The brilliant Morning Star Venus continues to shine as “that bright star” in the east-southeast before sunrise. The moon appears to be caught in the Bull’s Horns this morning as the lunar orb shines from the west-northwest. In the evening sky, Jupiter continues to waltz toward Saturn for their Great Conjunction on December 21, 2020. Mars moves eastward among the stars of Pisces in the east-southeast after sunset.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:59 a.m. CST; Sunset, 4:20 p.m. CST. Check local sources for sunrise and sunset times in your location.
Morning: Brilliant Venus is in the east-southeast before sunrise. It is above the star Zubenelgenubi. The star is in the constellation Libra. During the next few mornings use a binocular note the changing position of Venus compared to the star. The binocular reveals a dimmer star nearby, Mu Librae (μ Lib on the chart above).
At this hour, the bright gibbous moon is low in the west-northwest, between the Horns of Taurus. Zeta Tauri (ζ Tau) and Beta Tauri (β Tau) are the tips of the horns. Block the moon’s brightness with your hand to see the horns. The featured photo above shows a way to block the moon’s brightness. Although, at the mid-northern latitudes the trees are now leafless, find a creative way to see the stars near the bright moon.
Mercury is rapid disappearing into the sun’s glare. It’s very low in the east-southeast during the final phase of twilight before sunrise about 30 minutes before sunrise. You’ll need a binocular and a very clear natural horizon to see it.
Morning detailed note: One hour before sunrise, brilliant Venus (m = −3.9) – low in the east-southeast – is the lone bright morning planet. It is among the stars of Libra, 3.8° to the upper right of Zubenelgenubi (α Lib, m = 2.8). Use a binocular to spot the brilliant planet 2.1° to the upper right of Mu Librae (μ Lib, m = 5.3). Through a telescope, Venus is a morning gibbous, 89% illuminated and 11.6” across. The gibbous moon (16.3 days after the New phase, 99% illuminated) – nearly 21° up in the west-northwest – is between the Horns of Taurus. Block the moon’s glare to see the stars that mark the horn’s tips. Zeta Tauri (ζ Tau, m = 3.0) is 4.2° to the upper left of the moon. Beta Tauri (β Tau, m = 1.6) is 5.8° to the upper right of the lunar orb. Mercury (− 0.8) rises about 50 minutes before sunrise. By 30 minutes before sunrise, the planet is less than 3° in altitude in the east-southeast, clearly a challenge to see. Daylight is a minute less than 9.5 hours long. Until the solstice, daylight loses less than 25 minutes. The shortest daylight of the year is with us.
See our summary about Venus during December 2020 and the feature article about Venus as a Morning Star.
Evening: In the evening, Mars, Jupiter and Saturn to gleam from the sky. Jupiter continues to waltz toward Saturn in the southwest. Jupiter is the brightest “star” in that region of the sky. Saturn is 2.1° to the upper left of the Jovian Giant. Make nightly observations to watch the gap close. Notice on the chart that they are near 56 Sagittarii (56 Sgr). Use this star as a reference for their changing nightly positions through a binocular. If you hold the binocular steady you could see up to four of Jupiter’s brightest moons on either side of the planet. Look for Jupiter early after sunset, it sets about 7:40 p.m. CST or about 3.3 hours after sunset. The Great Conjunction occurs in 20 days.
Bright rusty Mars is in the east-southeast. It is moving eastward compared to the starry background. Turn your binocular toward Mars and notice two stars Epsilon Piscium (ε Psc on the chart) and 80 Piscium (80 Psc). During the next few evenings, Mars moves between them. The Red Planet sets in the west at about 2:30 a.m. CST tomorrow morning, nearly 4.5 hours before sunrise.
Evening detailed note: One hour after sunset, Jupiter (m = −2.0) and Saturn (0.6) are about 19° up in the southwest. The gap between the planets is 2.1°. Saturn is to Jupiter’s upper left. Great Conjunction Countdown: 20 days. In the starfield, Jupiter is 2.1° to the lower left of 56 Sagittarii (56 Sgr, m = 4.8), while Saturn is 3.7° to the upper left of that star. Additionally, Saturn is 4.5° to the lower right of Sigma Capricorni (σ Cap, m = 5.2). Use a binocular to track the progress of the planets compared to these stars. Jupiter sets about 7:40 p.m. Saturn follows several minutes later. Mars (m = −1.1) is 80.9° of ecliptic longitude east of Jupiter. The gap between them opens during December as Mars picks up eastward speed after the conclusion of its recent retrograde. Through a telescope, the Red Planet is 14.4” across. At this hour, the planet is over 38° in altitude above the east-southeast horizon. While its brightness is diminished since its October 13 opposition, the rusty tint and brightness makes it the brightest “star” in the eastern sky at this hour. It seems to move across the sky during the night, setting in the west about 2:30 a.m. CST, long before Venus rises. Among the stars, Mars is 1.2° to the lower right of Epsilon Piscium (ε Psc, m = 4.2) and 1.7° to the upper right of 80 Piscium (80 Psc, m = 5.5). With a binocular, watch the planet move between the two stars during the next few evenings. About 3 hours after sunset (7:20 p.m. CST), the bright gibbous moon (16.8d, 97%) is nearly 20° up in the east-northeast. Now outside the Horns of Taurus, the lunar orb is 5.1° to the lower left of ζ Tau and 8.4° below β Tau.
For more about the Great Conjunction, read our feature article. This is the closest Jupiter – Saturn conjunction since 1623.
Here is more about the planets during December 2020.
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