Facts About Comet's Tails, Composition, Orbit And More
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Comet Hyakutake |
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Quick Facts About Comets
- The nucleus of a comet can be small as few hundred metres but can be substantial as tens of kilometres.
- However, the length of its tail can stretch up to one astronomical unit (the distance between earth and sun).
- It is theorised that comets might have brought water and essential components for life on earth.
- Great comets are those comets which are incredibly bright and can be easily seen by the naked eye.
- There are 6,619 (as of July 2019) comets are known.
- Astronomers estimated that in the outer solar system, there could be one trillion comets.
- Comets are only visible when they are near to the sun.
- When Earth passes through the orbit of a comet, the debris left by the comet falls on earth which results in meteor showers.
Detailed Facts About Comets
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Comets are often referred to as dirty snowballs of the space
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Different Parts Of A Comet © Wikimedia |
A research conducted in 2014, suggests that comets are like "deep-fried ice cream" as their outer surface is the composition of ice and organic compounds while the interior is cold and less dense.
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The nucleus of a comet is darker than asphalt
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Nucleus Of Comet Tempel 1 (9P/Tempel) |
The comets are among the darkest object in the solar system.
The exterior surface reflects very less sunlight, about 3% of the light that hits its surface. By comparison, asphalt reflects only about 7% of light. As it reaches close to the sun, the heat of the sun evaporates the lighter volatile compounds from the outer surface and leaves behind darker like crude oil, larger organic compounds.
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The coma of a comet can be larger than the size of the sun
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Coma of comet 17P/Holmes © Wikimedia |
The coma can grow as large as the diameter of the Jupiter. The "Great Comet of 1811" had an incredibly large coma, about the size of the width of the sun. At the distance of about 1.5 AU from the sun (at the Mars orbit), the solar winds become too strong that it blows the gas and dust away from the coma and extend its tail.
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There are two types of comet tails
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Ion and dust tail of a comet during its orbit around the sun © Wikimedia |
Due to their composition, the two tails point in a slightly different direction and reflect distinct colours. The gaseous tail interacts with the magnetic field of the solar wind and always points along the streamlines of the solar wind. In comparison, the dust tail does not influence by the solar wind. It follows the comet's orbital trajectory and is slightly curved, also called "anti-tail".
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Comets can break apart or smash into another celestial body
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Brown spots left after the impact of Comet Shoemaker-Levy 9 |
The collision of these fragments caused fireballs, and the released energy is equivalent 6,000,000 megatons of TNT. After the impacts, it left dark spots of thousands of kilometres wide that were eventually wiped out by the Jupiter's strong winds. There are some comets called Kreutz Sungrazers that broke apart when passing too close (within a few thousand kilometres) to the sun. They sometimes meet a more astonishing end by diving into the sun (though they do not really fall instead wipe around it).
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Comets can take up to thousands of years to complete an orbit
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Location of Kuiper Belt and Oort Cloud in the solar system |
Short Period Comets
Short-period comets are also known as periodic-comets because they have periodic orbits. A short period comet has an orbital period of less than or around equal to 200 years. Periodic comets can be seen once or twice in a person's life. They are thought to originate from Kuiper Belt, a disk-shaped region of icy objects beyond the Neptunian world. The gravitation pull of giant planets drags them inwards towards the sun, making them active. The periodic comets can be seen once or twice in a person's life.The short-period comets are further divided into Halley Type (whose orbital period is over 20 years) and Jupiter Type (whose periods are under 20 years).
Long Period Comets
Long-period comets are the highly eccentric comets whose orbital period ranging from 200 years to thousands of years. They originate from the Oort cloud, a dark region even farther from the Kuiper Belt. At aphelion, they can get a trip of the outer solar system and take thousands of years to return. Single-apparition or non-periodic comets are similar to Long-period comets. Unlike Long-period comets, they are not bound to the sun and may escape the solar system.-
Comets may have more than one name
Old Naming System
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The great comet of 1882, named after its discovery year |
Present Naming System
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Halley's Comet, named after Edmond Halley, now has the numerical designations 1P/Halley and 1P/1682 |
- A prefix is used that indicates the comet type. The prefixes are:
- P/ is used to indicate a periodic comet.
- C/ is used to indicate a non-periodic comet.
- X/ is used for those comets whose orbit cannot be determined.
- D/ is used for a periodic comet that has disappeared, broken up, or been lost.
- I/ is used to indicate an interstellar comet.
- The year on which the comet has been discovered.
- An uppercase letter (except I ) which indicates the half-month of the discovery (A for the first half of January, B for the second half and so on).
- A number that represents the order of discovery within that half month.
For example, Comet Hale–Bopp was discovered on the second half of July 1995, so it is renamed to C/1995 O1. If a periodic comet is observed after its second perihelion passage, an additional prefix number is added. The number indicates the order of their discovery. So Halley's Comet, the first observed periodic comet, has the systematic designation 1P/1682 Q1.
To complete the name, a comet is given the last names of the first two people who have discovered the comet, separated by hyphens. Exceptionally, a comet name may consist of three people. If the discoverer is a team of astronomers or observatory or agency, one word or acronym is used. Examples are C/1995 O1 (Hale-Bopp) and C/2012 S1 (ISON).