Planet nine

Astrophysicists have recently begun hatching plans to find out just how weird Planet Nine might be.

How can something so gargantuan just remain hidden from our eyes for so long?

Astronomers have found the coolest star. This star is cooler than the human body. Not all stars are hot. Learn more on EarthSky.

Astronomers have been scouring the outer solar system for signs of a hypothetical ninth planet for almost a decade, without success. However, we may finally be on the cusp of finding it, experts say.

Planet Nine

In the search for the hypothetical 9th planet in our solar system, scientists may have uncovered another explanation for the patterns in the orbits of Kuiper Belt objects.

Astronomers believe that Planet 9 may be a super-Earth, roughly 10 times more massive than our planet, with a highly elongated oval loop as an orbit, taking roughly 15,000 years to orbit the Sun

A planet spotted 336 light-years from Earth could help scientists learn more about whether there is a large "Planet Nine" or "Planet X" lurking in the outskirts of our solar system.

Astronomers argue that there’s an undiscovered giant planet far beyond the orbit of Neptune. A newly discovered rocky body has added evidence to the circumstantial case for it.

Planet Nine: A world that shouldn't exist. Earlier this year scientists presented evidence for Planet Nine, a Neptune-mass planet in an elliptical orbit 10 times farther from our Sun than Pluto. Since then theorists have puzzled over how this planet could end up in such a distant orbit. New research by astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) examines a number of scenarios and finds that most of them have low probabilities.