New discoveries of objects in the Kuiper Belt have also presented challenges for the Planet Nine theory. The latest is known ...

Evidence that rocky planets beyond Jupiter formed as rapidly, and at the same time, as the inner planets could transform our ...

These strange objects could explain how water arrived on Earth, but may also be a previously unrecognised threat to our ...

Planet Nine has as much angular momentum as the entire solar system combined, because its orbit is so big.” Over the course of several billion years, that could be enough to explain the six ...

Data from a new study published in the Astrophysical Journal suggests that there might be a ninth planet in our Solar System, located well beyond the orbit of Neptune. The motion of small bodies ...

A mysterious object eight times the size of Jupiter may have flown through our solar system about four billion years ago and swept the giant planets into new orbits, researchers say ...

Here’s how it works. The planet Mercury is a weird one in our solar system. Here's how the giant planets made it so. (Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie) ...

And they think the Neptune-sized planet - which they've dubbed Planet 9 - could change our view of the Solar System. Ironically, one of those astronomers is the man who helped to kill Pluto's ...

Astronauts may experience harsh circumstances when travelling to outer space, and planets such as the Moon and Mars, which are rife with health risks. Nasa has now launched an investigation into ...