Eloquent Images by Gary Hart
Insight, information, and inspiration for the inquisitive nature photographer
Gifts From Heaven
Posted on November 3, 2024
Heaven Sent, Comet Tsuchinshan–ATLAS Above the Sierra Crest, Alabama Hills
Sony a7R V
Sony 24-105 f/4 G
ISO 3200
f/4
5 seconds
As much for its (apparently) random arrival as its ethereal beauty, the appearance of a comet has always felt to me like a gift from the heaven. Once a harbinger of great portent, scientific knowledge has eased those comet fears, allowing Earthlings to simply appreciate the breathtaking display.
Unfortunately, scientific knowledge does not equal perfect knowledge. So, while a great comet gives us weeks, months, or even years advance notice of its approach, we can never be certain of how the show will manifest until the comet actually arrives. For every Comet Hale-Bopp, that gave us nearly two years warning before becoming one of the most widely viewed comets in human history, we get many Comet ISONs, which ignited a media frenzy more than a year before its arrival, then completely fizzled just as the promised showtime arrived. ISON’s demise, as well as many highly anticipated comets before and after, taught me not to temper my comet hopes until I actually put eyes on the next proclaimed “comet of the century.” Nevertheless, great show or not, the things we do know about comets—their composition, journey, arrival, and (sometimes) demise—provide a fascinating backstory.
In the simplest possible terms, a comet is a ball of ice and dust that’s (more or less) a few miles across. After languishing for eons in the coldest, darkest reaches of the Solar System, perhaps since the Solar System’s formation, a gravitational nudge from a passing star sends the comet hurtling sunward, following an eccentric elliptical orbit—imagine a stretched rubber band. Looking down on the entire orbit, you’d see the sun tucked just inside one extreme end of the ellipse.
The farther a comet is from the sun, the slower it moves. Some comets take thousands, or even millions, of years to complete a single orbit, but as it approaches the sun, the comet’s frozen nucleus begins to melt. Initially, this just-released material expands only enough to create a mini-atmosphere that remains gravitationally bound to the nucleus, called a coma. At this point the tail-less comet looks like a fuzzy ball when viewed from Earth.
This fuzzy phase is usually the state a comet is in when it’s discovered. Comets are named after their discoverers—once upon a time this was always an astronomer, or astronomers (if discovered at the same time by different astronomers), but in recent years, most new comets are discovered by automated telescopes, or arrays of telescopes, that monitor the sky, like ISON, NEOWISE, PANSTARRS, and ATLAS. Because many comets can have the same common name, astronomers use a more specific code assembled from the year and order of discovery.
As the comet continues toward the sun, the heat increases further and more melting occurs, until some of the material set free is swept back by the rapidly moving charged particles of the solar wind, forming a tail. Pushed by the solar wind, not the comet’s forward motion, the tail always fans out on the side opposite the sun—behind the nucleus as the comet approaches the sun, in front of the comet as it recedes.
Despite accelerating throughout its entire inbound journey, a comet will never move so fast that we’re able to perceive its motion at any given moment. Rather, just like planets and our moon, a comet’s motion relative to the background stars will only be noticeable when viewed from one night to another. And like virtually every other object orbiting the sun, a comet doesn’t create its own light. Rather, the glow we see from the coma and tail is reflected sunlight. The brilliance of its display is determined by the volume and composition of the material freed and swept back by the sun, as well as the comet’s proximity to Earth. The color reflected by a comet’s tail varies somewhat depending on its molecular makeup, but usually appears as some shade of yellow-white.
In addition to the dust tail, some comets exhibit an ion tail that forms when molecules shed by the comet’s nucleus are stripped of electrons by the sun’s ultraviolet radiation. Being lighter than dust molecules, these ions are whisked straight back by the solar wind. Instead of fanning out like the dust tail, these gas ions form a narrow tail that points directly away from the sun. Also unlike the dust tail that shines by reflected light, the ion tail shines by fluorescence, taking on a blue color courtesy of the predominant CO (carbon monoxide) ion.
