Discovery of a Celestial Visitor
Astronomers have announced the discovery of a new comet, glowing green as it moves across the night sky. The comet, officially named C/2025 R2 (SWAN) or SWAN25B, was first observed on September 11 by Vladimir Bezugly. He detected it in images from the Solar and Heliospheric Observatory, a spacecraft primarily used to study the Sun. NASA described the comet as “surprisingly bright” despite being located close to the Sun’s glare. The greenish hue comes from gases in its atmosphere that emit light when struck by solar radiation, and a faint tail makes it especially captivating.
This discovery immediately drew attention from the astronomy community because of its unusual brightness and long orbital path. Unlike most short-period comets, which return within decades, SWAN takes an extraordinary 22,000 years to orbit the Sun. That means no human alive today will ever see it again after this passage.
Opportunities for Stargazers
Skywatchers will have two prime chances to spot the comet this October. The first opportunity comes on October 2, when SWAN will pass near Zubenelgenubi, the alpha star of Libra. From the southern hemisphere, the comet may be visible just above the western horizon after sunset. Binoculars or small telescopes are recommended for clearer viewing.
The second and most anticipated viewing window will occur around October 20, when the comet makes its closest approach to Earth. Astronomers say that under ideal conditions, especially in rural areas with little light pollution, the comet’s green glow should be visible to the naked eye. In urban environments, binoculars will greatly improve the experience.
NASA emphasized that observers should not expect the kind of spectacular display seen with famous comets like Hale-Bopp in the 1990s. Still, the uniqueness of SWAN’s orbit and composition makes this sighting an important and memorable astronomical event.
A Rare Phenomenon
Experts note that SWAN belongs to a category of rare interstellar or long-period comets. Max Gilbraith, planetarium coordinator at the University of Wyoming, pointed out that Earth has encountered only a few such objects in modern times. “It’s the third time we’ve ever discovered something coming from outside the solar system,” he explained in an interview, adding that these events suggest Earth may be passing through a region of space containing remnants of ancient interstellar debris.
Over the past eight years, three rare comets have been discovered, defying expectations about their scarcity. Some scientists now believe that more such objects may be detected in the future as technology improves and sky surveys expand. For astronomers, SWAN provides an opportunity to study the composition of a visitor that has spent millennia in the outer reaches of the solar system.
Once-in-a-Lifetime Encounter
The extraordinary orbital path of SWAN makes this event especially significant. With a 22,000-year journey around the Sun, the comet will not return within any conceivable human timeframe. EarthSky, an astronomy outlet, has called it a “true once-in-a-lifetime visitor.”
Comets like SWAN provide insights into the early solar system. Their pristine ices and organic molecules are preserved for billions of years, offering scientists a glimpse of the building blocks that may have contributed to the origins of life. The green color visible in SWAN’s atmosphere is believed to result from diatomic carbon, a molecule that glows when exposed to ultraviolet sunlight. Studying its chemical makeup could help scientists compare it with other comets and expand understanding of cosmic chemistry.
For the general public, the appearance of SWAN is more than a scientific milestone — it is also a reminder of the scale and mystery of the universe. Seeing the glowing visitor sweep across the night sky connects people across generations to the timeless human tradition of watching the heavens.
Looking Ahead
Astronomy enthusiasts around the world are preparing for October’s skywatching opportunities. From backyard telescopes to professional observatories, countless eyes will turn toward Libra and beyond to catch a glimpse of the green comet. While SWAN may not dominate the sky like Halley’s Comet once did, its rarity ensures that it will remain a highlight of 2025’s astronomical calendar.
In an era when light pollution often obscures the stars, events like this encourage renewed appreciation for the night sky. Whether seen through binoculars, telescopes, or even unaided eyes, the chance to witness a once-in-a-lifetime comet is a rare gift for this generation.