What is a Comet & where does it come from?
Comets provide an amazing night sky view to stargazers but where do they come from?
Comets are the most stunning objects decorating the night sky with glowing tails. Comets were thought to be ‘fire balls’ or ‘harry stars’ traveling through the atmosphere. Comets are irregularly shaped bodies.
Comet or Dirty Snowball?
Comet is a small rocky, icy body with two tails that burns up while entering the Earth’s atmosphere. It was Issac Newton who described that comets are solid bodies with thin tails of vapors heating by the sun. Comets are similar to an asteroid but unlike asteroids which mostly rock in the middle with a small amount of ice. They are made of ice, dust, and frozen gases. That is why comets are called ‘dirty snowballs.’
Don’t have time to read? Watch this https://youtu.be/AFvUgPmiIgE
Origin of the word comet:
The word comet comes from a Greek word that means ‘Wearing long hairs’.
When frozen, they are the size of a small town. As the comets come closer to the sun, they begin to heat up. The ice of a comet begins at the sublimate and turns directly into gas. This gas then creates a cloud around a comet making it seems fuzzy. This process is called sublimation. Sublimation occurs when a material changes from a frozen state to a gas state and skips the intermediate liquid phase.
Parts of Comets:
A comet is made up of the following parts. The nucleus, the coma, the ion tail, and the dust tail.
Nucleus:
The nucleus is a solid central structure made of mostly ice and gas with a small amount of dust. The nucleus of a comet is also known as the core. The nucleus may contain other frozen substances like carbon dioxide, ammonia, carbon monoxide, and methane. The nucleus can be as big as 100 kilometers.
Coma:
Coma is the envelope of evaporated gases (water vapor, ammonia, carbon dioxide) and dust that surrounds the nucleus of a comet.
Hydrogen Cloud:
The hydrogen cloud is a huge envelope, millions of kilometers in diameter. As the comet absorbs ultraviolet light, chemical processes release hydrogen, which escapes the comet’s gravity, and forms a hydrogen envelope.
Dust Tail:
A dust tail is formed by radiation from the sun. This tail is made up of small dust particles. Dust tail always points away from the sun by the solar wind. No matter, which way the comet is traveling this dust tail will be pointing away from the sun. As the distance from the sun increases, the dust tail fades and diminishes.
Ion Tail:
The ion tail is made up of charged ions. And these ions always face away from the sun. The ion tail is about 60 million miles in length.
Classification of comets:
Short Period Comet:
Short-period comets are the comets that orbit the sun in less than 200 years. Short-period comets have an orbital period of fewer than 200 years. The most famous short-period comet is Comet Halley with an orbital period of 75–76 years.
Long Period Comet:
Long-period comets are the comets that orbit the sun in 200 years. They are thought to originate from the Oort cloud.
Where do the comets come from?
Comets come from two places in the solar system. The short-period comets come from the Kuiper belt and the long-period comets come from the Oort cloud.
Kuiper Belt:
The Kuiper Belt is a disk-shaped region that orbits around the sun beyond the orbit of Neptune. The Kuiper belt is thought to be the source of most of the observed short-period comets.
Oort Cloud:
Oort cloud is an immense cloud of icy bodies. It revolves around the sun at 100,000 AU. The Oort cloud is sometimes called the Öpik–Oort cloud.
It lies beyond Pluto, it is farther away from the sun than the Kuiper Belt.
Halley’s comet:
The most famous comet in history is Halley’s comet named after Edmon Halley. He realized that the three bright comets seen in 1531, 1607 and 1682 are returning over and over. That is how he predicted that Halley’s comet will be seen again in 1759. Halley’s comet comes back after every 75 years and last appeared in 1986 means it will return in 2061.
