God Liked Saturn, So He Put a Ring On It!

Saturn is a truly beautiful sight in a telescope. It is my favorite planet to view but only edges out Jupiter by a small margin. Saturn is easily visible now in the evening sky but Jupiter isn’t, so I’ll talk about Saturn in this post and touch on Jupiter in a future post.

 A view of Saturn through a telescope is not as impressive as the pictures we see of it from the Hubble Space Telescope (often extended time lapse photos with a really good telescope outside our atmosphere) or unmanned spacecraft (much closer than we are to Saturn). A telescope view of Saturn from Earth is relatively small and less colorful but still a beautiful thing to see.

Saturn is the second largest planet (Jupiter is the largest).  Like Jupiter, Uranus and Neptune, it is a gas giant. They are made up mostly of hydrogen and helium gas as contrasted with the rocky planets: Mercury, Venus, Mars and, of course, Earth. Pluto, if it were still deemed a planet, would be a rocky planet, but a very small one.

When you look at Saturn with your naked eye it looks like a star. We humans didn’t know that the planets were so very different from the stars until Galileo started pointing a telescope to the heavens in 1609. Prior to Galileo, people knew that the planets were somewhat different from the stars as they moved about the celestial sphere, unlike the stars that seem to be fixed. The word planet actually derives from a Greek word for wandering star.  The celestial sphere seems to rise and set through the night, just like the Sun does during the day. This is just its appearance to us, as it is the Earth that is turning and changing our view of the sky. The stars appear fixed to us but they actually do move - they are so far away that it takes thousands of years for us to notice any significant changes in their positions relative to each other. The planets, on the other hand, move against the fixed stars fairly quickly, hence the name wandering stars. Plotting and explaining the movements of the planets was a huge task. There were many theories and explanations which evolved over the ages but it didn’t get figured out until after Copernicus explained that the Sun was the center of our solar system.

Saturn ranges from about 840 million to 940 million miles away from the Sun. Earth averages about 92 million miles from the Sun. So Saturn can be as close as 748 million miles from the Earth and as far away as 1,032 million miles, depending on where the Earth and Saturn are in their orbits around the Sun. The light from the Sun takes about 8 minutes to reach the Earth and about 80 minutes to reach Saturn. When we look at Saturn we see the light from the Sun reflected off Saturn back to us. Saturn, like Earth, doesn't generate any light - just reflects the Sun's light. So the light reflecting off Saturn left the Sun between 142 and 176 minutes before we actually see it, depending on where Saturn and the Earth are in their orbits around the Sun. The light travels the distance to Saturn and then back to Earth. Any way you look at it, Saturn is very far away.

There have been 62 moons discovered orbiting Saturn. Most of Saturn’s moons are very small but the largest, Titan, is larger than Earth’s Moon and has an atmosphere. Titan can often be seen as a small dot near Saturn in a telescope view.

Saturn’s most distinguishing feature is its rings. Although the other gas giant planets also have rings they are much dimmer and were only discovered when we sent unmanned spacecraft to visit them. Saturn’s rings are really stunning. They are made up mostly of ice and rocks, ranging in size from dust-like specks to chunks about 30 feet wide. The rings are a complex set of individual rings, with the Cassini Division being the most visible separation within the ring system. The Cassini Division is named after Giovanni Domenico Cassini who was the first to note the separation of the rings in the 17th century. At times, we see the rings edge on and they look like a line passing through the planet. At other times the rings are wide open from our point of view and look absolutely magnificent.

During this summer, Saturn is visible in the early evening. It is currently to the south just after sundown and about half way up from the horizon to the point directly overhead. Saturn is also to the east of Spica, a star in the constellation Virgo. To find Spica, start with the Big Dipper, which is currently nearly overhead. Follow the handle of the Big Dipper and the arc that it makes to Arcturus, a bright star in the constellation Bootes, then continue the same arc on to Spica. Remember - Arc to Arcturus and on to Spica. Saturn is the bright “star” to the east of Spica.

Try to see Saturn through a telescope this summer, you won’t regret it.

For more info see the following links:

Saturn: http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn

Galileo: http://plato.stanford.edu/entries/galileo/

Copernicus: http://www.biography.com/people/nicolaus-copernicus-9256984

Cassini: http://en.wikipedia.org/wiki/Giovanni_Domenico_Cassini

June Sky: http://www.skymaps.com/skymaps/tesmn1306.pdf