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Astro Bob: Celestial sights at the solstice

Happy first day of winter! The sun did the limbo today, dipping as low as it could go. Plus, I have an update on Comet Leonard's eruption and a map to find it.

Winter season Orion with snow pines Jan 3 2010 V2.jpg
Orion glides over snow-clad spruce trees on a winter night. Contributed / Bob King
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At 9:59 a.m. CST Tuesday morning (Dec. 21) the sun finally bottomed out in the sky, six months after it began its southward journey on the summer solstice. The start of winter lasted only a moment. Before the clock read 9:59:01, the sun had already turned the corner and was heading north again. Nothing stands still in the cosmos. Earth's motion around the sun is the cause of the sun's apparent motion in the sky. As long as the planet skedaddles along its orbit, the sun continuously slides east across the sky.

Ecliptic sun yearly motion Durham University Community Different take.jpg
The sun appears to move to the east (left in the northern hemisphere) throughout the year as Earth orbits the sun. It up-and-down movement is caused by Earth's 23.5° tilt. In summer, the sun dips south in the sky. In winter it climbs back to the north. The red line is called the celestial equator, located midway between the two extremes. It's the path the sun would follow if Earth had no tilt. Contributed / Durham University with additions by Bob King

If the Earth's axis were straight up and down instead of tilted at a 23.5° angle, the sun would rise due east, set due west and pass due south at the same altitude every day of the year. There would be just one season — spring, or if you like, fall. But the tilt of Earth's axis over the course of its orbit "plays" the sun, causing it to move north and south in the sky. And that's precisely why we have four seasons instead of one.

While the solstice is instantaneous, winter is not. In northern Minnesota, it's been here for a month already and has plans to stay until at least March. Waking up to four inches of fresh snow this morning was a further reminder of the new season. Give it to me! I'm ready for Orion, Gemini and full moons that light up the night like day.

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Venus Saturn Jupiter line Dec 20 2021 S ANNO.jpg
The three-planet-slant has become a familiar sight at dusk the past few months. But we'll soon lose Venus, which transitions to the morning sky in the next few weeks. I took this photo around 6 p.m. on Dec. 20, 2021. Contributed / Bob King

What I'm not ready for is seeing Venus depart its fellow bright planets Jupiter and Saturn in the southwestern sky at dusk. The trio has been hanging out together for months. Sadly, we're in the middle of a long goodbye as Venus prepares to shove off for the morning sky on January 8. That's when it will pass directly between the Earth and sun in inferior conjunction. For a couple weeks centered on that date, we'll lose sight of it in the solar glare. The three familiar dusk "stars" will dwindle to two.

Not so fast! Attempting to fill those big Venusian shoes, Mercury briefly comes to the rescue for a little more than two weeks starting around Dec. 28. Watch for it to pop up below and to the left of Venus in the final days of 2021. Venus disappears in the twilight glow around Jan. 2 but will reappear in the eastern sky at dawn around the 20th. Since this planetary hopscotch happens around the New Year, Venus serves as a delightful metaphor of transition and change, topics topmost on minds of many as the old year gives way to the new. Follow your inner star.

Comet Leonard dusk Dec 20 2021 S.jpg
Comet Leonard, though relatively bright, appears very low in the southwestern sky during evening twilight and is difficult to spot. While its recent outburst helped, the comet looks like a very dim smudge in typical binoculars for skywatchers in the northern U.S. states — because it's so low, the atmosphere soaks up most of its light. The farther south you live, the higher the comet climbs and the easier it is to see. Folks living in the southern U.S. and farther south should have little difficulty spotting it in binoculars. I took this photo on Dec. 21, 2021 at around 5:45 p.m. when Leonard stood just a few degrees high. A tail trailing to the left is faintly visible. Details: 200-mm lens, f/2.8, ISO 3200 and 2-second exposure. Contributed / Bob King

Comet Leonard has been a big topic on the Internet this past week, with lots of hyperventilating about how bright it's become after a recent explosion. Well, it's definitely brighter. When the comet arrived in the evening sky a week ago, it wasn't particularly obvious. But a recent disruption in the icy heart of the comet called nucleus on Dec. 19 vaulted its brightness to around magnitude 2.5-3. Suddenly, it was possible to see it from places like Minnesota.

Just one little problem. Altitude. By the time the sky gets reasonably dark (about one hour to 75 minutes after sunset), the comet is so low (between 3-5°) that it's virtually impossible to see unless you know exactly where to look. Even then, Leonard looks like a faint puffball in binoculars. I know because I went out under very clear skies last night, and although I found and photographed Leonard, it was faint. The view in the telescope was better, with the comet showing a bright, glowing core and short tail pointing east-southeast.

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Comet Leonard Dec 19 Arizona 150 mm lens Chris Schur.jpg
From Payson, Arizona Comet Leonard stood about 11° high on Dec. 19 and displayed a beautiful tail during its recent bright outburst. Details: 150-mm lens, f/2.8, stacked 5-second exposures. Contributed / Chris Schur

Its brightness at the time was about magnitude 3. If it were higher up in a dark sky, as it is in the southern U.S. and particularly in southern hemisphere, we'd see it without optical aid. I'm including a map here to help you find it. I used the bright planets and the two labeled stars in the bottom of Capricornus to guide me to the location. I first spotted this faint fuzzy by taking pictures and studying the back viewfinder on the camera. Once I knew where to look, I could point my binoculars to the spot and see it. But again, not easy!

Comet Leonard Duluth Dec 21_25 2021 S.jpg
This map shows the comet's nightly position about 60-70 minutes after sunset from the northern U.S. The map faces southwest. The comet will be in the same position from other locations but will appear higher in the sky the farther south you live. In the north, it's about 3-5° high compared to Phoenix, where it stands at 11-12°. Contributed / Stellarium with additions by Bob King

Comet Leonard will gradually pull away from the sun in the next few weeks but remain stubbornly low for observers in the northern half of the U.S. I hope you find it just the same — good luck!

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob .

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune.
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