2021, August 23: Moon’s Star Tails


August 23, 2021:  Later during the evening the moon appears in the region of stars that have tail names.

Chart Caption – 2021, August 23: As midnight approaches, the moon, Jupiter, and Saturn are in the southern sky, along with stars that are tails.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:08 a.m. CDT; Sunset, 7:38 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Notice today’s sunrise and sunset times.  Daylight in Chicago is 13 hours, 30 minutes.  During the next month, sunlight decreases over an hour.

After sunset this evening, brilliant Venus continues to appear low in the western sky after sunset.  It sets 88 minutes after sundown.

The bright moon is to the east of Jupiter and Saturn.  It is above the east-southeast horizon about 2 hours after sunset.

As the calendar day closes, the lunar orb is nearly one-third of the way up in the southeast.  Jupiter is over 26° to the right of the moon.  Saturn, dimmer than Jupiter, is 18.0° to the lower right of the Jovian Giant.  The Ringed Wonder is about 30° up in the south.

The name “Deneb” indicates tail.  The tail of Cygnus takes that name.  For other stars, another word is attached to distinguish the stars with their constellations.

Jupiter is 3.1° to the upper left of Deneb Algedi – “the kid’s tail.” The star marks the tail of Capricornus, a creature that is part goat and part fish.

Deneb Algedi is 2.6° below the plane of the solar system.  It is the brightest star near the ecliptic in this region of the sky that has only one first magnitude star – one of the twenty brightest.

The star is less than 50 light years away and it shines with the intensity of over 20 stars like our sun.

Another star with a tail name is Deneb Kaitos – “the sea monster’s tail.”  The creature is Cetus, sometimes referred to as a whale.  The star is about the same distance and brightness as Deneb Algedi, although Deneb Kaitos is topaz in color, similar to the bright star Arcturus.  To be this bright Deneb Kaitos is large, perhaps 20 times the sun’s diameter.  If it were empty, it could hold about 8,000 suns.  (Remember that the volume of a sphere is determined by the cube of the radius.)

At this hour, Deneb Kaitos is over 18° to the lower left of the moon and over 10° above the southeastern horizon.

Another star, without a tail name, is to the lower left of Jupiter and lower right of the moon.  With Jupiter and the lunar orb tonight, Fomalhaut makes nearly an equilateral triangle.  The star is nearly 15° up in the south-southeast.

Fomalhaut marks the mouth of the Southern Fish.  It is one of the twenty brightest stars (18th).  In his Celestial Handbook, Robert Burnham wrote, “ Sometimes called the ‘Solitary One,’ Fomalhaut lies in a rather empty region of the southern skies, and to dwellers at the mid-northern latitudes, it is the southern-most of the visible 1st magnitude stars. (p. 1485).

The star is south at midnight during early September.

Fomalhaut is about 20 light years away, and about 15 times brighter and twice the size of the sun. 

Take a look at the starry region around the moon tonight for planets and stars that are tails (and a mouth) of celestial creatures.

Detailed Daily Note:One hour before sunrise, the bright moon (14.8d, 99%) is over 18° above the southwest horizon.  It is 15.0° to the upper left of Jupiter that is nearly 8° up in the west-southwest. Twenty-five minutes after sunset, Mercury is about 4° up in the west, 18.5° to the lower right of Venus.  Use a binocular. Forty-five minutes after sunset, brilliant Venus is nearly 8° up in the west-southwest.  It is 4.4° to the upper left of Zaniah, 2.7° below Porrima, and 15.0° to the lower right of Spica. Use a binocular to see the planet with the stars. Venus continues its eastward trek at a rate of nearly 1.2° of ecliptic longitude each day.  Farther eastward, Saturn is nearly 16° above the southeast horizon.  Jupiter – 18.0° to the lower left of the Ringed Wonder – is over 9° up in the east-southeast. As midnight approaches, the bright moon (15.6d, 96%) is nearly one-third of the way up in the southeast.  Jupiter, over 33° above the south-southeast horizon is 26° to the right of the lunar orb.  Jupiter is retrograding against the starfield of eastern Capricornus.  It is 2.5° to the upper right of ι Aqr, 0.7° to the lower left of μ Cap, and 3.1° to the upper left of Deneb Algedi.  With this bright moon, use a binocular to spot the starfield with the planets.  At this hour, Saturn is nearly 30° up in the south, 1.2° to the lower left of υ Cap.  Saturn continues its retrograde trek in Capricornus.


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