Over the next two weeks, we’ll have the chance to see a rare green comet that is flying by the Earth for the first time in about 50,000 years.
At its closest point on Wednesday, it will come within 26 million miles of our planet. It’s expected to be at its brightest around Jan. 31 and Feb. 1 and just barely visible to the naked eye.
But what makes this green-hued comet, officially named C/2022 E3 (ZTF), so special?
“This literally is current humankind’s one and only chance to see this comet because even if it does return to our part of the solar system, we’re talking like 50,000 years in the future,” said Michelle Nichols, Adler Planetarium’s director of public observing. “That alone kind of makes it a little special.”
While it could potentially come back in several tens of thousands of years, it may also just keep going and exit the solar system completely if a large gravitational object, such as a planet like Jupiter, adjusts its orbit enough, she said.
Its origin and hue also make it special. There are a couple of different reservoirs for comets, Nichols explained, such as the Kuiper belt out past the orbit of Neptune. This green comet is from the Oort cloud, which is much farther out in space in an area that we actually have never observed. Its distance also means we rarely see comets from the Oort cloud since it takes them so long to orbit the sun.
Green-hued comets are seen a little less frequently than comets that are yellowish-white (which might be due to dust) or blue (which is a different kind of gas). The color all depends on the type of stuff the comet is made of, what it is emitting and what happens when light hits it, Nichols said. For comet C/2022 E3 (ZTF), when ultraviolet light from the sun hits it, a specific molecule emits a green light.
What does the name mean?
While comets are often named after people who discovered them, such as the Hale-Bopp comet, named after Alan Hale and Thomas Bopp, the green comet’s official name is more complicated.
The “C/” portion of C/2022 E3 (ZTF) indicates that it’s a comet. Next, 2022 is for the year it was discovered, while “E” indicates the specific time period, in this case, the first half of March. The “3? means that it’s the third comet to be discovered in that time period. Finally, “ZTF” stands for Zwicky Transient Facility, which is the facility in California that discovered the comet.
Comet vs. asteroid
“Comets and asteroids basically are all leftovers from the formation of the solar system,” Nichols said. “So comets and asteroids are old.”
The main difference between them is what they’re made of: asteroids tend to be rocky, while comets have more ice.
Meanwhile, meteorites, like the one a Field Museum research scientist helped discover recently in Antarctica, are pieces of space rock that didn’t fully burn up once they entered the Earth’s atmosphere and reached the Earth’s surface.
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While comets can impact Earth, Nichols said it doesn’t happen often.
How to see the green comet
If you want to get a glimpse of this comet, there are some steps you’ll need to take. Since it’s just on the cusp of being considered naked eye visible, it’s recommended to use binoculars or a small telescope to really see the comet.
“You’re looking for a faint fuzzball,” Nichols said.
Getting away from the bright lights of the city is usually always better when it comes to looking out for comets, but a big problem that people will run into is that the moon will be in its waxing gibbous phase, so its bright light will compete with the comet. If you can’t get away from bright lights, trying to mitigate them as much as possible will help viewing efforts. That could be as simple as making sure any lights are to your back.
In terms of where to look in the sky, it will all depend on the day and the time. Nichols recommended searching for the comet on an app that shows you the night sky, such as Stellarium. The Adler also has a viewing chart with details on where to look for the comet at 9 p.m. from Feb. 1-8.
And don’t forget to check the weather. Weather permitting, the Adler hopes to get its telescope rigged up with a camera and broadcast a live view on its YouTube channel of the comet from the Doane Observatory on Feb. 1 and Feb. 8. The ‘Scopes at the Adler Facebook group will post updates on if the observatory will be open. The National Weather Service currently is predicting mostly clear skies Tuesday night, partly cloudy Wednesday for Chicago, though bitterly cold.
“We’ll probably know a day or two in advance if the weather is going to cooperate enough to at least try,” Nichols said. “It all depends on if these clouds move out of the way.”