Comets

Comets (kometes – long-haired).
Objects approaching the Sun along highly elongated trajectories, as a rule, are formations of gas, dust and plasma. Their appearance is caused by the evaporation of small icy bodies with sizes from several centimeters to tens of kilometers, which are called cometary nuclei. Among all, most of these cometary “embryos” are located in the Oort cloud on the outskirts of the Solar System. Having started moving towards the center of the Solar system for some reason, the core gradually approaches the Sun, while it heats up. At the moment of its melting, its ice sheets begin to evaporate, forming a cometary head and tail, which can reach enormous sizes.
Being on the surface of the spheres of attraction (see gravitational field) of large planets, first-generation comets can become short-period, i.e. have an orbital period of less than 200 years and remain within the Solar System. As they approach the Sun, they gradually collapse and generate meteor swarms that continue to move in the same orbits.
If a comet that came from the Oort cloud does not have a gravitational effect on large planets, it is moving away almost to its original distance from the Sun. At the same time, the comet no longer moves in the Oort cloud, but returns to our central luminary and becomes periodic, with an orbital period of up to several million years.
There is a possibility that some of the comets come to the Sun from interstellar space.
Asteroids and comets can also pose a danger to Earth. This is evidenced by a relatively recent event. A fragment of the nucleus of comet Schumacher-Levy-9, measuring about 10 kilometers, crashed into the atmosphere of Jupiter in July 1994. Thanks to this, it was possible to achieve an explosion power of 6 million hydrogen bombs with a capacity of one megaton each. The scale of the disaster can be concluded by analyzing that already 45 minutes after the event, a spot was discovered in the cloud layer of Jupiter, the diameter of which exceeded the diameter of the Earth by 2-2.5 times. It is absolutely possible to say that in the event of the fall of such a small celestial body to Earth, it is highly likely that not only the conditions for the existence of highly developed life on our planet will disappear, but also the path of further development of geological evolution will be changed.
Given the extremely low probability of a collision of this body with our planet, it would be wise to create a simple protection system around the Earth against this threat. In a few years, during which all the necessary technical and organizational capabilities for the implementation of this project will be ready, it will be implemented.
You can observe comets in the sky quite often. Their appearance and brilliance depend on the characteristics of cometary nuclei, their trajectories relative to the Sun and the Earth. As a rule, they can only be observed with a telescope. Often, once every hundred years, they become visible to the naked eye (see Radiation receiver, eye) and arouse genuine public interest. To date, there are about a hundred comets that have an orbital period of less than a hundred years. But every year, several new comets are discovered that have long periods of rotation. Astrologers and astronomy enthusiasts are engaged not only in the search for new comets, but also in their study. It should be added that comets receive the names of their discoverers.