Comet Tsuchinshan-ATLAS Climbs, Brightens and Delights!

By: Bob King October 15, 2024 7

Treat yourself to a comet bright enough to see plainly even in moonlight. Tsuchinshan-ATLAS beckons at dusk!

C/2023 A3 Oct 13 — Comet Tsuchinshan-ATLAS (C/2023 A3) was a beautiful naked-eye and binocular sight at dusk on October 13th from near McGregor, Minnesota, about 90 minutes after sundown. The tail extended 7° in binoculars and 5° with the naked eye — even in bright moonlight! A faint segment of the antitail glows pink below and right of the comet's head. Image details: 100-mm lens, f/2.8, ISO 3200, 2-second exposure, single shot. Don't think you need a fancy camera to photograph this comet — I've seen some great images of it taken with ordinary smartphones.
*Bob King*

Rising from the solar fire, Comet Tsuchinshan-ATLAS (C/2023 A3) triumphantly returned at dusk on October 11th after intense anticipation by amateur astronomers and the public alike. That evening, I drove 15 miles north of home and methodically swept the sky to the right of Venus with binoculars. Exactly 40 minutes after sunset I stopped — there it was! The comet exhibited a tiny, bright coma and a ghostly tail that showed up best in short time exposures with a telephoto lens. Despite excellent sky conditions I saw nothing with the unaided eye.

C/2023 A3 Oct 12 — "Comet Tsuchinshan-Atlas glows low in the western sky above the fog covered Pacific Ocean as seen from Southern California," writes photographer Chris Cook. "The comet was easily naked eye with a fan shaped tail visible out to over 7° in 7×50 binoculars." Image details: October 12th, Canon EOS 6D Mark II, Tamron 150-600-mm lens, ISO2000, 20 × 2 second exposures.
*Chris Cook*

But just one night later, the comet's altitude had risen sufficiently that many observers had no problem seeing it without optical aid. Through binoculars the tail grew to 7°. Both single and stacked images revealed rays within the tail and the first signs of the antitail below the comet's head. Already the antitail has narrowed dramatically (as of October 14th) and should continue to mimic a laser beam on Tuesday night, October 15th, as Earth crosses through C/2023 A3's orbital plane.

C/2023 A3 crosses LASCO C3 — Comet C/2023 A3 crosses the 16°-wide field of view of the LASCO C3 coronagraph from October 7th through October 14th. After the head we see the bright dust tail, comprised of recently ejected fine dust particles, followed by the fainter antitail, formed from dust deposited along the comet's orbit in recent months. On the final date, the antitail narrows to a line as Earth passes through the comet's orbital plane.
*ESA / NASA / SOHO*

Even before C/2023 A3 slipped back into the evening sky we watched its progress across the LASCO C3 coronagraph on the orbiting Solar and Heliospheric Observatory (SOHO). The comet's head arrived first, followed by a bright and brilliant dust tail set aglow by forward-scattered sunlight. The combination dust-and-anti-tail extends for at least 50°!

C/2023 A3 on Oct. 11 — Comet Tsuchinshan-ATLAS is steeped in dusk on October 11th, the night of its return to northern evening skies. The image reveals a compact nuclear region and faint 3° tail pointing east. Image details: 600-mm lens, f/6.3, ISO 3200, and a 0.4-second time exposure.
*Bob King*

Altitude makes a big difference in being able to trace the full breadth of a comet's tail(s), and we'll have that in spades in the next few weeks as this feathery gem climbs the southwestern sky rung by rung, gaining about ~3° elevation per night. On October 11th when I first spotted the comet at dusk, I needed binoculars to identify it. Two nights later, after it had climbed an additional 7°, not only was the head visible but 5° of tail, too. On October 14th it was a feather of light in the west with a 10° tail visible even in bright moonlight.

C/2023 A3 and M5 — Don't forget! The comet will be in conjunction just 1° south of the 6th-magnitude globular cluster M5 on the night of October 15th.
*Stellarium with additions by Bob King*

Parting is such sweet sorrow

The comet is currently visible in the western sky about 2½ fists to the upper right of Venus and dimly visible with the naked eye and binoculars as soon as 45 minutes after local sunset. You'll see it best between 1 and 2 hours after sunset as the sky gets darker. Use this sunrise-sunset calculator to determine when the Sun sets at your location.

