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Astro Bob: I see a Cold Moon rising

The Cold Moon will make you shiver again tonight (Sunday, Dec. 19), plus we update what's happening with Comet Leonard.

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The full Cold Moon rises in the northeastern sky Saturday night, December 18 along the purple-gray edge of Earth's shadow. Tonight (Dec. 19) it will be nearly as full and rise shortly after sunset. Contributed / Bob King
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I stepped outside at midnight last night under the full Cold Moon and sucked in the 1-degree air (-17° C). After rising in the clear, the moon shined through clouds, donned in a ruff of pearly pink light.

We're nearing the winter solstice, when the sun enters the constellation Sagittarius the Archer and arcs lowest in the sky. Meanwhile, the full moon, which lies directly opposite the sun, occupied the very spot sun did on the summer solstice in June. I had to bend back and look up high to take in the sight just as I would the summer sun. But no matter how bright, the moon makes a poor substitute for a star. Shining by reflected light its rays hold no warmth.

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An aureole surrounds the high full moon at midnight last night. Contributed / Bob King

On Saturday (Dec. 18) December's Cold Moon rose shortly before sunset. On Sunday night (Dec. 19) it rises not long after. In Minneapolis for instance, sundown occurs at 4:34 p.m. with moonrise following 15 minutes later at 4:49 p.m. While the moon's phase is slightly past full it will still appear practically full to the unaided eye. And because it comes up after sunset rather than before, the moon will appear brighter and more dramatic at the horizon.

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So if you missed last night's moon — or even if you didn't but just love moonrises — find a location with a view down to the northeastern horizon and check your local rising time here . As a bonus, there will still be enough light in early twilight to capture the moon and landscape simultaneously. Take your photo within about 15 minutes of moonrise, when daylight and moonlight briefly strike a balance.

Comet Leonard sequence Eliot Herman Dec 2021 S.jpg
This sequence of images taken with a 4-inch telescope show changes in Comet Leonard's appearance over three successive nights. Contributed / Eliot Herman

Last night, I joined my friends Eric and Jim to see Comet Leonard one last time before it fades away. While it became the year's brightest comet it barely reached the naked-eye limit when it was still easy to find before dawn in early December. Binoculars showed it as a fuzzy blob with a short tail. On Dec. 11-12, Leonard disappeared in morning twilight and then swiveled around into the evening sky. Disappointingly, it remains stubbornly low in the southwestern sky below Venus for observers in mid-northern latitudes.

Southern hemisphere, who've waited patiently for the comet to head south, now have the best views. From below the equator Leonard will remain visible in binoculars for perhaps another week or two 1-2 hours after sunset. On Dec. 15-16, it brightened up to about magnitude 3, but it's now fading as its distance from the Earth increases.

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This photo shows the comet's appearance in 7x binoculars on Dec. 18, 2021 from the southern hemisphere. Contributed / Piqui Diaz

Armed with binoculars and small telescopes, our impromptu group set up at a road intersection last night and waited for twilight to ebb. Despite our best efforts, not one of us saw the comet in binoculars, but we did pick it up in a 6-inch telescope around 5:30 p.m. Located 6.2° south of Venus and just 4° above the horizon (from Duluth, Minn.), Leonard was a tailless blob of fuzz with a brighter center and a hint of blue-green color. Minutes later, clouds slithered in, and that was that.

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I'd make a map to point you to it, but I think the comet's time is past for northern observers. Like striking up a deep conversation with someone on an airplane who you'll likely never meet again, I hope you were able to make Leonard's acquaintance. And if not, more comets on the way.

Sun sunspots Dec 18 2021 ANNO S.jpg
On Saturday, Dec. 18, no fewer than five sunspot groups were visible in my 3-inch telescope equipped with a safe solar filter. Increased sunspot activity could lead to solar storms that spark auroras. Contributed / Bob King

Finally, I want to share the latest aurora forecast. It's been quiet lately, but we'll see a chance for a minor geomagnetic storm on Dec. 27-28. due to a recurring coronal hole in the sun's atmosphere. Holes are portals for high-speed winds of protons and electrons that stream from the sun and tangle with the Earth's magnetic field. I'll update as we approach the time. There's also a small possibility for aurora from the current gaggle of sunspot groups. They've been subdued so far, but their appearance indicates that solar activity is quickly ramping up. If you have a safe solar filter for your telescope, place it over the front end of the tube and have a look. I haven't seen so many spots in a long time.

"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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