For years, astronomers have been searching for a mysterious ninth planet lurking in the dark outer reaches of our solar ...

In the remote outer reaches of planetary systems, far beyond the orbit of known planets, enormous and mysterious worlds ...

A new paper examining and simulating the formation of wide-orbit planets has put the chances of our own Solar System ...

A recent study found that Jupiter was once twice the size that it is now, making it big enough to swallow up 2,000 Earths.

"[T]he puzzle for theoretical astrophysics ... Because many close-matching simulations had the planet-like object swooping through the inner solar system, the researchers created an additional ...

Pluto was reclassified as a dwarf planet in 2006. Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far into the solar ...

All of our solar system’s planets are lining up to parade through the night sky at once. This extraordinary celestial event will see the sky scattered with seven visible planets in what is known ...

So many unexplored secrets still lie at the outskirts of our solar system, where a potential candidate for a new dwarf planet lies. Although space beyond Neptune was thought to be mostly devoid of ...

Astronomers have discovered that the Jupiter, the largest planet in our Solar System, was once so big that ... formation is essential to solving the puzzle," said Konstantin Batygin, professor ...

Observations of the potential Planet Nine are extremely difficult, as it's so far out in the Solar System that it would reflect only the tiniest amount of sunlight. Predictions estimate that the ...

This article was originally featured on The Conversation. Are planets in the solar system that are closer to the Sun older than the ones further away? – Gavriel, age 10, Paducah, Kentucky A ...