Green comet approaching Earth: Visible to the naked eye

The newly discovered comet, named Lemmon, will reach its closest approach to Earth this month. Scientists say it could become bright enough to be seen with the naked eye.

This comet, scientifically named C/2025 A6, is a non-periodic comet, meaning its orbit exceeds a thousand years and is difficult to predict. According to calculations, Lemmon's orbit around the Sun takes approximately 1,350 years, and it spends most of this time in the Oort Cloud, the outermost part of the Solar System.

SPEED OF 209 THOUSAND KILOMETERS PER HOUR

Lemmon was spotted on January 3rd at the Mt. Lemmon SkyCenter in Arizona, USA. At the time, it was traveling toward the inner Solar System at 130,000 mph (209,000 kilometers per hour). However, it has since been overshadowed by more popular comets like SWAN R2 and 3I/ATLAS.

Lemmon will make its closest approach to Earth on October 21st, coming within 90 million kilometers of the planet—more than 230 times the distance between the Moon and Earth. Then, on November 8th, it will reach perihelion, its closest approach to the Sun, before heading back toward the outer Solar System.

VISIBLE WITH THE NAKED EYE

It is thought that the comet, which will become brighter as it approaches, will be visible to the naked eye.

Lemmon's most striking feature is the emerald green glow it emits. This color is believed to be caused by diatomic carbon gas (dicarbon) found in the comet's coma.

Other green comets have been observed in recent years, including C/2022 E3 in 2023 and 12P/Pons-Brooks, which passed the Sun in 2024.

Lemmon's tail, composed of ice, gas, and dust, was rippled by a powerful solar wind in late September, creating a striking image in space.

Experts believe this close pass could alter Lemmon's orbit, shortening its orbital period around the Sun by 200 years. The recent gravitational pull of Jupiter may also have played a role in this change.

HOW CAN WE SEE?

Lemmon is currently visible with telescopes and powerful binoculars, but as its brightness increases, it will become visible to the unaided eye. The best time is expected to be mid-October.

The comet will be visible in the constellation Lynx, between Jupiter and the Big Dipper. For those in the Northern Hemisphere, the best time to observe is in the morning just before sunrise or after sunset.

It will also be possible to see comets SWAN R2 and 3I/ATLAS in the sky along with Lemmon during the same period.