Jupiter is the closest, boasting an obliquity (tilt) of simply 3.12 degrees. Saturns tilt is more severe yet, with an obliquity of 26.73 degrees (though its no place near as extreme as Uranus, which is almost sideways, spinning at a 97.86-degree angle to its orbital aircraft).
We know, for example, from geological evidence collected throughout the Apollo objectives, that Earths tilt was most likely the outcome of massive impacts with other rocky objects early in the planets history, the largest of which broke off and formed our Moon. According to this model, the culprit accountable for Saturns tilt was Neptune, which pulled the ringed giant over as it swept out towards the Kuiper belt (in fact, evidence from the Cassini mission showed that Saturns rings are relatively new: they probably werent around throughout the excellent migration. They suggest instead that a migration of Titan in the current past (about 1 billion years ago) is equally capable of explaining the tilt Saturn has today.
We understand, for instance, from geological evidence collected throughout the Apollo missions, that Earths tilt was likely the outcome of massive impacts with other rocky objects early in the worlds history, the biggest of which broke off and formed our Moon. Simply as archeologists examine clay pots and pieces of bone to piece together ancient cultures, physicists can take a look at planetary tilts to understand the Solar Systems past. Modern-day wobbles are evidence of dramatic occasions long earlier. Or, as a new paper recommends, perhaps not-so-long-ago.
A team of researchers from the Paris Observatory and the University of Pisa, led by Melaine Saillenfest, recommend that the origin of Saturns tilt may be much more recent than previously thought, which its biggest moon, Titan, may be to blame.
Astronomers traditionally thought that Saturns tilt had nothing to do with its moons, however rather more to do with interactions in between it and its fellow gas giants. One mainstream theory of solar system formation, referred to as the Nice design, recommends that about four billion years back, a great migration took place in which the giant worlds moved slowly outwards, under the gravitational influence of each other and smaller planetesimals.
Graphic by James ODonoghue (with images from NASA), showing the axial tilt of the worlds.
According to this design, the culprit responsible for Saturns tilt was Neptune, which yanked the ringed giant over as it swept out towards the Kuiper belt (in fact, proof from the Cassini objective revealed that Saturns rings are fairly new: they most likely werent around during the great migration. However I digress). If the Nice model is to be believed, planetary obliquities were set in stone a long period of time back, and have actually stayed fairly stable considering that.
The new theory proposed by Saillenfest and the team disagrees. They recommend rather that a migration of Titan in the current past (about 1 billion years ago) is equally capable of discussing the tilt Saturn has today. Titans orbit might have remained regular for billions of years, however their design shows that an orbital resonance with Saturn could have happened recently, at the same time altering the moons orbit and requiring a nearly upright Saturn to fall sideways.
Titan passes in front of Saturn, as seen by the Cassini Spacecraft on June 8, 2015. Credit: NASA/JPL-Caltech/Space Science Institute.
Its difficult to be sure which model is proper without more evidence (maybe the upcoming Dragonfly objective to Titan can turn up something). However the possibility of such a current migration opens up possibilities for future modifications to the Solar System. As the researchers put it, the obliquities of giant worlds “are not settled once for all, however constantly progress as a result of the migration of their satellites.” The Solar System as we understand it today may not be as constant or stable as it seems, and might remain in for future disruptions to come (though I would not lose sleep over it– not for a billion years approximately).
Saillenfest and coauthors Giacomo Lari and Gwenaël Boué published their paper in Nature Astronomy earlier this year.
Resources:
Melaine Saillenfest, Giacomo Lari and Gwenaël Boué “The big obliquity of Saturn described by the quick migration of Titan.” Nature Astronomy.
Manuscript available at: https://arxiv.org/abs/2110.04104.
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Huge planets like Saturn dont simply tilt over all on their own: something has to knock them over, or pull on them gravitationally, to push them off axis. Researchers anticipate that when brand-new worlds are born, they form with almost no tilt at all, lining up like spinning tops, with their equators level to the orbital aircraft in which they circle their sun.
Jupiter is the closest, boasting an obliquity (tilt) of just 3.12 degrees. Saturns tilt is more extreme yet, with an obliquity of 26.73 degrees (though its no place near as severe as Uranus, which is practically sideways, spinning at a 97.86-degree angle to its orbital plane).
We can find out a lot from these obliquities.
