A Rare Green Comet Not Seen Since the Ice Age Is Swinging by Earth—Here’s How to View It Before It’s Gone

Comet C/2022 E3 (ZTF) doesn’t have a glamorous name, but it does have an exotic pedigree and it’s the talk of the backyard astronomy world right now. Though it’s currently only visible through a telescope (or maybe binoculars, if your sky is dark enough), it’s getting brighter and easier to spot in Western skies each day, and may become visible to the naked eye before it starts its trip back to the far reaches of the solar system, where it has spent most of the past 50 millennia.

What Will I See?

Comets are notoriously variable and hard to predict. Their paths can be calculated, but how bright they get and how magnificent of a tail they develop is largely down to chance. A few things are clear already from telescope observations: The comet does already have a tail, and the coma, or head, is a striking green color. It’s also approaching a brightness that would allow it to be seen by the naked eye, although no one is sure whether or not it will get quite that bright. It seems safe to say that in terms of visual impressiveness, it will be somewhere in between Comet NEOWISE, which you may remember being able to see easily in the summer of 2020, and the dim spark that was Comet Halley’s anti-climactic return in 1986. 

How Do I Spot It?

Thomas J. Story

Although you will want some sort of visual aid to see the comet, it won’t take much. If you have access to a telescope, by all means, use that, but any pair of binoculars should do it. 

Actually finding C/2022 E3 (ZTF) is a bit of a challenge. Comets don’t streak across the sky like shooting stars, but they do change position from night to night, making it hard to say where to look. Generally speaking, this one is currently visible in the northern sky in the evening, and is near the constellation Bootes. Where’s that? Find the Big Dipper and follow the curve of its handle for a distance about as long as the dipper itself. That will have you looking in approximately the right portion of the sky. 

By Jan. 22, the comet will be in the constellation Draco. By Jan. 31, when it should be at its brightest, it will be near Polaris, the North Star. On Feb. 12, the comet will be very close to Mars, which will make a handy reference point even though C/2022 E3 (ZTF) will be fading by then. The comet will theoretically be visible until mid-April when it will only be above the horizon during daylight hours. But it will be too dim to see in all but professional telescopes by then, so look up earlier than that. 

Anton Petrus/Getty Images

This page has real-time updates about the comet’s rise and set times, position, and brightness. If the constellations pictured aren’t familiar to you, a smartphone app can help get you oriented. I like SkyView, which is available for both iOS and Android, but there are lots out there.

Once you know the general direction you should be looking, sweep slowly across the sky with binoculars. You should see a bright but slightly fuzzy green blob, and if you’re lucky, a fainter wispy tail trailing behind. To get the best view, go to a place where the sky is as dark as possible, away from city centers. Give your eyes time to adjust to the dark—it can take 20 minutes or more for them to recover from the florescent dazzle that surrounds us so much of the time. Resist the temptation to kill time by looking at your phone—those screens really blow out your night vision. 

If you think you’ve spotted the comet, try a trick known as averted vision. The center of your field of view is optimized for seeing color, but the rest of your retina is made to pick up faint light. When you’ve got the comet in your sights, focus your gaze just to the side of it, and the comet may pop more brightly against the dark sky.

What’s Next for Comet C/2022 E3 (ZTF)?

Scientists have been studying the comet’s speed and trajectory through the solar system for several months now, and are fairly confident that Comet C/2022 E3 (ZTF) originated in a debris field at the far periphery of our Solar System called the Oort Cloud, and that it last swung by Earth about 50,000 years ago, when ice covered much of the world and wooly mammoths roamed North America. What’s less clear is when we’ll see our green visitor again—it all depends on how much the sun’s gravity affects the comet’s orbit. Some say it could be another 50,000 years before it turns back to the inner Solar System. Some say it may never come back this way. Time will tell, but to be safe, better look up in the next few weeks to catch a glimpse of this icy space rock last spied by Neanderthals.

Comet C/2022 E3 (ZTF): What’s in a Name?

Quite a bit of information, as it turns out. Here’s a breakdown:

The “C” is a designation scientists give comets that take more than 200 years to orbit the sun. 2022 is the year the comet was discovered (by modern humans, anyway). The “E3” part means that the comet was the third one discovered during the fifth half-month of that year—the first two weeks of a year get an “A” designation, the second two weeks are noted with a B, and so on through the alphabet. (This method of tracking time apparently makes complete sense to people who got through high school calculus without crying.) Finally, “ZTF” is an abbreviation for Zwicky Transient Facility, the San Diego-area observatory where the comet’s discoverers were working when they spotted it.

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