We still don't know for sure if there's a ninth planet in our solar system, but a new discovery could help to prove that ...

Learn more about a sednoid called Ammonite that has been detected in the outer reaches of the Solar System.

A tiny object far beyond Pluto, newly discovered by the Subaru Telescope, could reshape our understanding of the early Solar ...

"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 ...

In the icy, dark expanse beyond Neptune, a cosmic fossil has surfaced that threatens to upset decades-old assumptions about the solar system’s secret structure. The new discovery of “Ammonite,” a ...

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

Planet Nine's composition is probably "most like Neptune," due to its distance from the sun, Brown said. "That would put its diameter at something like two times the width of Earth," he added.

If their calculations serve them correctly, Planet Nine would have a mass that is about 1.5 to 3 times that of Earth, at 500 times the distance between our home and the sun.

If Planet 9 is on the smaller side, dark, and really far away, he explains, "it's going to be on the edge of Vera Rubin detection, and Vera Rubin may not find it." ...

But even if it doesn't spot Planet 9 directly, the Rubin Observatory might find some more minor planets, ones whose orbits might be affected by Planet 9. And that could provide additional evidence ...