2021, May 13: Evening Star Venus, Mercury, Moon

May 13, 2021: Venus, Mercury, the crescent moon, and Mars are in the western sky after sunset. 

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:32 a.m. CDT; Sunset, 8:02 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

The evening portion of the planet parade, displaying five planets and the crescent moon, unfolds after sunset.

Jupiter and Saturn are visible each morning before sunrise.

Brilliant Venus, Mercury, the crescent moon, and Mars perform in the western sky after sunset.

Thirty minutes after sundown, brilliant Venus is over 5° up in the west-northwest.

Bright Mercury is 9.1° to the upper left of Venus. Use a binocular to locate the planets.

The crescent moon, 3.2° to the upper left of Mercury and 11.2° to the upper left of Venus, fits in the same binocular field with Mercury.

Find one with the binocular and move the binocular slightly to see the other, keeping the original object in the field of view.

Venus as an evening star article.

Read more about Venus in our summary document.

By 45 minutes after sunset, three planets and the moon are visible.  Mars is visible to the upper left of Mercury and the Moon.

Mercury is in its best evening appearance of the year.  The plane of the solar system makes a large angle with the horizon.  Mercury stands above the horizon in a darker sky.

Locate all three planets.  They lie along the solar system’s plane, known as the ecliptic. Draw an imaginary line between them to the horizon.  You can estimate the large angle the ecliptic makes with the horizon, opening a very good viewing window to see Mercury in the sky.

The planet is rarely seen in a completely dark sky from the mid-northern latitudes.  Even at its best, Mercury sets at the end of evening twilight, when the sky reaches its natural darkness.

Through the binocular note that the night portion of the moon is gently illuminated.  This is from sunlight reflected from Earth’s oceans, land, and clouds.  This lights up nighttime on the moon, in a manner similar to the bright moon illuminating terrestrial features and casting shadows on the ground.

As viewed from the moon, Earth’s phase is waning gibbous.

Here’s more about Mercury during May 2021.

An hour after sunset, Mars – about one-third of the way up in the west – is in front of the stars of Gemini, near Mebsuta (ε Gem on the chart), “the outstretched paw of the lion,” and Mekbuda (ζ Gem), “the folded paw of the lion.”

The constellations that we recognized are fusion of star names from several ancestral cultures. Castor and Pollux, the names of the Gemini Twins, are from western mythology.  Other stars in Gemini, such as Alhena, Wasat, Mebsuta, and Mekbuda, have their names rooted in Arabic traditions and constellations.

In 1944, George Davis wrote an article about the origins of star names.  Divided by constellations, the writing summarizes the names, pronunciations, and meanings of many stars.

Today’s Gemini, looks like a two stick figures with their arms around the other’s shoulders.

The ecliptic goes through Gemini from the lower right corner of the chart to the upper left. Mars ends the month to the lower left of Pollux.

Here’s more about Mars during 2021.

Find a detailed chart of the motion of Mars during the month here.

Detailed Note: Jupiter and Saturn continue to climb into the southeastern sky.  One hour before sunrise, Saturn is nearly 25° above the south-southeast horizon. It is approaching θ Cap.  The gap is 0.7° with the planet to the right of the star.  Jupiter – over 20° up in the southeast – is 16.5° to the lower left of Saturn. The Jovian Giant is 1.5° to the upper left if ι Aqr and 5.0° to the lower right of Theta Aquarii (Ancha, θ Aqr, m = 4.2). The sun is in the sky for 14.5 hours. Three planets and the moon are visible after sunset.  Start about 30 minutes after sundown.  Brilliant Venus is over 5° above the west-northwest horizon.  Use a binocular to locate the thin crescent moon (2.3d, 4%), 11.2° to the upper left of Venus.  Mercury (m = 0.0) is 3.2° to the lower right of the lunar slice.  As the sky darkens, the moon and Mercury are easier to locate, but Venus is lower.  This may be the last evening to locate Aldebaran without optical assistance. By 45 minutes after sundown, Venus is 3.0° above the west-northwest horizon; the moon is 12.2° up; and Mercury is 11.4° in altitude.  Mars – in Gemini over 32° up in the west – is about 25° to the upper left of the lunar crescent.  By one hour after sunset, Venus is barely above the horizon.  The moon is nearly 10° up, while Mercury is about 9° above the west-northwest horizon.  The moon is 7.3° to the lower left of Elnath (β Tau, m = 1.6).  Mars is 2.4° to the upper left of ε Gem and 4.4° to the right of ζ Gem.

Read more about the planets during May 2021.