A new paper discusses the possible existence of an unseen planet in the outer solar system, the so-called "Planet X" or ...

Test your knowledge on our solar system, from the biggest and smallest planets to the behemoth mountain on Mars.

Learn how you can see bright Jupiter from Earth, helped by its massive size and banded, reflective cloud tops, in December's ...

The Hubble Space Telescope has been imaging the outer planets of our solar system for a decade, learning about their strange ...

Planet Nine is a theory about a massive planet that could be located far beyond Neptune, as per the studies and reports ...

Encountering Neptune in 1989, NASA’s Voyager mission completed humankind’s first close-up exploration of the four giant outer ...

If there is some planet nine, or "Planet X" lurking out there ... gravitational tugs of a super-Earth at the edge of the solar system. If we assume that is the solution to the orbital bias ...

JUPITER is set to peak in brightness tonight, and will be visible all night as its orbit turns to align with Earth. It won’t ...

Astronomers have just found one of the youngest planets ever. At only 3 million years old, planet TIDYE-1b (also known as ...