International Space Agencies – Missions and Discoveries

Rare Comet ‘C/2020 F3 Neowise’


From UPSC perspective, the following things are important :

Prelims level : Various terminologies mentioned

Mains level : Not Much

The C/2020 F3 comet also dubbed NEOWISE will be visible with the naked eye for around 20 minutes every day for 20 days across India.

Try this question from CSP 2014:

Q.What is a coma, in the content of astronomy?

(a) Bright half of material on the comet

(b) Long tail of dust

(c) Two asteroids orbiting each other

(d) Two planets orbiting each other

What are Comets?

  • Comets or “dirty snowballs” are mostly made of dust, rocks and ice, the remnants from the time the solar system was formed over 4.6 billion years ago.
  • The word comet comes from the Latin word “Cometa” which means “long-haired” and the earliest known record of a comet sighting was made by an astrologer in 1059 BC.
  • Comets can range in their width from a few miles to tens of miles wide.
  • While there are millions of comets orbiting the sun, there are more than 3,650 known comets as of now, according to NASA.

How do they illuminate?

  • Comets do not have the light of their own and what humans are able to see from Earth is the reflection of the sun’s light off the comet as well as the energy released by the gas molecules after it is absorbed from the sun.
  • The visibility cannot be precisely predicted since a lot depends on the way the “outbursts” of gas and dust play out determining how much of a “good show” the comet will put out for observers.
  • As they orbit closer to the sun, they heat up and release debris of dust and gases that form into a “glowing head” that can often be larger than a planet.

Why do they get close to the sun?

  • Comets may be occasionally pushed into orbits closer to the sun and the Earth’s neighbourhood due to forces of gravity of other planets.
  • The appearance of some comets, like those that take less than 200 years to orbit around the sun is predictable since they have passed by before.
  • These may be referred to as short-period comets and can be found in the Kuiper belt, where many comets orbit the sun in the realm of Pluto, occasionally getting pushed into orbits that bring them closer to the sun.
  • One of the most famous short-period comets is called Halley’s Comet that reappears every 76 years. Halley’s will be sighted next in 2062.
  • Comets in this cloud can take as long as 30 million years to complete one rotation around the sun.

Significance of the comets

  • NASA tracks all Near Earth Objects (NEOs) that includes comets and asteroids using telescopes placed all around the Earth, as part of its NEO Observation Program.
  • Comets hold important clues about the formation of the solar system and it is possible that comets brought water and other organic compounds, which are the building blocks of life to Earth.


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