Green Comet: The rare celestial body that orbits the earth once in 50,000 years 

Almost all of us, at some point or the other, have seen a bright, shiny, star-like object with a gorgeous tail blazing through the night sky. It almost appears as if a star is broken. But guess what? What you have just seen and described is a comet! Scientifically speaking, it is a distinct celestial body comprised of ice, dust and gas that eccentrically orbits the Sun and its path is often influenced by the solar wind. 

Now, comets are essentially categorised into four groups: Periodic comets such as the world-famous Halley’s Comet that appears once every 76 years; non-periodic comets such as Comet Hale-Borpp that may or may not appear every 1000 years or more;  non-meaningful orbit comets (also called hyperbolic comets) like the Great Comet of 1106 that only travel through the solar system once and are forced out by Sun’s gravity with such an enormity that it can never stay in a single orbit of its own; lost comets that exist but are often invisible to the human eye until its long gone. Comet Brorsen is the most popular example that passed the Earth in 1842 but was later discovered by Danish astronomer Theodor Brorsen (after whom it is named) in 1846.  

Until March 2022, these were the only four categories of comets known to mankind. However, things changed on the comet front early last year when scientists discovered the Green Comet. Turns out it doesn’t belong to any of the above categories and is all on its own. Recently, this exotic comet has been creating quite a stir all around the globe as it is supposed to make its appearance today after the Stone Age, a broad prehistoric period that lasted for roughly 3.4 million years, and ended between 4,000 BC and 2,000 BC. 

Yesterday, the Green Comet was visible in the western parts of the world including the USA, Europe and Brazil. Today, it will reach its peak and can be seen across Asia in countries like India, China and Bangladesh among others. With only little known so far, let us take a sneak peek at this new-found comet. 

A long-period comet 
Scientifically known as C/2022 E3 (ZTF), the Green Comet is a long-period comet, that is it is neither periodic nor non-periodic. A long-period comet can appear in intervals of hundred, thousand years or million years. Not only that, it also has potentially highly eccentric orbits. As for the Green Comet, it is said to orbit the Earth once every 50,000 years. So, the last time it was visible was during the Stone Age when modern humans didn’t exist.  

Has a bright green glow 
Discovered by NASA-based astronomers Bryce Bolin and Frank Masci in March 2022 at the Zwicky Transient Facility in California, the Green Comet earned its nickname because it has a vibrant verdant glow around its nucleus (centre). The astronomers chanced upon it accidentally while conducting research on Oort Cloud which the Green Comet is believed to have been born out of. Oort Cloud is a collection of icy bodies that are present in the farthest region of the solar system. It has a unique green glow which has been credited to the unusual interaction between sunlight and its molecules comprising of diatomic carbon and cyanogen. Both of these are present in high amounts.  

For those unaware, diatomic carbon is an unstable, gaseous element that has carbon atoms bound together in the form of pairs. Likewise, cyanogen is a colourless chemical compound with a pungent odour and high toxicity. Now, as it turns out, both diatomic carbon and cyanogen are formed near the centre of the Green Comet which are broken down by sunlight as and when it approaches the Sun. When the ultraviolet rays hit the duo, a green halo of sorts is produced. Interestingly, the tail isn’t green as the molecules aren’t present anywhere near it. 

Where to look for the Green Comet? 
Well, the simple answer is to find out the darkest part of the night sky and look for a faint green blob. However, the comet is said to appear in the northern part of the sky, especially near Polaris, the pole star. At midnight, it is supposed to reach its highest point and should be visible at its best. While astronomers have managed to trace it without telescope a few times, they do suggest keeping a binocular handy, just in case. Why? Because even when the Green Comet will be nearest to Earth, it will still be 26 million miles away.