One significant unknown upon discovery of a new comet is whether it will survive its encounter with the sun at all. While comets that pass close to the sun are more likely to shed large volumes of ice and dust, many sun-grazing comets approach so close that they’re overwhelmed by the sun’s heat and completely disintegrate.
With millions of comets in our Solar System, it would be easy to wonder why they’re not a regular part of our night sky. Actually, Earth is visited by many comets each year, though most are so small, and/or have made so many trips around the sun that they no longer have enough material to put on much of a show. And many comets never get close enough to the sun to be profoundly affected by its heat, or close enough to Earth to shine brightly here.
Despite all the things that can go wrong, every once in a while, all the stars align (so to speak), and the heavens assuage the disappointment of prior underachievers with a brilliant comet. Early one morning in 1970, my dad woke me and we went out in our yard to see Comet Bennett. This was my first comet, a sight I’ll never forget. I was disappointed by the faint smudges of Comet Kohoutek in 1973 (a complete flop compared to its advance billing), and Halley’s Comet in 1986 (just bad orbital luck for Earthlings). Comet Hale-Bopp in 1996 and 1997 was wonderful, while Comet ISON in 2012 disintegrated before it could deliver on its hype.
In 2013 Comet PANSTARRS didn’t put on much of a naked-eye display, but on its day of perihelion, I had the extreme good fortune to be atop Haleakala on Maui, virtually in the shadow of the telescope that discovered it. Even though I couldn’t see the it, using a thin crescent moon I knew to be just 3 degrees from the comet to guide me, I was able to photograph PANSTARRS and the moon together. Then, in the dismal pandemic summer of 2020, Comet NEOWISE surprised us all to put on a beautiful show. I made two trips to Yosemite to photograph it, then was able to photograph it one last time at the Grand Canyon shortly before it faded from sight.
October 2024 promised the potential for two spectacular comets, Comet Tsuchinshan–ATLAS (C/2023 A3) in the first half of the month, and Comet ATLAS (C/2024 S1) at the end of the month. Alas, though this second comet had the potential to be much brighter, it pulled an Icarus and flew too close to the sun (RIP). But Comet Tsuchinshan–ATLAS was another story, brightening beyond expectations.
I shared the story of my trip to photograph Tsuchinshan–ATLAS in my October 16 I’m Not Crazy, I Swear… blog post, but have a couple of things to add about this image. First is how important it is to not get so locked into one great composition that you neglect capturing variety. I captured this wider composition before the image I shared a couple of weeks ago, and was pretty thrilled with it—thrilled enough to consider the night a great success. But I’m so glad that I changed lenses and got the tighter vertical composition shortly before the comet’s head dropped out of sight.
And second is the clearly visible anti-tail that was lost in thin haze near the peaks in my other image. An anti-tail is a faint, post-perihelion spike pointing toward the sun in some comets, caused when larger particles from the coma, too big to be pushed by the solar wind, are left behind. It’s only visible from Earth when we pass through the comet’s orbital plane. Pretty cool.
When will the next great comet arrive? No one knows, but whenever that is, I hope I’ve kindled enough interest that you make an effort to view it. But if you plan to chase comets, either to photograph or simply view, don’t forget the wisdom of astronomer and comet expert, David Levy: “Comets are like cats: they have tails, and do precisely what they want.”
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I’m Not Crazy, I Swear…
Posted on October 16, 2024
Comet Tsuchinshan–ATLAS and Mt. Whitney, Alabama Hills, California
Sony α1
Sony 100-400 GM
5 seconds
f/5.6
ISO 3200
Crazy is as crazy does
In college, my best friend and I drove from San Francisco to San Diego so he could attend a dental appointment he’d scheduled before his recent move back to the Bay Area. We drove all night, 10 hours, arriving at 7:55 a.m. for his 8:00 a.m. appointment (more luck than impeccable timing). I dozed in the car while he went in; he was out in less than an hour, and we drove straight home. I remember very little of the trip, except that each of us got a speeding ticket for our troubles. Every time I’ve told that story, I’ve dismissed it with a chuckle as the foolishness of youth. Now I’m not so sure that youth had much to do with it at all.
