Over the past decade or so, astronomers have speculated about the characteristics of rogue planets in the Milky Way galaxy.

An alternate explanation that fits the evidence is that Vesta was once part of a planet – but which planet that might been ...

Earth has four seasons, but do other planets in our solar system also have hot summer days and cold winter nights?

Discovered in 1930, Pluto was long considered our Solar System's ninth planet, but was unseated in 2006 after the discovery ...

Researchers say they found a curious dot on infrared images taken 23 years apart that seems to be moving in a manner consistent with a large, distant planet.

A ninth planet the size of Neptune may be hidden in the far reaches of the solar system, but the evidence has left some experts skeptical.

The Hubble Space Telescope time-lapse captured footage of Jupiter, Saturn, Uranus and Neptune. Credit: SCIENCE: NASA, ESA, ...

To understand how chaotic the early solar system was, we need only gaze at the moon. Its cratered surface bears the scars of ...

Astronomers have long speculated about an unseen planet lurking in the solar system's outer edge. This hypothetical world, ...

For years, astronomers have been searching for a ninth planet in our solar system (after giving Pluto the old heave-ho and demoting it to a dwarf planet) and now researchers say they’ve found a ...