Don Machholz originally wrote this article for EarthSky in March 2022. Sadly, Don passed away from Covid-19 in August 2022. Recent updates on the article have been by Eddie Irizarry and the editors at EarthSky.
Comet closest to Earth on February 1 and 2
On February 1 and 2, Comet C/2022 E3 (ZTF) will reach its closest point to Earth (0.29 AU/ 27 million miles/ 44 million km). At that point, it’ll still be more than 100 times the moon’s distance away. With a first quarter moon on January 28, the moon is setting just after midnight.
For those who wish to view the comet around closest approach (perigee), the viewing is better in the morning hours after the moon has set. The comet is reported to be visible without optical aid by experienced observers under dark skies. Try observing from a dark-sky site for your best chance to see it with your eye alone. No luck? You can always use binoculars or a telescope to spot this green visitor from the outer solar system.
During its closest approach to Earth, the comet will be in the direction of the constellation Camelopardalis. It will also be close to the borders of Ursa Major and Ursa Minor. 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. Use the star charts below to help you track it down.
Clouded out? The Virtual Telescope Project will show the comet’s close pass live starting at 10:00 p.m. CST (04:00 UTC) on February 1.
The last time this comet passed near the sun was 50,000 years ago, when Neanderthals walked the Earth. Now, as the comet returns, it could be the brightest comet of 2023, so be sure to catch it while you can!
And, don’t miss the photo gallery of the comet at the end of this post.
How bright is it?
So, how bright is it, and how bright might it get? To be sure, we continue hearing reports that it is brightening. And, as you can see from the light curve chart at astro.vanbuitenen.nl, the comet has pretty much followed the predicted curve as it has approached the sun. Will the comet get as bright as magnitude 5.0 when it’s closest to Earth? We’ll keep tracking it to find out.
Also, keep in mind that magnitude 5 is only as bright as the dimmest stars that you can see from a dark-sky site. Additionally, the light from a comet is not a bright point, but a fuzzy, diffuse spot. So, train your eyes to look for the lighter haze on the background sky and you might see it! It helps to find it first in binoculars and then look without optical aid.
Whole-sky finder map for Comet 2022 E3 ZTF
Finder map for the comet on January 31
The comet and Mars on February 10
If it’s your first attempt to locate a comet, try on February 10, 2023, when the comet will appear extremely close to Mars. Also, sky enthusiasts as well as casual photographers can try to capture images of this comet that night. You can point a camera toward its approximate location in the sky and take long-exposure photos of 20 to 30 seconds. The images may reveal a fuzzy, tailed object. Indeed, using this technique, many have been able to photograph a comet even if they don’t see it visually.
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.
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 3rd such object discovered in the fifth half-month (A, B, C, D, E) of the year. Thus, 2022 E3 (ZTF).
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.
Interesting #comet confirmed:
C/2022 E3 (ZTF)
After perihelion on Jan 13, 2023 it approaches earth to 0.29 AU on Feb 2. By then it may be brighter than magnitude 6 while conveniently located for N. hemisphere observers in Camelopardalis.
MPEC 2022-F13 and https://t.co/a7m73XRPFh pic.twitter.com/MDEuGcGxNd— Gideon van Buitenen (@giddgvb) March 21, 2022
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 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.
Most recent photos of Comet E3
Photos of Comet E3 ZTF from 2023
Photos of Comet E3 ZTF from 2023
Photos of Comet 2022 E3 ZTF from 2022
Bottom line: The green comet – Comet 2022 E3 (ZTF) – will be closest to Earth on February 1 and 2. It’s prime time to view this comet, which might be the brightest of 2023.
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