If you live where it snows, you know the noises it makes when stepped on. In warmer temperatures, the snow emanates with a krunk-krunk-krunk rumble. As the air cools, it rises in height. In sub-zero weather the snow squeaks loudly and sounds like stepping on styrofoam.
Comets are made up of ice, dust and rock at low temperatures. Walking on them might not be different from walking on rocks. But I would like to think that there would sometimes be slippery spots, clumps of dust to hit and lift, and brittle, rotten ice ready to crumble at the slightest glance. Certainly, it will be a long time before someone sticks a boot in there. But that shouldn’t stop us from imagining the possibilities when we point our telescopes at those winter comets the next crisp and clear night.
Comet Leonardo (C / 2021 A1)
Comet Leonard (C / 2021 A1) has stolen the show in recent weeks with its cyclical explosions, disconnect events and spectacular photogenic tail. On December 29, from the dark skies of the Atacama Desert, Daniele Gasparri captured a 60 ° long fluffy ion tail that looked like chimney smoke twisting in the wind. Not bad for a mile-wide comet that peaked at around 3rd magnitude during its brightest eruption.
“Parked” for now in the southwest corner of Piscis Austrinus, Comet Leonard passed perihelion on January 3 and vanished at magnitude 5.5 to 6 (January 7). He still sports a bright coma and a faint east-pointing tail visible through binoculars from dark skies, but only to southern hemisphere observers. For the most part, he left the northern skies at the end of December. My last sighting was on Christmas Eve, when Leonard barely came out for the twilight air.
Expect the comet to reach magnitude 10 by mid-February. If you can, say goodbye to him – Leonard has arrived in a parabolic orbit, but he’s going into a hyperbolic orbit and will never make a smile again.
Comet 19P / Borrelly
I was happy to start the New Year with my first look at this well-known periodic comet during its current appearance. Despite the light pollution amplified by a recent snowfall, 19P / Borrelly exhibited a small, well-condensed 2-minute arc coma in my 15-inch Dob (used for all of these observations) at 64x magnification. I applied a Swan Band filter, which improves the apparent brightness and contrast of gas-rich comets, but saw no change in its appearance.
Comet 19P / Borrelly appears near magnitude 2 Deneb Kaitos, also known as Beta (β) Ceti, earlier this month as it heads northeast of Cetus towards Pisces at a bit less of 1 ° per day. Hunt it early in the evening as soon as it gets dark when the comet peaks in the southern sky. Borrelly will hover around magnitude 9 to 9.5 all month, then slowly fade, although it will remain brighter than 11th magnitude until March. Good news as it will pass just one degree south of the complicated reflection nebula NGC 1333 on March 15-16 and roughly the same distance off the southern coast of the California Nebula (NGC 1499) on March 26-27. . These should make for good photo opportunities. (See the January 2022 issue of Sky & Telescope for a detailed graph of Comet Borrelly’s path this month.)
Comet 104P / Kowal
On January 2 UT, after jumping for stars between 30 and 33 Piscium, I landed on a large, soft, circular glow about 4 inches in diameter with a magnitude of 9.8. Even through the light pollution, 104P / Kowal was easy to spot at low magnification (64x), and this time the Swan filter made the difference, increasing the comet’s contrast and further brightening the internal coma.
On January 5 and 6, it passes from the south of Pisces to Cetus, moving northeast. Kowal will peak at magnitude around 9.5 this month and then fade away. Watch it pass just north of magnitude 4 Alpha (α) Piscium on the night of January 27 – about 8 ′ from Europe and Africa and 12 ′ from the Americas.
American astronomer Charles Kowal, who worked at the Mount Wilson and Palomar observatories, discovered the object in 1979. It is a member of the Jupiter comet family, so called because their current orbits are mainly shaped by the gravitational influence of this planet. Kowal died in 2011, but his comet returns to the inner solar system every 5.7 years.
ATLAS (C / 2019 L3)
Now at full brightness with a magnitude of 9.5, this wonderful little comet is ideally located in Gemini for sky watchers in the Northern Hemisphere. Don’t be fooled by its small size. The coma has a high surface brightness and a bright, star-like pseudo-nucleus (DC = 7 as of January 1.05 UT). ATLAS clings to it between magnitude 9 and 10.5 until March while slowly forming an arc southwest through Gemini. On the nights of January 30 and 31, it passes approximately 20 ′ east-southeast of the attractive open cluster NGC 2266.
ATLAS is an acronym for Asteroid Terrestrial-impact Last Alert System and consists of two telescopes 100 miles apart on separate Hawaiian islands that automatically scan the sky several times a night for moving objects. To date, the investigation has discovered hundreds of near-Earth and potentially dangerous asteroids, 65 comets and more than 10,000 supernovae.
Comet 67P / Churyumov-Gerasimenko
“Chury” has lasted, having provided excellent views since the fall. Although slowly fading, the comet continues to glow around magnitude 9.5 in early January as it slides east to southeast across northern Cancer. To find it, start with Iota (ι) Cancri of magnitude 4, a magnificent and colorful double star (magnitudes 4.2, 6.6; separation 30 ″). Comet 67P passes within ½ ° north of this gem on January 15th.
On Jan 2, 23 UT I observed a moderately condensed coma 2.5 arcmin wide (DC = 5) with a brighter, fuzzier false core and a beautiful pale tail about 12 inches long pointing to the west. Average magnifications of around 100 × help bring out this dusty trail better.
Thanks to the incredibly detailed images returned by the European Space Agency’s Rosetta mission, we can easily imagine the genius two-lobed shape of the 67P, the jets of dust and the crumbling cliffs every clear January evening.
PanSTARRS (C / 2017 K2)
Watching this eagerly awaited comet means getting up early. I observed it just before the start of early morning twilight low in the eastern sky at Ophiuchus on January 2, 50. It appeared small – about 1.5 ′ in diameter – and moderately compact with DC = 5 and a magnitude of 11, 8. It seems small until you realize that K2 is currently 5.1 au from Earth, almost the same distance as Jupiter is from the Sun.
Its distance decreases as it slowly clears up for the rest of the year. After heading east through Ophiuchus, it crosses Aquila in early March, makes a steep, slow turn, and leaves the constellation on May 10. As it picks up speed, K2 slopes southwest through Ophiuchus and clears up to a magnitude of 8 to 8.5 during the summer. On July 15, it passed ½ ° northwest of the brilliant globular cluster M10.
The comet plunges into evening twilight by September for northern observers, but southern hemisphere sky watchers will be able to follow it to its December 7 perihelion and beyond. Although the comet is rather low in Ara and Pavo, it could reach 6th magnitude when it is brightest in late December and early January 2023.