planets

Kelly Beatty, senior editor at Sky & Telescope, talks about where to look to see this rare arrangement.

Something very big, out beyond Neptune, is warping the orbits of small, icy objects circling our sun. Astronomers haven't seen it yet, but say the culprit could be a planet with 10 times Earth's mass.

Messenger was launched from Earth in 2004. After 4,104 orbits of Mercury and billions of miles of space travel, the orbiter ended its mission with a quiet bang Thursday.

Astronomers using telescopes in Hawaii and California have found two exoplanets orbiting a star a mere 54 light-years away. The discovery is important for two big reasons.