Titan_is_migrating_away_from_Saturn

Saturn is the second largest planet in the solar system, formed approximately 4.5 billion years ago. But the idea of development its ring and moons is not quite clear to the scientists. Presently 82 moons are orbiting the planet.

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Among these 82 moons, Titan is the largest natural satellite of Saturn, which is even larger than planet Mercury. It is about 1.2 billion kilometres (or 7,59,000 miles) away from Saturn. But this distance is gradually increasing as Titan is rapidly drifting away from Saturn 100 times faster than previously presumed, which is mentioned as “orbital expansion of Titan” by scientists.

True_colour_image_of_Titan-Study_Probe

True colour image of Titan. The thick atmosphere is full of dense organonitrogen, for which it looks orange | Image Courtesy : NASA


It is important to note that Titan is the only known natural satellite in our solar system which consists of its own atmosphere, and the only celestial body which might have existence of rivers and lakes on its surface like that of the Earth.

A newly concluded study, entitled as ‘Resonance locking in giant planets indicated by the rapid orbital expansion of Titan’, reveals this fact. Valéry Lainey, the lead author, in collaboration with other researchers, discovered this outward migration of Titan. The study has been published in the journal Nature Astronomy, on 8th June 2020.

Why and how is it happening?

Not only Titan, but actually almost all the moons of our solar system are migrating away from their planets, even the planets are also drifting away from the sun in considerably slow pace. However, the mechanism of this drifting of moons is known as ‘tidal acceleration’.

The phenomenon of tidal friction is the key to the mechanism of tidal acceleration. If we discuss this phenomenon in terms of earth and moon, then the matter will be better understandable to us.

The gravitational tugging of moon on the planet causes the tide and ebb to the oceans (mainly water bodies, and sometimes slightly to the earth surface) of the earth. This results to the conversion of earth's rotational energy to frictional heat, which consequences to a gap on the Earth's rotation. Henceforth, this frictional energy is necessary to this tidal bulge on the ocean surface on the  earth, and this swelling or deforming is slightly ahead of moon, as Earth's orbital speed is faster than that of the moon. All these result to the pervert the gravitational field of the Earth, that creates an additional tug on the moon. Which, in face, yielding the moon to chronologically migrating away from Earth, at a pace of about 1.5 inches (or 3.82 centimetres) each year.

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The same mechanism is playing the role in the case of Titan's outward migration from Saturn. Titan's gravitational tugging on Saturn generates a temporary swelling in the planet and the energy is pushing back Titan further away. But researchers speculate that the friction might not be so obvious as Saturn is gaseous, not consists of hard rocks and water bodies like the Earth.

Scientists have got the stunning result that Titan is migrating away from Saturn at a rate of almost 11 centimetres (or 4.33 inches) per year. Though it looks like very slow, but on cosmic timescale, it is drifting away at a rapid pace.

They used astrometry and radiometry to obtain datasets from NASA's Cassini-Huygens mission to Saturn. Valéry Lainey, from Observatorie de Paris, stated,

By using two completely independent datasets- astrometric and radiometric- and two totally different methods of analysis, we obtained the results that are in full agreement.

All these reveal that planetary system of Saturn is expanding along with the whole solar system as well.

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