IN THE NEWS: NASA’s Kepler Mission Discovers Its First Rocky Planet and a Cornucopia of Planet Candidates

NASA news releases in January and February 2011 announced the following exciting discoveries.

This artist’s depiction shows an imagined view from planet Kepler-10b (January 10, 2011).

• January 10: Kepler mission confirmed the discovery of its first rocky planet, named Kepler-10b, 1.4 times the size of Earth—the smallest planet ever discovered outside our solar system.
• February 2: Kepler mission releases data from the first four months of continuous simultaneous observations of 156,000 stars in Lyra and Cygnus, including evidence for 1,235 new planets. What’s even more exciting is that 54 new planet candidates are in the habitable zone of their star (where liquid water can exist) and of those, five are near Earth-sized. The remaining 49 habitable zone candidates range from super-Earth size to larger than Jupiter. It’s possible they could have habitable moons.
• February 2: Kepler mission announces the discovery of six planets orbiting a sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system. Kepler-11, located approximately 2,000 light years from Earth, is the most tightly packed planetary system yet discovered. All six of its confirmed planets have orbits smaller than that of Venus, and five of the six have orbits smaller than Mercury’s.

“All of Kepler’s best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun,” said Natalie Batalha, Kepler’s deputy science team lead at NASA’s Ames Research Center in Moffett Field, California, and primary author of a paper on the discovery accepted by the Astrophysical Journal. “The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it’s beginning to pay off.”

Kepler’s ultra-precise photometer measures the tiny decrease in a star’s brightness that occurs when a planet crosses in front of it. The size of the planet can be derived from these periodic dips in brightness. The distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star.

Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet’s surface. Though Kepler-10b is the first rocky planet discovered outside the solar system, it’s definitely not in the habitable zone. A “year” on Kepler-10b is less than one Earth day! It orbits once every 0.84 days and is more than 20 times closer to its star than Mercury is to our Sun, so its temperature is over 1,800 °C, hot enough to melt iron. Nonetheless, “the discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own,” said Douglas Hudgins, Kepler program scientist at NASA headquarters in Washington, D.C. In a New York Times article on February 2, 2011, after the Kepler data release announcement, Dennis Overbye wrote, “Astronomers have cracked the Milky Way like a piñata, and planets are now pouring out so fast that they don’t know what to do with them all.”

The FOSS Planetary Science Course, Second Edition, to be released in Fall 2011, culminates in an investigation about finding exoplanets, featuring the technique used by Kepler mission: observing transits of the planets in front of their stars.

For more information about the Kepler mission, visit: http://kepler.nasa.gov.