por What are comets?
The kites They are small irregularly shaped stars that belong to the solar system, since they are linked to the Sun by the force of gravity. PThey come from the original cloud of matter that gave rise to our solar system, currently they are rather towards the outskirts of it, although sometimes their orbit brings them close to Earth.
These occasional visitors are made up of grains of non-volatile material, such as dust and rocks, along with frozen gases. Although today they are respectable members of the solar system, in ancient times their unexpected appearance was an omen of catastrophes and wars.
What are comets made of? Composition
The material that makes up comets is the same that makes up the rest of the solar system, which came from an immense cloud of dust and gas. This cloud in turn probably originated from a supernova explosion.
About 4.6 billion years ago the cloud, composed mostly of hydrogen and helium, slowly revolved around a young Sun, its particles colliding with each other. The force of gravity caused many particles to clump together to become planets, but the collisions also fragmented other objects.
Many of them became asteroids and comets, or helped form other planets. For example, the composition of Uranus and Neptune, giant outer planets, is very similar to that of comets.
comet size
The size of a typical comet is, on average, about 10 km in diameter, although there are those larger than 50 km. It is not a very impressive size and its appearance far from the Sun is very close to that of an asteroid: a more or less amorphous and icy body.
When the comet approaches the Sun and is exposed to radiation, its appearance changes considerably, appearing a distinctive structure.
structure of a comet
A comet contains the following parts:
-Core
-Hair
-Line
The hair of the comet or eatmade of dust and gas, is a halo of diffuse, glowing material that surrounds an icy center called core. The structure formed by the nucleus and the hair is the comet head.
They also develop tails, called caudas. Usually there are two, although a spectacular comet seen in 1744 came to develop six tails.
Where do comets come from?
In its early days, the solar system was teeming with comets on all sides, but over time they have drifted away from the inner solar system, perhaps due to the strong gravity of the outer planets, although they do visit us from time to time.
There are usually about fifteen or twenty visible at any given time with the aid of telescopes. But when it comes to comets visible to the naked eye, on average there is one every decade.
Astronomers believe that comets come mostly from three outer regions of the solar system:
The Kuiper belt.
The Oort cloud.
The scattered disc.
Kuiper belt
Many comets left the vicinity of the solar system to reach this region, due to gravitational interaction. There, too, new comets are formed.
The Kuiper belt is also home to trans-Neptunian objects, which are members of the solar system whose orbit is beyond Neptune. The diameter of these objects ranges from 100 to 1,000 kilometers, so Pluto and its moon Charon are the largest trans-Neptunian objects known to date.
Possibly the trans-Neptunian objects were destined to become another large planet, however for some reason this did not happen. Perhaps it was because the material that composes it was too dispersed after the formation of Neptune and gravity was not enough to compact it.
oort cloud
Some of the most striking comets come from this area of space, as well as the so-called long period comets. The period is the time it takes the comet to complete its orbit, if it is very long, the period is greater.
Astronomers believe that perhaps the best-known comet of all, Halley’s Comet, although it does not have a long period, comes from the Oort Cloud and not from the Kuiper belt, as would be expected. For its part, the long-period comet Hale-Bopp also comes from there.
What produces the luminous tail of comets?
Comets’ tails, their most striking feature when viewed from Earth, form when they get close enough to the Sun.
The comet’s gas particles collide with the current of the solar wind and interact with the highly energetic photons of the Sun, managing to displace them and move them away from the star. That is why we always see that the comet’s tail points away from the Sun.
The closer the comet gets to the star, the brighter it gets. This is why comets are best seen just after sunset in the western sky, or just before sunrise in the eastern sky.
What shape is the orbit of comets?
The orbits of comets are conical curves, almost always ellipses with great eccentricity. That is to say, they are very flattened ellipses, unlike the orbits of the planets, whose eccentricity brings them quite close to the circumference. Sometimes the orbit can even be parabolic or hyperbolic.
The force of gravity exerted by the Sun and the other components of the solar system is responsible for the orbit. And to a lesser extent, the gases that the comet itself gives off.
The orbit of many comets brings them quite close to Earth’s neighborhood, the so-called inner solar system, but they are almost always observable only through telescopes.
short period comets
The period of a comet, that is, the time it takes to complete its orbit, is proportional to its size. There are comets with a very short period, such as Encke, which takes 3.3 years to visit Earth. Halley’s Comet takes between 74 and 79 years to be seen again.
These comets are classified into short period comets, whose orbits take them close to Jupiter or even beyond the orbit of Neptune. They take less than 200 years to complete. About a dozen of them arrive each year in the inner solar system, but you need a telescope to observe them.
long period comets
For his part, long period comets they take more than 200 years to travel their path and their orbits are usually parabolic. They are believed to come from the distant Oort Cloud.87
Comet Examples
Halley’s Comet
It is undoubtedly the most remarkable comet of all and the best documented. It visits Earth approximately every 75 years and numerous chroniclers around the world have recorded its appearance as early as 240 BC, although they did not realize it was the same object until Edmund Halley calculated its orbit and predicted its return.
Tempel Tuttle
The Tempel-Tuttle is famous for being the parent of the Leonids, another notable meteor shower. It was discovered in the 19th century and is a short-period comet: it takes 33 years to complete its orbit.
Hale Bopp
This comet visited Earth at the end of the 20th century and is known as the Great Comet of 1997, being visible for just over a year. Its brightness was unusual, and so was the size of its core: 40 km across. Many people believed that an alien ship would arrive on Earth along with him.
Shoemaker-Levy 9
This is the comet notable for having impacted the surface of Jupiter in 1994. It allowed scientists to discover in part the composition of Jupiter’s atmosphere, in which sulfur, ammonia, carbon sulfide, and hydrogen sulfide were found, among other compounds. .
References
Astronomy for beginners. you comet them. Recovered from: astronomia-iniciacion.com.
Chodas, P. Introduction to Comets and Asteroids. Retrieved from: stardustnext.jpl.nasa.gov.
Maran, S. Astronomy for Dummies.
Oster, L. 1984. Modern Astronomy. Editorial Reverté.
Wikipedia. Kite. Recovered from: es.wikipedia.org.