In Search of Planet 9

By Matt Zhang

Since elementary school, we have been taught that there are eight planets: Mercury, Venus, Mars, Earth, Saturn, Jupiter, Neptune and Uranus. Pluto was unfortunately demoted in 2006 to a dwarf planet. Yet, scientists are currently debating the possible existence of a ninth planet. Some believe that this planet must exist, while others dismiss the evidence to be a coincidence and wishful thinking. Interestingly, this new movement is being spearheaded by the very scientist that “killed” Pluto: Michael Brown.

The planet is hypothesized to be around six times the mass of Earth, and in the far reaches of our solar system. Its supposed orbit is 400 times the distance from the Earth to the Sun at its closest point, and is probably similar to Neptune in its composition. The main evidence supporting the theory comes through the peculiar orbits of many objects near Pluto in the Kuiper Belt, as shown in the image below. These suggest the existence of a massive object to influence their orbits. Even more compelling is the previous discovery of Neptune, which was discovered in similar fashion due to the deviation of Uranus’ predicted orbit.  According to a study published last month, there is only a 0.4% chance that these statistics are a coincidence. However, many scientists still doubt these conclusions. Kevin Napier led another study to oppose these claims, suggesting that it was a statistical illusion and that “There is only just so much statistical power one can draw from a dozen data points”. Is Planet 9 real, with hard evidence? Or is it just wishful thinking, with a psychological bias towards believing its existence? Whatever the case, there is much to explore and discover, and events such as these show us just how little we understand of our solar system and astronomical surroundings.