How does Halley’s comet

Halley’s comet is a bright, unique comet with a period of return to the Sun of about 75-76 years, which is visible even to the naked eye. The official astronomical name of this celestial body – 1P/Halley. For the comet Halley for the first time managed to determine the elliptical orbit and set the frequency of motion in the Solar system than did the Englishman Edmond Halley (1656-1742) the astronomer Royal, physicist, geophysicist, meteorologist, mathematician and demographer, in whose honor was named the comet.

In ancient times, people observed the appearance of Halley’s comet, but did not suspect that I see the same cosmic body. The first surviving written evidence about the emergence of a “heavenly sign” dates back to the year 249 BC, and since then the approaching comet was observed at least thirty times. The last observation of the comet Halley was possible in 1986, and the next is expected in the summer of 2061. I must admit that if an event of this magnitude is regarded as an auspicious time for space exploration, once the appearance of comets were regarded by the people as a “terrible sign” of the coming change, wars, government coups. For the most part, it’s because of “strong world” of those times. It is known that Genghis Khan saw a comet, regarded it as a personal message and a call for conquest of neighboring lands. The same happened in ancient China, and even at the dawn of our era in Europe.

As for the scientific point of view, in Europe for a long time dominated the view of Aristotle. He believed that the appearance of comets is caused by atmospheric disturbances of our planet (despite the fact that at that time there already existed quite close to the facts of the hypothesis of the extraterrestrial nature of comets belonging to the ancient philosophers). Seneca inclined to the version space of the origin of comets, and even modeled a way of proving the periodicity of their motion, which was subsequently implemented by Halley. However, even these facts could not dispel the doubts of scientists: whether comets have their orbits in the Solar system and revolve around the Sun, or whether this is an isolated “guests” who once crossed our finest house in a straight trajectory.

In the 17th century that all changed when in Europe in 1680-1681 saw a bright comet C/1680 V1, sometimes called the comet of Newton. Scientist noticed that the first celestial body was approaching the Sun, and then moved away from it. This was contrary to the hypothesis of rectilinear motion, and physics led to the opening of the force that caused the comet to revolve around the Sun – gravity. Apparently, the joke falling on Newton’s head, Apple has been only in the salons of the time, but now this story appears as true in school textbooks (“Viva” compilers!)

At the same time 24-year-old Edmond Halley studied this issue and came to the conclusion that the force acting on the comet from the Sun centripetal force should decrease inversely proportional to the square of the distance. In 1682 Halley went to Isaac Newton in Cambridge, and he shared his thoughts – according to his calculations, the motion of this comet occurs on the ellipse. Newton continued to study the question of the motion of bodies under the action of gravity, refining their calculations, and two years later was sent to Halley over the treatise “of the Motion of bodies in an orbit” (“De Motu Corporum in Gyrum”).

Halley was fascinated by this work, and on 10 December 1684 at the meeting of the Royal society of London issued a report on the results obtained by Newton. Then he asked a scientist to publish a treatise that Newton said Yes and promised to write a sequel, later named as “Mathematical principles of natural philosophy” (1687 year). In this work, the scientist formulated the laws of gravitation and motion, suggested that the two comets of 1680 and 1681 were in fact the same comet before and after passing near the Sun.

However, to fully describe the motion of the comet within the framework of the Newtonian model became only the Halley. In 1705 he published his treatise “a Review of cometary astronomy” (“Synopsis Astronomiae Cometicae”), in which the scientist took into account the gravitational influence of Jupiter and Saturn on the comet. Halley also took up the study of the historical evidence of the astronomers, and compiled the first catalogue of orbital elements of comets. In it he emphasized the coincidence of the paths of the comets of 1531, 1607 and 1682 years, which brought the frequency of rotation equal to 75-76 years (although the more early entries we will consider, the more this period stretched from 74 to 79 years). So, based on rough calculation, Halley predicted the return of the comet in late 1758 or early next year. Unfortunately, the scientist himself did not live to Christmas 1758, when jubilant astronomers noticed in the sky a legendary space traveler. This was the first demonstration of the fact that to revolve around the Sun can not only planet, and confirmed the validity of celestial mechanics of Newton. For the first time the comet was named Halley in 1759, thanks to the French astronomer N. Luckily. It is obvious that the foundations of modern mathematical physics laid hot a renewed scientific interest in comets.

As the comet glow?

The nucleus of the comet is a kind of “dirty snow”: it consists of substances with a low boiling point of water, organic matter, methane, nitrogen, carbon monoxide, carbon dioxide and minor amounts of other frozen gases. Approaching the sun, lifeless icy asteroid begins to heat up, and the substance of the nucleus start to evaporate more and more actively. So under the influence of the solar wind (the flux emitted by the Sun charged particles) formed trace of the comet – its tail, or “coma”, which can reach across 100 000 000 kilometers. During the evaporation of the ice are released as dust particles which are emerging from the core gas. Glowing tail of the comet two “ways”: the dust merely reflects sunlight, and gases absorb ultraviolet light, resulting in ionized, and then emit light at different wavelengths, visible from Earth as a bluish. This phenomenon is also called fluorescence. As a result, the tail of a comet is divided into two parts. The solar wind accelerates the ions to velocities in the tens and hundreds of kilometers per second, so the coma is formed of the first type, directed almost exactly in the direction from the Sun. The dust is dispersed light is much weaker, so it lags behind the ion and forms the slightly curved tail of the second type.

The size of the coma of Halley’s comet is huge, but the kernel is relatively small and has an irregular shape potatoes size 15*8*8 km, Detailed image, obtained during the space missions, testify to the extremely complex topography of the comet: hills, valleys, mountain ranges, and perhaps craters. Scientists believe that Halley’s comet has been around for 10 million years – during this time the core was reduced in mass by 80-90 %. And now she is experiencing her “old age,” it remained to be 100-150 thousand years, – or to evaporate it completely, or disintegrate into small fragments or will be ejected from the Solar system.

How to make a comet with your own hands?

In a large and sturdy plastic bag, pour water, stir with the ground, the sauce, put the dry ice. Last added Epsom salts and quickly tie the package, as it begins a chemical reaction with the gas outlet. After a minute open the package in front of you is the “dirty snowball” – even has a small Smoking tail. But if you bring home a comet to the lamp or the battery… Guess yourself!

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