Planet seeking Kepler Spacecraft readies for launch
February 26, 2008 On March 5, NASA will launch the largest camera ever sent into space in an attempt to find the holy grail of astronomy: an Earth-like planet. The $591 million Kepler craft will orbit the sun for at least 3.5 years, using an unprecedented 0.95-meter diameter Schmidt telescope packing an array of 42 CCDs, each with 2200x1024 pixels, to scan over 100,000 stars in the Cygnus-Lyra region of the galaxy. The craft is seeking planets in the “goldilocks” zone – not too close to the sun, and not too far – but the scope of the project means that no matter what scientists find, our understanding of the universe will be greatly enhanced.
Using its 96 million pixel camera, Kepler will measure fluctuations in the brightness of stars as planets pass over them. 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. In scientific terms, the measure of the brightness of stars is known as photometry, and the use of photometric data to determine planetary orbits is known as the Transit method. In real terms, Natalie Batalha, professor of astronomy and physics at San Jose University, describes the Kepler approach as “looking at a headlight from a great distance and trying to sense the brightness change when a flea crawls across the surface.”
While the Kepler craft is advanced enough to precisely measure the output of distant stars, only an estimated 1-10% of the stars surveyed will have orbiting planets that line up with the telescope. Consequently, though the telescope can examine a field of ten degrees squared, an area containing 6.5 million stars, only 200,000 are likely to yield useful data.
The mission is named after Johannes Kepler, a 17th Century German scientist who calculated the three laws of planetary motion – the same mathematical formulas that will allow scientists to determine which planets have Earth-like characteristics.
"Kepler is a critical component in NASA's broader efforts to ultimately find and study planets where Earth-like conditions may be present," said Jon Morse, the Astrophysics Division director at NASA Headquarters in Washington. "The planetary census Kepler takes will be very important for understanding the frequency of Earth-size planets in our galaxy and planning future missions that directly detect and characterize such worlds around nearby stars."