by Elena Polinsky
If you were looking to the western skies at any point month of October, you may have spotted a small streak of light, just visible to the naked eye. That small streak was the comet Tsuchinshan-ATLAS, or C-2023-A3. The comet was discovered by a team of astronomers at the Purple Mountain Observatory in China, which is where it got its name. “Tsuchinshan” (紫金山) translates to “purple mountain” in Chinese. The “ATLAS” part of the name comes from the “Asteroid Terrestrial-impact Last Alert System,” which is one of four robotic survey telescopes deployed by NASA. ATLAS detected the comet in February, independently of Purple Mountain. It was named in honor of both observatories. The other name, C-2023-A3, is its scientific code name. The “C” indicates that the comet has a long orbital period, followed by year of discovery. The A3, indicates that it was actually the third comet discovered in the first half of January.
The comet reached perihelion, or the closest point in its orbit to the sun, in late September of this year, just after it became visible to the naked eye. It continued to brighten until its peak closeness to earth on October 12th. Due to its timely arrival, some have taken to calling it “the Halloween Comet,” and personally, as a lover of both astronomy and Halloween, I like that one best.
What’s a comet? You may have heard comets referred to as “dirty snowballs” and this is not inaccurate. Comets are primarily composed of the ices of various elements, like H2O, methane, carbon dioxide, or ammonia, as well as rock and other bits of space dust and debris.Using spectroscopic astronomy, or the study of colors spectrum to indicate chemical makeup, thetail and coma of the comet, Tsuchinshan-ATLAS was observed to have a strong cyanide emission, as well as to be carbon depleted. Comets originate from two possible places: comets with short orbital periods from the Kuiper belt, which is a massive and expansive ring of ice and rock that extends beyond Neptune’s orbit. These comets have orbits of 200 years or less, like Halley’s Comet.
Fun Fact! Pluto is a Kuiper belt object!
On the other hand, comets with long orbital periods, like Tsuchinshan-ATLAS, are believed to come from the Oort Cloud, which is a spherical shell of a similar composition to the Kuiper belt that encases the entire solar system, almost like a snow globe. Unlike, the Kuiper belt, it is not considered to be a part of the solar system, but rather is something that lies outside it. Speaking of orbits, some news reports on the time frame for the Halloween Comet’s orbit have been false, saying that it visited 60,000 years ago, and that it would again in another 60,000. In truth, the time frame is much, much longer, as in at least 300,000 years. In fact, it’s possible that this is the first time the Halloween comet has passed our sun. to me, this makes its name as the Halloween comet even more fitting. This October could have been the first time this comet ever entered our solar system and was seen by human eyes. It was also, unfortunately, the last. The Halloween Comet is part of a class called sungrazing comets, of which the name is quite self-explanatory. According to NASA, as the already in shambles Halloween Comet reentered perihelion on approximately October 29th, it was completely vaporized (ironically, just missing Halloween).
Fun Fact! Some theories suggest that the Star of Bethlehem from the biblical Christmas story might have been a comet!
Photo by NASA astronaut Matthew Dominick, while aboard the International Space Station on Sept. 22, 2024
Elena Polinsky is a first-year MFA student studying poetry at Chatham University.