A hypothetical planet that has been described as "the solar system's missing link," Planet 9 (also known as Planet X) has been part of the lexicon for several years, first mentioned in 2014.

For years, astronomers have searched the outer reaches of our solar system for Planet 9, a theoretical planet that could ...

The possible existence of Planet Nine and its impact on distant objects in the solar system has fascinated researchers for some time. But a new study suggests that the theoretical object, may not ...

Planet 9 likely isn't a stolen exoplanet after all. New research shows the probability of ideal planet-swapping positions between young stars is near zero.

Some experts believe that the solar system's hypothetical ninth planet could be just a few years away from being discovered. If this is the case, how long would it take for humans to send probes ...

For years, astronomers have searched for evidence of a hidden giant planet at the edge of our solar system. New data suggests ...

Something is throwing icy bodies past Neptune, and scientists have an interesting idea about what it might be.

Planet 9 Takes ShapeAstrophysicists at the University of Bern have modeled the evolution of the putative planet in the outer solar system. They estimate that the object has a present-day radius ...

A newly found object could be a dwarf planet that contradicts the Planet Nine hypothesis.

Planet 9 may actually be a long-sought-after primordial black hole. Astronomers will use the forthcoming LSST observatory in Chile to find out.

In a new paper, Caltech researchers Michael Brown and Konstantin Batygin put some constraints on the possible existence of Planet 9, which they believe is a Super-Earth planet orbiting in the far ...

In April 2016, scientists led by Alexander Mustill, from Sweden's Lund University, said their computer simulations indicate Planet 9 is an exoplanet, a planet from outside our solar system.