Researchers say they found a curious dot on infrared images taken 23 years apart that seems to be moving in a manner ...

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, ...

A ninth planet the size of Neptune may be hidden in the far reaches of the solar system, but the evidence has left some experts skeptical.

Science textbooks may be in for another revision. Our solar system shrank from nine planets to eight after the International Astronomical Union demoted Pluto in 2006. But there may yet be ...

Over millions of years, these objects grew larger, sweeping up material in their orbits and becoming the planets we know today. This model of solar system formation is known as the nebular hypothesis.

If the object really is Planet Nine, it would be larger than Neptune ... The possibility of additional planets in our solar system has been proposed many times, going under names such as "Planet ...

While scientists are still trying to confirm Planet Nine's existence, NASA says proving that this ice giant is real would help astronomers explain several mysteries within our solar system.

Researchers have found a candidate for the hypothetical Planet Nine, which could be an undiscovered giant planet way out in our solar system. However, as with all ninth planet research, the new ...

TIM:When I was up on the ISS, that different perspective really brought home the sheer scale of the ... it's a little mechanical model of our solar system. You can see the planets here, orbiting ...

There have been questions about a mysterious ninth planet in our solar system for nearly a decade. Pluto was unseated as number nine in 2006. Now, a group of international researchers say they may ...

Astronomers claim to have discovered a new ninth planet in our Solar System. Planet Nine, also known as Planet X, is a hypothetical celestial object that would distantly orbit our Sun – but ...