The newly discovered ZTF comet is approaching its closest point to Earth in 50,000 years, becoming visible to the naked eye, and making headlines. Some call it an “extremely rare” and “bright green” comet, but will it live up to the hype? We explain.
Facts about Comet ZTF
Comet ZTF was discovered on March 2, 2022 by a robotic camera attached to a telescope known as the Zwicky Transient Facility (ZTF) in Palomar Observatory in Southern California. The ZTF scans the entire northern sky every two days, capturing hundreds of thousands of stars and galaxies in one shot. Many comets have been found with this tool. The most recent one is designated C/2022 E3 (ZTF), Comet ZTF for short.
Why is it rare?
Comet ZTF has traveled 2.8 trillion miles and will reach its closest point to Earth in 50,000 years on February 1, 2023. Orbital calculations indicate that Comet ZTF may never return.
What makes ZTF a green comet?
The green color is likely caused by a molecule made of two carbon atoms bonded together, called a carbon atom decarbon. This unusual chemical process is mainly confined to the head, not the tail. If you look at a Comet ZTF this green is probably very faint (if visible at all). The appearance of green comets due to carbon dioxide is fairly uncommon.
Recent photographs show the head (coma) distinctly green and trailed by an impressively long, thin blush tip (tail). But that’s what a camera that takes a long exposure sees. The tint will appear less green to the naked eye.
When and where to see Comet ZTF
During the latter part of January to early February, ZTF may become bright enough that it can be seen with the naked eye. Use a reliable star chart to track the night-to-night change in position relative to the background stars and constellations. Here are approximate dates and locations.
January 12-14
Look toward the constellation Corona Borealis just before sunrise.
January 14-20
Look towards the constellation Boötes just before sunrise.
Jan 21
The comet will be visible in the night sky (previously it was visible only in the early morning hours). Look to the north, above and to the left of the Big Dipper.
January 22-25
Look near the constellation Draco (the Dragon).
January 26-27
Look several degrees to the east of the little gauntlet bowl. On the evening of the 27th, it will be about three degrees to the upper right of orange Kochab, the brightest of the two outer stars in the Little Dipper bowl.
January 29-30
Look towards Polaris.
Feb 1
Look near the constellation Camelopardalis.
Feb 5th
Look towards the bright yellow-white star Capella (from the constellation Gemini).
Feb 6
Look inside the triangle known as Auriga’s “Children’s” star pattern, right at around 8 p.m. local time.
February 10th
Look two degrees to the upper left of Mars.
Note: If you live in a large city or a remote suburb, seeing this comet will be difficult – if not an impossible task. Even for those blessed with dark, starry skies, finding ZTF can be quite a challenge.
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As for the tail, comets can throw out two types, consisting of dust and gas. Dust tails are much brighter and more eye-catching than gas tails, because dust is a very effective reflector of the sun’s rays. The coolest comets are dusty and can produce long, bright tails that make for impressively beautiful celestial sights.
On the other hand, gas tails appear fainter and glow with a bluish tint. The gas is activated by the ultraviolet rays of the sun, which makes the tail glow in the same way that black light causes phosphorescent paint to glow. Unfortunately, the gas tails produced by most comets appear long, thin, light, and quite dim. Impressive in pictures but underwhelming. And that’s what we’re seeing right now with ZTF.
Finally, when ZTF is at its peak in late January and early February, it will have to compete with another celestial body: the Moon. During the same time frame, the Moon will be close to its full phase (The Snow full moon on the fifth of February). Blazing across the night sky like a giant searchlight, the full moon will make trying to see a relatively dim and dispersed object like Comet ZTF much more difficult.
Other comets viewable
There are approximately a dozen comets available to view in the night sky tonight. However, most of these telescopes can only be seen with large-format telescopes. You’ll also need a good star atlas as well as exact coordinate positions to know where to point your device to see any of these things. Most amateurs hunting for them call such comets “faint fuzz” because that’s pretty much what they look like through the lens: a faint, fuzzy point of light. These are known as “common comets”.
Every now and then, maybe two or three times over the course of 15 or 20 years, a bright comet or “great comet” will come up. These are the kind that impress those of us who don’t have binoculars or telescopes — the kind that all you have to do is get out, look up and yell, “Look at that!Such comets tend to be much larger than average. Most of these have a core or cores less than two or three miles wide. But there are other things that can reach several times greater.
As a general rule, the closer a comet is to the Sun, the brighter it will be. Large ones that sweep closer than Earth’s distance from the sun (92.9 million miles) tend to get very bright. Good examples include Comet Hale-Bopp in the spring of 1997 and Comet Niues (discovered by an automated space telescope) in the summer of 2020.
So what category does ZTF fall into? In many ways, it’s a fairly common comet, but compared to most other dim marriages, ZTF is very bright.
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