Before dawn on July 26, 27 and 28, 2019, watch for the waning crescent moon to travel in front of Taurus the Bull. Assuming your sky is dark enough, the Bull is instantly recognizable; it’s one of the more prominent constellations of the zodiac. Look for this constellation’s bright reddish star Aldebaran plus its two signpost star clusters, the V-shaped Hyades and the tiny, misty, dipper-shaped Pleiades.
The moon is close to the Pleiades on the morning of July 26.
It’s closer to the Hyades on the mornings of July 27 and 28, at least as seen from North America. Your exact view will vary. How can you see your personalized view? We hear good things about the free open source planetarium software called Stellarium.
On all of these mornings, it’ll be easy to spot Aldebaran, which represents the ruddy eye of the Bull. The lit side of the moon will point directly at this star, Taurus’ one and only 1st-magnitude star, on July 26 and 27. Look closely and you’ll see this star atop the famous V-shaped pattern of stars that outlines the Bull’s face.
The V-pattern is the Hyades, and it’s an actual star cluster in space, comprised of sibling stars that were born from the same cloud of dust and gas over 600 million years ago. Although Aldebaran isn’t a true member of the Hyades star cluster, this bright star accentuates the V shape of the Hyades on the sky’s dome. Aldebaran is about 65 light-years away, whereas the farther-off Hyades stars lie at about 2 1/2 times Aldebaran’s distance.
The more compact Pleiades cluster, on the other hand, is thought to be more distant (about 430 light-years versus 150 light-years), yet more youthful (100 million years versus 625 million years) than the Hyades. The constellation Taurus is a rarity indeed in that it showcases two easy-to-see open clusters.
The lit side of a waning moon points in its direction of travel: east or toward sunrise. So watch the moon throughout the final week of July 2019, as the waning crescent sweeps through the constellation Taurus the Bull and then disappears into the glare of sunrise.
Depending on where you live worldwide, the upcoming new moon will be the second of two July 2019 new moons or the first of two August 2019 new moons. When there are two new moons in a month, some people call the second one a Black Moon.
Bottom line: On the mornings of July 26, 27 and 28, let the waning crescent moon show you Taurus the Bull and introduce you to the constellation’s two outstanding features, the Hyades and the Pleiades clusters.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.