Just an update regarding all this talk of 'Earth-like'.
As one can read in the two statements below from the Kepler site, these are not 'Earth-like' planets as opposed to 'Earth-sized' planets. Most of them are in tight fast orbits about their parent stars. It is exciting to think that small rocky planets may be common, but these are not 'Earth-like' or habitable.
I realize most of the more knowledgeable posters on the board understand this, but since I saw the posts on the main Kepler website I thought I would reproduce them here:
Earth-size is not Earth-like: the TED Talk by Dimitar Sasselov
[For Dimitar's full statement, see the Kepler blog, July 28, 2010 entry.]
Two weeks ago, I gave a talk at TED Global 2010 which was very well received, but caused confusion. I talked about Earth-like planets, which many people would equate to Earth-size and 'habitable'.
Earth-size and Earth-like are certainly not the same. Take the example of Venus, an Earth-size planet whose surface will melt lead. I understand that the term "Earth-like" was misleading to most of the media coverage. The Kepler Mission is designed to discover Earth-size planets but it has not yet discovered any; at this time we have found only planet candidates.
The June 2010 Kepler data release with 306 candidates is an encouraging first step along the road to Kepler's ultimate goals, and specifically - the goal to determine the frequency of Earth-size planets in and near the habitable zone. However, these are candidates, not systems that have been verified sufficiently to be considered true planets. It will take more years of hard work to get to our goal, but we can do it.
Statement from the Kepler Science Council
KEPLER SCIENCE STATUS: STATEMENT TO AMES CENTER DIRECTOR
The following NASA statement was sent to Dr. S. Pete Worden, Director, NASA Ames Research Center from the Kepler Science Council on Aug. 2, 2010.
“Recently there have been reports to the effect that Kepler has discovered many Earth-like planets. This is not the case. Analysis of the current Kepler data does not support the assertion that Kepler has found any Earth-like planets.
Kepler is producing excellent results and is on a path to achieving all its mission requirements and actually determining the frequency of Earth-size planets, especially in habitable zones. We will announce our results when they become available and are confirmed.”
Edward W. Dunham, Kepler Science Team Lead
Thomas N. Gautier, Kepler Project Scientist
William J. Borucki, Kepler Principal Investigator
for the Kepler Science Council