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

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

As a result of the International Astronomical Union’s 2006 demotion of Pluto from planet to dwarf planet, our solar system ...

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

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

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

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

For the unversed, "Planet Nine" is a hypothetical planet which is reportedly larger than Earth that is thought to orbit ...

U.N. Secretary-General Antonio Guterres on Monday urged world leaders to ratify a treaty that would allow nations to ...

As it orbits the sun once every 25,000 years, the celestial body 2017 OF201 travels beyond the Kuiper Belt into a region ...