This morning’s sky extravaganza includes a thin crescent near Morning Star Venus and Spica. The trio make a pretty triangle. Mercury appears to the lower left of the celestial trio. In the evening sky, Mars ends its retrograde motion, as Jupiter closes in on Saturn before their Great Conjunction on December 21, 2020.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:39 a.m. CST; Sunset, 4:31 p.m. CST. Check local sources for sunrise and sunset times for your location.
Morning: This morning look toward the east-southeast about an hour before sunrise. Brilliant Venus appears 8.1° to the upper right of a thin crescent moon that is only 4% illuminated. In the clear morning sky Venus, Spica, and the moon make a nice triangle. Spica is the bright star to the lower right of Venus and upper right of the lunar slice.
Photograph the scene with exposures up to 10 seconds, depending on the camera’s settings. (For this a camera should be attached to a tripod.) Exposures of a few seconds will show that the nighttime portion of the moon is gently bathed in reflected sunlight from Earth’s oceans, land and clouds. This is known as Earthshine. It is visible through a binocular as well.
On our planet the same occurs when the bright moonlight of a full moon or gibbous phase lightly illuminates the landscape, casting shadows.
Use a binocular to note that the brilliant planet is to the lower left of Theta Virginis (θ Vir on the chart). Venus is closing in toward a widely-spaced conjunction with Spica.
Depending on your view toward the horizon, Mercury is over 9° to the lower left of Spica. If you look at the scene about 45 minutes before sunrise, Mercury is nearly 9° in altitude above the east-southeast horizon.
This is Mercury’s best morning appearance of the year. Because of its proximity to the sun, this speedy planet zips around the sun in 88 days, but it never strays far from the sun and is visible during either morning twilight or evening twilight.
During autumn mornings, the plane of the solar system, known as the ecliptic, is tilted favorably to see Mercury when the first rock from the sun moves into favorable view. The same occurs during springtime evenings.
We last saw Mercury in the morning during the summer when all five planets were visible. Luckily on July 19, 2020, the crescent moon was nearby to help us spot the planet during twilight. At its next appearance, in the evening sky, Mercury set about 45 minutes after sunset, making it nearly impossible to locate in the bright twilight.
Morning detailed note: One hour before sunrise, sparkling Venus – nearly 18° up in the east-southeast – is 8.1° to the upper right of the old moon (27.7d, 4%) and 5.5° to the upper left of Spica. Venus, the moon, and Spica make a nice triangle. Venus is closing in on a widely-spaced conjunction with Spica. Among the dimmer stars, Venus is 1.5° to the lower left of θ Vir. The lunar crescent is 6.9° to the lower left of Spica and 5.1° above Mercury. The Venus – Mercury gap is 12.8°. Forty-five minutes before sunrise, Mercury is nearly 9° in altitude above the east-southeast horizon.
Evening: Mars stops moving westward compared to the ecliptic. Tomorrow it ends moving westward compared to the celestial equator. The planet begins to move slowly eastward again compared to the starry background. The planet is the “rusty” star in the east-southeast after sunset among the dim stars of Pisces.
During the night the planet appears to move across the sky. It is south about 9:15 p.m. The Red Planet sets in the west about 3:40 a.m., before Venus rises in the east.
The motion compared to the starry background is from the combined motion of Mars and Earth. As our planet catches and passes the outer planets, they appear to move westward. The proof that earth revolves around the sun did not occur until after the invention of precise telescopic equipment to measure the parallax of the stars that is from the earth’s revolution around the sun. A book by the same name (Parallax: The Race to Measure the Cosmos) outlines how this occurred.
Use a binocular to observe that the Red Planet is 3.2° to the lower right of Epsilon Piscium (ε Psc on the chart) and 3.1° below Delta Piscium (δ Psc).
Jupiter and Saturn are farther west among the stars of eastern Sagittarius. Both worlds are moving eastward against a faint starry background. A binocular helps here as well to make nightly observations of their changing places.
Bright Jupiter is less than a third of the way up in the sky above the south-southwest horizon. Saturn is 3.9° to the upper left of the Jovian Giant.
In the starfield Jupiter is 2.8° to the lower right of dim star 56 Sagittarii (56 Sgr on the chart), while Saturn is 2.5° to the lower left of the star. Jupiter is also 2.7° to the upper left of 50 Sgr.
Jupiter is slowly overtaking Saturn as a prelude to the Great Conjunction of December 21, 2020.
For more about Mars during November, see this article.
Evening detailed note: Evening: Mars’ retrograde ends today along the ecliptic. Retrograde ends tomorrow in equatorial coordinates. One hour after sunset, Mars is over 28° up in the east-southeast, 3.2° to the lower right of ε Psc and 3.1° below δ Psc. Farther west, Jupiter is nearly 23° in altitude in the south-southwest, 3.9° to the lower right of Saturn. Compared to 56 Sgr, Jupiter is 2.8° to the star’s lower right, while Saturn is 2.5° to the lower left. Jupiter is 2.7° to the upper left of dimmer 50 Sgr.
Read more about the planets during November.
May 28, 2021: This evening Mercury passes brilliant Venus for the second of three conjunctions during this evening apparition of the second planet from the sun. Use a binocular about 45 minutes after sunset to see the speedy planet 0.4° to the lower left of Venus. This is the closest visible conjunction until 2033.
May 24, 2021: Morning planets Jupiter and Saturn are in the southeast before sunrise. In the evening sky, brilliant Evening Star Venus, Mercury, and Mars line up along the solar system’s plane. The bright moon is in the southeast near Zubenelgenubi, “the southern claw.”
May 23, 2021: Five bright planets parade across the sky. Jupiter and Saturn are visible before sunrise in the southeastern sky. The star Fomalhaut is becoming visible below bright Jupiter and near the horizon. After sundown, Evening Star Venus, Mercury, and Mars are in the western sky. The bright moon is in the southeastern sky during the nighttime hours.
May 22, 2021: Five planets parade across the sky. Jupiter and Saturn are in the southeast before sunrise. Evening Star Venus, Mercury and Mars are in the western sky after sunset. A bright moon is in the southeastern sky.
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.