Kepler: The Planet Finder

I really should have put the Kepler Space Telescope on my list of Great Accomplishments in 2012 since the little spacecraft was very busy in 2012 identifying more possible Earth-like planets in our galaxy. Launched in March 2009, Kepler has already investigated the brightness of more than 150,000 stars, identified more than 2,400 planet candidates, and confirmed more than 100 planets.  Many of these planets are Earth-sized and many are within the "habitable zone."  As part of its next mission, Kepler will begin to focus on Earth-like candidates in 1-year orbits around stars similar to our sun. 

At a January 7, 2013, press conference during the American Astronomical Society Meeting in Long Beach, CA, we learned that we are far from alone:

A new analysis of Kepler data shows that about 17 percent of stars have an Earth-sized planet in an orbit closer than Mercury. Since the Milky Way has about 100 billion stars, there are at least 17 billion Earth-sized worlds out there.

This is a pretty amazing discovery from this little spacecraft.  We went from guessing about our lonely status only a few years back to confirming that we are only one of billions of planets in a similar scenario - talk about a "Kepler moment."  Carl Sagan's book Cosmos provides this quote from the first Kepler that sums it up:

We do not ask for what useful purpose the birds do sing, for song is their pleasure since they were created for singing. Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens. The diversity of the phenomena of nature is so great and the treasures hidden in the heavens so rich precisely in order that the human mind shall never be lacking in fresh nourishment.

You can get more information on this latest announcement by viewing the accompanying paper on Kepler.