Seven Sisters

Pleiades courtesy the Cassini spacecraft
Pleiades courtesy the Cassini spacecraft

Well this is kind of cool. The Cassini spacecraft orbiting Saturn took a fabulous view of the Pleiades as a “calibration” test for its camera electronics.

You can see some of the nebulosity that makes up the reflection nebula around several of the hundreds of stars that make up the Pleiades. It’s a nice, clear shot that I imagine lots of amateur astrophoto enthusiasts would love to get.

The Pleaides is one of my favorite clusters to watch, and every year I await its appearance in our autumn skies. It’s such a famous cluster and many cultures have stories about it in their star-lore. A few years ago I wrote a planetarium show that included the lore of the Pleiades in one section and I had a blast digging out stories like the one about the hen and her chicks, the seven sisters, the seven maidens, the little eyes of the heavens, the herd of camels, the Japanese name “Subaru,” and many, many others. One of the best write-ups was in a book called Burnham’s Celestial Handbook, Vol. 3, where the author compiled a culturally rich guide to this cluster. While the book is in need of updating with some more recent scientific discoveries, it’s still a treasure trove of information.

The Pleiades come in for a LOT of attention from fringe believers who think that some ancient civilization is visiting us from the Pleiades and bringing “enlightenment” and other useful goodies like using mind energy to go into other realms. It’s all very amusing, and useful to distinguish people who are interested in science from those who will believe anything if somebody plasters a mysterious astronomy-sounding name on it.

Truth is, the Pleiades are all hot young blue stars that formed sometime over the last 100 million years is too young for a star to have formed any planets around it (provided there’s anything left over from the starbirth sequence to form planets). So, if there’s a planet out there full of loving, helpful beings who are beaming their thought energy toward us, nobody’s seen it yet. The evidence just isn’t there.

This doesn’t mean the Pleiades aren’t an interesting bunch to study. There ARE brown dwarfs among the Pleiades stars, but these aren’t planets. They’re substellar objects that are somewhere between a giant planet and a small star, and they do NOT have nuclear fusion at their cores (as stars do). There are also white dwarfs in the cluster, which seems a little strange for such a young cluster. Most white dwarfs take longer than the life of the Pleiades to evolve. But, these white dwarfs could well be the remains of very massive stars that are born hot, live fast, die young, and leave shrunken little bodies behind to glow for millions or billions of years. Bad news for Pleiadeans believers: those stars would not have lived long enough to evolve planets with life on them either, or the planets would have been destroyed when the original stars lost much of their mass in old age. But, great news for astronomers, since this cluster gives us a great testbed to study stars at both ends of the age spectrum and categorize their chemical makeup and how they influence space around them!