Using eclipses to calculate the transparency of Saturn’s rings

A Lancaster College Ph.D. pupil has measured the optical depth of Saturn’s rings utilizing a brand new technique based mostly on how a lot daylight reached the Cassini spacecraft whereas it was within the shadow of the rings.

The optical depth is related to the transparency of an object, and it reveals how far gentle can journey by means of that object earlier than it will get absorbed or scattered.

The analysis, led by Lancaster College in collaboration with the Swedish Institute of House Physics, is revealed within the Month-to-month Notices of the Royal Astronomical Society.

The NASA-ESA Cassini spacecraft was launched in 1997 and reached Saturn in 2004, finishing up essentially the most intensive survey of the planet and its moons so far. The mission led to 2017 when Cassini plunged into the Saturnian environment, after diving 22 instances between the planet and its rings.

Lancaster College Ph.D. pupil George Xystouris, underneath the supervision of Dr. Chris Arridge, analyzed historic knowledge from the Langmuir Probe on board Cassini, an instrument that was measuring the cold plasma, i.e., low power ions and electrons, within the magnetosphere of Saturn.

For his or her research they targeted on solar eclipses of the spacecraft: durations the place Cassini was within the shadow of Saturn or the principle rings. Throughout every eclipse, the Langmuir Probe recorded dramatic adjustments within the knowledge.

George stated, “Because the probe is metallic, at any time when it’s sunlit, the daylight can provide sufficient power to the probe to launch electrons. That is the photoelectric effect, and the electrons which might be launched are so-called ‘photoelectrons. They’ll create issues although, as they’ve the identical properties because the electrons within the chilly plasma round Saturn and there may be not a simple technique to separate the 2.”

“Specializing in the information variations we realized that they have been related with how a lot daylight every ring would enable to cross. Ultimately, utilizing the properties of the fabric that the Langmuir Probe was made from, and the way vivid the sun was in Saturn’s neighborhood, we managed to calculate the change within the photoelectrons quantity for every ring, and calculate Saturn’s rings optical depth.

“This was a novel and thrilling consequence! We used an instrument that’s primarily used for plasma measurements to measure a planetary characteristic, which is a novel use of the Langmuir Probe, and our outcomes agreed with research that used high-resolution imagers to measure the transparency of the rings.”

Τhe most important rings, which prolong as much as 140,000 km from the planet, however have a most thickness of solely 1km, are to vanish from view from Earth by 2025. In that yr the rings can be tilted edge-on to Earth, making it nearly not possible to view them. They may tilt again in direction of Earth through the subsequent phase of Saturn’s 29-year orbit and can proceed to develop into extra seen and brighter till 2032.

Professor Mike Edmunds, the President of the Royal Astronomical Society, added, “It’s all the time good to see a postgraduate pupil concerned in utilizing space probe instrumentation in an uncommon and creative manner. Innovation of this type is simply what is required in astronomical research—and an method which many former college students who’re in quite a lot of careers are making use of to assist tackle the world’s issues.”