Skywatchers around the world are being treated to a spectacular celestial event — two glowing green comets streaking across the evening sky. But time is running out, as astronomers warn this may be the last opportunity to see them for more than a millennium.
The star of the show is Comet C/2025 A6 (Lemmon), a long-period comet discovered earlier this year. Scientists estimate its orbital period at around 1,150 years, meaning it won’t return to Earth’s skies until the year 3175. The comet has been steadily brightening as it approaches the Sun, releasing gas and dust that form its vivid emerald glow.
Joining it is Comet C/2025 R2 (SWAN), another green-tinged traveler currently visible near Lemmon in the twilight sky. Though fainter, it adds to the rare sight of two comets appearing simultaneously — a phenomenon that only occurs once in many generations.
The green coloration comes from molecules like diatomic carbon and cyanogen that emit a bright green light when exposed to sunlight. As the comets move closer to the Sun, these gases vaporize, giving the objects their ghostly hue and distinctive tails.
To catch a glimpse of this fleeting display, look toward the western horizon shortly after sunset. Observers in the Northern Hemisphere, especially in regions with clear skies and minimal light pollution, stand the best chance of seeing the comets with the naked eye. A pair of binoculars will enhance the view, revealing the hazy coma and faint trailing tail.
Experts advise patience and preparation: find a dark, unobstructed location and allow your eyes to adjust to the darkness for several minutes. The comets are visible for only a short window each evening before they dip below the horizon.
Events like this remind us of the immense scale and rhythm of the cosmos. These icy wanderers spend thousands of years traveling through deep space before briefly gracing our skies. For many on Earth today, this is a once-in-a-lifetime opportunity to witness two ancient messengers from the far reaches of the Solar System.
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