It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the ...

A potential new dwarf planet has been discovered in the outer reaches of the solar system, and its existence poses the ...

U.S. astronomers hunting for "Planet Nine" have instead stumbled on what appears to be a new dwarf planet in the solar system ...

In the cold, dark outskirts of planetary systems far beyond the reach of the known planets, mysterious gas giants and ...

The chance of a planet forming in the outer reaches of the solar system - a hypothetical Planet Nine - could be as high as 40 ...

The TNO, which are described as minor planets that orbit the sun at a greater distance than Neptune, were found on the edge ...

The small world was found during a search for the hypothetical Planet Nine, and astronomers say the next time it will reach ...

They said: ‘The discovery of 2017 OF201 is significant because it’s found in a region of the Solar System thought to be empty ...

The object is about 700 kilometres wide and lies nearly three times farther from Earth than Neptune. Its highly elongated ...

Less than 1% of this dwarf planet candidate's orbit is close enough to detect, which means astronomers are lucky to have ...

Some astronomers say the strange, clustered orbits of icy rocks beyond Neptune indicate that something big is out there, ...