April 19, 2021: Venus begins to appear in the west after sunset. The moon lines up with Pollux and Castor, while Mars is above Bull’s horns in the western evening sky.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:04 a.m. CDT; Sunset, 7:36 p.m. CDT. Check local sources for sunrise and sunset times for your location.
Venus begins its evening apparition. Find it low in the west-northwest about 20 minutes after sunset.
Read more about Venus in our summary document.
One hour after sunset, the nearly half-full moon is over two-thirds of the way up in the sky in the southwest. It is 5.0° to the lower left of Pollux, a Gemini Twin. Notice that the moon, Pollux, and Castor appear along the same imaginary line.
At this time, Mars is less than halfway up in the west. It is above the Bull’s horns, Elnath and Zeta Tauri (ζ Tau on the chart). This evening the Red Planet is 4.6° to the upper right of Zeta Tauri.
In five evenings, Mars moves into Gemini.
Here’s more about Mars during 2021.
Read about Mars during April.
Detailed Note: One hour before sunrise, Saturn – nearly 18° above the southeast horizon – is 1.5° to the upper right of θ Cap. Jupiter (m = −2.2) – over 13° up in the east-southeast – is 13.9° to the lower left of Saturn. In the starfield, Jupiter is 3.3° to the upper left of Deneb Algiedi, 0.4° to the lower left of μ Cap, and 2.8° to the upper right of Iota Aquarii (ι Aqr, m = 4.3). Use a binocular to find the starry background and to observe Jupiter’s eastward trek compared to it. In six mornings, Jupiter crosses into Aquarius. Twenty minutes after sunset, Venus (m = −3.9) is making its first naked-eye evening appearance. This prediction is from factors described by Jean Meeus’ book, Mathematical Astronomy Morsels. Find it about 2° up in the west-northwest. In a darker sky, forty minutes later, the moon (8.0d, 48%) is over two-thirds of the way up in the southwest. It is 5.0° to the lower left of Pollux. The half-full moon, Pollux, and Castor (α Gem, m = 1.6) are in a line. Meanwhile, farther west, Mars is about 40° up in the west. It is 4.6° to the upper right of ζ Tau.
Read more about the planets during April 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.