How to watch the ‘green comet’ in night skies

A green comet from the outer solar system is swinging through Earth’s neighborhood for the first time in 50,000 years.

The comet has gradually brightened and will make its closest approach on Thursday, when it comes within 26.4 million miles of the planet. This is 110 times the distance to the moon.

From the Northern Hemisphere, the cosmic visitor will be faintly visible to the naked eye – so faint that you’ll want to grab your favorite binoculars and drive far away from city lights. And be warned that it will look nothing like many of the images you’ve seen on the internet. But this year is your best chance to see an object from the solar system’s far, icy reaches.

“I get this tingling, magical feeling when I look at something alive through a telescope,” said Andrew McCarthy, an astrophotographer in Florence, Arizona. “You just can’t beat what your eyes can see.”

Q: What is the comet’s name?

A: The comet is known as C/2022 E3 (ZTF) because astronomers discovered it in March 2022 using a telescope on Mount Palomar in California called the Zwicky Transient Facility (or ZTF).

At the time, the cosmic intruder was just within the orbit of Jupiter and about one-25,000th as bright as the faintest star visible to the naked eye. But ZTF, with a camera that has a wide field of view, scans the entire visible sky every night and is well suited to discover such objects.

Q: What are comets, and why is this one green?

A: Comets are clumps of dust and frozen gases, sometimes described by astronomers as dirty snowballs. Most of the distant, icy regions are believed to originate in the solar system, where gravitational perturbations sometimes push them towards the sun – an interaction that transforms them into beautiful cosmic objects.

When they leave their deep freeze, the sun’s heat erodes their surfaces. They begin spewing gases and dust until they harbor a glowing core, called a coma, and a flaming tail that can stretch for millions of kilometers.

“Their activity makes it look like they are alive,” said Laurence O’Rourke, an astronomer at the European Space Agency. “When they are far from the sun, they sleep, and when they get close to the sun, they wake up.”

C/2022 E3 (ZTF), for example, now glows green because ultraviolet radiation from the sun is absorbed by a molecule in the comet called diatomic carbon – that is, two carbon atoms fused together. The reaction emits green light.

Q: How bright will this comet be?

A: The brightness of comets can be unpredictable. When scientists first discovered the object last year, they only knew that it had the potential to be visible from Earth.

“Because each comet is its own living thing, you don’t know how it’s going to react until it passes the sun,” O’Rourke said.

Comet C/2022 E3 (ZTF) made its closest approach to the sun on January 12 and is now gradually brightening as it swings towards Earth. While the comet won’t pass us until Thursday, it’s already visible to the naked eye — an encouraging sign for viewing opportunities, said Mike Kelley, an astronomer at the University of Maryland and a co-leader of the Solar System Working Group. the Zwicky Transient Facility.

Still, many agree that dark skies and binoculars are a must.

Q: How do I see the green comet?

A: To catch the comet, look north.

This green comet is unusual because it is well positioned near the North Star, meaning that most people in northern latitudes can see it. In fact, for anyone living in or above the continental United States, the comet is now visible all night long. It’s rare: Many comets are only visible in the evening or morning twilight because they hover close to the sun.

But on Monday, comet C/2022 E3 (ZTF) resided directly between the two stars at the end of the Big Dipper and Polaris, the North Star. Through Thursday, it crawls along an imaginary line roughly parallel to the back of Ursa Major, also known as the Great Bear.

That recognizable location will give many viewers the chance to search the skies for the comet. And the hunt will be fun.

“It’s like looking for an endangered species, and then it appears,” said EC Krupp, director at Griffith Observatory in Los Angeles. “It really is a charm of an experience.”

Q: What is the best location and time to see it?

A: There is one major opponent in this hunt: light.

Your best bet is to drive out of the city and even the suburbs. “Get to really, really dark skies, like dark enough to where there are more stars than you can count,” McCarthy said.

Then, even if you manage to escape the city lights, you will have to contend with moonlight. The next full moon will be on Sunday – just days after the comet’s closest approach. This means it may be best to view the comet as soon as possible, when you can see it after the moon has set and just before sunrise.

Q: What equipment do I need?

A: Although this comet is technically visible to the naked eye, it is most likely that you will need binoculars.

“Even with relatively modest binoculars, the powdery, hazy or smoky character of the ‘star’ should make it clear that it is a comet,” Krupp said. And their wide field of view helps you scan large areas of the sky at once.

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Even if you don’t have binoculars, the investment may be worth it. “Space is so accessible,” McCarthy said. “You can see the whole sky – like nebulae and galaxies – with binoculars, and it looks amazing.”

Q: Will the comet really look green?

A: The comet, even through binoculars or a telescope, is going to be far from many images shared on the Internet. The human eye is not sensitive enough to pick up the green color in such low light.

“Most astronomical objects appear black and white, even with the help of a telescope,” said Alan Dyer, an amateur astronomer in southern Alberta. “It’s just the camera, the long exposure, that picks up the colors.”

Q: How do I photograph the green comet?

A: On Jan. 18, McCarthy took a photo of Comet C/2022 E3 (ZTF) in which the coma is the color of a green apple and the ion tail fans out like rays of purple sunshine. He used his telescope to take 45 60-second pictures and then spent 18 hours composing those pictures into one final image. “A lot of processing wizardry goes into getting that final image,” he said.

“But you don’t need fancy equipment to photograph it,” McCarthy said. If you’re using a tripod and a standard DSLR camera, “you’ll be able to spot it, and you’ll be able to resolve the green color and everything.”

And then there’s the biggest trick of all: “cast your own pain and suffering on it by staying up all night,” McCarthy said.

Q: It’s cloudy. Is this my last chance?

A: No! In fact, given the brightness of the moon on Thursday, it might be smart to wait a little longer. At that point, the darker evening hours before moonrise would be an excellent time to look for it. It’s true that the comet will fade at that point, but it most likely won’t fade too quickly – meaning it will still be an easy capture with binoculars.

“It’s going to be up in the air with us for a while,” Dyer said.

Comet C/2022 E3 (ZTF) will pass the bright star Capella on Sunday night and then swing past Mars on February 10. Those bright objects might make them even easier to find, Dyer argued.

So be sure to try again if your sky is cloudy, but don’t wait too long. Comet C/2022 E3 (ZTF) is expected to be the brightest comet visible this year.

Q: Why are astronomers excited about this green comet?

A: Comets are remnants of the early solar system, and they may have been responsible for seeding early Earth with the building blocks for life.

“It’s really a situation where we most likely wouldn’t exist without their existence,” O’Rourke said.

And yet we don’t have many opportunities to study these objects, since only a few each year are bright enough to be seen with the naked eye. As such, comet astronomers around the world will be observing C/2022 E3 (ZTF) over the coming months.

“We’re looking for the place of our solar system in the universe,” said Kelley, who will use the James Webb Space Telescope to observe the comet at the end of February. He wants to better understand how our planet formed in order to pay attention to the conditions that gave rise to life on Earth.

But Kelley and others must work quickly. After its cameo in the night sky, it is unclear where C/2022 E3 (ZTF) might go. Because these objects are so loosely bound to our solar system, the sun’s gravitational influence may force the comet to make another trip around our star – perhaps not for another 50,000 years. Or the sun could throw the comet completely out of the solar system.

This article originally appeared in The New York Times.