I’m having second thoughts on the whole foolishness of youth thing because on Monday, my (non-photographer) wife and I drove nearly 8 hours to Lone Pine so I could photograph Comet Tsuchinshan–ATLAS setting behind Mt. Whitney. We arrived at my chosen location in the Alabama Hills about 15 minutes after the 6:20 sunset, then waited impatiently for the sky to darken enough for the comet to appear. I started photographing at around 7:00, and was done when the comet’s head dropped below Mt. Whitney at 7:30. After spending the night in Lone Pine, we left for home first thing the next morning, pulling into the garage just as the sun set. For those who don’t want to do the math, that’s 16 hours on the road for 30 minutes of photography.
In my defense, for this trip I had the good sense (and financial wherewithal) to get a room in Lone Pine Monday night, and didn’t get pulled over once. That this might have been a crazy idea never occurred to me until I was back at the hotel, and that was only in the context of how the story might sound to others—in my mind this trip was worth every mile, and I have the pictures to prove it.
I say that fully aware that my comet pictures will no doubt be lost in the flood of other Comet Tsuchinshan–ATLAS images we’ll see over the next few weeks, many no doubt far more spectacular than mine. My excitement with the fruits of this trip is entirely personal, and to say I’m thrilled to have witnessed and photographed another comet would be an understatement—especially in light of last month’s Image of the Month e-mail citing comets as one of the three most beautiful celestial subjects I’ve ever witnessed. And of those three, comets feel the most personal to me.
Let me explain
When I was ten, my best friend Rob and I spent most of our daylight hours preparing for our spy careers—crafting and trading coded messages, surreptitiously monitoring classmates, and identifying “secret passages” that would allow us to navigate our neighborhood without being observed. But after dark our attention turned skyward. That’s when we’d set up my telescope (a castoff generously gifted by an astronomer friend from my dad’s Kiwanis Club) on Rob’s front lawn (his house had a better view of the sky than mine) to scan the heavens hoping that we might discover something: a comet, quasar, supernova, black hole, UFO—it didn’t really matter. And repeated failures didn’t deter us.
Nevertheless, our celestial discoveries, while not Earth-changing, were personally significant. Through that telescope we saw Jupiter’s moons, Saturn’s rings, and the changing phases of Venus. We also learned to appreciate the vastness of the universe with the observation that, despite their immense size, stars never appeared larger than a pinpoint, no matter how much magnification we threw at them.
To better understand what we saw, Rob and I turned to illustrated astronomy books. Pictures of planets, galaxies, and nebula amazed us, but we were particularly drawn to the comets: Arend-Roland, Ikeya–Seki, and of course the patriarch of comets, Halley’s Comet (which we learned was scheduled to return in 1986, an impossible wait that might as well have been infinity). With their glowing comas and sweeping tails, it was difficult to imagine that anything that beautiful could be real. When it came time to choose a subject for the annual California Science Fair, comets were an easy choice. And while we didn’t set the world on fire with our project presentation, Rob and I were awarded a ribbon of some color (it wasn’t blue), good enough to land us a spot in the San Joaquin County Fair. (Edit: Uncovering the picture, I see now that our ribbon was yellow.)
Here I am with the fifth grade science project that started it all. (This is only half of the creative team—somewhere there’s a picture that includes Rob.)
The next milestone in my comet obsession occurred a few years later, after my family had moved to Berkeley and baseball had taken over my life. One chilly winter morning my dad woke me and urged me outside to view what I now know was Comet Bennett. Mesmerized, my smoldering comet interest flamed instantly, expanding to include all things astronomy. It stayed with me through high school (when I wasn’t playing baseball), to the point that I actually entered college with an astronomy major that I stuck with for several semesters, until the (unavoidable) quantification of the concepts I loved sapped the joy from me.
While I went on to pursue other things, my affinity for astronomy continued, and comets in particular remained special. Of course with affection comes disappointment: In 1973 Kohoutek fizzled spectacularly, a failure that somewhat prepared me for Halley’s anticlimax in 1986.
