A couple of astronomers announced five years ago that they had discovered evidence for another planet in our solar system, dubbed “Planet X.” Though it’s now known as Planet Nine, the cosmic object — much larger than Earth and lying somewhere in the solar system’s furthest reaches — is still purely theoretical, though the same team has now fine-tuned the likely orbit of such a planet.
Mike Brown and Konstantin Batygin of the California Institute of Technology are the authors of the new study. Brown, as Gizmodo put it in 2016, is “the person who murdered Pluto and is proud of it.” The research, which is currently available on the pre-print service arXiv and has been accepted for publication in the Astrophysical Journal, claims that, if Planet Nine exists, it is closer and brighter than previously assumed.
What led to Scientist o Hypothesize?
The close grouping of objects in the Kuiper Belt, broadband of icy objects beyond Neptune’s orbit, led scientists to hypothesise the possibility of an unnamed planet. If there were an undiscovered planet beyond the belt, it would have the farthest orbit of any planet orbiting the Sun, taking thousands of years to complete one rotation (compared to Neptune’s 164-year orbit, which is the longest of the known planets).
A handful of Kuiper Belt objects appear to be clustered in the same orientation in space, similar to how Neptune was discovered in the 1840s when astronomers realised Uranus was being dragged by some unseen object. This could be a random event, but some astronomers believe it is due to an undiscovered planet.
Theory around Planet Nine
Other theories have been proposed: some believe Planet Nine is a debris ring large enough to have gravitational effects akin to a giant planet, while others believe it is a primordial black hole, a postulated relic of the early cosmos too small to be detected with present means. Others argue that such a thing does not exist.
“The Planet 9 idea is a fun idea, it’s exciting, but it’s taking a bit of the oxygen at the moment,” Michele Bannister, a planetary astronomer at the University of Canterbury in New Zealand, told Gizmodo in 2017, and “We have this interesting problem…and the very shiny solution at the moment is called Planet 9.”
The current study was more selective in the Kuiper Belt objects it selected in order to figure out Planet Nine’s mass, orbit, and gravitational pull. Because some of the objects in the belt have orbits that are influenced by Neptune’s gravity, including them would distort the results. The researchers chose the final collection of featured objects—11 in total—based on their strict criteria. Planet Nine, according to their calculations, would have slightly more than six times the mass of Earth and orbit the Sun once every 7,400 years, according to National Geographic.
The researchers also evaluated the chances that the clustering of orbits was caused by something other than a big asteroid. They calculated that there was a 99.6% possibility that anything was interfering with the Kuiper Belt orbits. As NatGeo points out, this is a significant rise in the probability of a fluke (1 in 250) from the 1-in-10,000 odds the pair calculated in 2016.
Brown and Batygin believed the planet was more massive (10 times Earth’s mass) and orbited the sun for a considerably longer time (over 10,000 years) than the latest article claims. According to their new calculations, Planet Nine should be closer to the Sun than previously thought—close enough to be observed in the near future by the Vera Rubin Observatory, which is scheduled to begin operations in 2023. I’m crossing my fingers.