Binocular Delights of Winter
Observer's Notebook for January 1999
by John Rummel
The popular image of astronomy seems to imply a telescope, but for some purposes, a telescope is exactly the wrong instrument to use. This month's challenge is a perfect example.
Galactic clusters, or open clusters as they're more commonly known, are loose clumps of young stars numbering from dozens to hundreds. They are closely associated in both proximity and motion - meaning they're traveling through space as a true group, and not just a convenient group created by our line of sight. Two of the best known open clusters can be viewed with the naked eye easily, the Hyades and Pleiades.
Early evening skies in January find the familiar figure of Orion the Hunter posted high in the south. Follow the three bright belt stars of Orion up to the right and you'll come to the bright star Aldebaran in Taurus. Aldebaran is embedded in a V-shaped asterism. The stars of the V are the Hyades cluster, which make up the head of the bull, with Aldebaran as the eye. Though this cluster is larger and less conspicuous than the Pleiades (a little beyond Hyades in the same direction), it is a very attractive region to explore with the right tool, and luckily, you probably have the right tool stuck away in a closet somewhere in your house; binoculars. The Hyades and Pleiades need a wide-field view and low magnification, for which binoculars are perfect.
For viewing these gems you'll want the darkest skies possible, so make sure not foiled by the moon (new moon is January 16th. Any night with a week either way should be fine).
After a few minutes of naked-eye appreciation (and a chance to let your eyes dark adapt), try the Hyades with the binoculars. The number of stars visible should at least double, and depending on the kind of binoculars you have, you'll probably do better than that. Even my little 7x35's provide a breathtaking view.
Aldebaran's "membership" in this cluster is accidental. It is twice as close as the other stars and moving through space in a different direction. In a few hundred thousand years, it will have moved off to join some new star pattern, but the Hyades will remain.
The Pleiades is undoubtedly one of the most famous objects in the sky, and one which has been known since antiquity. It garners two mentions in the Bible (Amos 5:8 and Job 38:31) and has led to countless myths, including those in ancient Greece, Japan, aboriginal Australia, Africa, and Borneo.
To novices, the Pleiades has actually been mistaken for the Little Dipper since its six brightest stars look like a little dipper (and it is tiny). The real Little Dipper is stuck forever at due north, while the Pleiades roams the heavens and is actually visible to over 80% of the world's population, which accounts for its popularity in legend.
After you've tested the limits of your vision to see how many of the "seven sisters" you can see (most people can make out six easily, sharper eyes and darker skies may get up to a dozen!), reach for the binoculars again.
First time observers have been heard to gasp when viewing the Pleiades through good binoculars for the first time. At least 20 stars within the cluster are just below naked eye limits and spring into view suddenly when viewed with low magnification. If you ever doubted the value of binoculars as an astronomical instrument, a glance at the Pleiades will remedy your opinion!
Modern long exposure photos reveal no less than 2000 stars within the confines of the Pleiades, of which about 250 are actually "true members." A good binocular view of the Pleiades will cement the concept of a cluster in your mind; a dazzling collection of stars surrounded by blackness.
As a bonus, scan back down to Orion and zero in on the "sword" hanging just below his belt. The belt is made up of three tiny groups of stars. The middle one is fuzzy and indistinct. This is the site of the famous "Orion Nebula," which is in fact a stellar nursery even now busily engaged in hatching new stars. It's a rich binocular sight all by itself, and in a few hundred thousand or a million years, might be a new Pleiades, gracing the skies of some as yet unborn civilization.
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