When astronomers measure the rotation speed of planets, like the Earth, it is an elementary task. To do this, they see how long it takes for a certain point on the surface to come into view again. Though, the gas giants in the Solar System, like Jupiter and Saturn, are a little more difficult for planetary scientists, due to their lack of a solid surface. This hinders direct visual observations by space telescopes. Saturn presents an even greater challenge. Different areas on Saturn are known to rotate at various speeds. Atmospheric currents on the bulbous hydrogen and helium gas giant rise and fall, creating makeshift weather patterns on the planet. Therefore, Saturn has a precarious speed, unlike the Earth, which rotates on an axis and has aligned magnetic poles.
A new study published in the most recent issue of the journal Nature, proposes a new way to identify Saturn’s rotation period, offering new information into the inner structure, atmospheric patterns, and how the planet formed. Dr. Ravit Helled, a researcher at Tel Aviv University, along with a team of scientists, stated their new method has measured the planet’s gravitational field and axis, which was found that its north to south axis is longer than its east to west axis. The team discovered that one day on Saturn is the Earth equivalent of 10 hours, 32 minutes, and 44 seconds. When they applied their method to measure Jupiter’s rotation period, they arrived at an identical conclusion. Thus, realizing the accuracy and consistency of the method.
For the last few decades, scientists have had problems calculating the exact measurement of Saturn’s rotation. The accepted rate previous to this study, measured by Voyager 2 in the 1980s, was 10 hours, 39 minutes, and 22 seconds. Dr. Helled stated when the Cassini probe passed by Saturn three decades later, the measured rotation period was eight minutes longer – giving Saturn a precarious rotational quality. Though, it has now been discovered that the rotation period of the gas giant cannot be surmised from fluctuations in radio wavelength measurements linked to the planet’s magnetic field, considering it is different than others.
Since these findings came out, scientists have been hard at work trying to find the best way to calculate the planet’s rotation. Helled stated the best way to do this is based on a statistical optimization method, involving the reproduction of Saturn’s observed properties, its gravity and mass, juxtaposed with the best correlation of rotation period. By doing this, Helled’s team accurately calculated that the rotational period of Saturn is 10 hours, 32 minutes and 44 seconds.
Without this new method, finding the rotational period for a planet like Saturn would be daft, considering the mass of a solid, rocky surface affects planetary rotation, thus giving it a more stable quality. Therefore, this narrows the margin of error when looking at gaseous bodies. Researchers now hope to apply the same method to other gas giants in the Solar System, such as Uranus and Neptune. Moreover, this could be applied to hitherto precarious planets similar to Saturn found throughout the Milky Way Galaxy and further into the cosmos.
By Alex Lemieux
Photo by Kabsik Park – Flickr License