2021, August 29: Morning Moon, Pleiades

Astronomy, Sky Watching
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August 29, 2021: Before sunrise, the gibbous moon appears near the Pleiades star cluster.

Chart Caption – 2021, August 29: The Pleiades star cluster and the morning moon appear in the same field of view of a binocular.

This article as a podcast

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:14 a.m. CDT; Sunset, 7:29 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

This morning the slightly gibbous moon is over two-thirds of the way up in the southern sky,  It is 6.2° to the lower right of Alcyone, the brightest star in the Pleiades star cluster.

In a binocular, place the moon to the lower right side of the field of view.  The Pleiades are to the upper left edge.  Then move the binocular so that the moon is outside the field and the star cluster is near the middle.  This reduces the glare from the moon.

In the binocular a dozen or so stars might be visible.  The entire gathering has perhaps a thousand members.

The cluster is frequently known as the “Seven Sisters.” It is one of the closest (400 light years) and brightest star clusters visible in the skies of Earth.  It is described in poetry, religious writing, and stories across the globe.

In the Friendly Stars, Martin & Menzel summarize this fascination with the Pleiades. “Of all the groups of stars in the heavens none has excited so universal and so romantic an interest as the Pleiades.  The magic of their quivering, misty light has always made a strong appeal to men of imagination.  Minstrels and poets of the early days sang of their bewitchment and beauty, and many of the great poets, from Homer and the author of Job down to Tennyson and the men of our own day, have had their fancy enlivened by them, and in one form or another have celebrated their sweetness mystery and charm” (p. 124).

Alcyone, the cluster’s brightest star, is possibly 1000 times brighter than the sun and 10 times larger. 

According to astronomical theory, stars are formed in bunches, but the clusters’ gravity is not strong enough to keep the bundles together and they eventually scatter as they revolve around the Milky Way.

The cluster is thought to be 100 million years old.  The dominate blue stars fiercely burn their nuclear fuels and rapidly, in astronomical terms, convert into red giants.

During the next several mornings, the moon passes the Hyades (September 30), Messier 35 (September 1), and the Beehive star cluster (September 4).  Including this morning, the moon appears in the same binocular field as the clusters on those mornings.  Take a look!

Detailed Daily Note:One hour before sunrise, the moon (20.8d, 58%) is nearly 65° up in the south.  The lunar orb is 6.2° to the lower right of Alcyone and 13.8° to the upper right of Aldebaran. Twenty-five minutes after sunset, Mercury is over 4° above the western horizon, 16.5° to the lower right of Venus.  Use a binocular to see them at this level of twilight. Forty-five minutes after sunset, brilliant Venus is about 8° up in the west-southwest, 8.0° to the lower right of Spica.  Farther eastward, Saturn is nearly 18° above the southeast horizon, 17.6° to the upper right of Jupiter.  The Jovian Giant is nearly 12° up in the east-southeast.  As midnight approaches, the moon (21.6d, 51%), nearly 5° above the east-northeast horizon, is 7.8° to the lower left of Alcyone.  At this hour, Jupiter is nearly 34° up in the south and east of the meridian.  Retrograding in Capricornus, it is 3.2° to the right of ι Aqr, 0.5° to the lower right of μ Cap, and 2.5° to the upper left of Deneb Algedi.  Saturn is over 28° up in the south-southwest, 1.0° to the lower left of υ Cap.

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