Add Yahoo as a preferred source to see more of our stories on Google. An illustration showing Planet Nine, a hypothetical, undiscovered planet in our solar system. New research now suggests the ...

Far beyond Neptune, a cluster of small icy worlds appears to be orbiting in a pattern that should not exist by chance. That alignment is the strongest evidence behind one of the more persistent ...

Is there a massive undiscovered planet on the outer reaches of the Solar System? The idea has been around since before the discovery of Pluto in the 1930s. Labelled as planet X, prominent astronomers ...

A team of scientists at the Institute for Advanced Study School of Natural Sciences in Princeton, New Jersey, might have found a new dwarf planet, potentially leading to more evidence of a theoretical ...

A new paper hypothesizes that there could be a Mars-sized object on the outskirts of the Kuiper Belt. If true, this would be distinct from the hypothesized Planet 9. Share on Facebook (opens in a new ...

In 2006, Pluto was famously demoted from a planet to a dwarf planet. It remains the most famous dwarf planet today, but there are others in our solar system, including potentially hundreds that ...

A TNO is classified as any minor planet — an astronomical object in direct orbit around the sun that is exclusively ...