Moon and Pleiades

The Moon charges at the Pleiades late tonight. As seen from most of the United States, it will pass especially close to the star cluster – either just skimming its edge or briefly covering some of its stars. The cluster is home to more than a thousand stars of all varieties. The ones that are visible to the eye alone are especially big, hot, and bright. But they’re greatly outnumbered by stars that are much smaller, cooler, and fainter. Many of the stars belong to systems of two stars or more. And the cluster also hosts many “brown dwarfs” – objects that are more massive than planets, but not heavy enough to shine as true stars. Over the decades, there’s been a lively debate about the distance to the cluster. Different telescopes and techniques have provided measurements that vary by many light-years. The best current number puts the distance at about 440 light-years. But that’s the distance to the center of the Pleiades. The cluster actually spans several dozen light-years in all directions. So as you look at the cluster, the light you see from the stars that are closest to Earth headed our way dozens of years earlier than the light from the stars that are farthest – an out-of-sync view of a well-known star cluster. The cluster’s brightest stars form a tiny dipper shape, although it’ll be tough to make out through the moonlight. The cluster will be especially close to the Moon at dawn. Script by Damond Benningfield