Comet A3 Tsuchinshan ATLAS's return is statistically more likely for extraterrestrial beings than for Earth dwellers, given its orbit spans over 100,000 years.
Get Ready to Wave Goodbye to Comet A3 Tsuchinshan-ATLAS, Possibly Forever
The next few weeks offer your last chance to catch a glimpse of Comet A3 Tsuchinshan-ATLAS before it disappears from Earth's view, but will this comet make a comeback?
For months, this celestial beauty has captivated stargazers, yet, a crucial detail about its orbit often goes unmentioned in online reports - its orbital period, the time it takes to orbit around our Sun.
Contrary to the widespread belief that it's a long-period comet visiting Earth every 80,000 years, experts say the truth is far from it. In fact, they believe it might be the comet's first - and potentially last - visit to the inner Solar System.
"A3 likely hasn't penetrated Earth's vicinity before, and it won't again," declares Karl Battams from the Naval Research Laboratory in Washington, who's been running the Sungrazer Comets Project since 2003.
As the comet approached the Sun, its journey seemed to follow a long, elliptical path with an orbital period estimated to be in the range of hundreds of millions of years. This suggests its origins lie far beyond the Sun's gravitational pull.
"A3 didn't spend its entire existence on our orbit; instead, it was nudged onto it, most likely due to gravitational forces, long ago," explains Battams.
What is the Comet's Orbit?
However, this doesn't mean A3's orbit remains hundreds of millions of years long. As the comet neared its closest approach to the Sun, known as perihelion, on September 27, 2024, the Sun's gravity altered its path, making its orbit less elongated.
"Now A3 follows an orbit that seems more like a few hundred thousand years long," says Battams, "But even at that length, it would eventually find itself so far out in space that minor gravitational influences from other star systems could sway it off-course or steal it away entirely."
Uncertainty in Measuring a Comet's Orbit
The main hurdle astronomers face when measuring a comet's orbit is that comets can only be observed during the short window they are within the inner Solar System.
"All we can do is observe the comet's apparent path during the relatively short window we've had observations, and use that information to guess at its complete orbit," explains Battams. By measuring the current motion of the comet in the sky, astronomers like those at the Sungrazer Comets Project are able to trace the comet's path and determine its orbital path.
"For objects with short-period orbits, this measurement is usually very precise. But for comets like A3, which travel vast distances in space, uncertainty is unavoidable regarding its position in the distant past and future."
The wiggle-room in projected path measurements means the comet's orbital parameters continue to be updated as more observations are collected.
It's possible that various media outlets based their reports on outdated measurements of the comet's orbit, which were published shortly after its discovery when data was scarce.
Where Can I Find the Latest Information?
One of the biggest challenges is the absence of a centralized repository for comet information. According to Battams, "NASA's JPL Horizons" is a reliable source for up-to-date data on the comet's orbit. For details about its past, present, and predicted future brightness, the Comet Observation Database is quite useful.
"Of course, there's a legion of skilled astrophotographers who will continue to enjoy this comet's show for a few more weeks," says Battams, despite the comet now being too faint to see with the naked eye.
So, before A3 disappears entirely, take a look at our gallery featuring some of the best photographs of the comet.
Where Did Comet A3 Tsuchinshan-ATLAS Come From?
Though it's possible the comet may have been nabbed from another star, the most likely scenario is that it has spent its life floating around in the Oort Cloud, a theorized 'reservoir' of comets lurking at the Solar System's outskirts.
A passing star, another comet, or a collision might have given A3 just enough of a push to steer it into our Solar System. Such comets are dynamically new, meaning they have never approached the Sun, and their ices and gases remain untouched since the formation of the Solar System.
"A3's new orbit points it right back into the 'comet limbo' from where it came, where it will be so weakly bound to our Sun that it may leave the Solar System forever," says Battams. In essence, it's more likely that an extraterrestrial civilization will get to see this comet again instead of Earth.
- A3 Tsuchinshan-ATLAS's orbital period, contrary to popular belief, is not 80,000 years; instead, scientists estimate it to be in the range of hundreds of millions of years.
- As the comet neared its closest approach to the Sun, the Sun's gravity altered its path, making its orbit less elongated, possibly extending to a few hundred thousand years.
- The main challenge astronomers face when measuring a comet's orbit is the short timeframe comets are within the inner Solar System, causing uncertainty regarding their position in the distant past and future.
- For up-to-date data on Comet A3 Tsuchinshan-ATLAS's orbit, one can rely on NASA's JPL Horizons, while the Comet Observation Database provides details about its past, present, and predicted future brightness.