By the time Halley’s arrived, word had come down that it was poorly positioned for its typical display (“the worst viewing conditions in 2,000 years”), making it barely visible this time around, but I can’t wait until 2061! (No really—I can’t wait that long. Literally.) Nevertheless, venturing far from the city lights one moonless January night, I found great pleasure locating without aid (after much effort), Halley’s faint smudge in Aquarius.
After many years with no naked-eye comets of note, 1996 arrived with the promise of two great comets. While cautiously optimistic, Kohoutek’s scars prevented me from getting sucked in by the media frenzy. So imagine my excitement when, in early 1996, Comet Hyakutake briefly approached the brightness of Saturn, with a tail stretching more than twenty degrees (forty times the apparent width of a full moon).
But as beautiful as it was, Hyakutake proved to be a mere warm-up for Comet Hale-Bopp, which became visible to the naked eye in mid-1996 and remained visible until December 1997—an unprecedented eighteen months. By spring of 1997 Hale-Bopp had become brighter than Sirius (the brightest star in the sky), its tail approaching 50 degrees. I was in comet heaven. But alas, family and career had preempted my photography pursuits and I didn’t photograph Hale-Bopp.
Comet opportunities again quieted after Hale-Bopp. Then, in early 2007, Comet McNaught caught everyone off-guard, intensifying unexpectedly to briefly outshine Sirius, trailing a thirty-five degree, fan-shaped tail. McNaught put on a much better show in the Southern Hemisphere; in the Northern Hemisphere, because of its proximity in the sky to the sun, it provided a very small window of visibility, and was easily lost in the bright twilight. This, along with its sudden brightening, prevented McNaught from becoming the media event Hale-Bopp was. I only found out about it by accident, on the last day it would be easily visible in the Northern Hemisphere. By then digital capture had rekindled my photography interest (understatement), so despite virtually no time to prepare, I grabbed my camera and headed to the foothills east of Sacramento, where I managed to capture the McNaught image I share in the gallery below—my first successful comet capture.
Following McNaught, I vowed not to be caught off guard by a comet again. After enduring the frustration of promising (over-hyped?) comets disintegrated by the sun (you broke my heart, Comet ISON), and seeing others’ images of spectacular Southern Hemisphere-only comets (I’m looking at you, Comet Lovejoy), my heart jumped when I came across a website proclaiming the approach of Comet PANSTARRS (a.k.a, C/2011 L4 in less glamorous astro-nerd parlance), discovered not by an individual, but by the Pan-STARRS automated telescope array atop Haleakala on Maui.
Researching further, I learned that PANSTARRS could (fingers crossed) hang low in the western sky at magnitudes brighter than Saturn, for about a week right around its perihelion (closest approach to the Sun) in March 2013, remaining visible as it rises but dims over the following few weeks. Checking my calendar to see if I had any conflicts that week, I realized I’d be on Maui for my workshop during PANSTARRS’ perihelion! Turns out my first viewing of PANSTARRS was atop Haleakala, almost literally in the shadow of the telescope that discovered it. I also got to photograph a rapidly fading PANSTARRS above Grand Canyon on its way back to the farthest reaches of the Solar System.
Then, in 2020, came Comet NEOWISE to brighten our pandemic summer. I was able to make two trips to Yosemite and another to Grand Canyon to photograph NEOWISE (the Yosemite trips were for NEOWISE only).
One more time
Comet Tsuchinshan–ATLAS has been on my radar for at least a year, but not something I monitored closely until September, when it became clear that it was brightening as, or better than, expected. By the end of September I knew that the best Northern Hemisphere views of Tsuchinshan–ATLAS would be in mid-October, but since I was already in the Alabama Hills at the end of September, just a couple of days after the comet’s perihelion, I went out to look for it in the pre-sunrise eastern sky (opposite the gorgeous Sierra view to the west). No luck, but that morning only solidified my resolve to give it another shot when it brightened and returned to the post-sunset sky.
