Israeli Scientists Accurately Determine The Length Of A Day On Saturn

A team of Israeli scientists from Tel Aviv University and the Weizmann Institute of Science in Rehovot have finally figured out how long a day lasts on Saturn. The team published a paper in Nature journal this past Wednesday.

The team includes Dr. Ravit Helled, a senior lecturer in planetary sciences at TAU, as well as having been involved in projects with the US National Aeronautics and Space Administration. She’s also worked with the European Space Agency, including the Cassini Solstice Mission with Saturn, and NASA’s upcoming Juno mission to Jupiter in 2016 and their JUNICE project due for 2022. Dr. Eli Galanti and Dr. Yohai Caspi of the Weizmann Institute were also involved in the project.

Figuring out the length of a day on a planet would seem simple enough, using physical measurement to determine a clear amount of time it takes for a full rotation. However for certain planets, Saturn included, it’s more complicated than that. Regardless, the Israeli team has now come up with an accurate way to determine how long a day on the planet really is, and that their technique could be used to determine day length on other planets.

“Since Saturn is composed of gas, it does not have a stable surface, so one can’t determine the time of its rotation in the same way solid planets are measured,” explained Helled in an interview with The Jerusalem Post. “The conventional technique for solid planets is to choose an identifying sign on the surface and measure the amount of time that passes until it is seen again. In addition, the gases are always covered by a layer of clouds which makes the measurement even more difficult.”

“According to Voyager 2 observations,” Helled continued, “the time it takes for Saturn to make a complete rotation is 10 hours, 39 minutes and 22 seconds, and this has been regarded as accurate for the last three decades - until the measurements from the Cassini spacecraft, which entered the path around Saturn in 2004 and found the measurement technique of Voyage 2 was not accurate. The puzzle of Saturn’s day was reopened.”

Voyager 2 was a 1977 NASA project which launched the spacecraft to different planets in the solar system. Information was gathered from Saturn, Jupiter, Uranus and Neptune in the hopes of better understanding them, and the passing of time on those planets.

Using a technique called “statistical optimization,” they were able to more accurately determine the length of a day on Saturn based on the planet’s gravitational field, density of the material, and it’s shape. They determined that a day on Saturn lasts 10 hours, 32 minutes and 45 seconds. To test for accuracy they used the technique on Jupiter where their results matched the already discovered figures.

“Our findings have broad significance, way beyond the solution of an interesting puzzle,” Helled continued. “First, the rotation time has a strong effect on winds and the weather over Saturn. And maybe more important, in our previous study, we find a gap of seven minutes in the rotation that has major implications on the study of the internal structure of the planet. One can reach important conclusions on how Saturn was formed, as well as other giant masses of gas, and the conditions that existed there when it formed. The information adds an important pillar to research into the development of our solar system and other systems in the galaxy.”

Helled and her team are currently planning to use their statistical optimization technique for other planets, including gas giants Uranus and Neptune, as well as other solar systems.