A team of researchers from the University of Tel Aviv have published a study in the Nature journal which aims to answer the long-debated question of the duration of a day on Saturn, setting a planet’s full rotation at 10 hours, 32 minutes and 45 seconds.
The result was attained by using NASA’s Cassini spacecraft to take measurements of the gas giant’s gravitational field, by observing how much it affected the spacecraft’s orbit. After also using data regarding the planet’s oblatement – which refers to how much does a planet start to distort around its equator while spinning – the researchers reached a theoretical model that provided them with the earlier quoted estimate of one full rotation on the planet.
The model was then applied to Jupiter, whose day-length is already established, and it provided the same result as known measurements, providing strong basis for the confirmation of the results.
“While an uncertainty of 15 minutes may appear small compared to the approximately 10.5-hour rotation of Saturn, it is actually important to know [the rotation] accurately. The rotation period has an important effect on understanding Saturn’s atmosphere dynamics and internal structure.” lead scientist and author study Ravit Helledtold Space.com via email.
Saturn’s rotation measurement is more difficult than those of other planets from the Solar System because it does not have a solid surface, and has very thick layers of atmosphere obtruding view to its planetary mass. This means that the tried-and-tested technique of observing the duration needed for a feature on the planet’s surface to reach back its initial point is obsolete in the ringed giant’s case.
The first measurement of a Saturn day was attained in 1981 by means of the Voyager 2 probe, which attained a 10 hours, 39 minutes and 22 seconds duration for a full spin, after making radio measurements of the gas giant’s magnetic field.
However, when the Cassini spacecraft arrived in 2004, it did the same type of measurement and yielded a different result, adding 8 minutes more to a Saturn day. This proved the unreliability of the radio measurement method. Alternative methods, such as tracking cloud movement in the gas giant’s atmosphere, proceeded to also give different results, adding to the debate of Saturn’s actual day-length.
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