If all goes well on March 6, the Kepler telescope will blast off from Cape Canaveral’s launch pad 17-B aboard a Delta II rocket and usher in a new era of space exploration. NASA’s Kepler mission will begin an unprecedented 3 1/2 year mission to locate Earth-like extrasolar planets. While over 250 planets outside our solar system have been discovered to date, the vast majority of those planets are massive “gas giants” similar to the outer planets found in our solar system. In some cases, however, these giant worlds are located much closer to their stars—roughly the distance Earth is from the Sun—and thus dubbed “hot jupiters.” Regardless of the distance, though, their large masses make them easier to find than planets of more modest mass so the discovery of rocky, earth-like planets lags far behind the discovery of these hot gas giants. Kepler’s mission is to improve the odds of finding those smaller, terrestrial bodies.
Kepler is the first telescope specifically designed to locate Earth-like planets by measuring the periodic dimming of a star as it is eclipsed by its planets. If the plane of a planet’s orbit is aligned with the telescope, the planet will transit the star’s disk and cause it to decrease in brightness. While astronomers are not sure how many Earth-like planets might exist around other stars, they hope that a survey of 100,000 stars in the Cygnus-Lyra region of the Milky Way will turn up dozens or hundreds of rocky planets. If any of those planets are located in the “Goldilocks zone” (where temperatures are neither too cold nor too hot, but just right for liquid water to exist), they may be habitable. Kepler’s photometer is so sensitive that it can detect a decrease in a star’s magnitude of only 20 parts in a million. As described by James Fanson, Kepler project manager, if turned on Earth at night, the telescope could detect the dimming of a porch light as a person walks in front of the light! To accomplish this feat of technology, Kepler will have use the most sensitive detector ever launched into space—a 95 megapixel array.
According to Debra Fischer of San Francisco State University, Kepler is essential to our understanding of the kind of planets that form around other stars. Scientists chose to name the mission after the German astronomer Johannes Kepler in honor of his fundamental discoveries in the fields of optics and celestial mechanics. Although he initially studied theology, Kepler became fascinated with the work of Nicolaus Copernicus and while a professor of mathematics, openly embraced Copernicus’ sun-centered model of the heavens in his 1596 book Mysterium Cosmographicum. Throughout 2009, we celebrate the 400th anniversary of the publication of his first two laws of planetary motion. Kepler’s three laws of planetary motion are the cornerstone of celestial mechanics and can be used to describe all closed orbits.
For further information: Kepler Mission home page, highlights of the life of Kepler, and suggestions for further reading.
