The planets of our solar system come in two basic varieties: small and dense, and big and fluffy.
A representative of each group is in the western sky this evening. Venus, the brilliant “evening star,” is one of the small planets, while Jupiter, which is just to the left of Venus, is the largest of the big planets.
It’s not just size and density that sets these two worlds apart, though. Jupiter has an entourage of more than 60 known moons, while Venus has none at all.
In fact, the four largest moons of Jupiter are impressive worlds in their own right. The smallest is about the size of our own Moon, while the biggest is bigger than the planet Mercury. And at their brightest, all four of them are bright enough to see with the unaided eye. But they’re all so close to Jupiter that they’re lost in the planet’s glare. You need binoculars to find them; they look like tiny stars near the brilliant planet.
Astronomers searched for moons of Venus throughout the 19th century, but they came up empty. There were a lot of sightings, but they all turned out to be stars that happened to line up close to the planet, or other false alarms. And since Venus is only a fraction as far away as Jupiter is, any moons bigger than a few city blocks would have turned up long ago.
Again, look for the dazzling pairing of Venus and Jupiter as darkness begins to fall, and descending the western sky later on. The planets set in late evening.
Script by Damond Benningfield, Copyright 2012
For more skywatching tips, astronomy news, and much more, read StarDate magazine.