Saturn is one of the easiest planets to identify, with its rings and the tilt at which it spins. A new study has now given an explanation for both of these. The gas giant rotates at an angle of 26.7 degrees relative to its orbital plane. For long, astronomers have believed that the likely reason for the tilt was the influence of Neptune, which neighbours Saturn. In the new study, published in the journal Science, astronomers from the Massachusetts Institute of Technology (MIT) and other institutions have proposed that the cause is actually a missing moon. Saturn and Neptune may have interacted gravitationally once, but the authors believe that this is no longer the case.
Saturn Once Had 84 Moons
Saturn has 83 moons today, and the study proposes that it once had 84. The authors have named the missing moon ‘Chrysalis’. Their modelling study looks at what might have happened to Chrysalis, leading to Saturn’s present tilt and the rings around it.
When Chrysalis was orbiting Saturn, their interactions kept the planet’s tilt in sync with Neptune. But around 160 million years ago, Chrysalis came too close to Saturn and was pulled apart. As a result of losing Chrysalis, the modelling showed, Saturn was taken away from Neptune’s influence, which gave it the tilt that we observe today.
Meanwhile, Chrysalis was shattered and most of it made an impact with Saturn. But some of its fragments could have remained in orbit, the study proposes. These broke into small chunks and formed part of Saturn’s rings.
“Just like a butterfly’s chrysalis, this satellite was long dormant and suddenly became active, and the rings emerged,” a statement on the MIT website quoted Jack Wisdom, lead author of the study, as saying.
The idea that Saturn’s tilt is a result of Neptune’s influence was first proposed by scientists In the early 2000s. But when NASA’s Cassini spacecraft orbited Saturn during 2004-17, it found that Saturn’s largest moon, Titan, was moving away from Saturn at a rate of 11 cm per year, which was faster than expected. This led to the theory that Titan was likely responsible for Saturn’s tilt and keeping Saturn in sync with Neptune.
Saturn And Neptune May Once Have Been In Sync
In the new study, using data from some of Cassini’s observations, the team calculated a physical property of Saturn, known as the moment of inertia. This calculation showed that Saturn was not in resonance with Neptune, but close. This suggested that the two planets may have once been in sync, but not any longer.
So, how did Saturn go out of sync? The team first carried out simulations to figure out how the interactions between Saturn and its moons evolved over time. They reasoned that if one moon were removed, it could affect the planet’s dynamics. From there, they calculated the size of Chrysalis, and the fate it met.