Does Planet 9 exist and will it ever be found?

Does Planet 9 really exist? The evidence about the possibility of a ninth planet is mounting.

"The radius of the earth's orbit around the sun is about the space between my fingers," said Jason Kendall, an astronomer at William Patterson University.

He stood in a square in the South Street Seaport Tuesday evening and gestured with his fingers, his hands, and then his arms to indicate the size of the orbits of each of the known eight planets in the Solar System around the sun in comparison to a hypothesized ninth planet.

Before explaining the evidence for this possible giant ninth planet we must first address a technicality.

"Wow, Planet 9. Let's call it Planet 9," Kendall said, using air quotes because he studied at New Mexico State under the man who in 1930 discovered what some still regard as Planet 9—Pluto.

The International Astronomical Association declared Pluto a dwarf planet in 2006 thanks to the work of Caltech astronomer Mike Brown and his team who discovered a belt of these icy dwarfs.

"The Solar System hosts this extensive field of debris beyond Neptune," Caltech astrophysicist Konstantin Batygin said. He said he believes the disruption in that belt indicates the presence of a large planetary body that only rarely swings into our solar system.

"Depending on its orbit, it'd probably be like a 200- to 400- to 500-year orbit or even longer," Kendall said.

Because of its vast distance from the sun and its non-reflective appearance, Planet 9 appears very dim.

"Mike Brown and his associates and many others think that there will probably be no telescope that will ever be able to observe this object," Kendall said.

But Brown told Quanta Magazine earlier this summer that he remains confident someone someday will succeed in proving its existence.

"I'm very optimistic and quite confident that we will see Planet 9 in five years, 10 years," Batygin said.