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.

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

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 ...

Astronomers have discovered a "fossil" world lying in the outskirts of the solar system, according to new research.

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.

Nicknamed "Planet Nine," the real-life Planet X appears to have the mass of 10 Earths and is 20 times farther from the sun than Neptune. Skip to main content. Open menu Close menu.

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." ...

In October 2017, NASA released a statement saying that Planet Nine may be 20 times further from the Sun than Neptune is, going so far as to say "it is now harder to imagine our solar system ...

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 ...