Kepler

Tomorrow night NASA is scheduled to launch the Kepler satellite, which is designed to search for extrasolar planets roughly the same size and distance from their suns as earth. Finding planets has gotten routine -- as of today the official count is 342 planets orbiting 289 stars. But all of these are either very large or very close to their suns. No earthlike planet has yet been found.

So here's to Kepler and the brains behind it, hoping they find many worlds for us to dream about. It's going to take some time, though. To confirm a planet's orbit takes three or four transits, and a planet in an earthlike orbit has a period of about a year.

The picture shows the part of the sky Kepler will be searching.