2021, May 21: Evening Planet Ballet

May 21, 2021: Three bright planets are dancing in the western sky after sundown.  Evening Star Venus is entering the sky for a months-long residency after its solar conjunction two months ago.  Mercury is heading for a conjunction with Venus after its best evening appearance of the year.  Mars continues its eastward march in Gemini, but time is running out on its appearance as it approaches brighter evening twilight and a conjunction with Venus.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:25 a.m. CDT; Sunset, 8:10 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

During the evening, three bright planets, Venus, Mercury, and Mars, continue their dance in the western sky.

Forty-five minutes after sunset, brilliant Venus about 5° above the west-northwest horizon.  It is slowly entering the sky after its solar conjunction nearly two months ago.

Venus as an evening star article.

Read more about Venus in our summary document.

Speedy planet Mercury is coming off its best evening display of the year.  The planet is dimmer each evening.  This evening Mercury is 6.4° to the upper left of Venus.  On May 28, Venus and Mercury have a very close conjunction.

Both planets easily fit into the same binocular field.  Use the optical assist to initially locate Mercury, then look for it without the assistance.  The star Elnath – “the one butting with horns” – is 3.6° to the upper right of Mercury.

In a typical binocular, either Mercury and Venus fit into the field of view or Mercury and Elnath fit in the field, but not all three. 

Here’s more about Mercury during May 2021.

At this time look for Mars 25.0° to the upper left of Mercury and about one-third of the way up in the sky.  Mercury and Mars do not have a conjunction during this evening apparition of Mercury, but they are together in a difficult to see conjunction later during the summer.

Mars is beneath Castor and Pollux as it marches eastward in Gemini.

Here’s more about Mars during 2021.

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

The bright moon, 74% illuminated, is over halfway up in the south, 11.5° to the lower left of Denebola, “the lion’s tail.”

Detailed Note: Bright Jupiter (m = −2.4) is over 24° above the southeast horizon.  Jupiter moves eastward in Aquarius.  This morning it is 2.1° to the upper left of ι Aqr, 4.5° to the lower right of θ Aqr, and 4.9° to the lower right of σ Aqr. Saturn – nearly 27° up in the south-southeast – is 17.2° to the upper right of Jupiter.  Tomorrow, the Ringed wonder stops its eastward trek and begins to retrograde, slowly at first.  This morning the planet is 0.5° to the right of θ Cap. The Pleiades star cluster has the same ecliptic longitude as the sun. During the early evening, three bright planets are in the western sky.  Thirty minutes after sunset, brilliant Venus is nearly 7° above the west-northwest horizon.  Use a binocular to spot Mercury (m = 1.0), 6.4° to the upper left of Venus. The moon (10.3d, 74%) is over 50° above the southern horizon. As the sky darkens further, brighter stars, Mercury, and Mars become visible. Forty-five minutes after sunset, Venus is over 4° above the horizon, while Mercury’s altitude is over 10°.  This speedy planet is 3.6° to the lower left of Elnath. Mars – over 25° to the upper left of Mercury – is 29.0° up in the west, 2.1° to the right of δ Gem and 8.0° to the lower left of Pollux.  The gibbous moon is 11.5° to the lower left of Denebola.  By one hour after sunset, Venus is over 2° above the west-northwest horizon; Mercury is nearly 8° above the horizon; and Mars is over 26° above the western horizon.

Read more about the planets during May 2021.