Mystery of Planet Nine

A University of Michigan researcher has logged in two key pieces of evidence that support the existence of another planet in the Solar System – one that is beyond Neptune.

Scientists have long speculated if there is a ninth planet in the Solar System.

Background

The Solar System is a gravitationally bound system in the Universe that comprises of the Sun and all the objects that orbit around it. This includes the main eight planets of which Earth is one of them. Pluto was once considered a planet, however, it has been downgraded to a dwarf planet. There are other celestial objects such as asteroids and satellites in the Solar system but they are significantly smaller in size.  

A planet in the Solar System is a celestial object that orbits the Sun and is massive enough for its own gravity to make it round. It should have also have also "cleared its neighborhood" of smaller objects around its orbit. The eight planets in the Solar System are – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

In addition to the eight main planets of the Solar System, there are also five dwarf planets that have recognized as such by scientists. They are - Pluto, Ceres, Eris, Makemake and Haumea. According to scientists there are likely to be hundreds of dwarf planets that have yet to be discovered.

Analysis

In early 2016, researchers Konstantin Batygin and Mike Brown, from California Institute of Technology (Caltech) in Pasadena, predicted that an unidentified new planet existed in the outer Solar System. At the time Brown said, “This would be a real ninth planet. There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting.”

However, scientists have yet to spot this mysterious object only known as Planet Nine. The U-M research, led by Juliette Becker, a graduate student in the Department of Astronomy, consisted of a large set of computer simulations. Her research has shed more light on a certain space phenomena, known as Trans-Neptunian Objects (TNOs). TNOs exist beyond Neptune and orbit the Solar System. Becker analyzed hundreds of these TNOs. She has hypothesized that the TNOs behave and function the way they do in the Solar System due to the influence of Planet Nine.

Speaking about her research she noted, "From that set of simulations, we found out that there are preferred versions of Planet Nine that make the TNO stay stable for longer, so it basically increases the probability that our solar system exists the way it does. Through these computer simulations, we were able to determine which realization of Planet Nine creates our solar system—the whole caveat here being, if Planet Nine is real."

She added, “The ultimate goal would be to directly see Planet Nine—to take a telescope, point it at the sky, and see reflected light from the sun bouncing off of Planet Nine. Since we haven't yet been able to find it, despite many people looking, we're stuck with these kinds of indirect methods."

In each simulation, the team tested different scenarios for Planet 9 to study whether that version of the planet, complete with its gravitational forces, resulted in the same solar system that we have today.

Assessment

Our assessment is that it is still too early to definitively prove the existence of a ninth planet in the Solar System. However, as scientists continue to collate more data, the existence of the mysterious Planet Nine is looking more likely than ever.