Celestial News: Spotlight on Saturn
Steamboat Pilot & Today
Saturn is the second outer planet to reach opposition this year. Every 12½ months, the Earth gains a lap on sluggish Saturn and passes directly between Saturn and the sun, placing the two planets as close together as possible.
When Saturn reaches opposition on Tuesday, July 9, it will be 839 million miles from Earth, its closest point for 2019. That’s a little more than twice as far away as Jupiter was at its opposition last month. Saturn will rise in the southeastern sky at dusk and shine brightly all night long from near the Teapot asterism in the constellation of Sagittarius, the Archer.
Here are 10 things that you might not know about planet number six. Limited space won’t allow me to go into too much detail, but if anything arouses your curiosity, you can always search for more information on the Internet.
1. Saturn would float in a giant tub of water. It’s the only planet that would float because it is the only planet with a density less than 1.0 gram/cubic centimeter, the density of water. Earth’s density is more than 5.0 grams/cubic centimeter. It would sink like a rock, because it is a rock. Saturn is made of 96% hydrogen, 3% helium, and 1% everything else, making it very buoyant. Even Saturn’s rings would float, because they are composed of water ice.
2. Winds in Saturn’s upper atmosphere blow at supersonic speeds of over 1100 mph. The fastest winds on Earth blow at about 250 mph. Scientists suspect that the supersonic winds are driven by heat rising from the planet’s core, rather than atmospheric heating by the sun. Saturn radiates more than twice the energy that it receives from the sun.
3. A colossal hurricane is spinning over Saturn’s north pole. Surrounding this hurricane is a bizarre hexagonal cloud formation that is large enough to swallow the Earth. First glimpsed by NASA’s Voyager fly-by mission in 1981, the polar vortex and hexagon were studied in depth by the orbiting Cassini spacecraft, beginning in 2006. Nothing like this hexagonal storm is found anywhere else in our solar system.
4. Although Saturn takes nearly 30 years to creep around the sun, it spins on its axis very fast. A day on Saturn only lasts for 10 hours, 33 minutes. A person floating in Saturn’s atmosphere would experience two sunrises and sunsets in the span of one Earth day. Only Jupiter spins faster on its axis, once every nine hours and 50 minutes.
5. Jupiter has its Great Red Spot, Neptune has its Great Dark Spot and Saturn has its Great White Spot. A Great White Spot appears in Saturn’s northern hemisphere about once every Saturn year — 29 Earth years —near the time of its summer solstice and lasts for many months. Typically, a Great White Spot begins as an Earth-sized cluster of violent thunderstorms that sprouts a white tail that grows in length until it completely encircles the planet. The most recent Great White Spot was observed at close range by the orbiting Cassini spacecraft back in 2010-11.
6. Although Saturn is nearly 100 times more massive than Earth, it is also about 10 times Earth’s diameter. Combine these two features, and we find that if Saturn had a solid surface upon which you could stand, which it most certainly does not, you would weigh about the same as you would on Earth. A 150-pound astronaut on Earth would tilt the scale at about 159 pounds on Saturn’s hypothetical surface. For comparison, our 150-pound astronaut would weigh in at 380 pounds in Jupiter’s oppressive gravity and only about 9 pounds on Pluto.
7. Saturn’s beautiful icy rings are easily visible from almost a billion miles away through backyard telescopes here on Earth. The rings are not solid but are composed of countless particles of water ice, ranging in size from tiny specks to large boulders. They cover an area equal to the surface area of 80 Earths and contain about half of the amount of ice in the Antarctic ice sheet, and yet, they are remarkably thin. At only 30 feet thick, most of the trees in your backyard are taller than Saturn’s rings are thick.
8. In the epic 1968 science fiction movie “2001: A Space Odyssey,” the original plan was to send the Discovery spacecraft to Saturn, but the special effects team could not come up with a realistic looking rendition of Saturn’s rings, so the destination was changed to Jupiter. At that time, it wasn’t known that Jupiter also has a set of rings, much darker and less visible than Saturn’s.
9. In addition to its iconic rings, Saturn also boasts a family of 62 moons. Most of these are small icy objects captured by Saturn’s gravity as they wandered too close, but there are seven medium-sized moons — Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion and Iapetus — along with one giant moon, Titan. Titan possesses more than 20 times the mass of all of the other 61 moons combined and is larger in diameter than the planet Mercury. It is the only moon in the solar system that has a thick atmosphere and the only object other than Earth known to have lakes of liquid on its surface. In Titan’s case, the lakes are filled with liquid methane and ethane instead of water.
10. We’re going to Titan. NASA announced last month that it has approved a mission to explore Saturn’s moon Titan. Called Dragonfly, this mission will feature the first helicopter-like drone to fly over the surface of another world. Dragonfly is tentatively scheduled to launch from Earth in 2026 and reach Titan in 2034. Being able to fly through Titan’s frigid but thick atmosphere will allow the Dragonfly to explore over a hundred miles of territory, much more than all of the Mars rovers combined. Titan has all of the ingredients necessary for life as we know it, so scientists are eager to learn more about its prospects for life.
Look for Saturn this month in the southeastern sky after 10 p.m., about two hand spans to the east — left — of brighter Jupiter.
Jimmy Westlake retired from full-time teaching at Colorado Mountain College’s Steamboat campus in 2017, after 19 years as their professor of physical sciences. His “Celestial News” column appears monthly in the Steamboat Today newspaper. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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