Rare Green Comet Visits Earth for the First Time Since Ice Age

Comet C/2022 E3(ZTF)
Comet C/2022 E3(ZTF), Credit: flickr.com/Edu INAF

A rare comet – named the C/2022 E3 (ZTF) – is predicted to pass by Earth on February 1, 2023. Because it takes 50,000 years to orbit the Sun, C/2022 E3 (ZTF) may be classified a long period comet. C/2022 E3 (ZTF) is passing by Earth again after 50,000 years – its previous visit was during the last ice age, when early humans roamed the Earth.


C/2022 E3 (ZTF) was identified by Bryce Bolin and Frank Masci using the Zwicky Transient Facility (ZTF) survey on 2 March, 2022. The Zwicky Transient Facility is a wide-field survey, meaning that it employs wide-field cameras to scan the sky, using the Samuel Oschin Telescope at the Palomar Observatory in southern California.


At first, C/2022 E3 (ZTF) was misidentified as an asteroid. However, further observations showed the presence of a condensed coma. A coma is a cloudy covering made of ice and coma dust present around the head of a comet. A coma gives a comet a “fuzzy” appearance. Comets are believed to have formed early in the history of the solar system. Comets are made of dry ice, mineral grains, other frozen gases like methane and ammonia, and some organic compounds.


The green color of C/2022 E3 (ZTF) is mostly because of the presence of diatomic carbon around the head of the comet. Ultraviolet radiation from the Sun causes the carbon molecules to undergo a photodissociation reaction, which is the separation of molecules into atoms because of light. The carbon molecules breaking causes the green glow.


C/2022 E3 (ZTF) will be visible from Earth to the naked eye as a bright green comet, according to NASA. The comet may be visible in the morning sky in the Northern Hemisphere during January. In the Southern hemisphere, the comet may be visible in the morning sky in early February.


When the comet C/2022 E3 (ZTF) passes the Earth, and then later on the Sun, the makeup of the comet will be examined and more details may be revealed about the evolution of the solar system from 50,000 years ago. When C/2022 E3 (ZTF) reaches closer to the Sun, the heat will melt the comet’s layers, allowing scientists to better study its makeup.

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