The rare Green Comet, C/2022 E3 (ZTF), discovered in March 2022, at the Zwicky Transient Facility, in California, USA made its closest approach to the Earth on February 2, 2023. According to the National Aeronautics and Space Administration (NASA), the Green Comet passed its closest to both the Sun (on January 12, 2023) and Earth. Now it is on its return journey back to the outer solar system. It was visible from the Australian skies. The last time the comet passed by the Earth was 50,000 years ago. It was first spotted inside the orbit of Jupiter and was initially misidentified as an asteroid.
The Green Comet is one of the icy objects known as small solar system bodies, which orbit around the Sun in elliptical trajectories. This comet takes around 50,000 years to orbit the Sun.
Comets were first postulated by the American astronomer, Fred Lawrence Whipple, as the conglomerates of ice and dust. In general, a comet is simply made up of silicate dust and a smattering of the organic molecules, coated with ice. A comet can form itself in about 1,00,000 years, according to Stuart Weidenschilling of the San Juan Institute. The comets (or the hairy stars) have a tail or coma, which distinguishes them from other celestial objects like asteroids and meteoroids.
When it was close to the Earth, it was visible with two dippers and was about 26 million miles away from the Earth. NASA had published its image with a Big Dipper and a Little Dipper. (The Big Dipper is a popular term used to describe the shape formed by the seven brightest stars in the constellation Ursa Major or ‘the Great Bear’.) The stars of the Big Dipper are part of a larger asterism known as the North Star, and are among the most recognisable stars in the night sky. These stars form a unique dipper-shaped pattern. (The Little Dipper is a smaller, less well-known dipper-shaped constellation. ‘It also consists of seven stars, including the North Star, Polaris’ which is one of the brightest stars in the night sky and serves as a useful reference for navigation.)
The comet, C/2022 E3 (2TF), has a green glow—a phenomenon, thought to arise from an interaction between the sun light and diatomic carbon. (Diatomic carbon is an unstable and gaseous form of the element in which carbon atoms are bonded together in pairs.) According to scientists, the phenomenon occurs on the head of the comet, when larger carbon-based substances are broken down by sunlight as the comet approaches the Sun.
When diatomic carbon is excited by the ultraviolet rays, it gives off light, surrounding the nucleus of the comet, and results in the Green Comet. However, ultraviolet light could also cause diatomic carbon breakdown. Hence, the tail of the comet is not green.
After passing closely from the Earth, the comet would move nearly in front of Mars.
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