Saturn up all night

Astronomy blog for the week ending April 9, 2011

Saturn’s at opposition this week. That’s when it’s on the opposite side of the sky as the sun. So, it’s up all night. Being able to see it any time of night is just one reason opposition is a great time for viewing it.

A planet at opposition is as close to Earth as it gets. Whatever magnification you can get out of your telescope, you get a head start by being closer. Saturn’s almost 1,300,000,000 kilometers (800,000,000 miles) from Earth now. That’s 8.6 times as far from the Earth as the earth is from the sun. Saturn will be 10.6 Earth-Sun distances away from us this September. Looking at it now will give your optics a 23% boost over that view.

It gets better. When a planet is farthest from the sun, you’ll look at it no more than a few hours after it rises or a few hours before it sets. The image goes through more atmosphere before it gets to your telescope. And the atmosphere itself is a lens with a mind of its own. If you can watch Saturn when it’s high overhead, you’ll get the sharpest image.

If you recognize just one planet in pictures, it’s certainly Saturn. The rings tell you what it is. There’s something about them that makes seeing magnified Saturn with your own eyes special. If you’ve never looked at the planet through a telescope before, you will approach the eyepiece expecting to see the rings. And you’ll feel a thrill when you do.

Galileo didn’t have great optics. When he turned his telescope to the heavens, he saw a new view but a blurry one. In 1610, he described Saturn as having ears. He thought he was likely looking at moons very close to the planet since he had already seen moons of Jupiter. A better telescope was available 45 years later to Christian Huygens who explained that the ears were really a ring.

Huygens and others thought the ring was one solid piece. But in 1675, Giovanni Cassini discovered what appeared to be a gap between two rings. That gap is now called the Cassini Division. Cassini also saw actual moons orbiting Saturn.

In the following centuries, scientists came to believe the rings must be made of many fairly small space rocks. Pictures taken by Voyager 1 in 1980 proved that to be the case. Some believe those rocks are chunks of moons that were somehow destroyed. So in a way, Galileo may have been right to think he was looking at moons.

The lenses available today are pretty good. If you have a telescope or can borrow one, you owe yourself a look at the ringed planet. On a good night, you can spot one or more of Saturn’s moons. You’ll find Saturn in Virgo somewhat close to the bright star Spica. A spacecraft named after Cassini is out there now gathering data about Saturn and its moons.