Undoubtedly, among the wonders of the solar system, Saturn’s angelic rings stand out as a fan favorite. In 1997, with its eye on the prize, the Cassini spacecraft embarked on a seven-year journey to Saturn on the mission to perform the most rigorous survey ever of the planet, its moons and, of course, those amazing rings.
Before the spacecraft dove into Saturn’s atmosphere in 2017, Cassini repeatedly flew between the planet and its rings while collecting a wealth of data. Now, using that data captured by the Langmuir probe on board, Planetary scientists have measured The visual depth of Saturn’s rings, albeit in an unconventional way. It is about a solar eclipse that the spacecraft “saw” during its flight. Here’s what that means.
First, it is important to know that the optical depth of a material is related to how far light travels through that material before it is absorbed or scattered. Visual depth is also related to how transparent an object is.
Related: Saturn’s rings shine in this James Webb Space Telescope image of the gas giant
Cassini, eclipse
Ph.D. Student George Zistoris of Lancaster University realized that there could be a relationship between the “solar eclipse” events witnessed by the spacecraft, referring to when the probe moves into the shadow behind Saturn or its rings, and the optical depth of the rings. If this is true, the transparency of Saturn’s rings would be directly present in the Cassini data.
“We use all available solar eclipses as seen from Cassini either by Saturn or its rings, which are the periods during which Cassini goes into the shadow of Saturn or its rings,” the study authors wrote.
It was already known that the Langmuir probe aboard Cassini was an instrument designed to measure the cold plasma — a mixture of low-energy ions and electrons — in Saturn’s magnetosphere. But because the probe itself was metallic in composition, when Cassini was in sunlight, the rays provided enough energy for the probe’s material to release some electrons in a process known as the photoelectric effect. Therefore, the probe was not only detecting electrons from the magnetosphere, but also electrons generated by the Sun’s collision with its metallic body.
Thus, the probe recorded significant changes in the electron data density as it moved in and out of the planet’s shadow and rings. Xystouris realized that these changes would be related to the amount of sunlight moving through each of Saturn’s rings, which would allow him to calculate the optical depth of the rings inversely.
“Ultimately, using the properties of the material from which the Langmuir probe was made, and the brightness of the Sun in the vicinity of Saturn, we were able to calculate the change in the number of photoelectrons per ring, and calculate the optical depth of Saturn’s rings.” He said In the current situation.
“We used an instrument used primarily for plasma measurements to measure a planetary feature, a unique use of the Langmuir probe, and our results agreed with studies that used high-resolution imagers to measure the transparency of the rings.” He added.
While Saturn’s main rings extend 140,000 km (about 87,000 miles) from the planet, the team found that the maximum thickness of the rings is only 1 km. The distinctive rings are also scheduled to disappear from Earth by 2025, tilting toward us in the next phase of Saturn’s 29-year orbit. But don’t worry, it won’t be out of stargazers’ telescopes for long. They should only be out for a few months.
The research was published in September in the journal Monthly Notices of the Royal Astronomical Society.
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