August 16, 2013

The Kepler space telescope is officially down–but the Kepler mission is definitely not out, NASA announced on August 15. The space agency said that engineers have given up efforts to repair the satellite’s broken fine-pointing navigation system, which kept the telescope steady enough to hunt for orbiting planets around faraway stars in the Milky Way Galaxy. Engineers had been trying to repair the system since mid-May. NASA stressed, however, that the end of Kepler’s observational abilities did not signal the end of Kepler’s mission. The analysis of data collected by Kepler since it became operational in 2009 will keep scientists busy for years. NASA also said the Kepler team would be exploring other uses for the telescope, including studying asteroids and comets as well as large exoplanets.

A planet about the size of  Saturn, known as Kepler-35b, orbits a binary star (pair of stars) in an artist’s illustration of a planetary system discovered by Kepler. (Lynette Cook/NASA)

Kepler’s main mission was to search one section of the Milky Way for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to allow liquid water to form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the sun.

Kepler has searched over 150,000 stars for signs of orbiting planets. It has detected 135  as well as more than 3,200 planet candidates. Kepler was designed to detect the decrease in brightness that occurs when a planet passes in front of its star, an event called a transit. During a transit, a terrestrial planet blocks a small fraction of the star’s light from reaching Earth—roughly 1 part in 10,000. The tiny dimming for such planets typically lasts from a few hours to as long as 16 hours. Kepler hunted for transits that repeat at regular intervals ranging from a few days to two years.

Additional World Book articles:

• Binary star
• In Search of Other Worlds (a special report)
• Space exploration (2011) (a Back in Time article)