2021, July 19: Gibbous Moon, Scorpion

Astronomy, Sky Watching
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July 19, 2021:  Gibbous moon is in front of the stars of Scorpius this evening.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:33 a.m. CDT; Sunset, 8:21 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

With the brilliant planet Venus in the western sky after sunset, the gibbous moon – 79% illuminated – takes a position in Scorpius.

With a binocular note that the moon is between Graffias, “the crab,” and Dschubba, “the forehead.”

In his Celestial Handbook, Robert Burnham echoes other writers who think the translation of the name Graffias to crab is because early writers sometimes used the same word for crab and scorpion.  Some folks thought that scorpions were transformed crabs.

The star is very bright compared to our sun.  It shines with an intensity of 2,700 suns.  At a distance of over 600 light years, Graffias has a companion star that is visible through a small telescope. This companion is sometimes reported to have a green tint.

Dschubba is a very bright star.  With a brightness of 3,300 suns, the star is in Graffias’ neighborhood.

Step outside about an hour after sunset, to see the gibbous moon with the head of the Scorpion.  With a binocular spot the two stars nearby.  If you have a spotting scope or small telescope, can you see the green color of Dschubba’s companion?

Detailed Daily Note: One hour before sunrise, Saturn – 20° up in the southwest – is retrograding in Capricornus, 2.9° to the lower right of θ Cap.  Bright Jupiter – over 33° above the south-southwest horizon – is 19.7° to the upper left of Saturn.  Retrograding in Aquarius, the Jovian Giant is 2.1° to the upper left of ι Aqr, 4.6° below θ Aqr, and 4.8° to the lower right of σ Aqr.  Thirty minutes before sunrise, Mercury is nearly 6° up in the east-northeast.  With a binocular note that Betelgeuse (α Ori, m = 0.4) is nearly 21° to the right of the speedy planet. The star is making its first morning appearance (heliacal rising). Forty-five minutes after sunset, Venus is over 8° above the west-northwest horizon.  Use a binocular to see Mars 3.8° to the lower right of Venus and Regulus to the left.  The trio fits into the field of a binocular this evening.  An hour after sunset, use a binocular to note that Graffias (β Sco, m = 2.5) and Dschubba (δ Sco, m = 2.3) bracket the moon (10.0d, 79%), nearly one-third of the way up in the south, from above and below. Saturn rises 42 minutes after sunset, followed by Venus setting 51 minutes later.  Have you seen them in nearly opposite directions in the evening sky?  Jupiter rises three minutes after Venus sets.  The Venus – Jupiter opposition (celestial longitude 180° apart) occurs in two evenings.  As midnight approaches, the moon is over 17° above the southwest horizon.  Farther eastward, Saturn is 23.0° up in the south-southeast, while bright Jupiter, 18.0° up in the southeast, is to the Ringed Wonder’s lower left.

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