Two Remarkable Comets Could Illuminate the October Sky… Here’s How to Spot Them!
October promises a celestial treat for skywatchers with the potential visibility of not one, but two comets: A6 Lemmon and C/2025 R2 (Swan). Both offer opportunities for observation, potentially even with the naked eye under dark skies.
Currently, Comet A6 Lemmon displays a magnitude of 8.5, but is predicted to brighten substantially, potentially reaching a magnitude of 3.9 around october 21st.This increase in brightness could make it visible without the aid of instruments under optimal viewing conditions. this notable brightening is due to the comet’s favorable trajectory, positioned at a distance that allows for observation without being overwhelmed by the sun’s glare. Astronomers suggest the best viewing will be in the days leading up to its closest approach, when it will be nearly as shining but positioned higher in the sky after twilight, offering a clearer view with a distinct horizon and recognizable celestial landmarks.
How to Observe A6 Lemmon:
To locate A6 Lemmon, binoculars are recommended, along with a dark sky location, far from light pollution. On October 21st, the comet will be approximately 42 degrees from the sun in the western sky, becoming visible roughly an hour after sunset. While low on the horizon, it should be distinguishable through binoculars. The bright star Arcturus, the fourth brightest in the sky, will be nearby, and Izar (Epsilon Bootis) will be even closer, serving as helpful guides for amateur astronomers. observing a few days before October 21st is optimal, as the comet will be higher in the twilight sky, providing a better view of its tail and coma – the clouds of gas and dust surrounding the nucleus.
Despite the promising outlook, comets are inherently unpredictable. they can fragment or diminish in brightness as they approach the sun. Though, Comet Lemmon currently has favorable conditions; its closest approach to Earth occurs before its perihelion (closest approach to the sun), reducing the risk of fragmentation and increasing the likelihood of a bright and stable display.
A Second Comet in Sight: C/2025 R2 (Swan)
Discovered on images of the Swan constellation by Ukrainian amateur astronomer Vladimir Bezugly, Comet C/2025 R2 (Swan) is a long-period comet with an estimated orbital period of 22,554 years. Its tail is reported to be roughly the same length as five full moons.
Currently, Swan R2 is near the sun, visible primarily from the southern hemisphere just after twilight. However, its position will improve significantly on October 21st, when it will be just 0.27 astronomical units (AU) from Earth – about a quarter of the Earth-Sun distance. This proximity could bring its magnitude to 4, potentially making it visible to the naked eye in dark skies, even from locations like France. There’s even a possibility of Earth passing through the comet’s debris trail between October 4th and 6th,potentially resulting in an exceptional meteor shower.
Even if it doesn’t shine brightly enough for naked-eye viewing, Comet Swan should be easily observable with binoculars or a telescope.
[Image of Comet 2025/A6 Credit: Dimitris Katevainis via Flickr]
