In a recent article on astronomynow.com, one of Saturn’s many moons was found to carve a channel through its ring, causing waves as it passes through the icy particles. This notion got me thinking about the way particles in space act and their motion as compared to the motion of the planets in general.
As stated in the previous objective on the Heliocentric Model of our Solar System, we have learned in class that nobleman, Tycho Brahe, and his assistant, astronomer Johannes Kepler, confirmed that our solar system is indeed centered around the sun. In addition, Kepler found that, to better fit the data collected by Tycho, the orbits of the planets around the sun must be elliptical rather than perfectly circular. With his findings rooted in mathematics, Kepler came up with three laws to further explain his findings.
Kepler’s first law states that the orbit of each planet around the sun is an ellipse with the sun being at one focus. Taking the Earth for example, we have learned in a previous objective that in the Earth’s path around the Sun, the Earth passes closer to the Sun during the winter than in the summer. This fact could only be made possible if the orbit was elliptical, because a perfectly circular orbit would be equidistant at all times. The other planets in our solar system, such as Saturn, also follow this simple guideline of being elliptical. The article even specifically mentions an instance that Saturn is proven to have an elliptical orbit. When approaching its equinox, Saturn’s rings become inline with the Sun’s rays, which happens when the planet is at a specific point in its elliptical orbit that allows for the Sun to heat up a different side of its rings. If the planet were to have a circular orbit, the same instance would not happen.
Kepler’s second law states that a planet moves faster in the part of its orbit where it is nearer to the Sun and slower when it is farther from the Sun; However, when the time spent in orbit is the same, then the sweeping arc area near and far from the sun are equal. This law is best explained by a picture:
In this diagram, each arc section represents a months worth of time. As you can see, the planet moves most quickly when it is nearest to the sun, which is representative of part of Kepler’s second law. However, equally as important is that each sliver of the elliptical orbit from month to month is equal in area to one another. The sliver from July to August has the same amount of galactic pizza as the one from December to January. In relation to the article, Saturn’s moons also run a course that is rather elliptical, meaning they similarly experience the time and area coverage as the way described in Kepler’s second law.
Finally, Kepler’s third law states that the farther the planet is to the Sun, the slower its average speed. According to the article, Saturn’s orbit around the Sun takes about a whopping 30 Earth years, or get this, ONE SATURN YEAR. Revolutionary. In comparison to the Earth, it can be seen that, due to its great distance, the ringed planet does indeed follow its path much slower around our Sun because it takes more time to complete its orbit.
When completing this objective, I recall the Lecture-Tutorial we completed on Kepler’s Second Law. Back then, the idea of the Earth moving around the Sun faster when it was near it was completely new (it wasn’t until the beginning of the semester when I learned that the Earth comes closer to the Sun in January, blew my mind). At that moment in time, I never thought that I could fully grasp these concepts, not because they are hard, but rather because they are so niche and inapplicable. However, now when I look back at these objectives, I can see how far I’ve grown in understanding about space. As I progressed in this course, I started the piece together the astronomic puzzle of our universe. Nevertheless, there is still so much more I would hope to learn.