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

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

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.

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

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

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

For months, President Trump has taunted Canada by claiming it should become America's 51st state. But the country's new prime ...

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 ...

For years, astronomers have toyed with the idea that the Sun hides an extra planet so distant and dim that even the best ...

Billions of years ago, in the frozen edges of the solar system, a violent impact shaped one of space’s oddest pairs. Instead ...