Catch a Glimpse of a Rare Green Comet This Month

Skywatchers should be able to spot the once-in-a-lifetime spectacle with binoculars

a green-blue comet against stars
Comet C/2022 E3 (ZTF) viewed through a telescope on December 24, 2022. It will reach its nearest point to Earth in early February. Dan Bartlett

This month, a recently discovered comet with green glow will make its first trip through our inner solar system in thousands of years—and maybe even for the first time ever.

Comet C/2022 E3 (ZTF), named for its discovery last March at the Zwicky Transient Facility in California, will reach its closest position to the sun on Thursday night, January 12, before proceeding en route toward our planet. The mass of ice and organic material will reach its closest point to Earth—just over 26 million miles away—on February 2.

Over the course of this month, viewers in the Northern Hemisphere should look for the icy body as it moves to the northwest in the morning sky, right before dawn. (Southern Hemisphere hopefuls will have to wait until the beginning of February to catch a glimpse.)

Stargazers should have the best chance of seeing the comet on January 21, when the new moon phase will “provide the ideal dark skies needed to spot” it, per’s Robert Lea. On January 30, it will appear near the North Star, report Don Machholz and Eddie Irizarry of EarthSky.

Without a telescope, the comet “will most likely look like a faint, greenish smudge in the sky rather than a bright object,” writes Kate Howells of the Planetary Society. But it should be easy to spot with binoculars, and potentially even visible to the naked eye in dark skies.

Still, “comets are notoriously unpredictable,” says Preston Dyches of NASA’s Jet Propulsion Laboratory in a video. And, because C/2022 E3 is a long-period comet, its appearance is even less predictable than its brethren that take shorter trips around the sun.

Whether they take 200 or 20 million years to complete an orbit, these “dirty snowballs” are more than just spectacular cosmic sights. They may have delivered life essentials like water and organic compounds to our early planet, and studying them could reveal clues about the beginning of our solar system.

A comet develops its eye-catching atmosphere from the sun’s heat, which transforms some of its icy center directly into gas. This forms a cloud of dust and gas that can be pushed away from the sun by solar wind and radiation, creating the characteristic tails.

While C/2022 E3 is no Neowise—it’s expected to be less bright than that comet’s spectacle in 2020—it will be worth taking a look for. After all, if you do catch a glimpse of its green coma, you’ll get a once-in-a-lifetime sight: Jon Giorgini, a senior analyst at the Jet Propulsion Laboratory, tells NPR’s Juliana Kim that “if C/2022 E3 has ever passed through the solar system before, it would have last been seen in the sky more than 10,000 years ago.”

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