goes on, Kepler will find more planets with lower masses, that orbit farther from their stars, and are more Earth like.

There are hundreds of signals Kepler has to follow up and see if they are planets or something else. The good news is that it is working well and that in a few years we will be one step closer to finding out how common planets like ours are.

Reprinted with permission from the Half-Astrophysicist Blog.