From the furthest reaches of space to our own cosmic backyard, we count down the discoveries that changed everything we know about our universe.

Scientists have discovered a mysterious ninth planet on the very edge of our solar system. Ten times the size of Earth, this strange world could have moons with extraterrestrial life.

Recent discoveries could explain how supermassive black holes grow so big, one of the universe's most mysterious questions. Neither dark matter nor cannibalism can fully explain these monsters, but the latest science might finally provide an answer.

The first close-up images of Pluto revealed unimaginable secrets of this mysterious frozen world. Now, scientists investigate if Pluto is home to a warm ocean of liquid water beneath its surface, and whether this underground ocean could harbor life.

The universe is a dangerous place, and we explore the deadliest spots in the cosmos. Between earth and the edge of the universe, there are a million ways to die, and our crash test dummy is on a mission to reveal the worst.

Life once existed on Mars, but a series of devastating mass extinctions have made present-day life nearly impossible. The latest science shows how Martian life keeps bouncing back as it transforms from a watery world like Earth into a desert planet.

Dark matter is the biggest mystery of the cosmos. Scientists know that it has been vital to our universe since its birth, and new discoveries reveal that it could create black holes, cause mass extinctions, and might even shape life on Earth itself.

Discoveries of new planets have revealed countless worlds much stranger than Earth. Some of these worlds don't have stars, others are made out of diamonds. Will we ever find a planet like Earth, or are these distant worlds stranger than fiction?