If the object really is Planet Nine, it would be larger than Neptune and exist 700 times further from the sun than Earth.

Science textbooks may be in for another revision. Our solar system shrank from nine planets to eight after the International ...

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, ...

A planet has been predicted to orbit the sun with a period of 10,000 years, a mass 5x that of Earth on a highly elliptical ...

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about ...

The presence of another planet in the solar system could explain the odd movements of some of the bodies in the Kuiper Belt.

Scientists may have just spotted Planet Nine — a massive object orbiting 700 AU from the Sun. Data from two space telescopes ...

The hunt for Planet Nine—the solar system’s ghostly gravitational troll—is longstanding, and is based on the peculiar clustering of rocky bodies in the Kuiper Belt beyond the orbit of Neptune.

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.

Researchers for objects that moved slowly between IRAS and AKARI detections. IRAS and AKARI are far-infrared, all-sky surveys completed 23 years apart. They ...

This could be humanity's first glimpse at the long-theorized Planet Nine, which — if it exists — is a giant, undiscovered world distantly orbiting our sun. However, the ninth planet proposal is ...