At that point I had no detailed plan, and hadn’t even plotted its location in the sky beyond knowing it would be a little above the western horizon shortly after sunset in mid-October. My criteria were a nice west-facing view, distant enough to permit me to use a moderate telephoto lens. After ruling out the California coast (no good telephoto subjects) and Yosemite Valley (no good west-facing views), I soon realized I’d be returning to the east side of the High Sierra.
At that point I started working on more precise coordinates and immediately eliminated my first (and closest) candidate, Olmsted Point, because the setting comet didn’t align with Half Dome. My next choice was Minaret Vista (near Mammoth), a spectacular view of the jagged Minaret range and nearby Mt. Ritter and Mt. Banner. This was a little more promising—the alignment wasn’t perfect, but it was workable. Then I looked at the Alabama Hills and Mt. Whitney and knew instantly I’d be reprising the long drive back down 395 to Lone Pine.
Though its intrinsic magnitude faded each day after its September 27 perihelion, Tsuchinshan–ATLAS’s apparent magnitude (visible brightness viewed from Earth) continued to increase until its closest approach to Earth on October 12. While its magnitude would never be greater than it was on October 12, the comet was still too close to the sun to stand out against sunset’s vestigial glow. But each night it climbed in the sky, a few degrees farther from the sun, toward darker sky.
Though Tsuchinshan–ATLAS would continue rising into increasingly dark skies through the rest of October, and each night would offer a longer viewing window than the prior night, I chose October 14 as the best combination of overall brightness and dark sky. An added bonus for my aspirations to photograph the comet with Mt. Whitney and the Sierra Crest would be the 90% waxing gibbous moon rising behind me, already high enough by sunset to nicely illuminate the peaks after dark, but still far enough away not to significantly wash out the sky surrounding the comet.
At my chosen spot, I set up two tripods and cameras, one armed with my Sony a7RV and 24-105 lens, the other with my Sony a1 and 100-400 lens. I selected that first location because it put the comet almost directly above Mt. Whitney, 16 degrees above the horizon, at 7 p.m. But since the Sierra crest rises about 10 degrees above the horizon when viewed from the Alabama Hills, I knew going in that the comet’s head would slip behind the mountains at 7:30, slamming shut my window of opportunity after only 30 minutes.
When it first appeared, Tsuchinshan–ATLAS was high enough that I mostly used my 24-105 lens. But as it dropped and moved slightly north (to the right), away from Whitney, we hopped in the car and raced about a mile south, to the location I’d chosen knowing that Tsuchinshan–ATLAS would align perfectly with Whitney as it dropped below the peaks. Most of my images from this location were captured with my 100-400 lens.
I manually focused on the comet’s head, or on a nearby relatively bright star, then checked my focus after each image. The scene continued darkening as I shot, and to avoid too much star motion I increased my ISO rather than extending my shutter speed.
As I photographed, I could barely contain my excitement at the image previews on my cameras’ LCD screens. Tsuchinshan–ATLAS and its long tail were clearly visible to my eyes, but the cameras’ ability to accumulate light made it much brighter than what we saw. The image I share today is one of my final images of the night. Even with a shutter speed of only 5 seconds, at a focal length of right around 200mm, if you look closely you’ll still see a little star motion.
My giddiness persisted on the drive back to Lone Pine and into our very nice (and hard earned) dinner. When our server expressed interest in the comet, I went out to the car and grabbed my camera to share my images with her. Whether or not the enthusiasm she showed was genuine, she received a generous tip for indulging me. And even though I usually wait until I’m home to process my images on my large monitor, I couldn’t help staying up well past lights-out to process this one image, just to reassure myself that I hadn’t messed something up (focus is always my biggest concern during a night shoot).
And finally…
FYI, neither Rob nor I became spies, but we have stayed in touch over the years. In fact, the original plan was for him to join me on this adventure, but circumstances interfered and he had to stay home. But we still have hopes for the next comet, which could be years away, or as soon as late this month….
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My Comet History
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Eloquent Images by Gary Hart 