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.

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

In the remote outer reaches of planetary systems, far beyond the orbit of known planets, enormous and mysterious worlds ...

Orbit diagram for the outer solar system. The sun and terrestrial planets are at the center. The orbits of the four giant planet Jupiter, Saturn, Uranus and Neptune are shown by purple solid circles.

Alien planets captured by our sun's gravity could could hide in the shadows of the outer solar system. (Image credit: Wikimedia Commons reproduced under a Creative Commons BY-SA 4.0) ...

One challenge to the Planet Nine theory is that while it explains the odd orbits of objects astronomers see today, theorists aren’t sure how such a huge planet could exist in the outer solar system.

The new object, named 2017 OF201, was discovered by researchers in an astronomical image database while searching for trans-Neptunian objects (TNOs) and possible new planets in the outer solar system.

This discovery has significant implications for the current understanding of the layout of our outer solar system. 5 2017OF201 takes about 25,000 years to orbit the sun.

Deep in the outer solar system, billions of miles from Earth, lurks a realm of small, icy worlds called dwarf planets. Astronomers know relatively little about these dim and distant objects, but ...

The giant planets formed in a drastically different environment from the terrestrial planets. It was much colder in the outer solar system, so water was ice, but in the region near where Earth ...