Astronomy EssentialsTonight

Green comet passes Aldebaran on February 14 and 15

Circular star chart (binocular view) showing arrow of comet's motion past orange dot of Aldebaran.
Binocular view of comet’s path and Aldebaran on February 14 and 15. Chart via John Jardine Goss/ EarthSky.

Show your sweetie the green comet

Okay, it’s not bright. And you’ll need a little patience and a dark-sky site to see it. Plus you’ll need binoculars, at least. But the comet is in a good place to try to see on this Valentine’s Day, 2023. Tonight and tomorrow night, those using optical aid can spot the green comet (C/2022 E3 ZTF) near the orange star Aldebaran, in the constellation Taurus the Bull. The green comet is dimming as it speeds out of the inner solar system. Catch it before it’s gone.

Astrophotographers can point a camera toward its approximate location in the sky and take long-exposure photos of 20 to 30 seconds. Your images might reveal a fuzzy, tailed object. Indeed, using this technique, many have been able to photograph a comet even if they can’t see it visually. Did you get a photo of Aldebaran and the comet? You can submit it to our EarthSky Community Photo page!

Current estimates of the comet’s brightness show that it should be shining around magnitude 6.5 by mid-February. That’s beyond the limit of visibility to the unaided eye. If you want to see it with your own eyes, you’ll need binoculars, or a small telescope, and a dark-sky site.

The moon will rise after midnight local time on February 14, leaving a small window for viewing. Be aware that the comet sets around 1 a.m. local time (the time on your clock, no matter where you are on the globe).

The 2023 EarthSky lunar calendar is on sale! A unique and beautiful poster-sized calendar showing phases of the moon every night of the year. Treat yourself!

Star chart with arrow and dates showing location of comet passing a red dot (Mars) and orange dot (Aldebaran).
See that green line across our chart? That’s the ecliptic, or path the sun travels during the course of the day. Look along that line for 2 bright reddish objects, a planet and a star. The green comet swept past red Mars around February 10 and 11. It’s now going to pass the red-orange star Aldebaran, Eye of the Bull in the constellation Taurus. The comet is faint now and moving fast away from our sun. You’ll need binoculars and a dark sky to see it. Chart via John Jardine Goss/ EarthSky.

How to see the comet

Use the star charts here to track down the comet. Its northern location on our sky’s dome means Southern Hemisphere stargazers don’t have a good view of this comet. For them, the body of Earth will block it from view. Be sure to check Stellarium for a precise view from your location, at the time you want to watch.

The comet is dimming as it leaves the solar system, but observers are still picking it out with binoculars. Look for a faint smudge. It won’t be a bright point, like a star. Instead, it will look like a spot that is just a bit lighter gray than the surrounding background of space. It can help to use averted vision to spot it.

Comet C/2022 E3 map for February

A curve drawn on a star map to indicate the comet's path.
The path in our sky of comet C/2022 E3 (ZTF) after its perihelion (closest point to the sun) on January 12-13, 2023. Image via Don Machholz/ EarthSky.

The comet was closest to Earth on February 1 and 2

On February 1 and 2, 2023, Comet C/2022 E3 (ZTF) reached its closest point to Earth. That’s when it passed 27 million miles away (that’s 44 million km, or 0.29 AU). At that point, it was still more than 100 times the moon’s distance away.

The last time this comet passed near the sun was 50,000 years ago, when Neanderthals walked the Earth. Now, as the comet returns to the outer solar system, we can enjoy what could be the brightest comet of 2023 before it gets too dim to see.

And don’t miss the photo gallery of the comet at the end of this post. Plus you’ll find more images of the comet here.

