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Visit the Pleiades and Taurus ... and That's No Bull!


Last updated 2/15/2024 at 11:42am

If you look just slightly away from Pleiades, you'll be able to see it better. Why? It's just science!

The moon returns to our evening sky this week.

It begins its trek as a thin crescent in the southwestern sky at dusk and ends the week as a bright gibbous moon high in the east. Before it becomes too bright, however, I encourage you to head outdoors and check out the early evening stars.

If your sky is relatively free from light pollution, you'll surely spot a hazy smudge of light high in the east just after dark. This is the Pleiades star cluster; it's also known as the Seven Sisters because the stars here represent the seven daughters of Atlas and Pleione from ancient Greek mythology.

Most people looking at the Pleiades with the unaided eye see can six stars rather than seven, and even these can be tough to count if your eyesight and sky conditions aren't the best. But this star cluster offers an interesting demonstration of just how your eyes work under low illumination.

Try this experiment. Gaze directly into the center of the Pleiades. You may be surprised to discover that the cluster nearly or completely vanishes! Now cast your gaze just a tiny bit off to the side of the Pleiades. What happens now? Amazing how you can see it more clearly when you don't look directly at it!

This "averted vision" technique is one that astronomers use regularly to see faint objects in the sky. It works because the eye's color-sensing "cones" (near the central part of the retina) are not activated unless incoming light is sufficiently bright. When you avert your vision just slightly, you're focusing the faint light onto the eye's gray sensors (known as the "rods"). These see faint light quite well but, of course, do not register any color.

As faint as the Pleiades is, you may be shocked to learn that this cluster can be seen easily in broad daylight. That's right; just look around any parking lot for a Subaru and examine its emblem!

Below the Pleiades lies the constellation of Taurus, the bull, on whose back this cluster is said to ride. Seeing an image of a bull isn't possible, of course, but you will notice a V-shaped grouping of stars known as the Hyades. It represents the head of the bull, with the orange star Aldebaran marking its "fiery red eye." Aldebaran is not actually part of the Hyades cluster but lies closer to us and only coincidentally appears along the same line of sight.

From the Hyades, you can trace the bull's two long horns extending off to the north, where they intersect the constellation of Auriga. Here we find the bright star Capella. The ancient Greeks often depicted Auriga as a charioteer with a whip in one hand and a goat and her kids in the other. You can spend your night searching for this character if you wish, but I find it easier to see a slightly distorted pentagon of five stars or, if you prefer, the Chrysler logo.

Don't wait too long to visit with these stars, though, because by the end of the week the moon's brilliance will obliterate most of them from view.

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