The solar system consists of our star, the sun, and everything bound to it by gravity: the planets Mercury, Venus, Earth, ...

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

If the object really is Planet Nine, it would be larger than Neptune and exist 700 times further from the sun than Earth.

Astronomers have detected a promising sign of a ninth planet lurking at the the farthest reaches of the Solar System.

Astronomers have found new evidence that a mysterious ninth planet may be hiding at the edge of the solar system - rewriting what we know about the cosmos again. An international team from Taiwan ...

And these observations are giving us hints about what's going on? A new "Tatooine-like" planet outside the solar system may orbit two failed stars, scientists reported Wednesday.Related video ...