Curious green comet is paying us a visit. Here’s how to see it

Don’t look now, but we’ve got a visitor.

Better yet, do look now.

C/2022 E3 (ZTF) is a comet — which is rare enough. A green one, which is rarer still. And one that, just maybe, could be visible from your backyard, using the naked eye.

Provided that you have ideal weather conditions, know exactly where to look, and live in a very dark, remote area, away from city lights.

Which may be the rarest thing of all.

“If you’re going to use the naked eye, you have to be very careful to get away from the bright lights,” said Gary Swangin, Warren County astronomer-at-large and past director of both the Newark Museum Planetarium and the Panther Academy Planetarium in Paterson.

If your neighborhood isn’t dark enough, or your eyes aren’t keen enough, there are workarounds.

Binoculars. A small telescope. Or something new that is beginning to revolutionize amateur astronomy: your home computer screen.

Linked to a large telescope — possibly as far away as California or South Africa — that you control remotely, your laptop can show you images of the comet that would have staggered Galileo or Edwin Hubble.

“Now, even if you don’t have a good location, you can still look at the night sky,” Swangin said.

The comet, which was first spotted last March, will mark its closest approach to Earth — its perigee — on Feb. 1. It will be a mere 26 million miles away from us. Practically a beer run. “That’s less than the distance Venus would be from us,” Swangin said. “Venus is around 35 million miles away.”

The green color, though uncommon, is not unique.

There was, for instance, another green comet, Lulin, in 2009. “The ultraviolet radiation from the sun hits the carbon molecules, and when they break up they form a stream of these green particles,” Swangin said. “They radiate green.”

This newly-discovered <a href=green comet is nearing Earth and it may be visible to the naked eye” src=”–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNTtoPTM5Nw–/”/>

This newly-discovered green comet is nearing Earth and it may be visible to the naked eye

Can you see the green comet with the naked eye?

How to see it? Naked-eye viewing is, to repeat, possible — though not easy — under the right conditions. Clear skies, and no lights anywhere.

“It would be kind of a green smudge,” Swangin said. “But you’re not going to be able to see it in the city.”

Better yet is a good pair of binoculars, or a small telescope.

Gary Swangin

Gary Swangin

Binoculars are particularly good, Swangin said, because they have a wide “field of view” — taking in a large expanse of sky all at once. That makes them more useful than a telescope for searching out objects. You may want to rest yours on a fence post or table to steady the image.

“Most telescopes have a small field of view, which is not what you want when you’re looking for comets,” he said.

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Locating C/2022 E3 (ZTF) is easy, in theory. Start, Swangin said, by looking for Polaris, the North Star.

Most of us learned this trick at the planetarium. First, find the Big Dipper. Next, use the two “pointer” stars on the outer rim of the Dipper, Merak and Dubhe, and follow them to Polaris — last star on the handle of the Little Dipper.

The comet will be in that area of the sky. Comet C/2022 E3 (ZTF) is a “circumpolar” object, meaning that it stays within close range of the pole star as the sky does its nightly revolution. “Chances are you are going to have some success,” Swangin said.

How else can you see the green comet?

Then there’s remote stargazing.

It’s only started to become commonplace in the last few decades, but already it has transformed the way professional astronomers work.

Instead of spending their nights in cold observatories, peering through giant tubes, scientists now buy time on remote-control telescopes — sometimes thousands of miles away, in Africa or Australia or California — steering them from afar, and viewing the images they send on a computer screen.

What professionals do, amateurs can do.

“There are all types of telescopes located all around the world,” said Swangin, who is himself in the process of setting up a 24-inch dedicated telescope, in California, for the astronomy students of Delaware State University — the first such arrangement ever made with a historically Black university.

Gary Swangin, with the 24-inch reflecting telescope that is now being installed in California

Gary Swangin, with the 24-inch reflecting telescope that is now being installed in California

You might even be able to watch the stars by day — remotely using a telescope located halfway across the world, where it’s night. Check out websites like,, and to see what’s available.

“We’re improving the software, so it becomes just like using a cellphone now,” said Christian Sasse, general manager and astronomer in charge of itelescope. “You don’t have to know anything.”

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Some 25 of its telescopes are scattered all over the world: Utah, California, Spain, Australia, Chile. And because C/2022 E3 (ZTF) is a popular object, the experts are constantly updating its whereabouts via computer. Just visit the website, put in the comet’s name and make a reservation, Sasse said.

“There is a menu called ‘Comets and Near Earth Objects,’ and you click on there, and it gives you an explanation of what to do,” he said.

For $50 to $100, you can take a series of one-minute photo exposures of C/2022 E3 (ZTF) in all its emerald glory. And because you’re controlling both telescope and camera, you can choose the color composition, and all other aspects of the image. It’s something that a photographer, as well as an astronomy buff, might find exciting.

“You have to remember this comet is moving through the sky,” Sasse said. “Sometimes, there’s a beautiful galaxy next to it. It’s changing day by day.”

And sometimes, those changes are dramatic.

Thereby hangs a tail

“We were observing it a couple of nights ago, and we noticed the comet seemed to split,” said Terry Hancock, director of Grand Mesa Observatory in Colorado, which has 10 remote telescopes available to the public (Hancock offers tutorials).

“I found out afterward that the comet was involved in some sort of solar storm,” Hancock said.

This comet has developed what is known as an “anti-tail” — a second stream of matter coming out the other end. “The storm caused the comet to split,” he said. “So it’s very unique. It doesn’t have just one tail.”

If you do see C/2022 E3 (ZTF), you’ll be seeing it on its way out the door.

Comet C/2022 E3 ZTF was headed toward us last year. Now it's headed away

Comet C/2022 E3 ZTF was headed toward us last year. Now it’s headed away

The comet was coming toward us all last year, reaching perihelion — the closest approach to the sun — on Jan. 12. Now it’s headed back to the Oort cloud, the big band of debris on the edge of the solar system, four light years away. And it’s going tail-first.

“You would think, with the tail stretching out, that it’s behind,” Swangin said. “But that’s not the case all the time.”

The long, glowing streamer that is the comet’s key characteristic — the thing that makes a comet a comet — always points away from the sun. Solar radiation, blowing particles away from the nucleus, creates the tail.

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When the comet is heading toward the sun, the tail is behind. When it’s receding, the tail is — oxymoronically — in front.

“Comets are dirty snowballs out there,” Swangin said. “There could be countless millions of them. The nucleus of this one is about 3,281 feet wide, a little bit over a half-mile. Small comet. Largely ice.”

Comet C/2022 E3 (ZTF) was discovered by astronomers using the wide-field survey camera at the Zwicky Transient Facility this year in early March.

Comet C/2022 E3 (ZTF) was discovered by astronomers using the wide-field survey camera at the Zwicky Transient Facility this year in early March.

When C/2022 E3 (ZTF) goes, it goes for good. It’s a “long-period” comet. Halley’s comet, the mailman of the solar system, makes regular rounds every 76 years. But C/2022 E3 (ZTF), for us humans, is a one-off. It made its last appearance in Neanderthal times, 50,000 years ago. The next visit, you and I won’t be there.

“Seeing a comet is such a rare event, not an everyday thing,” Swangin said. “And keep in mind, you’re not going to see this comet again.”

This article originally appeared on Green comet 2023: How to see it

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