As the year goes by, the seasons change, and the earth goes around the sun in its orbit, the patterns in the sky shift positions night by night. Constellations rise earlier and earlier; the winter constellations are now giving way to spring ones. And traveling along in those constellations are “wandering stars” that we now know as planets.
Right around sunset this week a bright, pale-gold point of light rises in the eastern sky, hitching a ride in the stars of the constellation Leo. It’s the great ringed jewel of our solar system, Saturn.
On the 24th, Saturn is at “opposition” which means that it is opposite the sun relative to us here on earth. As seen from above, earth would be between the Sun-Saturn line of sight. So as the sun sets in the west, Saturn rises in the east. It is basically the same principle as with other planets which are at opposition, and also when our own moon is at it’s full phase. Last week’s lunar eclipse was a fine example, as the moon rose just a few minutes before the sun set in the west.
As the planets travel in their own orbits around the sun, they seem to follow the stars as they rises earlier and earlier each night, but at a different speed, and at times, different directions. This is directly related to our position on the earth, relative to the planet and the background constellations. Sometimes a planet seems to stop, back up, and then go forward again. That is called retrograde motion.
With Saturn at opposition this week, if the skies are clear you can see it the entire night, and at midnight is will be nearly straight overhead, not far from the star Regulus in the constellation Leo (graphic). And then, as the days and weeks go by, Saturn will rise earlier and earlier, until later this summer when it is rising so close to the sun it cannot be seen.
However, in the meantime, the ringed planet takes command of the night skies and, if you are fortunate to see it through a telescope, is a wonderful sight as it shows off its ring system and moons. The rings look a little narrower this year, and that is due to the position of Saturn in its orbit relative to the tilt of the Earth’s axis (and our own orbit). Every 14.7 years (Saturn orbits the Sun once every 29.4 years) the Earth crosses the “ring plane” of Saturn, and the rings seem to disappear from view for earthbound observers. That will happen again in September 2009, so this year will be the last time until 2010 to see the rings with any detail.
With now through July being the prime Saturn observing season this year, it will be a prominent featured object at the public nights at the Veen Observatory this year.
So if it is clear, go out and take a look at the solar system’s Lord of the Rings.