Students enter the classroom in their neatly-pressed school robes. Their hairstyles are remarkably well-done tonight, especially given that this is a 10pm class. At the front of the room, Professor Turing is being handed a magical astronomy publication by Janvier Mathieu, the guest speaker. After a few minutes of talking with Mathieu, Professor Turing checks his timepiece and then turns to the class.
Good evening, students! As I have mentioned, today’s lesson and next week’s lesson will be rather busy. I will quickly complete the Martian example, and then I will turn the floor over to Janvier Mathieu, our guest speaker.
Extended Example: Martian Moons, Part Two
Another View of Phobos
Image Source: NASA
Let us briefly talk about the magical effect that Phobos and Deimos have on Mars. Like the Earth’s Moon, both Phobos and Deimos reflect magical energy from the Sun onto the surface of their host planet. Because the moons are tidally locked to Mars, it is easy to predict the amount of magical energy that is reflected from the faces of each of the moons. However, predicting the amount of magic reflected onto Mars by its moons is slightly more complex than computing how much magic the Moon reflects onto the Earth - each of the two moons has phases, and both of the two moons orbit at different periods.
Of the two moons, Phobos - being the larger and closer one to Mars - will have a larger magical impact on Mars than Deimos will. However, there are times when an observer on Mars may experience an occultation. Due to the different orbital periods, Deimos may be occulted by Phobos. When this happens, this will form a powerful syzygy that strengthens magic.
In summary - yes, the moons of Mars have a magical effect on Mars. However, due to the fact that the planet has two moons, the magic effects may be slightly harder to predict.
Janvier Mathieu: Shepherd Moons of Saturn
Our featured portion of today’s class is a guest lecture by Janvier Mathieu. Mathieu, a renowned French Magical Astronomer, will discuss the importance of Saturn’s Shepherd Moons and how they build and maintain the rings of Saturn - which can, in turn, be used for magical applications. She will also give a hint on how Magical Astronomers use the location of these Shepherd Moons to their advantage.
As a graduate student of Magical Astronomy, I often see Mathieu’s work published in academic publications regarding Magical Astronomy; I have also seen Mathieu present at a conference. Her research is groundbreaking and innovative, and her passion, intelligence, and love for students is beyond compare. As I mentioned last lesson, Mathieu’s work inspired me to study magical astronomy. I am so honored to have Mathieu speak in my classroom today.
Let us give a warm Hogwarts welcome to Dr. Janvier Mathieu.
While the moons of Saturn play significant roles in the planetary system of the planet, they also are a vital aspect in maintaining the most well know and striking feature of the planet, the magnificent rings! Of the 62 fascinating moons, I would like to draw your attention to five in particular, known as Shepherd Moons.
Shepherd moons are those which orbit between or around the rings, using their gravitational influence to help shape, or "shepherd" the rings into the perfect orbits that we recognise. These moons prevent the individual rocks and particles which make up the ring system from drifting off into an unorganized mess, and help to keep the rings separated into their individual paths.
Ushering the A ring (the ring closest to the planet) is Atlas! Atlas resides close to the inner edge of the A ring, orbiting between it and the planet itself. It is believed to have a more erratic orbit due to strong influences by some of the larger moons orbiting nearby.
Around the F ring (the furthest ring from the planet) we can see two misshapen moons, Prometheus and Pandora! These two heavily cratered bodies orbit on either side of the F ring, constantly pushing and pulling upon it through gravitational forces, making it the most active ring in the system. Similar to Atlas, they have quite irregular orbits, due largely to their close proximity to the rings (which exert a gravitational pull on them as much as they do on the rings in return) and other nearby, larger moons. Despite wobbling in their orbits, they always stay close to the F ring acting as its guardians.
Prometheus (inside) and Pandora (outside) Shepherding the thin F Ring of Saturn.
Image Source: NASA
The two remaining shepherd moons act a bit differently. Instead of ensuring rings stay in place and maintain their shape, they cause gaps within the largest ring, the A ring. Pan is responsible for the Encke Gap within the ring, while Daphnis is the cause of the Keeler Gap. These moons were likely once part of the debris comprising the A ring which has been pulled together over time by gravitational forces to form the small moons. Because of their increasing size, further debris was attracted to them during their orbits, leaving their orbital plane devoid of further particles and causing the gaps we are able to observe.
When considering the strength and ability of the magic being harnessed from the ring system, it is important that you take the position of these moons into consideration. When using magical forces from the rings, consult a planet chart to determine the current location of these shepherd moons. When two moons are near one another, on opposite sides of a ring (such as Prometheus and Pandora in the previous picture), it can help amplify the magic being projected from that ring. In opposition, if the moons have moved to the far side of the ring or only one moon is present, the gravitational influence on the ring can warp it out of shape and diminish the quality of the magic.
Let us thank Janvier Mathieu again for her insights into the Shepherd Moons of Saturn. While harnessing the magic of Saturn’s rings is a concept of advanced Magical Astronomy, Mathieu’s discussion shows the many different and exciting possibilities that are available to those who develop their skills in Magical Astronomy.
Thank you again for your time. See you next lesson!