The solar system lost its ninth planet back when Pluto was demoted to a dwarf planet, but research might indicate that there ...

Pluto and some other known dwarf planets meet the first two criteria but not the third because they orbit in the Kuiper Belt, a region beyond Neptune filled with small icy debris.

It's much harder to find, but there are a lot more of them." The first interstellar object to visit the solar system may have ...

Astronomer and Pluto mission leader S. Alan Stern explores how the field has transformed during his decades-long career.

Astronomers say they have evidence that there may be a hidden planet in our Solar System. Named 'Planet Y', the Earth-sized ...

Astronomers have uncovered a massive new trans-Neptunian object, 2017 OF201, lurking at the edge of our solar system. With an ...

A study suggests an Earth-sized planet, dubbed Planet Y, may exist beyond Neptune, affecting the orbits of icy objects in the Kuiper Belt.

Discovery of 2017OF201, a large trans-Neptune Object, challenges previous beliefs about the Kuiper Belt and hints at the existence of a theoretical Planet Nine.

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

A new trans-Neptunian object, 2017 OF201, has been found with a vast orbit and potential dwarf planet size. The finding hints ...

Ceres is the only dwarf planet not found in the freezing cold, faraway Kuiper Belt. Rather, it orbits in the main asteroid belt between Mars and Jupiter, completing one lap around the sun every 4. ...

Peering to the outskirts of our solar system, NASA’s Hubble Space Telescope has spotted a small, dark moon orbiting Makemake, the second brightest icy dwarf planet after Pluto in the Kuiper Belt ...