For years, astronomers have been searching for a mysterious ninth planet lurking in the dark outer reaches of our solar ...

This hypothetical planet, theorized to be seven times the mass of Earth, could provide answers to some of the most puzzling phenomena observed in the outer solar system. Orbiting far beyond ...

Jupiter is already the biggest planet by far in our solar system, but new research suggests it was somehow once even larger than it is now. Twice as large, in fact. To put that into context ...

Jupiter is the largest planet in our solar system, and it might also be the oldest ... 5 years before joining Mashable to cover all things outer space. She took a ride in weightlessness on ...

A team of astronomers believe they may have discovered a new dwarf planet—just like Pluto—on the edge of our solar system.

At its upper size, it even approaches the scale of Ceres, the largest object ... hidden influences in the outer solar system, most notably the possibility of a ninth planet now that Pluto isn ...

Astronomers have discovered that the Jupiter, the largest planet in our Solar System, was once so big that it could have held 2,000 Earths. Jupiter is our system's oldest planet, forming from the ...

There’s a new frozen oddball orbiting the Sun, and it’s not your average space rock. It’s a planet—a minor one, to be fair—but one of the largest yet discovered and with an orbit around the Sun that ...

Planet Nine is a hypothesised planet that is five to 10 times the mass of Earth, orbiting in the outer solar system at about 400 to 800 times the Earth-sun distance. The best evidence for its ...

Jupiter, the largest planet in the solar system, was 2 to 2.5 times bigger ... That location, they said, should help determine the outer edge of the disk of gas and dust that once surrounded ...