C/2023 A3 will slowly fade as it departs Earth's vicinity, traveling faster than 195,000 kilometers per hour on October 15th. Moonlight has been and will continue to be an issue until about October 20th when we'll see the comet again in a dark sky with the Moon three days past full. On that date it should glow at 3rd magnitude, sport both ion and dust tails, and make a splendid naked-eye sight from the countryside. Although it will have dimmed to 6th magnitude by Halloween, rural observers might still glimpse it. The rest of us should easily spot it in binoculars.

C/2023 A3 with 8-inch RASA — The comet exhibits fountains of dust streaming from the nuclear region into the tail, delicate tail rays, and an antitail in this photo made on the night of October 13th. Image details: Celestron RASA 8-inch and ZWO ASI6200MC Pro
*Dan Bartlett*

This snowball from the cold version of hell will be with us for some time. Even as its brightness takes a slow tumble, the comet will keep a light on for ardent observers, glowing at around magnitude 10.5 in Aquila at year's end. We'll see it fade, shrink, and lose its tail as it returns to deep space. Although C/2023 A3's orbital parameters are still in flux, it will likely not return for millions of years.

US map for C/2023 A3 — Map dates show the comet's position during evening hours for time zones in the contiguous U.S. states. The comet quickly climbs away from the Sun into a dark sky, while steadily fading. On October 14th it will shine at around +0.5 magnitude; magnitude 2.5 on October 17th; and magnitude 4 on October 22nd.
*Sky & Telescope graphics*

Having watched Comet Tsuchinshan-ATLAS evolve from a 13th-magnitude fuzzball last winter into the bright and elegant object that now adorns the evening sky fills me with gratitude. Most comets don't become easy naked-eye objects, making this a precious opportunity for amateurs to witness the myriad facets of a comet's "life" cycle.

C/2023 A3 dust shells — These spectacular close-ups of the comet's inner coma / nuclear region reveal dust shells created by jets unwinding from the comet's spinning nucleus. I was able to spot one of the shells on October 13th in my 10-inch f/4.7 Newtonian using a magnification of 166×. Image details: October 13th, 25-cm Newtonian f/4.8, 60 10-second exposures
*Toni Scarmato*

Enjoy these additional images. You'll find many more in the Comet Watch and ICQ Comet Observations Facebook groups.

C/2023 A3 anti-tail — This is one of the best early images of the comet's antitail, taken on October 13th from Zacatecas, Mexico. Image details: Nikon D750, 150-mm focal length telephoto, f/2.8, ISO 800, stack of 10 images
*Da Ko*

C/2023 A3 and moon — There's no question that the brilliant Moon dims the comet, but there's a flip side. The Moon can serve as a light source to illuminate foreground scenes for your photographs. These are students in my community education astronomy class watching the comet on Oct. 15th.
*Bob King*

C/2023 A3 from Tucson — With its columnar profile, C/2023 A3 fits well among these saguaro cacti in Tucson on October 12th. Some beginning observers are confusing the comet with airplane contrails. When viewed at a great distance, contrails do indeed resemble comets, but they dissipate in a matter of minutes while a comet lingers for days and months.
*Scotty Bishop*

C/2023 with antitail — The comet displayed a strikingly narrow antitail the night of October 14th from near Floodwood, Minnesota. The same night I traced the main tail to 15°. Image details: 100-mm telephoto, f/2.8, ISO 3200, 1.3-second exposure.
*Bob King*

C/2023 C3 video — Amateur astronomer Suresh Sreenivasan of Hopkins, Minnesota, created this video of the comet as it sets through cloud bands on October 13th. Video details: Nikon D7200, 50-mm f/1.8, ISO 320, 5-second exposures. Video is 101 frames at 10 fps.

C/2023 A3 IR vs. RGB — These images from October 12th compare views of the comet taken through an RGB filter (left) and infrared (IR) filter. The IR filter broadens the dust tail and makes the head appear more compact.
*Eliot Herman*

About Bob King

I love the sky (day and night) and have been a skywatcher and amateur astronomer since childhood. I'm also a long-time member of the American Association of Variable Star Observers (AAVSO) and Astronomical League. I pen the Astro Bob blog and have written four books: Night Sky with the Naked Eye (2016); Wonders of the Night Sky You Must See Before You Die (2018) and Urban Legends from Space (2019) and Magnificent Aurora, published in 2024. The universe invites us on an adventure every single night. To accept the invitation, we only need look up.

Comments

bob kelly

October 16, 2024 at 1:26 pm

Where's the most solid information about where this comet came from, when it started heading to the inner solar system, and where is it going? I keep hearing '80,000 year' period, and 'fell in from the Oort Cloud' and 'may be ejected from the solar system'. What's the story with the most data backing it up?