Livable super-Earths? Two candidates among Kepler's latest finds.
Researchers unveiled a total of three planets Thursday, including two potentially livable super-Earths. The discoveries bring the Kepler team closer to its goal.
In Pictures Looking into the skies: Telescopes
Subscribe Today to the Monitor
Kepler is a space-based observatory whose unblinking gaze has rested on some 170,000 stars simultaneously since May 2009.
The three planets are the smallest the observatory has yet detected in stellar habitable zones. These zones represent distances where a planet receives enough light from its host star to harbor liquid water on its surface. Liquid water is essential for the emergence of organic life.
RECOMMENDED: Are you scientifically literate? Take our quiz
The discoveries bring the Kepler team tantalizingly close to its ultimate goal – to find Earth-mass planets orbiting sun-like stars at Earth-like distances, while also taking a broader census to see how many planetary systems with an Earth-like planet the Milky Way may hold.
Led by William Borucki, a researcher at the National Aeronautic and Space Administration's Ames Research Center near Mountain View, Calif., the team has confirmed 115 extra-solar planets so far, and it has amassed a roster of more than 2,700 planet candidates.
Two of the new planets are part of a five-planet system orbiting a star some 1,200 light-years away in the constellation Lyra. The star, Kepler 62, is about two-thirds the size of the sun and has 70 percent of the sun's mass. It's also about 3 billion years older than the sun.
The system's three inner planets, one comparable in size to Mars, are too close to their sun to be livable. Kepler 62-e, the fourth planet out, however, falls within the habitable zone. Orbiting once every 122 days, the planet is about 60 percent larger than Earth.
The team speculates that the planet is covered with water, although the system is too far away to take the measurements needed to estimate the planet's mass. Researchers need that measurement to determine the planet's density, a major clue as to its bulk composition.
Instead, modeling studies have indicated that planets ranging from 1.5 to two times Earth's size tend to be far more watery than planets closer to Earth's size. Thus, while the nature of the planet remains speculative for now, "the fascinating idea is that we've actually found the first ocean planet, the first water world out there," said Lisa Kaltenegger, an astronomer with the Max Planck Institute for Astronomy in Germany and the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., during a mission briefing Thursday afternoon.