Bakersfield Night Sky — December 21, 2024
Bakersfield College and the William M Thomas Planetarium are on winter break. We will resume evening shows in February, starting with the “Mesmerica” shows in early February. The Mesmerica shows will have a different scheduling than we had this semester: one Friday/Saturday night per month of shows. As before, the Mesmerica tickets will be sold through the Mesmerica website while the regular Planetarium shows will be sold through Vallitix.
Today marked the official start of winter with the December solstice. I use the past tense since the precise time of the solstice is when the sun reaches its absolute most southern point on the sky and that happened at 1:21 a.m. this morning, Pacific Standard Time. Today marks the shortest amount of daylight — the longest night of the year. Although the December solstice is the longest night of the year, the earliest sunset for the year was near the beginning of December, on December 6 and 7 and the latest sunrise for the year is near the beginning of January, on January 5 and 6.
This mismatch between the solstice and sunset/sunrise times is because of the tilt of the Earth’s rotation axis with respect to its orbit and the slight ellipticity of Earth’s orbit around the sun that makes Earth move slightly faster in January when we’re closest to the sun and slightly slower in July when we’re farthest from the sun. This causes the timings between when the sun crosses the meridian and the next day when it crosses the meridian, what is called a “solar day”, to vary slightly from the rock-steady uniform time of our clocks. This variation is described by the “Equation of Time”. I have diagrams explaining this a bit more in the “Astronomy Without a Telescope” chapter of my online Astronomy Notes textbook website. No subscription needed.
During late fall and early winter, the sun stays fairly low in the sky, so its light hits the ground at a shallower, more glancing angle. This dilutes the heating power of the sunlight. Also, with the sun up above the horizon for a shorter time during the fall and winter, the diluted heating power of the sun doesn’t have the time it needs to heat things up. The opposite of this happens in the spring and summer, so the concentrated heating power of the sun has plenty of time to heat things up. The result is significantly cooler temperatures in late fall/early winter than in late spring/early summer.
In the evening sky starting at shortly after 7:30 p.m. to about 7:50 p.m., you might be able to see four planets up in the sky at the same time, depending on the amount of haze near the horizon. Low in the southwest will be super-bright Venus. Higher up among the dim stars of Aquarius will be Saturn. A bit more than halfway up in the east between the two horns of Taurus, will be brilliant Jupiter. Low in the northeast will be orange-red Mars, shining brighter than all of the true stars except Sirius. The only planet missing from the show is Mercury. It’s currently visible in the predawn sky low in the east, long after Venus and Saturn have set.
A bit to the right of Jupiter will be yellow-orange Aldebaran at the eye of Taurus and above Aldebaran will be the Pleiades star cluster. Below Jupiter and Aldebaran, the famous winter constellation of Orion shines with Betelgeuse and Bellatrix at his shoulders, the three bright belt stars at his waist, and Saiph and Rigel at his knees. When Mars becomes visible in the northeast, you’ll see to the right of Mars, at about the same altitude, Procyon at one end of Canis Minor and Sirius at the nose or neck of Canis Major (depending on how you connect the dots of the constellation). The attached star chart shows the eastern sky at 9:30 p.m., when all of Canis Major is visible plus some details of Orion’s belt. Another way to find Sirius is to extend the line of Orion’s belt stars down to the left. When you extend the belt stars up to the right, you’ll hit Aldebaran.
The moon is now in the waning gibbous phase tonight, so we’ll see it rise at about 11:30 p.m. Tomorrow it will be at third (or last) quarter, appearing lit on just its left half. In the predawn hours of Christmas Eve, December 24, a waning crescent moon will be right next to Virgo’s brightest star, Spica. At less than three degrees apart from each other, both will fit comfortably in the same field of view of your binoculars. Four mornings later, on December 28, a very thin waning crescent moon will be almost on top of the bright star, Antares, at the heart of Scorpius in the southeast. People in the southern hemisphere below the tropics will be able to see the moon cover up (occult) Antares. To the left of Antares is Mercury, making its best predawn show of the year. By mid-February of next year, Mercury will have moved to the left (east) side of the sun, so we’ll be able to see it with the rest of the naked eye planets in the evening.
During this holiday season, I hope you’ll enjoy celebrations with friends and family and also take some time to gaze up at the night sky!
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Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com
