Smallest planet outside our solar system (YET..)

 

The smallest planet yet spied outside our solar system has been found orbiting a sunlike star about 560 light-years away, astronomers announced today. Known as Kepler-10b, the planet is just 1.4 times Earth's size and 4.6 times its mass.
The planet, found using NASA's Kepler spacecraft, is the first of the more than 500 known exoplanets that's definitively rocky—much like Earth, Mars, Venus, or Mercury—the study team says. Launched in March 2009, Kepler was designed to hunt for potentially habitable Earthlike planets.
Astronomers have been studying Kepler-10b (name of the planet) since its discovery in 2009, when the team detected a periodic dimming of the host star as the planet passed in front of the star.
Finding such a small planet this way was no easy feat—seen from a similar distance, Earth passing in front of the sun would cause a 0.01 percent reduction in the star's brightness, said Natalie Batalha of San Jose State University, lead author of an upcoming paper describing the find.
"Imagine you have 10,000 light bulbs and you take one away. That's the change in brightness we're looking for," Batalha said today during a meeting of the American Astronomical Society in Seattle, Washington.
Still, after using Kepler and other instruments to precisely calculate the new planet's size, mass, and density, Batalha said, "we know without question that this is a rocky world."