Heavier than Jupiter, but lighter than a small star, brown dwarfs are difficult to distinguish from giant planets. For years, astronomers have searched for a yardstick that can separate the giant ...

Planet Earth is spinning a little faster today — resulting in one of the shortest days of the year. But the change will be so minuscule you won’t even notice. We’re talking even less time than the ...

Watch this video to find out more about the Earth, planets in our Solar System and other planets far off in outer space. From up here on the International Space Station I get a great view of Earth.

Two decades ago, the International Astronomical Union—which defines and names celestial bodies—redefined the criteria for ...

Somewhere deep below Saturn s cloud tops, the planet rotates at a constant speed. Determining this interior period of rotation has proven extremely complicated. Now, with new Cassini results, a team ...

The planets within our solar system are in constant motion in their orbits and as they spin on their axes. All planets in our solar system revolve around the Sun. But the time they take to complete ...

Astronomers have long been puzzled by a cosmic mystery: planets orbiting two stars—like Star Wars’ Tatooine—are surprisingly rare, even though they should be common. New research suggests the culprit ...

For four years, NASA’s planet-hunting telescope photographed the light of 2.2 million stars. The data sat in public archives, ...

The rusty world is full of mysteries—and some of the solar system's most extreme geology. Learn more about Earth's smaller, colder neighbor.

Pluto was reclassified as a dwarf planet in 2006, but new discoveries and fresh debate are reigniting calls to restore its planet status. Learn why Pluto lost its title, what scientists discovered ...