2021, April 19: Moon, Twins, Mars, Evening Watch


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.

Chart Caption – 2021, April 19: In the evening, the bright, nearly half-full moon falls in line with Pollux and Castor. Mars is above the Bull’s horns.

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.

2021, May 12: Spectacular Venus-Moon Grouping

May 12, 2021: Thirty minutes after sunset, the razor-thin moon is 1.2° to the left of brilliant Venus.  This is the closest grouping of the moon and Venus during this evening appearance of the brilliant planet.  Mercury is 9.1° to the upper left of Venus.  Mars maintains its eastward march in Gemini. Sirius and Aldebaran are near their heliacal settings, their final appearances in the evening sky for the year.

2021, May 12: Morning Planets Jupiter, Saturn

May 12, 2021: Before sunrise bright Jupiter, in front of Aquarius, is in the southeast before sunrise.  Saturn is to the upper right of Jupiter, in Capricornus.  In a few mornings, Saturn begins to retrograde.

2021, May 11: Planets March On

May 11, 2021: The planet parade continues today. Five planets are on display.  Bright Jupiter and Saturn are in the southeastern sky before sunrise.  After sundown, brilliant Venus, Mercury, and Mars are in the western sky.  The moon is at its New phase and at apogee today.

Categories: Astronomy, Sky Watching

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