The Importance of Planetary Ring Systems as Astrophysical Laboratories
Seminar Title: The Importance of Planetary Ring Systems as Astrophysical Laboratories
Speaker: Dr. Phil Sutton
Date: 15 October 2025
Looking back to your younger self (and maybe today too), the words “space” and “planet” both create a mental image of Saturn with its rings. However, Saturn isn’t the only planet in our solar system with rings - as Jupiter, Uranus, and Neptune also have less noticeable ones too. You might have always wondered: why do these planets come with rings? Are they getting married? Or is it just for decoration?
Saturn is a familiar example with its infamously noticeable rings, but why? The seminar explains that they’re “classed as dense rings” and are the “most studied” [1], so no wonder we’re all familiar with it! So, what are these “rings” made up of?
Imagine an exciting assortment of particles, each with its own unique shape and size ranging from 1 30 m, orbiting Saturn in the same direction as its rotation extending up to a whopping 140,000 km radially outwards whilst only being ~30 m high [1]. Wait, doesn’t that mean the further out the particle, the slower it moves and vice versa? This is known as the Keplerian Shear, where the inner part of the ring orbits faster than its outer bits [2]. Shear is everywhere in our natural world: picture a river where its middle bit flows faster than its edges by almost cutting through its flow. More generally, think of shearing as anything quickly sliding through a slower something else. This evidently creates more friction, due to more particles colliding with each other. As such, these collisions create the very flat-looking, circular, disc-like proportion that we envision these rings with.
If you have an eye for detail, your mental image of Saturn might consist of rings with many gaps. Within and near these gaps exist some of Saturn’s “shepherd” moons like Daphnis (8 km diameter) inside the Keeler gap (42 km wide), and their gravitational force tugs on nearby ring particles. This confines them into narrow bands by clearing out gaps entirely. A famous example is the Cassini Division, a large gap between Saturn’s A and B rings, formed by the moon Mimas because it “orbits once for every 2 orbits of a ring particle at the location” this is known as a 2:1 orbital resonance [3]. Visualise a child on a playground swing: if you give it a small push each time at the right time, then each swing gets longer. This is analogous to those resonant locations, where repeated gravitational pushes add up over time, destabilising particle orbits and effectively sweeping the region clean. You can even investigate which moon is responsible for which resonant feature: you just need to find the locations and the ratios of the different times they take to orbit!
Going beyond our own solar system, an exoplanet named “J1407b” has 20 times more mass than Jupiter [1], and its rings (which also have gaps) are 200 times larger than Saturn’s! So does that mean there are exomoons creating those gaps? This brings us to the current, cutting-edge research in this field, which will shape the future research of exoplanets with rings. Who knows, perhaps you might be the one discovering one in the future
References:
[1] P. Sutton, “The Importance of Planetary Ring Systems as Astrophysical Laboratories,” University of Lincoln, Lincoln, 2025.
[2] J. C. Maxwell, “On the Stability of the Motion of Saturn’s Rings,” Monthly Notices of the Royal Astronomical Society, vol. 19, no. 8, p. 297304, 10 June 1859.
[3] C. D. Murray and S. F. Dermott, Solar System Dynamics, Cambridge, UK: Cambridge University Press, 1999.
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1, Blogs overall presentation: The blog does include the date title and name of speaker throughout which is well done, the grammar is also well done throoughout the blog. 3/3
2, Accuracy of reporting the seminars take home message: The message that Phil was trying to convey throughout the seminar has been conveyed well through this blog and is shown excellently through each section.
3, Accuracy of contextualisation for the research: Throughout the blog there has been well thought through research context and at the end you touch upon the social context as well. 3/3
4, Additional research and use of external sources: There is additional research present throughout the blog which shows a wider reading and draws upon other sources however there needs to be one direct quote throughout and this hasn’t been done. 2/3
5, Writing style and level for audience: The blog is written in a way that is easy to read and is very helpful for people with limited knowledge about the topic. 3/3
Overall 14/15, this is a very well writen blog and is very informative, just needs a direct quote from a source.
42890
The content is accurate and engaging. You have listed external sources and it is understandable for audiences without a science background. You clearly understand the topic well.