This image zooms into a small portion of Kepler's full field of view — an
expansive, 100-square-degree patch of sky in our Milky Way galaxy. An
eight-billion-year-old cluster of stars 13,000 light-years from Earth,
called NGC 6791, can be seen in the image. Clusters are families of stars
that form together out of the same gas cloud. This particular cluster is
called an open cluster, because the stars are loosely bound and have
started to spread out from each other.
The area pictured is 0.2 percent of Kepler's full field of view, and shows
hundreds of stars in the constellation Lyra. The image has been
color-coded so that brighter stars appear white, and fainter stars, red.
It is a 60-second exposure, taken on April 8, 2009, one day after the
spacecraft's dust cover was jettisoned.
Kepler was designed to hunt for planets like Earth. The mission will spend
the next three-and-a-half years staring at the same stars, looking for
periodic dips in brightness. Such dips occur when planets cross in front
of their stars from our point of view in the galaxy, partially blocking
the starlight.
To achieve the level of precision needed to spot planets as small as
Earth, Kepler's images are intentionally blurred slightly. This minimizes
the number of saturated stars. Saturation, or "blooming," occurs when the
brightest stars overload the individual pixels in the detectors, causing
the signal to spill out into nearby pixels.