I’ve written about the Pleiades star cluster before (“Orion and the Pleiades,” Jan. 12, 2023), in which I focused on the ancient Greek myth of the hunter Orion endlessly pursuing Mom, Dad and seven sisters across the night sky. Here, I’m going to focus on the stars themselves, and what makes them so interesting to amateur and professional astronomers alike.
Perhaps they’re not quite as well known today as they were to the ancients, thanks to the dearth of dark skies these days — although the recent county ordinance is a step in the right direction (“Protecting the Night,” Oct. 16). I took the accompanying photo from near Schoolhouse Peak in Redwood National Park, an official “dark sky” area, on a particularly clear night last October. Still, because the Pleiades are quite bright (“apparent magnitude” 1.6), they can usually be seen even from urban locations on cloudless nights.
They’re comparatively close, a mere 444 light years away, so the light we see has been traveling since just before Christopher Columbus sailed to the “New World.” Although most people can only make out about six individual stars — up to 14 if you have the eyes of a hawk — the cluster actually contains over 1,000 stars. The brightest are hot blue stars that formed about 100 million years ago, youngsters by star-age.
As such, they’re intriguing to astronomers who would like to nail down the exact process by which stars form in the first place. Most stars, including those in the Pleiades cluster, develop as part of a group in a “stellar nursery” where dense molecular clouds collapse due to their mutual gravitational attraction. The pressure at the core becomes so great that hydrogen nuclei fuse, causing the stars to “turn on.” Because the Pleiades are so close, it’s easy to investigate them in detail, something astronomers have been doing for the past century.
The lovely blue “clouds” of nebulosity in my photo were once thought to be leftover dust from the stars’ formation. This now appears unlikely, since 100 million years is more than enough time for radiation pressure to have dispelled any such dust. More likely, what we’re seeing is interstellar dust (that just happens to be passing through the cluster) reflecting light from the brightest of the Pleiades.
The Pleiades are easy to find, especially in winter. Trace a line up and to the right of Orion’s Belt, past bright orange Aldebaran, and you’ll see them as a misty cluster of stars. Do check them out with binoculars!
Barry Evans (he/him, barryevans9@yahoo.com, planethumboldt.substack.com) wants you to know that The New Humbook (perfect Christmas present!) is on sale at local bookstores and gift shops.
This article appears in Sacred Groves.