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Rings of Saturn

QUESTION: With what material are Saturn's rings made up of?

David Jayaprakash, Pondicherry

ANSWER: The rings around Saturn were first identified by astronomer Gallileo Gallilee in 1610. It was, however, Dutch Physicist Christian Huygens, who in 1659, recognised them as a broad, flat, thin ring, separated from the body of the planet.

In 1675, the Italian Astronomer G. D. Cassini identified two rings around it.

Until 1969, it was believed that there were just three rings around Saturn "A", "B" and "C"&151; "A" being the outermost and "C", close to the planet. In 1969, the fourth ring was discovered by Pierre Guorin and soon, another one was also identified.

Pioneer Satellite Data (1971) had indicated that there was one more ring ("F").French Astronomer, Edourd Albert Roche in 1849 postulated that the rings were the remnants of a satellite that strayed too close to Saturn and due to which reason, disintegrated. His theory was that, if a satellite approaches its primary, closer than a certain distance (known as "Roche Limit''&151; 2.44 times the radius of the planet), the satellite would break up and the broken pieces would gradually get distributed around the planet in a circular path.

The distance of the rings of Saturn are within the "Roche limit''. This would suggest that the rings are the remnants of a disintegrated satellite only.

The present thinking is that the rings are made up of countless small objects (varying in size from very small grains to small chunks of rocky material, covered by ice) and that each revolves around Saturn in its own orbit like a satellite.

That the rings contain particulate matter has been confirmed by the fact that Rings "A'' and "C'' exhibit certain transparency due to which, the body of Saturn could be seen through them, as also the light from the stars.

Furthermore, the satellites of Saturn are not completely eclipsed too, when they pass into the shadow of the rings. Very little information is available as to the precise composition of the matter in the rings. As per the observations of C. P. Kupier (1952), the Infra Red Spectrum is similar to the reflection spectrum of hoar-frost.

It quite likely that these particles must have been of much bigger size earlier (even some metres in diameter), but there might have been a continuous reduction in their sizes due to their abrasion with objects like the meteoroids.

Scientists are of the view that the continuous erosion may ultimately (at a far distant future) result in the rings slowly vanishing for ever!

K. Ramamurthy,

Bangalore

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