Titan Drifts Away from Saturn by About 11 Centimeters Per Year
takyon writes in with a story which was slightly augmented to become:
Saturn's Moon Titan Drifting Away Faster Than Previously Thought
Just as our own Moon floats away from Earth a tiny bit more each year, other moons are doing the same with their host planets. As a moon orbits, its gravity pulls on the planet, causing a temporary bulge in the planet as it passes.
Over time, the energy created by the bulging and subsiding transfers from the planet to the moon, nudging it farther and farther out. Our Moon drifts 1.5 inches (3.8 centimeters) from Earth each year.[*]
Scientists thought they knew the rate at which the giant moon Titan is moving away from Saturn, but they recently made a surprising discovery: Using data from NASA's Cassini spacecraft, they found Titan drifting a hundred times faster than previously understood - about 4 inches (11 centimeters) per year.
The findings may help address an age-old question. While scientists know that Saturn formed 4.6 billion years ago in the early days of the solar system, there's more uncertainty about when the planet's rings and its system of more than 80 moons formed. Titan is currently 759,000 miles (1.2 million kilometers) from Saturn. The revised rate of its drift suggests that the moon started out much closer to Saturn, which would mean the whole system expanded more quickly than previously believed.
"This result brings an important new piece of the puzzle for the highly debated question of the age of the Saturn system and how its moons formed," said Valery Lainey, lead author of the work published June 8 in Nature Astronomy. He conducted the research as a scientist at NASA's Jet Propulsion Laboratory in Southern California before joining the Paris Observatory at PSL University.
cf: tidal acceleration:
Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon), and the primary planet that it orbits (e.g. Earth). The acceleration causes a gradual recession of a satellite in a prograde orbit away from the primary, and a corresponding slowdown of the primary's rotation. The process eventually leads to tidal locking, usually of the smaller first, and later the larger body. The Earth-Moon system is the best-studied case.
Journal Reference:
Valery Lainey, Luis Gomez Casajus, Jim Fuller, et al. Resonance locking in giant planets indicated by the rapid orbital expansion of Titan, Nature Astronomy (DOI: 10.1038/s41550-020-1120-5)
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