Wandering Saturn

I did want to see Mercury yesterday, but unfortunately it was cloudy around sunset. One planet I have seen a lot of recently, in the night sky, has been Saturn. It is really easy to spot right now as it is up in the evening so you don't have to stay up all night. So, for those of you who don't know where it is, here are some directions.

Go outside on a clear evening and, if you're in the northern hemisphere, look towards the south. If you don't know which direction south is, try to remember where the Sun set earlier on and come around to the left of that. What you want to find first is Orion (the Hunter) who can be spotted by looking for the three stars that make up his belt. I have included a screenshot (from Stellarium) to make things a bit easier although I haven't put on any constellation lines as there aren't any in the real sky. Once you've found the belt, you should move in a line up and left through the top left shoulder (the red giant star Betelgeuse) towards three bright objects. Two of these are Castor and Pollux, which form the heads of Gemini (the Twins). The lower of the three objects is the planet Saturn.

Finding chart for Saturn

During a single night, planets seem to move from east to west along with the stars. If you follow them from night to night you will see that they actually travel west to east as they orbit the Sun. This is what Saturn was doing until November last year when it made a straight line with Castor and Pollux. Since then it has been moving backwards (east to west) in what is known as retrograd motion. In a few weeks, Saturn will come to a stop (relative to the stars) and once again begin to move towards the east. This strange dance on the sky, is the reason planets are called planets; it comes from the Greek meaning 'wandering star'. The strange motion of the planets caused confusion for thousands of years because people thought that the planets, Sun and stars orbited the Earth. It was finally Nicolaus Copernicus who came up with a neat mathematical model to explain the motions. This required the Earth and the planets to be orbiting the Sun and so the Copernican model of the Solar System was created.

Posted in astro blog by Stuart on Sunday 13th Mar 2005 (14:16 UTC) | Permalink
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