BellaOnline Forums Education Astronomy Saturn's Moon Rhea discovered Dec 23, 1672

Giovanni Cassini discovered Saturn's moon Rhea on December 23, 1672 - 342 years ago.

Rhea was Saturn's wife in classical mythology. She was also his sister, but we'll gloss over that. Rhea the moon zips around Saturn in four and a half days. Although it has an oxygen atmosphere, we won't be moving there anytime soon. Even in direct sunlight, it's -281 degrees Fahrenheit and the "atmosphere" is similar to a vacuum on Earth.

Rhea Moon of Saturn

It's December the 23rd. On this day in 1672 Italian-born French astronomer Giovanni Domenico Cassini (1625-1712) discovered a new moon of Saturn. Cassini had already discovered one of Saturn's moons and would discover two more. He didn't bother to name them - except to christen the quartet Sidera Lodoicea (the stars of Louis) to honor King Louis XIV. It was another 175 years before John Herschel suggested names for them.

Cassini the spacecraft has studied the moon Rhea that Cassini the astronomer discovered. In this photo of Rhea centered on the south pole you can see the two very different types of terrain on the moon.

On Astronomy Picture of the Day I saw a picture of Rhea crossing in front of Saturn - they were both in a crescent phase. Unfortunately, you could only see Rhea as a large black dot. The image came from a short video of the transit. In the video we see the crescent Rhea approaching Saturn and then gliding past it. I got a screen shot which actually shows Rhea's crescent over Saturn's night side.

More fantastic pictures from Cassini the spacecraft of the discovery of Cassini the astronomer!