The Importance of Planetary Rings as Astrophysical Laboratories
When someone mentions the planet Saturn, one of the first things that probably comes to mind is its rings. Whilst everyone would probably recognise them, fewer understand the range of astrophysical processes they can teach us. This was the focus of Phil Sutton’s talk, “The Importance of Planetary Rings as Astrophysical Laboratories,” held on Wednesday, 15th October, using Saturn as his primary example to demonstrate what these structures can teach us.
So, what exactly are planetary rings? Sutton explains they are simply a collection of particles orbiting in the same direction as their planet’s rotation. The key point is that each particle follows its own individual path. Images may mislead you to think Saturn’s rings are solid, but this illusion comes from how densely packed they are; the number of particles is similar to how many grains of sand are on Earth [1]! This explains why Saturn’s rings are visible from Earth, whilst rings around planets like Jupiter or Uranus were only more recently discovered when spacecrafts got close enough.
Since Saturn’s rings are visible, their circular and thin shape are widely known, but there are a couple reasons for this structure. Imagine walking in a crowded school corridor where everyone walks in the same direction; even if you tried to turn around and walk against the flow, you would end up being swept up by the amount of people and result to moving in the same direction as them. This is the same idea as if a particle tried to leave the orbit of the ring, the strong gravitational force at the equator plus the sheer number of collisions will always move the particle back into place, maintaining its famous shape.
Within the rings, embedded moons can be located orbiting Saturn, causing a gap at the point they reside, where some can even be seen with a telescope! This is because the particles are scattered due to the moon’s gravitational force, or if the moon isn’t big enough, it just causes a local disturbance. Sutton explains how we can measure the width and shape of these gaps to estimate the mass of unseen moons, with the gap width scaling with the mass of the moon. We can apply this principle on a larger scale when looking at protoplanetary disks (disks of gas orbiting a star where planets tend to form [2]), estimating the weight of planets that are causing gaps in their own disk. This is just one example that highlights the benefit of studying Saturn’s rings, so we can apply similar methods on systems that we cannot directly observe.
However, not only does observing Saturn’s rings teach us about the present, but it also uncovers the past. An example was offered during the seminar, where after a comet struck Jupiter in 1994. The impact caused vertical ripples in its rings, leading scientists to deduce a similar event must have happened over a decade before in another system in 1983, where similar ripples could be observed.
Sutton closed the seminar linking his current research on the first discovered exoplanet with a ring system [3], J1407b (catchy name!), to the observation of Saturn’s rings. It orbits the star J1407 and was found to have a ring system 200 times larger than Saturn’s. It was discovered through a light curve, which measures the brightness of a star overtime, as an abnormal amount of light was blocked from J1407 temporarily before the light passed through again, raising questions on what caused this.
Scientists discovered that this was caused by a huge ring system with many gaps, similar to Saturn’s. When modelling J1407b, scientists thought a moon might be causing one of the biggest gaps, but when they ran simulations, they decided that it would be difficult for a moon to form or survive there. This is because when it moves close to its star, the ring becomes unstable, which makes it a harsh environment for a moon to form, and would most likely pull it apart.
Overall, Saturn acts as a reference for studying these larger and complex systems due to its accessibility, helping scientists understand how ring systems form and change elsewhere.
[1] “Ask Astro: Why do Saturn’s rings look solid when they’re not?”, Astronomy, Oct. 11, 2021, [Online] Available: https://www.astronomy.com/science/ask-astro-why-do-saturns-rings-look-solid-when-theyre-not/
[2] “Protoplanetary Disk”, Springer Nature Link, 2011, [Online] Available: https://link.springer.com/rwe/10.1007/978-3-642-11274-4_1299
[3] “The story of J1407b, the first exoplanet discovered with a ring system like Saturn”, SkyatNightMagazine, Feb. 27 2024, [Online] Available: https://www.skyatnightmagazine.com/space-science/j1407b
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This report is well-structured and flows nicely. I like the double spacing between paragraphs as it breaks it down into manageable segments and allows for short reflection after each. The body of the report is accurate and demonstrates that you have understood the topic clearly with strong references to the key scientific points provided by Dr Sutton in the seminar.
The context of the report is established clearly at the beginning and as the reader I immediately began to picture Saturn and it’s rings in my mind. Connecting Saturn’s rings to the lesser-known ring systems of other planets takes the reader on a short journey to other parts of the solar system proving the link to wider astrophysical implications and this was hammered home by the information provided regarding the recently discovered ring system of an exoplanet. Also, a small nod to the humour regarding the naming convention of exoplanets!
The writing style is smooth, clear and concise and at no point did I feel there was any jargon used that I didn’t understand. The tone of the report is well-suited to an academic audience.
The conclusion you have ended the report with could be stronger, could more detailed comment be made as to what the information in the seminar could mean for future research in the field?
Your references are credible, relevant and recorded correctly in line with IEEE standards.
All in all, I enjoyed reading this report and it is an excellent piece of work. A little more detail included in your conclusions would finish it off strongly and perhaps pose questions to the reader that would generate further interest in the field.
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Following the 5 criterion of the module handbook:
The presentation of this blog is beautiful, all relevant information is included about the seminar and all grammar looks up to standard.
The take-home-message is captured nicely, the key example of Saturn and its relevance of understanding the deeper topics and examples like J1407b.
The context of the research topic is well covered.
The references of additional research were lay out comfortably. However, perhaps any direct quotes could’ve been outlined a bit more obviously, but no issues.
The writing style is definitely applicable to any one who has no previous mathematical/astrophysical knowledge and/or background.
Overall very good.