The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

As the gatekeepers to the Kuiper Belt, Charon and Pluto are a unique double dwarf planet system ... Christy had been imaging Pluto with the USNO's 1.5-meter (4.9-foot) telescope.

The building blocks of life could have been delivered to Ceres by one or more space rocks from the outer asteroid belt.

When we first began searching for planets around other stars, one of the surprising discoveries was that there are planets orbiting white dwarfs. The first exoplanets we ever discovered were white ...

The dwarf planet is a bizarre, cryovolcanic world. However, the organic deposits discovered on its surface so far are unlikely to originate from its interior. The organic material found in a few areas ...