Astronomy Essentials

Comet 2022 E3 might brighten to binocular range

Starry sky with yellow object in the middle of the image. It is leaving a short trail behind it.
View at EarthSky Community Photos. | Eliot Herman in Mayhill, New Mexico, took this image on September 17, 2022. Eliot wrote: “Comet 2022 E3 is brightening and is now showing a little color. Hopefully the best is yet to come.” Thank you, Eliot!

Don Machholz wrote this article for EarthSky in March 2022. Sadly, Don passed away from Covid-19 on August 9, 2022. If you would like to support his family in their time of need, this is a link to his GoFundMe. Recent updates on this article are by editors at EarthSky.

Comet 2022 E3 might be a bright one

Back on March 2, 2022, astronomers discovered a new comet. It was far from the sun, at a distance of 4 astronomical units (AU, or Earth-sun units of distance). The comet is drawing closer, currently located in the direction of Corona Borealis. Although it is brightening, as of October it’s still too dim to see without a large telescope. But when it comes nearest the Earth and sun in early 2023, the comet should become easily visible in binoculars.

Astronomers call this comet C/2022 E3 (ZTF). Here’s how the comet got its name. Astronomers discovered it 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 in 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.

The comet reaches its closest point to the sun – perihelion – on January 13, 2023. At that time, it will be 1.11 AU from the sun. The comet reaches its closest point to the Earth, 0.29 AU or 27 million miles (44 million km), on February 2, 2023. Use the simulation here to watch the comet’s movement through the inner solar system.

How to see the comet

The comet is currently in the northern evening sky. As of October 2022, Comet 2022 E3 shines at magnitude 13. From mid-September through December, the comet makes a slow loop in Corona Borealis. Starting mid-November, the comet begins following a line out of Corona Borealis toward the north celestial pole and Polaris. It will be in the general vicinity of Polaris on January 30. Hopefully by then, it will be visible in binoculars. At its brightest, the comet may attain visibility to the unaided eye in late January 2023. Use our finder charts below to help locate it in your skies.

Finder maps for comet 2022 E3 ZTF

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

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! It stays in the dark sky for most of its trip through the inner solar system, even when it passes from the evening sky to the morning sky at 44 degrees north of the sun on November 21, 2022.

The tilt of the orbit 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. This means it will, at some point, move quickly through our sky. 

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 will have a good view of the comet until early October 2022. After that, it will disappear into their evening twilight as it rapidly heads northward. They will get their next view of the comet in early February 2023, when it pops above their northern horizon.

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. 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, but don’t confuse the two comets. Today, we are talking about the 2022 one!

At its March 2022 discovery, this comet was a very faint 17th magnitude. 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

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, confirm the object. 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 the case of this object, 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? 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. Only several high-magnification images, stacked to increase contrast, will show the coma of a faint comet.

Three teams imaged this new object, and they did find a coma. 

Many grand photo opportunities

Comet 2022 E3 (ZTF) passed only a degree from M27, the Dumbbell Nebula, on May 31, 2022. The comet came within 1/4 degree of the double star Albireo in the constellation Cygnus on June 17. 

A week later it passed 1/4 degree from the globular cluster M56. And, on July 4, it passed 1/2 degree from the Ring Nebula (M57). 

The comet passed 2.5 degrees south of the Hercules Globular Cluster (M13), on August 23. It was heading south into the constellation Corona Borealis in September 2022. In a couple months, it makes a U-turn, then heads rapidly north. When at its expected brightest in late January 2023, the comet will be high in the evening northern sky in the area where the constellation Auriga sits.

Bright star with spikes next to fuzzy comet with tail pointing left.
View at EarthSky Community Photos. | David Chapman in Halifax, Nova Scotia, Canada, took this image on September 14, 2022. David wrote: “Comet C/2022 E3. This comet is currently in Corona Borealis and will get brighter into the new year. I enjoy following comets and asteroids using the free public robotic telescope at Saint Mary’s University. The photos are exposed under the user’s direction, automatically processed and made available for download.” Thank you, David!

Bottom line: Comet 2022 E3 (ZTF) is headed toward the inner solar system. In early 2023, you should be able to view it in binoculars as it graces our skies. Check back with EarthSky for updates as the comet approaches its perihelion. 

Submit your comet images to EarthSky Community Photos.

October 5, 2022
Astronomy Essentials

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