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.

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

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

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 ...

Over the past decade or so, astronomers have speculated about the characteristics of rogue planets in the Milky Way galaxy. These "free-floating" worlds don't orbit stars, but instead roam the ...

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

Some experts remain unconvinced about this discovery. It’s been almost two decades since our solar system lost its 9th planet. Pluto was officially reclassified from a planet to a dwarf 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.