What are Comets and how are they formed?
Comet NEOWISE a rare comet will be visible in the skies of the Northern hemisphere for the next 20 days. Recently discovered comet named C/2020 F3 which is also known as NEOWISE has been spotted from various parts of the world starting from 14 July, 2020 for the next 20 days and it will be visible from the naked eye for 20 minutes every day.
Comets are also known as the 'Dirty Snowballs' of Space. They are small icy objects that release dust or gas in space and orbit the Sun. The time that comet's take to complete the orbit is known as a comet's period. The comet periods range from a few years to millions of years. They are made up of dust, ice, carbon dioxide, ammonia, methane, etc. The building block of a comet is dust particles coated with water ice and other molecules. These dust particles combine to form icy rocks that join together under the force of gravity.
How are Comets formed?
The material present in the comet is from the time when the Solar System was formed. According to some astronomers, comets are formed around 4.6 billion years ago. Comets consist of an icy centre known as the nucleus which is surrounded by a large cloud of gas and dust known as Coma.
Do you know Comets develop two tails when they travel closer to the Sun? These two tails are straight gas tail and a curved dust tail.
A straight gas tail is created by the solar wind and pushes gas away from the coma of the comet and point straight back from the Sun. The dust present in the coma does not get affected by the magnetic fields but vaporises by the heat of the Sun. As a result, a curved tail is formed which follows the orbit of Comet.
How Comets got the name?
It has been seen that comets are named after their discoverer. For example, Comet Halley is named for Edmund Halley. He determined that Comets observed in 1531, 1607, and 1682 had the same orbits and were a single comet. According to Edmund Halley's calculations, he in 1758 predicted correctly about the comet's return but unfortunately, he did not live to see Halley Comet. Sometimes it is seen that more than one person reports a new comet at the same time. In this case, the names of comets are combined like Comet Hale-Bopp or Comet Shoemaker-Levy.
What is the size of the Comet?
The nucleus of a comet is usually 1 to 10 kilometres that is 0.6 to 6 miles across. The tail can stretch for tens of millions of kilometres.
Where do comets come from?
It is believed that comets have two sources namely Long-period comets and short-period comets.
Long-period comets take more than 200 years to complete an orbit around the Sun whereas short-period comets take less than 200 years to complete an orbit around the Sun. They originate from the Kuiper Belt.
According to Danish astronomer, Jan Oort comets reside in a huge cloud at the outer reaches of the solar system, far behind the orbit of Pluto. This is known as the Oort cloud. According to some statistics, it may contain trillion comets and may account for a significant fraction of the mass of the solar system. However, the individual comet is so small and so far away that we have no direct evidence about the actual existence of the Oort cloud.
It is believed that short-period comets are originated in the Kuiper belt. It is a disk-shaped region that extends beyond Neptune. This belt contains small, icy planetary bodies and out of them, only a few have been imaged.
Long-period comets like Comet Hale-Bopp or Comet Hyakutake take more than 200 years to orbit the Sun. In terms of direction and plane of orbit, the path of these comets is random. According to several observations, long-period comets are believed to originate in the Oort cloud.
What happens when Comet reaches close to the Sun?
Comets are just small chunks of ice and dust in the Kuiper belt region and Oort cloud. Basically, they are invisible except when they get close to the Sun.
When a comet comes close to the Sun, it begins to heat up and the ice begins to sublimate and changes directly from solid to a gas without changing into a liquid stage. When ice sublimates some of the dust is left behind. On the surface of the nucleus, it forms a dark protective crust and slows the process of melting. The gas and dust from the cloud of the coma.
So, we understood that when a comet gets closer to the Sun, the tails of the comet get longer and more impressive. When a comet approaches the Sun, it gets hotter and the material is released more rapidly. As a result, the tail is produced. According to the scientists when comet reaches close to the Sun it loses between 0.1 and 1 percent of its mass each time it orbits the Sun.