2021, September 4: Moon’s Morning Tour

Astronomy, Sky Watching
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September 4, 2021:   The moon’s star cluster tour continues this morning with the Beehive star cluster.  In the evening sky, just one day before its conjunction with Spica, find the brilliant planet in the west-southwest after sunset.

2021, September 4: Through a binocular, the thin crescent moon is 4.6° to the lower left of the Beehive star cluster (M 44).
Chart Caption – 2021, September 4: Through a binocular, the thin crescent moon is 4.6° to the lower left of the Beehive star cluster (M 44).

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:20 a.m. CDT; Sunset, 7:19 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Again today, daylight is a minute less than 13 hours.  Daylight rapidly decreases throughout the month.   By September 30, daylight’s length is about 11 hours, 45 minutes.

Morning Sky

This morning the crescent moon, 8% illuminated, is about 20° up in the east-northeast.  It is 4.2° to the lower left of the Beehive star cluster, also known by its catalog number Messier 44 or M44. Both fit easily fit into a binocular field.

Photo Caption – The Beehive or Praesepe star cluster (National Science Foundation Photo).

The cluster is also known as the Praesepe, “the manger.”

From a location free from streetlights, the cluster is visible to the unaided eye.  It seems twice the size of the moon, and it appears as a cloudy patch.

M 44 is a stellar bundle in the plane of the galaxy, like the Pleiades, Hyades and Messier 35.  The moon passed these clusters recently in the morning sky.

The cluster has over 350 stars and its distance is about 500 light years.

The Beehive has fewer blue stars than the Pleiades, indicating that it is older than the Seven Sisters. Blue stars burn their nuclear fuels very rapidly.  When the hydrogen at their cores is exhausted, the helium ash burns at a higher temperature.  This outrush of energy makes the star puff outward, turn brighter, and redden.  These topaz-color stars are known as red giants.  The cluster has several of these, along with some white dwarfs, the final stage of a star’s existence.  These hot cinders are the size of the earth. Several have been spotted in the cluster.

Evening Sky

Chart Caption – 2021, September 4: Forty-five minutes after sunset, Venus is 2.6° to the upper right of Spica.

Venus is one evening away from its widely-spaced conjunction with Spica.  Find the brilliant planet about 8° above the west-southwest horizon about 45 minutes after sunset.  It is 2.6° to the upper right of the star.

Bright Jupiter and Saturn are in the southeast after sunset.  Jupiter is the brightest “star” in the evening sky after Venus sets nearly 90 minutes after sundown.  Saturn is to the upper right of Jupiter.  After Jupiter, only two other stars this evening are brighter than Saturn; they are Arcturus and Vega.

As the evening progresses, find the planets higher in the south-southeastern sky.

Detailed Daily Note:One hour before sunrise, the waning crescent moon (26.8d, 8%) is nearly 19° above the east-northeast horizon.  Use a binocular to find the Beehive star cluster (M44, NGC 2632) 4.2° to the upper right of the lunar slice.  Twenty-five minutes after sunset, Mercury is nearly 5° up in the west-southwest.  Twenty minutes later, brilliant Venus, about 8° above the south-southwest horizon, is 2.6° to the upper right of Spica and 4.1° to the lower left of θ Vir.  Farther eastward, Saturn is nearly 20° above the southeastern horizon.  Jupiter, 17.2° to the lower left of the Ringed Wonder, is over 13° above the east-southeast horizon.  Two hours after sunset, bright Jupiter, nearly 25° above the southeast horizon, is 3.9° to the upper right of ι Aqr, 1.0° to the lower right of μ Cap, and 1.9° to the upper left of Deneb Algedi.  Saturn is to Jupiter’s upper left, nearly 27° up in the south-southeast and 1.0° below υ Cap.

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