Two side-by-side photos of fuzzy green comet with tail and antitail pointing almost opposite each other.
View at EarthSky Community Photos. | Eliot Herman in Tucson, Arizona, captured these images of Comet E3. Eliot wrote: “As Comet 2022 E3 (ZTF) moves beyond the plane of Earth’s orbit, the rarely seen anti-tail is fading. These images show the difference between January 25 (left) and 26 (right), 2023. The anti-tail is an illusion generated by the angle of the viewer as the comet passes through the Earth’s position on the plane of the ecliptic. The comet is a striking sight, just inside the magnitude of the unaided eye now. Through a telescope you can see the head and tail, and with photography or even a small backyard telescope it pops.” Thank you, Eliot!

Good geometry

Comet C/2022 E3 (ZTF) has favorable geometry with respect to Earth. Normally, a comet will pass near the sun’s vicinity, and the elongation, which is the angle in degrees between the sun and the comet as seen from Earth, grows small and the comet disappears in the sun’s glare for a few weeks. Not this one, though! In contrast, it stays in the dark sky for most of its trip through the inner solar system.

Moreover, the tilt of the orbit relative to our path around the sun is steep and retrograde, meaning the comet goes around the sun in the opposite direction than do the planets. As a result, this means it will, at some point, move quickly through our sky. 

To begin with, the comet entered our solar system from the north, and on February 12, 2023, passes to the south of our orbital plane.

Northern Hemisphere observers will have a view of the comet until the end of April 2023, when the comet, then a telescopic object, will disappear into the evening twilight.

Southern Hemisphere observers, however, lost their view of the comet in early October 2022. It disappeared into evening twilight as it rapidly headed northward. Subsequently, their next view of the comet will come in early February 2023, when it pops above their northern horizon.

Green comet photos and videos: Editors’ picks

How Comet C/2022 E3 (ZTF) got its name

Astronomers discovered Comet C/2022 E3 (ZTF) using the 48-inch (1.2-meter) Samuel Oschin robotic telescope, part of the Zwicky Transient Facility (ZTF), located at Mt. Palomar in southern California. They discovered it on March 2, 2022, and it was the third such object discovered in the fifth half-month (A, B, C, D, E) of the year. Thus, 2022 E3 (ZTF).

Green comet with long gray tail in starry background.
View at EarthSky Community Photos. | Jasna Maras of Vrlika, Croatia, captured this image of the comet on January 25, 2023. And Uros Todorovic Miksaj – also of Vrlika – processed it and wrote: “Maybe there will be more opportunities in February, but for now we have at least one memory of this once-in-a-lifetime visitor.” Thank you, Jasna and Uros!

The discovery story

Comet C/2022 E3 (ZTF) was in the morning sky, in the direction of the constellation Aquila the Eagle, when astronomers with the Zwicky Transient Facility first spotted it. 

The ZTF program images the whole Northern Hemisphere every two nights looking for supernovae, variable stars, binary stars, flashing merging neutron stars, asteroids and comets. Overall, it has discovered 10 comets in the past three years, and half of them carry the acronym ZTF in their names. One, discovered a year ago, was named C/2021 E3 (ZTF). Similar name, to be sure, but don’t confuse the two comets. Now, we are talking about the 2022 one!

A faint comet

At its March 2022 discovery, this comet had a very faint 17th magnitude brightness. Initially, it appeared as a stellar object, that is, as a dimly shining point. But, unlike the stars, whose distances make their motions undetectable except via special techniques, this object was moving in front of the stars.

New comet: A fuzzy object on a very pixelated field of stars.
View larger. | Italian amateur astronomer Ernesto Guido was 1 of the 1st to confirm the cometary nature of new comet C/2022 E3 (ZTF). Image via Telescope Live. Used with permission.

Confirming its cometary nature

Furthermore, newly discovered objects found to be moving go into the Minor Planet Center’s NEO Page. That’s how other astronomers know what to image and hopefully, thereby, to confirm the object. Now, as both professional and amateur astronomers do find the new object, they submit more positions for it to the Minor Planet Center. Then, scientists can determine a preliminary orbit. In this case, it originally looked more like a comet’s orbit than an asteroid’s orbit. That is, the path around the sun was oblong and not circular. 

