BOSTON—Planets like company. No less than one in three of all
planets around other stars found by NASA's Kepler space
telescope are in multiple-planet systems. What's more, the sheer
number of those systems suggests that they are more tranquil
places than our own solar system, say astronomers working with
the telescope. Since it was launched just over 2 years ago,
Kepler has found 116 systems with two planets, 45 with three,
eight with four, one with five, and one with six planets,
astronomer David Latham of the Harvard-Smithsonian Center for
Astrophysics in Cambridge, Massachusetts, reported here today at
the meeting of the American Astronomical Society. That's a total
of 171 multiple-planet systems. "We thought we might see a few
multiplanet systems," Latham says. "Instead, we found lots of
them." Kepler detects a planet when it passes in front of its
parent star, as seen from Earth. Such transits produce minute,
periodic dips in the brightness of the star. Kepler continuously
monitors 165,000 stars to sear