What if there’s a planet hiding in our solar system, 10 times larger than Earth? While this theory has yet to be confirmed, ...

For many of us, the idea of a solar system with just eight planets is a fundamental concept in science. However, since Pluto was reclassified as a dwarf planet in 2006, Neptune has stood as the last ...

The so-called theoretical world - dubbed Planet X - has still not actually been seen by anyone, and for the meantime remains just that, a theory. But are scientists any closer to solving the mystery?

Today, the Planet X hypothesis is largely considered to be discredited.However, that hasn't stopped astronomers from looking for planets in the far reaches of the solar system.And according to a ...

This artist’s concept depicts the distant, hypothetical, Neptune-sized Planet X in our solar system. Although astronomers are searching, catching a glimpse of this planet — if it exists — is ...

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.