Star Clusters Punctuated by Planets!

2/19/06 – 2/25/06

By C. Zaitz

If you’ve been glancing up into the evening sky lately, you’ve probably noticed Mars and Saturn in the southeast after sunset. The two planets glare down from on high as the distant stars wink and glitter around them. This week each planet is near a famous star cluster. In our local skies, we are lucky to see the few stars we do see, though the planets are visible because they are so bright. But star clusters are fainter and somewhat hazy to the unaided eye. One of the most famous is the Pleiades, and the other is called the Beehive Cluster. Both clusters are fairly easy to spot in a reasonably dark sky. This week both have bright pointers to show them off.

Mars is the planet with the ruddy glow, and is the more westerly of the two planets in the early evening sky. Mars is underlining the Pleiades as it passes below the cluster all week. The Pleiades (commonly pronounced PLEE a dees) have also been called the Seven Sisters since historically there have been seven visible stars in the cluster. In modern times, one star has faded a bit and is not easily visible anymore, leaving six sisters in the lurch! The Japanese logo for Subaru cars reflects this fact. If you count the stars in the logo, you will see only six, but they are indeed the Pleiades or Subaru as they are called in Japan.

Saturn is trailing behind Mars all evening, as it lingers in the gentle hazy glow of its temporary companion, the Beehive Cluster. Both the Pleiades and the Beehive are collections of stars loosely hanging together in a gravitational huddle. These clusters are made of hundreds of stars that are born roughly about the same time and in the same region of space, so we can study them in unique ways to understand stellar life cycles and even determine distances more accurately. The Pleiades lie some 400 light years from earth, and the Beehive is even further away at 500 light years. That means that when we look at these beautiful clusters of stars, we are seeing them as they looked several hundred years ago. But stars live for millions and even billions of years, so 500 years won’t see much change in a star.

We shouldn’t neglect the beauty of the morning sky, because although the two morning planets aren’t flirting with star clusters, they are both attention-grabbers as they herald the coming of the morning dawn. Jupiter hangs low in the southeast but still flies higher above the brightly glowing Venus. The skies will lighten as you’re looking at the two planets, but if it were pitch black, you would see the busiest part of our galaxy in the stretch of sky between the planets. In that direction lie countless star clusters, nebulae and even the giant black hole located in the center of our galaxy. But our eyes will only see the brilliant pinks, oranges and blues of the coming daybreak.

Until next week, my friends, enjoy the view!