A newly discovered green comet approaches Earth

A green comet with a long tail against a black starry background

Comet C/2022 E3 (ZTF) as seen through a telescope

A newly discovered comet will make its closest approach to our planet on Wednesday.

Astronomers say the object took about 50,000 years to travel towards us.

Photographs taken by the astronomers show a distinct green color around the body of the comet.

But those hoping for a brilliant emerald streak in the sky will be disappointed. Its brightness is right at the threshold of what is visible to the naked eye.

“You may have seen these reports saying that we are going to have this bright green object light up the sky,” says Dr Robert Massey, deputy executive director of the Royal Astronomical Society.

“Sadly, that will not be the case.”

However, away from light pollution and under dark skies, you might see a smudge in the sky – if you know what to look for.

Stargazers have a better chance of seeing it using binoculars, where it will appear as a white blur.

“Even a small pair of binoculars will help you find it,” says Massey.

Comets are composed mostly of ice and dust. As they approach the Sun, the ice evaporates and the dust is shaken to form the signature long tail.

“If you’re lucky, you’ll see a hint of the tail coming off, so it will look more like a classic comet,” says Massey.

Comet C/2022 E3 (ZTF) was discovered by astronomers last March at the Palomar Observatory in California.

It has been visible to those in the Northern Hemisphere through binoculars for the past few weeks.

But it will make its closest approach to Earth at about 41 million km (26 million miles) away this Wednesday.

The object originates from the Oort cloud, a collection of icy bodies at the edge of the Solar System.

To find it, Massey recommends first looking for the pole star, which is always in the same place in the sky.

You can identify the pole star by looking directly north and finding a star that hangs clearly on its own.

You can then use free planetarium software online to find out where the comet will be moving in relation to the pole star on the night you are looking at it.

The best time to see it is early Thursday morning when the Moon has set.

At that time the comet should be visible just to the right of the pole star.

The green appearance of comets is not uncommon and is usually the result of the breakdown of a reactive molecule called dicarbon – two carbon atoms joined together by a double bond.

Such color is best picked up with digital cameras, which are more sensitive to color.

The comet will be unmatched by Comet NEOWISE 2020 – the brightest comet visible from the Northern Hemisphere since 1997.

But the Planetary Society said it was a “once-in-a-lifetime opportunity to see”.

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