At that point, the object went on the Possible Comet Confirmation Page. Astronomers tried to image it to see if it had a coma or extended atmosphere surrounding the object’s nucleus or core. Why is that important? Basically, it’s important because, virtually, all asteroids – which tend to be rocky or metallic – appear starlike (the name asteroid means “starlike”) from Earth. But an icy comet will form a halo, or coma, around its nucleus as the material on the nucleus heats up when the comet is moving inward toward the sun. Indeed, only several high-magnification images, stacked to increase contrast, will show the coma of a faint comet.

In this case, three teams imaged this new object, and they did find a coma. 

Photos of Comet E3

Starry sky with fuzzy green smudge, marked with red arrows, next to a short trail.
View at EarthSky Community Photos. | Bob Kelly in Ardsley, New York, captured this image of Comet E3 on January 27, 2023. Bob wrote: “Caught the comet this morning in a 50mm lens on my Canon XS. The stars have some flare due to some issue with the lens, but the comet looks like how it looked in my 8×25 binoculars. Caught a satellite, too. The 2 stars to the lower right are the bowl stars in the Little Dipper.” Thank you, Bob!
Telescope blurry in foreground with image of large green comet in sky behind.
View at EarthSky Community Photos. | Peter Forister in Louisa, Virginia, captured the comet on January 24, 2023. Peter wrote: “Beautiful ion tail and anti-tail structure. I can confirm that it is barely unaided-eye visible! I was able to spot it, but only when it was nearly directly overhead (just northeast of the Little Dipper). It’s best to not look directly at the object, but rather use peripheral vision because it is more sensitive in low light! It looks like a little fuzzy spot with a very slight green tinge.” Thank you, Peter!
Fuzzy comet with green and white head and darker tail, with shadowy tail in 2nd direction.
View at EarthSky Community Photos. | Patrick Prokop in Savannah, Georgia, captured the comet on January 24, 2023. Patrick wrote: “The green color is from the out-gassing of several carbon compounds with cyanide being the most likely compound generating the green color.” Thank you, Patrick!
Greenish head with fanning white tail aiming downward.
View at EarthSky Community Photos. | Mohamed Usama Ismail in Fayed, Ismaila, Egypt, captured the comet on January 20, 2023. Mohamed wrote: “Prior to the comet’s recent jaunt near our sun, C/2022 E3’s orbit took it far beyond our solar system for roughly 50,000 years. Astronomers aren’t sure exactly how far the comet will travel after leaving Earth behind this time, but the consensus seems to be that C/2022 E3 is on course to leave our solar system entirely.” Thank you, Mohamed!
Fuzzy round comet head with long skinny tail, one pic in color and another black on white.
View at EarthSky Community Photos. | Steven Bellavia in New York state captured this image of Comet 2022 E3 – with its long ion tail – on January 16. Beautiful, Steven! Thank you. When we asked him about the comet’s brightness – and the possibility of seeing it with the eye alone – he said: “I thought I might have just barely seen it with the eye, with averted vision. But I am not 100% sure.” So we know the comet is faint! If you see it with the eye alone, let us know.
Starry sky scene with fuzzy spot circled in yellow.
View at EarthSky Community Photos. | Terry Reis in Waipahu, Hawaii, took this image of Comet 2022 E3 (ZTF) on January 17, 2023. Terry wrote: “Aloha! Since I was able to see the comet with my unaided eye, I decided to pull out my DSLR camera to see if I might be able to get some sort of image on it. I believe I did. It does have a green-tinged look to it.” Congrats on seeing it without optical aid, and thanks, Terry!

Bottom line: The green comet – Comet 2022 E3 (ZTF) – will pass near the bright star Aldebaran – in mid-February. Here’s how to see them.

Submit your comet images to EarthSky Community Photos

Green comet photos and video: Editors’ picks

February 10, 2023
Astronomy Essentials

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Don Machholz

View All