Comets of the Solar system
The science and basics of ecology
Small bodies of the solar system
In addition to the major planets around the Sun are also small bodies of the Solar system: a set of small planets and comets.
All thus far discovered more than 100 thousand small planets, called asteroids (starlike), because due to their small size they are even visible in a telescope as points of light, like stars. Until recently it was believed that they all move mostly between the orbits of Mars and Jupiter, making the so-called asteroid belt. The largest object is Ceres, which has a diameter of about 1000 km (Fig. 3). It is believed that the total number of small planets that are larger than 1 km, this belt can reach 1 million But even in this case, their total mass is 1000 times smaller than the mass of the Earth.
Fig. 3. The comparative sizes of the largest asteroids
No crucial differences between the asteroids we see in space with telescopes, and meteorites that fall into the hands of people after they fell from outer space to Earth. Meteorites do not represent any particular class of cosmic bodies are fragments of asteroids. They can hundreds of millions of years to move in their orbits around the Sun,like the other, larger bodies of the Solar system. But if their orbits intersect the Earth’s orbit, they fall on our planet as meteorites.
The development of observational means, in particular the installation of instruments on space vehicles has allowed to establish that in the vicinity of the Earth flies a lot of bodies ranging in size from 5 to 50 m (up to 4 per month). To date, there are about 20 bodies of asteroid size (from 50 m to 5 km), orbits that pass near our planet. Concerns about a possible collision of such bodies with the Earth has increased significantly after falling on Jupiter of comet chumacero – levy 9 in July 1995. Probably, there is no particular reason to believe that the number of collisions with the Earth can in any to increase significantly (in fact “reserves” of meteoritic material in interplanetary space are gradually depleted). From the number of collisions, with catastrophic consequences, can be called only in the fall of 1908 Tunguska event object, which according to modern ideas was the core of a comet.
With the help of spacecraft able to obtain images of some minor planets from a distance of several thousand kilometers. As expected, the rocks constituting the surface, was similar to those common on the Earth and the moon, in particular, found olivine and pyroxene. Confirmed the idea that small asteroids have irregular shape and their surface is covered with craters. Thus, the sizes of Gaspra 19x12x11 km of the asteroid IDA (sizes 56x28x28 km) was detected at a distance of about 100 km from the centre of the satellite of about 1.5 km. In such “duality” is suspected of about 50 asteroids.
Research conducted over the past 10-15 years, confirmed earlier assumptions about the existence in the Solar system another belt of small bodies. Here beyond the orbit of Neptune has already opened more than 800 objects with a diameter from 100 to 800 km, the size of some exceed 2000 km After all these discoveries, Pluto, the diameter of which is 2400 km, was deprived of the status of the large planets of the Solar system. It is assumed that the total mass “sanatornij” objects may be equal to the mass of the Earth. Probably, these bodies contain a considerable amount of ice and more like the nuclei of comets than asteroids, located between Mars and Jupiter.
The comet, which due to its unusual appearance (the presence of the tail) from ancient times attracted the attention of all people, don’t accidentally belong to the small bodies of the Solar system. Despite the impressive size of the tail, which can exceed a length of 100 million km, and the head, which diameter can surpass the Sun, the comet is rightly called “visible nothing.” Substances in the comet very little, almost all of it concentrated in the nucleus, which is a small (by space standards) snow-ice interspersed with small solid particles of different chemical composition. So, the core of one of the most famous comets is comet Halley, which image was obtained in 1986, the SPACECRAFT “VEGA”, has a length of 14 km and width and thickness is halved. In this “dirty March snow”, often referred to as cometary nuclei, contains about as much frozen water in the snow cover that fell during the winter on the territory of Moscow region.
The comet is distinguished from other bodies of the Solar system, primarily the surprise of their appearance, what at the time, wrote A. S. Pushkin: “How illegal the comet in the circle of light raschislennyh…”
This once again convinced us of the events of recent years, when in 1996 and 1997, there were two very bright, visible even to the naked eye the comet. Traditionally they are named after the names of those who opened them, Japanese Amateur astronomy Hyakutake and two Americans – Hale and BOPP. Such bright comets typically appear every 10-15 years (those that are visible only in a telescope, see every year 15-20). It is assumed that in the Solar system there are tens of billions of comets and the Solar system is surrounded by one or even several clouds of comets, which move round the Sun at distances in the thousands and tens of thousands of times larger than the distance to the farthest planet Neptune. There, in that safe space-the fridge, the billions of years since the formation of the Solar system “stores” comet nucleus.
When the comet nucleus approaches the Sun it heats up and loses the gases and solid particles. Gradually, the nucleus breaks up into more and smaller fragments. The particles included in its composition, start to revolve around the Sun in their orbits close to the one which moved the comet that spawned this meteor shower. When particles of this stream is encountered on the path of our planet, entering its atmosphere with escape velocity, they erupt in the form of meteors. Remaining after destruction of such particles, the dust gradually settles on the surface of the Earth.
When faced with the Sun or major planets, comets “die”. Repeatedly there were cases when upon moving in interplanetary space, the nucleus of the comet was split into several parts. Apparently, not escaped this fate and Halley’s comet.
Features of the physical nature of planets, asteroids and comets are good enough on the basis of the modern cosmogonic ideas, which makes the Solar system a set of bodies having a common origin.