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Moon sweeps through Taurus the Bull

In the predawn/dawn hours tomorrow – on August 15, 2017 – the moon will be at or near its last quarter phase, and in front of the constellation Taurus the Bull. Look for the moon in the vicinity of href=”http://earthsky.org/brightest-stars/aldebaran-is-taurus-bloodshot-eye”>Aldebaran, Taurus’ brightest star, and also the Pleiades star cluster. The moon, Aldebaran and the Pleiades go upward and westward throughout the wee morning hours.

If you’re a night owl, staying up past the midnight hour, you might see this celestial threesome – the moon, Aldebaran and the Pleiades – low in the eastern sky before your bedtime. To know precisely when Aldebaran and the moon rise into your sky, check out this U.S. Naval Observatory page.

From mid-northern latitudes, the moon, Aldebaran and the Pleiades shine high in the south to southeast sky in the dark hour before dawn.

Before dawn from the northern tropics, look high overhead for this threesome.

Before dawn from the Southern Hemisphere, look for the moon, Aldebaran and Pleiades in your northern sky.

The lit side of the waning moon always points in the direction that it travels in front the constellations of the zodiac. So as seen from around the world tomorrow morning, on August 15, the waning moon will be moving eastward toward the star Aldebaran at the rate of about one-half degree (one moon-diameter) per hour. That’s in spite of the fact that the moon always moves westward across the sky, due to the Earth’s rotation.

Contrast the position of the moon before dawn on August 15, and then 24 hours later, before dawn on August 16. You’ll see that the moon has moved eastward in front of the constellation Taurus. As seen from around the world, the moon will be much closer to the star Aldebaran on August 16 than August 15. See the feature sky chart above.

In fact, as seen from some parts of Earth, the moon will actually occult (cover over) Aldebaran in the predawn sky on August 16. We’ll talk about this occultation on tomorrow’s August 15 program.

Before dawn on August 15, look for the moon in the vicinity of the constellation Taurus’ two most prominent signposts: the star Aldebaran and the Pleiades star cluster.


Bruce McClure