Astronomy Year 1 Notes
My notes from Astronomy Year 1 to help anyone struggling with the class.
For any further questions, feel free to message me as I'm always happy to help
Last Updated
05/31/21
Chapters
12
Reads
2,384
Saturn
Chapter 9
- Saturn is ten times further away from than the sun than Earth is.
- Saturn is the sixth planet, and for a long time was though to be the last one.
- Saturn is a gas giant
- Saturn is named after the Roman God of Agriculture
- Observers identify Saturn by it's rings
- One day on Saturn is approx. Earth 10.5 hours
- One year on Saturn is 29 Earth years
Better Put a Ring on It!
In 1610 Galileo first spotted Saturn’s rings, but they appeared to him only as oddly shaped bumps on the planet, so he was unsure exactly what he was seeing. One of his speculations was that they might have even been some kind of triple planet configuration.
It was not until 1655 that the Dutch astronomer Christian Huygens recognized the bump as a clear, flat ring running all the way around the planet.
The two hypotheses of the origin of these rings are that the rings are either the remains of a destroyed moon of Saturn or that they are remnant material from Saturn’s formation as a planet.
Astronomers found that Saturn has four broader main ring groups and three smaller, narrower ring groups that run around the planet equatorially.
In 1980 and 1981, Voyager flyby observations confirmed that, beyond these major ring groups, Saturn’s rings are actually composed of over 10,000 narrow ringlets. As Saturn has a similar axial tilt to Earth, this means that as the planet orbits around the Sun, our view of Saturn’s rings changes as the planet is viewed tilting towards and then away from the Sun.
All Jovian planets (the four planets beyond the Asteroid Belt) have ring systems Saturn's just happens to be the most apparent.
It took astronomers quite some time to figure out what the rings are actually made of. s the rings reflect over 80 percent of the sunlight that hits them, it was thought that the primary composition of the rings was likely ice. Exploration and observation in the 1970s proved this to be true, and later research done by the Voyager and Cassini studies found that most of the particles that make up the rings have a large range, from millimeters to several meters. However, most of the particles are approximately the size and have similar composition to a large snowball on Earth.
The bands are not, in fact, completely continuous from the most inner to outer band.
Gaps appear in regions where moons and moonlets are present, their orbits clearing the area through which they move as they pass around Saturn. The three major gaps are:
The Cassini division, associated with Saturn’s moon
Atlas; the Encke gap, associated with Pan
The Keeler Gap, caused by Saturn’s small moon named Daphnis.
There are thought to be roughly twenty smaller gaps present in Saturn’s rings, and astronomers hypothesize that smaller moonlets and other celestial bodies create these gaps in the ring bands.
Data from the Cassini probe indicates that the rings themselves have their own atmosphere independent of Saturn’s. This atmosphere is composed of oxygen and hydrogen gas that is created when the Sun’s light interacts with the ice of the ring particles.
The Planet Itself, In Detail
Saturn’s atmospheric composition is similar to Jupiter’s, with helium and hydrogen dominating, although the percentage of helium present in Saturn’s atmosphere is far less than we saw in Jupiter’s.
Methane and ammonia are also present in smaller amounts in Saturn’s atmosphere. These elements and compounds are present in three cloud layers on the planet, with helium, a heavier element, sinking and being more present in the lower cloud layers. This lack of helium makes Saturn a very light planet, indeed: in fact, its density is so low, if you dropped the planet into a sufficiently large enough body of water, it would float!
Saturn’s internal temperature is lower than Jupiter’s. Most of the helium present in the planet’s atmosphere condenses into a liquid form and it essentially “rains” continually through Saturn’s core, depleting the outer atmosphere of the element.
It is thought that Saturn once had a greater concentration of helium in its atmosphere, much more similar in percentage to Jupiter’s, but about 2 billion years ago, the planet’s internal temperature fell to a range that caused the helium mist to begin to condense.
When considering images of Saturn, the color is fairly uniform throughout. The weather patterns are also similar to Jupiter’s with fairly stable east-west wind flow. This wind flow is considerably faster, on average, than Jupiter. While the equatorial stream on Jupiter is approximately 249 miles per hour heading eastward on Jupiter, on Saturn the speed reaches 932 miles per hour in this same region. There are also fewer bands alternating wind speed direction than observed on Jupiter. Astronomers are still determining why this difference in weather patterns exists between the two otherwise very similar planets.
What Else Lurks in Saturn’s Orbit?
It is often said that, even discounting the fascinating rings that circle Saturn, the planet also has the most complex system of satellites compare to any planet in our solar system.Although Saturn is thought to have many more satellites orbiting it, only 53 of its moons are currently named. Its largest moon Titan is so large, it comprises over 90% of the mass that is currently orbiting Saturn, including Saturn’s rings. The moon is so big, it is even larger than the planet Mercury, and its own gravitational pull impacts the other moons and moonlets that orbit Saturn.
Titan is the second largest moon in the solar system, and the only one to have its own dense atmosphere.
Titan is often compared to the Earth in its composition, for it is the only other celestial body in our solar system to have a nitrogen-rich atmosphere, in fact having one that is denser than that of Earth’s. The atmosphere is also comprised of methane, as well as trace amounts of argon and other elements. In 2004, the Cassini-Huygens probe reached Titan and discovered liquid hydrocarbon in the moon’s polar regions. This also makes it the only object other than Earth in our solar system on which there is confirmed stable surface liquid.
Other than this surface liquid, Titan has a rocky core that is covered with a thick mantle of ice. Oddly, the Cassini probe’s findings indicate that there is likely a layer of liquid several kilometers below this solid frozen mantle.
These similarities to Earth’s atmospheric conditions give Titan what is known as a prebiotic environment, and researchers are still investigating the possibility of current life on the moon’s surface as well as below the surface in the liquid water under Saturn’s frozen mantle. It is also thought that the environment of the moon will shift so as to make it more feasibly habitable in the future!
