Launched on March 6, 2009, the Kepler spacecraft is continuing to scan the heavens for Earth-like exoplanets. The $US591 million Kepler boasts the largest camera ever sent into space, incorporating a 0.95-meter diameter Schmidt telescope with an array of 42 CCDs, each with 2200x1024 pixels. NASA has recently released 43 days-worth of data covering more than 156,000 stars in the Cygnus-Lyra region of our galaxy, but more analysis is needed before any conclusive findings can be made.

When NASA talks about “Earth-like” planets, it’s referring to ones that are about the same size as Earth, and that orbit stars in a warm, habitable zone where liquid water could exist on their surface. In order to detect such planets, the Kepler has been using its 96 million pixel camera to measure fluctuations in the brightness of the Cygnus-Lyra stars. The degree to which a star dims when an object moves in front of it can be used to determine its proximity to the orbiting body. The disturbance in brightness caused by the orbit of an Earth-like planet would be roughly 1 part per 10,000.

The Kepler's target region in the Milky Way (Image: NASA)

From the data received so far, the 28-member Kepler team are taking a closer look at over 400 “objects of interest.” They are doing so through the use of ground-based telescopes, the Hubble Space Telescope, and the Spitzer Space Telescope. Such follow-up work is necessary to weed out false alarms, such as binary stars that orbit one another. Ground-based stereoscopic telescopes are also necessary for determining the size of the stars, which would in turn indicate the size of the planets passing in front of them.

"This is the most precise, nearly continuous, longest and largest data set of stellar photometry ever," said Kepler Deputy Principal Investigator David Koch. "The results will only get better as the duration of the data set grows with time."

A diagram of the Kepler spacecraft (Image: NASA)

The raw data was released to the scientific community last month and the team plan to release their findings based on that data in February 2011. Kepler is scheduled to continue its search until at least November 2012.