Green Comet to swing by Earth after 50,000 years

Sometimes also referred to as Neanderthal Comet, the Comet ZTF will be closest to Earth, about 44 million km away, on February 2

Hyderabad: A bright comet with a clear greenish-tinge known as Green Comet ZTF, which came nearest to the Earth about 50,000 years ago when Neanderthals and Homo sapiens roamed together, is making another swing by this January and February.

Sometimes also referred to as Neanderthal Comet, the Comet ZTF will be closest to Earth, about 44 million km away, on February 2.

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The once in a lifetime icy visitor was first discovered in March, 2022 by astronomers from Zwicky Transient Facility (ZTF) in California, US. Initially, they speculated it to be an asteroid but thorough subsequent observations revealed it was a comet.

Comets are small, irregularly shaped bodies in the solar system composed mainly of ice and dust that typically measure a few km across. They travel around the Sun in elliptical orbits that brings them very close to the Sun. Based on the time taken to orbit the Sun, there are two categories of comets and the Green Comet ZTF falls under the category of long period comets because it takes more than 200 years to complete one orbit of the Sun. There are comets that take less than 200 years to orbit the Sun and such comets are known as short-period comets.

According to NASA and the Planetary Society, ‘the massive snowball comet ZTF has been brightening while approaching the Sun and the Earth. As a result, sometimes in clear skies, it could be visible even without binoculars”.

The green glow of the Comet ZTF is because of the glowing carbon gas and appears on its head and not the tail. “As they near the Sun, brightness of the comets is notoriously hard to predict. The comet’s white dust tail will be visible but much shorter. The green glow is the comet’s coma, caused by glowing carbon gas. Comet ZTF is expected to pass nearest the Earth in early February, after which it should dim dramatically,” the NASA said.

The Comet ZTF was discovered by astronomers Bryce Bolin and Frank Masc using a 48-inch Samuel Oschin robotic telescope.