How to See the Green Comet: C/2022 E3 ZTF and What to Watch For Now
Quick Reference: The Green Comet
- Famous example: C/2022 E3 (ZTF), visible January-February 2023.
- Why green: diatomic carbon (C2) in the comet’s coma fluoresces green under sunlight.
- Other green comets: any comet rich in C2, including some recurring short-period comets.
- Where to look: low northeastern sky after dark when one is active.
- Brightness: the 2023 green comet peaked at magnitude +5, naked-eye in dark skies, binocular elsewhere.
In January and February 2023, comet C/2022 E3 (ZTF) became famous as ‘the green comet,’ visible to the naked eye in dark rural skies. The color was real: a fluorescent green from diatomic carbon in the comet’s coma. Here’s why some comets glow green, where to look for the next one, and what was special about the 2023 visitor.
Why the Green Glow
The green color comes from diatomic carbon (C2), a chemical compound that exists in the cold of space but is destroyed within hours by sunlight. Inside the comet’s coma (the bright halo around the nucleus), C2 fluoresces green when illuminated by sunlight, similar to how a fluorescent bulb works.
The green color is brightest near the nucleus, where C2 is freshly released by sublimating ice. The tail of the comet appears more yellow or white because the C2 has already been destroyed by sunlight by the time the gas reaches the tail.
The 2023 Green Comet
C/2022 E3 (ZTF) was discovered in March 2022 by the Zwicky Transient Facility at Palomar Observatory. It made its closest approach to Earth on February 1, 2023, at a distance of 26 million miles. Peak brightness was magnitude +5, which made it naked-eye visible from dark rural skies and binocular-visible from suburbs.
The comet was on a 50,000-year orbit. It will not return in our lifetimes.
How to Find Bright Comets
New comets are discovered constantly, but only a few become naked-eye objects. When one does, the path through the sky is published in star charts. To find a bright comet:
- Bookmark NASA’s comet observation page and Sky and Telescope’s bright comets list.
- Use Stellarium (free) or a sky app to plot the comet’s position for tonight.
- Go to a dark rural site at least 30 minutes from city lights.
- Look 30 minutes after sunset (for evening comets) or 30 minutes before sunrise (for morning ones).
- Binoculars (7×50 are ideal) significantly help finding faint comets.
Frequently Asked Questions
Was the green comet visible to the naked eye?
Yes, in dark rural skies it peaked at magnitude +5, which is at the limit of naked-eye visibility. From suburbs, binoculars were needed.
Why are some comets green and others white?
Green comets have more diatomic carbon in their coma. White or yellow comets have less. The color is a snapshot of the comet’s chemical composition.
Will the 2023 green comet come back?
Not in our lifetimes. C/2022 E3 (ZTF) was on a 50,000-year orbit.
How do I know if there’s a bright comet to watch right now?
Sky and Telescope, NASA, and the Almanac publish bright-comet alerts. The current month’s brightest comets are usually listed on the Almanac’s astronomy page.
Joe Rao
Joe Rao is an esteemed astronomer who writes for Space.com, Sky & Telescope, and Natural History Magazine. Mr. Rao is a regular contributor to the Farmers' Almanacand serves as an associate lecturer for the Hayden Planetarium in New York City.
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It says in the article: “9 p.m. local time.” … local to what region, State, part of the World? People on the East coast see 9 p.m. 3 hours before I do… People on are waking up at my 9 p.m.. Please define “local” time so we cna discern our own local time frames..
the “local time” is correct. The comet is not an instantaneous event. The best time to see it is when the sky is dark and the comet is close to the zenith. That happens at the stated time, anywhere in mid-latitude northern hemisphere. (It’s fairly close to the Big Dipper)
Thank you. We appreciate you sharing your knowledge with the communinity. You should be able to see the comet for several hours at a time if the conditions are right.
There are bible scholars who believe that the star of Bethlehem was a comet . It may or may not be true .
Pretty safe statement; “It may or may not be true.” ?
Watching the steaming video with the beautiful musical score, I was saddened for some reason. Such a long journey and all alone…never to find rest. I think I know that feeling and I cry for it and the senselessness of our existence, knowing our journey will end all to soon.
I want to join
Hi Barbara! It may be tough to keep up with that comet, but here’s something you can join: The Farmers’ Almanac Farmhouse! https://www.farmersalmanac.com/online-memberships
Great live shot but compass coordinates would help a newbie
Compases do not work for space objects. In space all is one and all you need to know is that the green comet is proof that people need to do more to save nature and ecosystems before humans ruin them.
how is the comet proof we need to do more for our ecosystem?
I’m going to hope you are baiting, being facetious. As it is quite possible you are not, it is pure hubris to think anything we do or don’t do as humans will impact a comet, or the rotation of the earth, or the tide, or the forces of Mother Nature. HUBRIS!
Politicians use the big lies to get elected. Scientists have studied about the ecosystem, the earth and its relationship to the universe for centuries. Anything you as a private citizen can do would be unlikely to change anything. What device would you use? A flex capacitor?