2021, December 21:  Winter Solstice

December 21, 2021: The winter solstice occurs at 9:59 a.m. CST. Mars is in the morning sky along with a bright moon. The planet pack, Venus, Jupiter, and Saturn, is in the southwestern sky after sunset.

2021, December 21: Mars makes nearly an equilateral triangle with Graffias and Dschubba this morning.
Image Caption – 2021, December 21: Mars makes nearly an equilateral triangle with Graffias and Dschubba this morning.

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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 reaches the winter solstice today at 9:59 a.m. CST.  The solstice is an imaginary mark on the ecliptic, the plane of the solar system.  This point is farthest south of the celestial equator, the extension of Earth’s equator into the sky.  The winter solstice is 270° along the ecliptic from the starting point, the vernal (or spring) equinox, when the sun seems to cross the celestial equator as it appears to move northward.

As Earth revolves around the sun, the solar globe appears to move along the ecliptic.  The tilt of Earth causes the sun to appear high in the southern sky during the northern hemisphere’s summer and low during the winter months.

Today, daylight lasts nine hours, eight minutes.

From today and until June 21 at 4:14 a.m. CDT, the sun appears higher in the sky, although its daily change does not seem to be much until February 1.

The southern hemisphere’s seasons are opposite the northern’s seasons.  So, our readers there welcome the first day of summer, long days and short nights, and Christmas at the beach!

Morning Sky

Mars is visible low in the morning sky before sunrise.  It is moving eastward through Scorpius.

About 45 minutes before sunrise, use a binocular to find the Red Planet nearly 10° up in the southeastern sky.  The star Graffias is 2.4° to the upper right of Mars.  Dschubba is 3.4° to the right of the planet.

The trio is nearly an equilateral triangle that fits easily into a binocular field.  Can you see Mars without a binocular?

Antares is making its first morning appearance.  Can you find it 6.3° below Mars?  Put the planet at the top of the binocular field.  The star is near the bottom.  This is a little challenging as Antares is only about 3° above the horizon.  During the next few mornings, the star appears higher.  In five mornings, Mars passes 4.5° to the upper left of Antares.

Farther westward, the bright gibbous moon, is 3.3° to the lower left of Pollux.

Evening Sky

2021, December 21: Venus, Saturn, and Jupiter are in the southwestern sky after sunset.
Image Caption – 2021, December 21: Venus, Saturn, and Jupiter are in the southwestern sky after sunset.

The evening planet parade continues in the southwest after sunset.  Brilliant Venus is easy to spot in the southwest as night falls.  By one hour after sunset, it is about 10° up in the sky.  It is by far the brightest “star,” but don’t confuse it with the lights on a distant airplane.

Through a modest telescope, Venus displays an evening crescent phase that is 10% illuminated.

Venus is retrograding as it moves toward its inferior conjunction, between Earth and the sun early next year.

Jupiter is the next brightest star in the evening sky.  It is over 30° to the upper left of brilliant Venus.  Moving eastward in Aquarius, the Jovian Giant is 5.1° to the upper left of the star Deneb Algedi.

Saturn is between Venus and Jupiter, 14.5° to the upper left of the Evening Star and 17.8° to the lower right of Jupiter.

A year ago, Jupiter passed closely to Saturn for their bi-decennial Great Conjunction.

Jupiter has opened this small gap to Saturn.  Both are slow-moving and as Jupiter ambles eastward, Saturn pokes along behind it.  Jupiter will complete its orbit around the sun and catch Saturn again before the Ringed Wonder completes a single orbit.

The moon rises about 3 hours after sundown this evening.

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