Rare Green Comet to Light Up Night Sky with Twin Companion

A rare celestial event is unfolding, as Comet Lemmon, a green comet, will make its closest approach to Earth on Tuesday, October 21, alongside another comet, C/2025 R2. Stargazers in North America will have a chance to witness this phenomenon, with both comets visible in the western and southern skies starting about 45 minutes after sunset. Comet Lemmon, in particular, can be seen with the naked eye, while its companion, C/2025 R2, may be visible using binoculars or a telescope.

Key Takeaways:

• Comet Lemmon, a rare green comet, will make its closest approach to Earth on Tuesday, October 21, at a distance of 45-to-50 million miles.
• The comet can be seen with the naked eye, while its companion, C/2025 R2, may be visible using binoculars or a telescope.
• Both comets are expected to be visible in the western and southern skies starting about 45 minutes after sunset and continuing into the night.
• Comet Lemmon takes about 1,350 years to complete one orbit around the Sun, but after November, its orbital period will be lowered to around 1,150 years.
• C/2025 R2, discovered in January 2025, is a rare comet that will not be seen again for over 1,000 years.
• Comet SWAN, another rare comet, was discovered in September 2025 and can be seen using a telescope.
• Comets are remnants from the early stages of the solar system, formed about 4.6 billion years ago, and consist primarily of ice mixed with dark organic material.

Statistics:

• Distance between Earth and Comet Lemmon: 45-to-50 million miles.
• Orbital period of Comet Lemmon: approximately 1,350 years (before November) and 1,150 years (after November).
• Number of years since Comet SWAN's discovery: approximately 6 months.
• Formation time of comets: about 4.6 billion years ago.
• Composition of comets: primarily ice mixed with dark organic material.

Sources:

• Forbes
• Royal Astronomical Society
• Starwalk
• Mount Lemmon Survey
• NASA
• The Oklahoman
• USA TODAY Network