An artist’s impression of the Kepler-10 star, rising over the horizon of its newly discovered, Earth-sized planet, Kepler-10b
Credit: NASA/Kepler Mission/Dana Berry

NASA's Kepler spacecraft confirmed its first discovery of a rocky planet, in orbit around a distant Sun-like star, termed Kepler-10. Planets outside the Solar System are known as exoplanets, or extrasolar planets. The new planet is termed Kepler-10b. It is the smallest exoplanet ever discovered, measuring 1.4 times the size of Earth (12,756 km across). The Kepler-10 system is located approximately 560 light years away.

(The light year is a unit of measuring distances in astronomy, and is equal to approximately 10,000 billion km.)
The discovery of Kepler-10b is the result of more than eight months of observation by the Kepler spacecraft, between May 2009 and early January 2010. Astronomers have discovered over 500 exoplanets, so far. Most of the exoplanets are not rocky, but rather are giant, Jupiter-like planets, consisting mostly of fluids.

When a planet passes in front of its star, the star’s brightness decreases slightly. Applying a highly precise photometer, a device that can measure the brightness of a star, Kepler can discover planets crossing in front of their parent stars. The size of the transiting planet can be inferred from these regular dips in the star’s light. The distance of the planet from its star is computed by determining the time between successive dips, as the planet circles the star.

Kepler is the first NASA mission capable of finding Earth-size planets in, or near the habitable zone, the region around a star where liquid water can exist on the planet's surface. However, since Kepler-10b orbits its star every 0.84 days, it is more than 20 times closer to its star than Mercury, the innermost planet, is to the Sun. Therefore, it is very hot, and lies outside the habitable zone.

The Kepler spacecraft is a space observatory, specifically designed to discover Earth-like planets orbiting other stars. It is named in honor of German astronomer Johannes Kepler (1571-1630), who discovered the laws of planetary motion. The spacecraft was launched on 7 March 2009, and is scheduled to operate for at least 3.5 years. Kepler deploys its photometer to continuously monitor the brightness of over 145,000 stars, within a fixed small area of the sky. Kepler was placed into an orbit around the Sun, and lasts a little more than a year to orbit the Sun once.

References

NASA
www.nasa.gov/

Kepler Mission
http://www.nasa.gov/kepler

Wikipedia

Aymen Mohamed Ibrahem
Senior Astronomy Specialist