"It is possible that a planet once existed in the solar system but was later ejected, causing the unusual orbits we see today ...

Researchers use the Subaru Telescope in Hawaii to find a small object on the outer edge of the Solar System. Nicknamed ...

Planet Nine should appear stationary over the course of a single day but show detectable movement over months.

Astronomers have hoped for the existence of Planet Nine for years. Things were looking promising, but this discovery might ...

A telescope has discovered a new world on the edge of the Milky Way – potentially confirming the ‘Planet X’ theory. Beyond ...

Ammonite was discovered using the Subaru Telescope in Hawaii, with follow-up confirmation from the Canada-France-Hawaii ...

The discovery was made by astronomers using the Subaru Telescope, which is situated atop a dormant volcano in Hawaii.

A ninth planet is one form the solar system’s mysterious mass could take. After centuries of watching the skies, the map of our local solar system has grown quite detailed. In the impenetrable ...

A Planet Nine probe would have to travel further than NASA's Voyager 1 space probe. (Image credit: NASA/JPL-Caltech) Seventy-five years may seem like a long time for a one-way trip.

That will allow the observatory to detect anything that changes — like, say, Planet Nine moving across the sky. "If it's there, we should be able to find it, pretty easily," says Blum.

When I was a kid, there were nine planets. Now we know of thousands! But that includes exoplanets, alien worlds that orbit alien suns. Only eight planets call our solar system home.

Mike Brown is convinced that beyond Neptune, at the far reaches of our solar system, there's an unseen giant planet. "This is the 5th largest planet in our solar system, lurking out there, waiting ...