Japanese astrophysicists suggest possibility of hidden planet in the Kuiper Belt

Two astrophysicists in Japan—one from Kindai University and the other from the National Astronomical Observatory of Japan—may have discovered proof that an Earth-like planet exists in the Kuiper Belt. Patryk Sofia Lykawka and Takashi Ito present features of the Kuiper Belt in their work published in The Astronomical Journal that they feel are consistent with the presence of a planet not much bigger than Earth.

In the last 10 years, a number of investigations have provided support to hypotheses about the potential presence of a planet in the solar system's furthest reaches, dubbed hypothetically Planet Nine. The astronomers' latest endeavor raises the possibility that a planet considerably closer exists—in the Kuiper Belt.

Starting slightly beyond Neptune's orbit, the Kuiper Belt is a circumstellar disk made up of objects in the outer solar system. Material in the Kuiper belt orbits the sun much like planets do. Previous studies have proposed that the objects in the disk include comets, asteroids, space rocks, and other tiny particles, most likely composed of ice. Through their investigation, the scientists discovered that some objects in the Kuiper Belt exhibit characteristics that point to the presence of a tiny planet—one that is around 500 AU from the sun—among them. Neptune, in contrast, is situated around 30 AU away from the sun.

Researchers examining trans-Neptunian objects (TNOs) discovered that some of them exhibited peculiar orbital behavior. This finding implies that the gravitational attraction of a bigger object than usual TNOs is influencing the TNOs. Along with this, they discovered a great deal of objects with high inclinations, or high tilt orbits. Astonished by what they saw, they set up many computer simulations to mimic the behavior they saw.

Based on the calculations, a planet in the Kuiper Belt was the most plausible explanation for their data. The simulations also revealed that, should such a planet exist, it would have an orbit that would carry it between 250 and 500 AU from the sun, a mass 1.5 to 3 times that of Earth, and an inclination of around 30 degrees.

Journal information: Astronomical Journal