On Feb. 2, everyone in a physics or astronomy class at Swarthmore received an email from the department’s administrative coordinator promoting an event hosted by the Society of Physics Students (SPS). This event was one of several observation nights hosted throughout the academic year, which have always been open to the entire student body and the general public. Typically, these events are sparsely attended, with mostly SPS members sharing the Peter van de Kamp Observatory with a few local parents bringing their children around to look at planets, the Moon, or sometimes the Pleiades cluster.
I always find them fun; I love the build of anticipation as I climb up the stairs of the Science Center and the excitement as I open the door and emerge onto the rooftop. Also, there’s almost always the pleasure of showing someone the way to the observatory for the first time. When new attendees reach the third floor, they look around nervously, seeing that there aren’t any other ways to the observatory, but feeling that it must be against the rules to just walk out onto the roof. That’s followed by a moment of wonder as someone signals to them that it’s okay to come outside, or even better, when their confusion is broken by a group coming through the door in the opposite direction to them. Although this observation night ended up being different than most, these moments were still present.
The most striking feature of this observation night was that it was packed. Whereas a usual night of telescopic stargazing might draw in a trickle of people over a few hours, this night had dozens of people crowding the telescope, standing on the roof, and even occupying the main computer room almost the entire time. The widespread excitement for the observation was probably due to the event’s star: comet C/2022 E3. Discovered in March of last year, the long-period comet has made a stir as a new object visible in the sky that is either a passing visitor from outside the solar system or won’t return to its current location for ~50,000 years. Pretty neat. Neat enough to draw a large gathering to a below-freezing temperature roof for three hours.
I arrived at the starting time, 8:00 pm, when the telescope had not yet been set up. The only things to do for about 30-40 minutes was to stand around, look at the light-polluted sky with some binoculars, and try to find constellations with an app on my phone. (As an Astronomy major, I’m a little embarrassed to say that I can only consistently find Orion and Ursa Major without a guide.) Seeing that there would be a rush to the telescope once it was ready, I decided to stay outside as long as possible. Still, because it was in the low tens and my tennis shoes didn’t offer much insulation, I ended up doing an awkward shuffle, standing outside until I stopped feeling my toes before warming up inside for a minute. Rinse and repeat maybe five or six times.
Unfortunately, I timed my last return inside just as it was announced that the telescope was ready. Everyone streamed out, leaving me freezing outside at the back of a line I had planned to be at the front of using my foolproof method of waiting out in the cold. Of course, everyone wants to get a good look through the telescope once they get there, so the line doesn’t exactly move fast once it forms, but it’s fun hearing the excited chatter about what they hope to see once they get to the front. After maybe ten minutes, I was finally at the doorway to the observatory, where I could shelter myself from the wind without losing my spot in line. Unfortunately, I also heard the first stirring of disgruntlement amongst the crowd. People were coming down the stairway, saying they couldn’t tell what they were supposed to be seeing or that it was blurry or other complaints. Undeterred and definitely not subject to the sunk-cost fallacy at this point, I persisted in line, finally reaching the telescope about an hour and a half into the night. I said hello to the host of the night, Professor Jesse Rivera of the physics and astronomy department, before looking through one of the available lenses. The person ahead of me had described it as what she imagined looking at a ghost would be like. I could see why: the comet was just a faint, semi-transparent blob of whitish-greenish light in the bottom corner of the lens.
But it’s so much more than that! This thing is a chunk of ice and carbon zipping through the solar system, and we can see it. We might be a little spoiled on fancy composite images that are color-coded to have lots of nice contrast to the human eye, but a raw observation like this is nothing to sneer at. Even those somewhat dismissive comments about its faintness, transparency, and color reveal cool physics. It’s so faint because it’s tiny, it’s transparent because what we can see through the telescope isn’t the solid core of the comet but the fuzzy, gaseous cloud around it caused by sunlight vaporizing its exterior, and it’s that greenish color because of the chemical composition. I thought it was quite a rewarding experience. Comet C/2022 E3 is already past its closest point to the Sun, and due to the nature of orbital mechanics, that means it’s on its way back out into the far reaches of space. So regardless of how the attendees felt about the experience, I hope they’ll find some satisfaction in knowing they were probably some of the last Swatties ever to see that comet.