Golden Comet C/2025 K1 (ATLAS) Survives Solar Flyby and Shows Rare Red‑Brown Hue

Comet C/2025 K1 (ATLAS) defies expectations and turns golden

Most comets appear white, yellow, blue or occasionally green — but a rare golden comet is now visible in the sky. C/2025 K1 (ATLAS), an icy visitor discovered in May 2025 by the Asteroid Terrestrial-impact Last Alert System (ATLAS), unexpectedly survived a close perihelion and is displaying an unusual red/brown/golden tint.

Amateur and professional astronomers have been tracking the object. Observer Dan Bartlett recently reported a sighting from June Lake, California, and additional amateur observations have come from Payson, Arizona, and Ballico, California.

"This comet was not supposed to survive its Oct. 8 perihelion (0.33 AU), but it did survive, and now it is displaying a red/brown/golden color rarely seen in comets," Bartlett told SpaceWeather.com.

The comet is dynamically new, arriving from the distant Oort Cloud — the spherical reservoir of icy bodies at the edge of the solar system. Spectroscopic observations by David Schleicher of Lowell Observatory indicate unusually low abundances of carbon-bearing species in the coma. "All of the carbon-bearing species, including CN, are unusually low," he reported in The Astronomer's Telegram #17362.

Normally, sunlight excites diatomic carbon (C2) and ionized carbon monoxide (CO+), producing characteristic green or blue glows. With those emissions weak or absent, dust and other components in the coma dominate the visible color, giving the comet its distinctive golden to reddish-brown appearance. Scientists do not yet know whether this depletion of carbon-bearing molecules is an intrinsic property of the comet or a consequence of its close solar encounter.

Bartlett and others report the comet around 9th magnitude, making it accessible to backyard telescopes. In September, NASA released an image showing the comet when it appeared fainter and greener while passing near C/2025 R2 (SWAN).

When and where to look

Observers in the northern hemisphere can spot C/2025 K1 shortly before sunrise near the boundary between the constellations Virgo and Leo. The comet's closest approach to Earth will be on Nov. 25, 2025, at roughly 0.40 AU. It passed perihelion on Oct. 8, 2025, at about 0.33 AU from the Sun.

Why it matters: This object offers a rare opportunity to study a dynamically new comet with an atypical chemical signature. Continued spectroscopic monitoring and imagery will help astronomers determine whether its unusual color stems from intrinsic composition, solar processing, or other causes.