What are comets?
Comets are frozen leftovers from the formation of the solar system composed of dust, rock and ices.
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.
They are often compared to dirty snowballs, though recent research has led some scientists to call them snowy dirtballs.
What is the size of comets?
They range from a few miles to tens of miles wide, but as they orbit closer to the sun, they heat up and spew gases and dust into a glowing head that can be larger than a planet. This material forms a tail that stretches millions of miles.
Where are comets generally found?
There are likely billions of comets orbiting our Sun in the Kuiper Belt and even more distant Oort Cloud.
What is the current number of known comets?
The current number of known comets is: 3,650
What are sun-grazers?
Some comets, called sun-grazers, smash right into the sun or get so close that they break up and evaporate.
What is the structure and composition of comets?
The solid nucleus or core of a comet consists mostly of ice and dust coated with dark organic material, with the ice composed mainly of frozen water but perhaps other frozen substances as well, such as ammonia, carbon dioxide, carbon monoxide and methane. The nucleus may have a small rocky core.
How the naming of comets is done?
In general, comets are named after their discoverer.
For example, comet Shoemaker-Levy 9 got its name because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy.
Spacecraft have proven very effective at spotting comets as well, so the names of many comets incorporate the names of missions such as SOHO or WISE.
Why do comets get close to the sun?
Comets may be occasionally pushed into orbits closer to the sun and the Earth’s neighborhood due to forces of gravity of other planets.
What are short-period comets?
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.
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.
Why do astronomers study and track 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.
Further, 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 characterise NEOs that are 140 meters or larger in size since they can pose a risk to the Earth because of the devastation a potential impact can cause.
Why the visibility of a comet cannot be precisely predicted?
Comets do not have 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 by 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.
PRACTICE QUESTIONS
QUES . What is difference between asteroids and comets ? UPSC 2011
1 . Asteroids are small rocky planetoids, while comets are formed of frozen gases held together by rocky and metallic material.
2 . Asteroids are found mostly between the orbits of Jupiter and Mars, while comets are found mostly
between Venus and Mercury.
3 . Comets show a perceptible glowing tail, while asteroids do not.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 1 and 3 only
(c) 3 only
(d) 1,2 and 3
(b) Comets found beyond Nepture i.e. Kupier belt. Asteroids are tiny planetary bodies revolving around the sun between the orbits of Jupiter and Mars. Comets are made up of ice and dust coated with dark organic material.
