Context

The recently discovered comet called C/2020 F3, also known as NEOWISE after the NASA telescope that discovered it, will make its closest approach to the Earth on July 22, 2020.

About

• On July 3, the comet was closest to the sun at 43 million km. On this day, the comet cruised inside Mercury’s orbit and, due to its proximity to the sun; its outer layer was released creating an atmosphere (referred to as coma) of gas and dust from its icy surface.
  • This atmosphere sometimes leads to the formation of a bright tail of debris that can extend for thousands or millions of kilometres.
• On July 22, the comet, which takes 6,800 years to complete one lap around its orbit, will be at a distance of 64 million miles or 103 million kilometers while crossing Earth’s outside orbit.

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. 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.
• The debris forms a tail that can stretch out to millions of miles. Each time a comet passes the sun, it loses some of its material and it will eventually disappear completely as a result.
• While there are millions of comets orbiting the sun, there are more than 3,650 known comets as of now, according to NASA.
• Comets may be occasionally pushed into orbits closer to the sun and the Earth’s neighborhood 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.
  • These 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.
• The less-predictable comets can be found in the Oort cloud that is about 100,000 AU from the sun, or 100,000 times the distance between the Earth and the sun.
  • Comets in this cloud can take as long as 30 million years to complete one rotation around the sun.

Visibility of the Comet

• 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 of a comet 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.

Importance of studying and tracking the comets

• Astronomers study comets since they believe that they 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.
• 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.
  • This program has a congressionally directed objective to find, track, and characterize NEOs that are 140 meters or larger since they can pose a risk to the Earth because of the devastation a potential impact can cause.