A rare green comet, last seen roughly 50,000 years ago, will come within 50,000 miles of Earth. C/2022 E3 (ZTF) is a cosmic object from the Oort cloud on the fringes of the Solar System. On February 1, it will pass within 45 million kilometres of Earth.
The frozen ball orbits the sun once every 50,000 years, implying that it last passed through Earth during the Stone Age, when Neanderthals roamed the planet. Many comets have such large orbits around our Sun that it can take decades for them to return to the skies of our planet. Comets, such as the well-known Halley's Comet, can be seen from Earth only once every 75 years or so, making them once-in-a-lifetime experiences.
In March 2022, C/2022 E3 was discovered in the Zwicky Transient Facility in California. UV light from the sun illuminates the atmosphere surrounding the comet, causing it to glow green. C/2022 E3 is now bright enough to see with the naked eye in low-light conditions.
The comet is thought to have formed in the Oort cloud, which is a spherical layer of frozen particles located between 2,000 and 100,000 astronomical units (AU) from our Sun.
One AU is equal to the average distance between the Earth and the Sun, which is approximately 93 million miles.
So, how can you see this comet, which won't be seen for another 50,000 years or so? The comet will pass within 27 million miles of Earth on Wednesday and Thursday of this week (1 and 2 February). The best time to see the comet is early in the morning, shortly before dawn.
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