• This artistic rendering provided by California Institute of Technology shows the distant view from Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Scientists reported Wednesday, Jan. 20, 2016, they finally have "good evidence" for Planet X, a true ninth planet on the fringes of our solar system. (R. Hurt/Infrared Processing and Analysis Center/Courtesy of California Institute of Technology via AP)

Looking for the newly discovered Planet Nine: could we have seen it before?

Friday, January 22, 2016

Most people learned in grade school that Pluto was one of the nine planets. But in the early 2000's astronomers began discovering other small icy bodies in the outer solar system. Pluto, as it turns out, is more similar to these worlds than the other eight planets. So Pluto was demoted, and reclassified as a dwarf planet. The distant world became part of a new club, along with the other newly discovered objects.

It seems though, there may yet be a ninth planet after all. Researchers at the California Institute of Technology (Caltech) have found evidence of a massive planet that orbits the sun in a very large, elongated orbit. Planet Nine, as it has been dubbed, is 20 times more massive than Earth, and 5000 times more massive than Pluto.

It orbits the sun about 20 times further from the sun on average than Neptune and takes 10,000 to 20,000 years to complete one orbit around the sun. This gigantic orbit keeps Planet Nine in the outer reaches of the solar system in an area known as the Kuiper Belt. Even at its closest approach to the sun, the distant planet would still be a faint object, requiring a telescope to see.

Although it hasn't been observed directly, there is a strong likelihood that Planet Nine exists. It's presence is inferred by the peculiar orbits of other bodies located in the Kuiper Belt. Six Kuiper Belt Objects (KBO)s all have the same inclined orbit to the plane of Earth and the other seven known planets, which orbit roughly on the same plane. The odds of all six of these objects having the same orbital inclination by chance is incredibly small - .007 percent. It is most likely that some fairly massive object is influencing their orbits. Computer simulations confirm the very probable existence of another undiscovered body, Plane Nine.

Are observations of other world's orbits a reliable method of detecting a new planet? Most definitely.

This is how Neptune was discovered in 1846. Before it was observed directly, Neptune was mathematically predicted because of irregularities in Uranus' orbit that could only be explained by the gravitational influence of a more distant planet. When Neptune was seen telescopically, it was within one degree of its predicted location. This is just twice the diameter of the full moon. It was a powerful testament to the predictability of Isaac Newton's gravitational theory.

Neptune had probably unknowingly been observed many times before its actual discovery. The same may be true of Planet Nine. It is likely that astronomers have already observed or imaged Planet Nine without realizing it. In any case, Planet Nine is not out of range of some of our finest ground-based telescopes.

Astronomers don't know exactly where to look for Planet Nine, but the hunt will be on for this elusive planet. It may just be a matter of time before we have confirmation that there are indeed nine planets, just as most of us were taught.