What is the Green Comet?

Context:

Appearing near Earth after nearly 50,000 years, and next estimated to come close to us after as many years, it might be possible to see a recently discovered green comet in the next week.

Relevance:

GS III: Science and Technology

Dimensions of the Article:

1. What is the ‘green comet’?
2. When and where can the green comet be seen?
3. But why is it green in colour?

What is the ‘green comet’?

• After approaching the sun in the middle of January, it is now moving away from it, along its own orbit.
• The orbit indicates it comes from the edge of our solar system, a distant reservoir of comets we call the Oort cloud.
• The Oort cloud is thought to be a big, spherical region of outer space enveloping our sun, consisting of innumerable small objects, such as comets and asteroids.
• NASA terms it “the most distant region of our solar system” and “Home of the Comets”.
• The Guardian reported that the green comet could be at a distance of 2.5 light minutes from Earth, meaning a “mere” 27 million miles.

Is the green comet rare?

• Coming under the category of long-period comets, which take more than 200 years to orbit the Sun, the green comet is not easily spotted.
• With a highly elliptical orbit, the comet will head back to the Oort cloud and make its next appearance roughly 50,000 years later.
• But given their orbits, it’s not unique for comets to reappear close to Earth only after many, many years.

When and where can the green comet be seen?

• The green comet, also known as C/2022 E3 (ZTF), can be seen in the morning sky in the Northern Hemisphere, moving towards the northwest. It will become visible in the Southern Hemisphere in early February.
• In India, it will be visible in the northwest direction, around 16° above the horizon in the Bootes constellation.
• To spot it, it is best to use telescopes, binoculars, or view it under dark skies. However, due to light pollution, it may be difficult to see with the naked eye.

But why is it green in colour?

• Comets are frozen rocky or gas-filled objects that are remnants of the formation of the solar system.
• Due to their composition, characteristics and the path they move in, they tend to leave a light “behind them”.
• Here, the comet itself is green (called the head of the comet) and emits a whitish light behind it (often called the tail of the comet).
• Just like other bodies in space, comets also have orbits. They are sometimes pulled in close to the sun because of the sun’s gravity acting on them.
• NASA explains that as they orbit near the Sun, “They heat up and spew gases and dust into a glowing head that can be larger than a planet”.
• The remains of dust following this burning up, from a distance, look like a trail of light to humans on Earth.
• Comets, therefore, have often been seen giving out blue or whiteish light, or even green.
• In this case, the green glow “is thought to arise from the presence of diatomic carbon – pairs of carbon atoms that are bound together – in the head of the comet.
• The molecule emits green light when excited by the ultraviolet rays in solar radiation,” The Guardian reported.

-Source: Indian Express