December 21, 2020: On Winter Solstice morning, brilliant Venus is low in the southeast before sunrise. Antares is near is annual heliacal rising.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:15 a.m. CST; Sunset, 4:23 p.m. CST. Check local sources for sunrise and sunset times for your location.
The sun makes its lowest arc across the sky today, rising and setting at its farthest south points. The sun’s rising and setting points slowly move northward along the horizon and the diurnal arc of the sun increases in height after today. The sun’s celestial coordinates place it at a point known as the winter solstice. The sun is 270° from its location on the first day of spring – the Vernal Equinox.
Astronomically, this is the first day of winter (in the Northern Hemisphere), beginning when the sun’s celestial coordinate is 270° at 4.02 a.m. CST.
As the sky brightens this morning, Venus is low in the southeast. It is slowly slipping back into the sun’s glare.
The star Antares is making its first morning appearance (heliacal rising) this week. If you have a clear horizon to the southeast, Antares is very low in the sky. A binocular helps. During the next few mornings, the star becomes visible without the help of a binocular.
Predicting heliacal rising dates is tricky. They occur when the star is at a threshold altitude above the horizon about 45 minutes before sunrise. A clear sky without any clouds or haze to the natural horizon is needed. The first observed date depends on the individual’s location and the weather.
This occurred with Sirius last summer. This writer observed Sirius with a binocular for a few mornings as clouds moved in and out of the region where the star appeared. Then one morning it is visible without the help of optics after a cloudy morning.
Detailed Note: The winter solstice occurs at 4:02 a.m. CST. Forty-five minutes before sunrise, Venus is less than 10° up in the southeast, 3.8° to the lower left of β Sco and 0.7° to the right of Psi Scorpii (ψ Sco, m = 4.5). Use a binocular to see the star. This morning’s test is whether Antares is visible. Venus is 6.2° to the upper left of Antares (α Sco, m =1.0). The star is less than 4° in altitude. You’ll need exceptional observing conditions and a binocular to see it.
Read more about the planets during December.
January 26, 2021: Visible high in the south after sunset, Mars is in Aries heading for an early March conjunction with the Pleiades star cluster.
Depending on the latitude, the time of equal light and equal darkness occurs during early February.
January 22-24, 2021: The bright gibbous moon moves through Taurus during the evening.