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

The Solar System does not have a clear border. The influence of the Sun in certain domains is small enough for the Voyager ...

Astronomers have picked up evidence of an Earth-sized world, distinct from the previously hypothesised Planet Nine and Planet ...

A mysterious new world may be hiding in the outer reaches of our solar system. According to arecent study published on arXiv ...

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

For the dwarf planet candidate, one trip around the sun takes over 24,000 years. Its orbit challenges a proposed path for a hypothetical Planet Nine.

A new dwarf planet, discovered beyond Neptune and described as Pluto's 'cousin,' could void the hypothesis of a Planet X in our solar system.

An object seen to have moved in the time between when it was imaged by the IRAS and AKARI surveys in 1983 and 2006 respectively could be Planet Nine.

"It's almost unfathomable to imagine what is happening to this planet. The planet's atmosphere simply cannot withstand the high X-ray dose it's receiving from its star." ...