Saturn's rings gave scientists the information they needed to finally determine how long a day the gas giant lasts.
Credit: NASA / JPL-Caltech / Institute of Space Sciences
Schedule your timers for 10 hours, 33 minutes and 38 seconds: Scientists have finally discovered how long a Saturn day lasts, discovering a lingering mystery about the ringed gas giant.
According to the recently published research that uses the data collected by NASA's Cbadini mission before the destruction of the spacecraft in September 2017. The new calculation eliminates several minutes of previous estimates for Saturn's day, which the Scientists have been performing for decades based on data from the Cbadini mission. and its predecessor, Voyager.
"The researchers used ripples in the rings to observe the interior of Saturn, and they brought out this fundamental and sought-after feature of the planet, and it's a really solid result," scientist Linda Spilker of the Cbadini Project said in a statement. "The rings sustained the answer." [In Photos: Cbadini Mission Ends with Epic Dive into Saturn]
It may seem that it should be easy to measure the duration of a day on a planet; just wait and watch how the world turns. But the exact duration of Saturn's day has perplexed scientists for decades. Because the planet is a gas giant, researchers can not observe stable landmarks through the clouds, as they could with a rocky planet.
Scientists also often use the inclination of a planet's magnetic field to measure the length of the day. But that did not work for Saturn, because the field aligns almost perfectly with the axis of rotation of the planet, hampering its calculations. A scientist who has studied the magnetic field of the planet said that the uncertainty throughout the day is "a bit shameful", in an interview with Space.com about the research published in October.
These challenges left scientists with rough estimates that fall between 10 hours, 36 minutes and 10 hours, 48 minutes, which is not particularly satisfactory.
The research published today took a completely different approach: to look not at the planet itself, but at its delicate rings. This idea was proposed in 1982, but not until the Cbadini mission made the scientists have the data to see if the technique would work.
The idea is that as Saturn rotates, its interior bobs a little, causing small changes in the gravitational field of the planet. Those small changes extend to the pieces of ice in the rings that decorate the gas giant, causing small waves in the rings.
"The particles along the rings can not help feeling these oscillations in the field of gravity," said lead author Christopher Mankovich, a graduate student in astronomy at the University of California, Santa Cruz, in a statement. "At specific locations in the rings, these oscillations trap the ring particles at the right moment in their orbits to accumulate energy gradually, and that energy is carried as an observable wave."
Therefore, Mankovich and his colleagues studied those observable waves and used them to retreat into the interior of the planet. This is how the researchers achieved the measurement of 10 hours, 33 minutes and 38 seconds. It is not yet written in stone: the error bars in that calculation extend between one minute and 52 seconds and one minute and 19 seconds more. But the range of the new calculation overcomes a window of 12 minutes.
The research is described in an article published yesterday (January 17) in The Astrophysical Journal.