May 4, 2021: Three planets are visible after sunset. Brilliant Venus is low in the west-northwest after sundown. Mercury is above Venus. It is visible lower as the sky darkens. As night falls, Mars is over a third of the way up in the west, under Castor and Pollux, the Gemini Twins.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 5:43 a.m. CDT; Sunset, 7:53 p.m. CDT. Check local sources for sunrise and sunset times for your location.
Five planets are visible during a 24-hour period. This evening, Venus and Mercury are visible during brighter twilight. Mars is visible when the sky is darker in the western sky.
Twenty minutes after sunset, brilliant Venus is about 5° up in the west-northwest. The window to see Venus is narrow, as it sets about 50 minutes after sunset. A binocular may be needed to initially see the brilliant planet.
Read more about Venus in our summary document.
Bright Mercury is nearly 7° to the upper left of Venus. The planet is enroute to its best evening appearance of the year. This speedy planet sets about 90 minutes after sunset. As the sky darkens, it is visible lower in the west-northwest sky.
Forty-five minutes after sunset, Mercury is about 7° above the horizon. With a binocular, spot the Pleiades star cluster to the lower right of Mercury. The cluster is not in the best observing location. The gap from Mercury to the cluster’s brightest star, Alcyone (η Tau on the chart), is 4.4°.
Here’s more about Mercury during May 2021.
When the sky is darker, around an hour after sunset, Mars is over 35° up in the west among the stars of Gemini, under Castor and Pollux. The planet is moving eastward compared to these stars. The plane of the solar system, known as the ecliptic, generally cuts across the constellation from the lower right corner of the diagram to the upper left.
Mars’ eastward march takes it from tonight’s place to the lower left of Pollux by month’s end.
This evening, Mars is 2.6° to the upper right of Tejat Posterior (μ Gem on the chart) and 3.2° to the lower right of Mebsuta (ε Gem).
Tomorrow morning look for the moon near Jupiter and Saturn.
Here’s more about Mars during 2021.
Detailed Note: One hour before sunrise, the moon (22.3d, 48%) is over 15° above the southeastern horizon. Bright Jupiter is 8.9° to the moon’s upper left, while Saturn is 9.6° to the upper right of the lunar orb. In the starfield, Saturn is 0.9° to the right of θ Cap. Jupiter is 1.3° above ι Aqr. Twenty minutes after sunset, Venus is nearly 5° up in the west-northwest. Mercury (m = −0.8) is 6.9° to the upper left of Venus. Mercury sets about 90 minutes after sunset. As the sky darkens it is lower in the sky above the west-northwest horizon. By 30 minutes after sunset, Venus is nearly 4° above the horizon, while Mercury is 10.0° up in the sky. Forty-five minutes after sunset, Mercury is over 7° in altitude and 4.4° to the upper left of η Tau. By one hour after sunset, Mercury is about 5° above the horizon. At this hour, Mars is visible over 35° to the upper left of Mercury among the stars of Gemini. The Red Planet is 2.6° to the upper right of μ Gem and 3.2° to the lower right of ε Gem.
Read more about the planets during May 2021.
October 23, 2021: This morning the bright moon is near the Pleiades star cluster. Mercury is making its best morning appearance. In the evening sky, Venus, Jupiter and Saturn are easy to spot.
October 22. 2021: Speedy Mercury is low in the east before sunrise. It is putting on its best morning performance of the year. Arcturus, in the east-northeast, is about the same altitude as Mercury.
October 21-November 1, 2021: Brilliant Venus steps through Ophiuchus to the upper left of the star Antares in the southwest after sunset . Afterward, the planet steps farther eastward.
October 21, 2021: The bright moon is low in the west about an hour before sunrise. Mercury is in the east at about the same altitude as Arcturus. Venus, Saturn, and Jupiter shine from the evening sky.
December 18, 2021: This is the anticipated launch date of the James Webb Space Telescope, the largest and most sophisticated space telescope view the universe.