A stunning celestial visitor, Comet C/2025 A6 (Lemmon), is lighting up the night sky this week with its brilliant emerald glow — and it’s not coming back for another thousand years. For sky watchers and astronomy lovers, this is a truly once-in-a-lifetime event.
A Celestial Visitor from the Edge of the Solar System
Comet Lemmon originated from the Oort Cloud, a distant icy region beyond Pluto where ancient remnants from the birth of our solar system reside. As it makes its rare journey into the inner solar system, sunlight heats the comet’s icy surface, releasing gas and dust that create its bright coma and long tail. According to National Geographic, scientists describe comets like Lemmon as “frozen time capsules,” preserving the original building blocks of our solar system.
Why Is the Comet Green?
The vivid green color of Comet Lemmon is caused by diatomic carbon (C₂) — a molecule that emits green light when excited by ultraviolet radiation from the Sun. As these molecules break apart near the comet’s head, they create a glowing green halo, making it one of the most visually striking comets of the decade. Astronomers say this hue is best seen through binoculars or a small telescope, though in darker areas, it might be visible to the naked eye. NVIDIA Supercharges Jupiter, Europe’s New Supercomputing Giant
When and Where to Watch
Comet Lemmon will be closest to Earth around October 21, coinciding perfectly with the new moon, which means the skies will be darker and ideal for viewing. Look westward shortly after sunset — near the constellations Scorpius or Libra — to spot its faint green glow. The comet’s brightness will gradually fade through early November, so this week offers the best chance to catch it. Using stargazing apps can help locate its exact position above your horizon.
A Double Sky Treat
Interestingly, Comet Lemmon’s close approach aligns with the Orionids meteor shower, peaking the same night. This creates a rare double treat for night-sky enthusiasts — a glowing green comet and a cascade of shooting stars sharing the same sky.
As astronomer Rhonda Stroud told National Geographic, “Comet Lemmon is definitely the best comet to view from Earth this year.” Considering it won’t return for over a millennium, this week’s spectacle is not one to miss.
