Scientists have been searching for some time for the ninth planet – not Pluto – in our Solar System which lies beyond Neptune’s orbit. Teams of scientists have hypothesized about “Planet Nine” for decades and haven’t been able to detect it. Now, a team of scientists are trying to explain that the “strange” orbits of other objects in the solar system could actually be caused by the gravitational pull of objects orbiting beyond Neptune, instead of the long sought mysterious Planet Nine.
A team of scientists at the University of Cambridge and the American University of Beirut believe that the disc located beyond Neptune called the Kuiper belt, consisting of small icy bodies, the combined masses of which could be as much as ten times that of Earth. In the simplistic model of the solar system, the gravitational forces of the hypothesized disc could make the mass and gravitational pull believed to be at the outer reaches of the solar system.
This theory is not the first to propose that the long sought mysterious Planet Nine is not necessary to exist in order to make up for the forces of the disc. However, it is the first study which looks into the features of the hypothesized orbits. The results of the study are published in the Astronomical Journal.
The icy bodies inside the Kuiper belt are leftovers from the time when the solar system was formed. Neptune and other large planets in the solar system gravitationally affect the belt, and beyond, known as trans-Neptunian Objects (TNOs). TNOs are orbiting the Sun in a nearly circular path observed from every direction.
“The Planet Nine hypothesis is a fascinating one, but if the hypothesised ninth planet exists, it has so far avoided detection,” co-author Antranik Sefilian, a Ph.D. student in Cambridge’s Department of Applied Mathematics and Theoretical Physics said in a statement. “We wanted to see whether there could be another, less dramatic and perhaps more natural, cause for the unusual orbits we see in some TNOs.”
“If you remove planet nine from the model and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs,” added Sefilian, who is a Gates Cambridge Scholar and a member of Darwin College.
What makes this study’s estimates more correct than the previous studies which looked at the long sought mysterious planet Nine, is that previous calculations have only resulted in around one-tenth the mass of the Earth in the total mass of the objects beyond Neptune. For Planet Nine not to exist, there is a requirement that the combined mass of the Kuiper Belt needs to be from a few to ten times more than our Earth.
“When observing other systems, we often study the disc surrounding the host star to infer the properties of any planets in orbit around it,” said Sefilian. “The problem is when you’re observing the disc from inside the system, it’s almost impossible to see the whole thing at once. While we don’t have direct observational evidence for the disc, neither do we have it for Planet Nine, which is why we’re investigating other possibilities.”
Sefilian, however, added that the study reveals huge remnant populations of debris, admitting that both theories could be possible – that there is a massive disc which makes for the gravitational pull as well as the long sought mysterious Planet Nine.
Nevertheless, further studies and revelations of more secrets our system hides could possibly reveal the existence of the mysterious planet, if there is one.