Titan Is Migrating Away From Saturn 100 Times Faster Than Previously Predicted

According to a study published in the journal Nature Astronomy, the orbit of Saturn's moon Titan is expanding at a rate about 100 times faster than expected. "The research suggests that Titan was born much closer to Saturn and migrated out to its current distance of 1.2 million kilometers (about 746,000 miles) over 4.5 billion years," reports Phys.Org. From the report: In the work detailed in the Nature Astronomy paper, two teams of researchers each used a different technique to measure Titan's orbit over a period of 10 years. One technique, called astrometry, produced precise measurements of Titan's position relative to background stars in images taken by the Cassini spacecraft. The other technique, radiometry, measured Cassini's velocity as it was affected by the gravitational influence of Titan. "By using two completely independent data sets -- astrometric and radiometric -- and two different methods of analysis, we obtained results that are in full agreement," says the study's first author, Valery Lainey formerly of JPL (which Caltech manages for NASA), now of Paris Observatory, PSL University. Lainey worked with the astrometry team. The results are also in agreement with a theory proposed in 2016 by Fuller, who predicted that Titan's migration rate would be much faster than standard tidal theories estimated. His theory notes that Titan is expected to gravitationally squeeze Saturn with a particular frequency that makes the planet oscillate strongly, similarly to how swinging your legs on a swing with the right timing can drive you higher and higher. This process of tidal forcing is called resonance locking. Fuller proposed that the high amplitude of Saturn's oscillation would dissipate a lot of energy, which in turn would cause Titan to migrate outward away from the planet at a faster rate than previously thought. Indeed, the observations both found that Titan is migrating away from Saturn at a rate of 11 centimeters per year, more than 100 times faster than previous theories predicted.

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