Planets are non—self-luminous celestial bodies, similar in shape to a ball, rotating around stars and reflecting their light. Due to its proximity to the Earth, the most studied are the planets of the Solar System moving around it in elliptical orbits. Our Earth, located at a distance of 150 million km from the Sun, also belongs to this group of planets.
Stars are luminous (gas) space objects formed from a gas-dust medium (mainly hydrogen and helium) as a result of gravitational condensation. The stars are separated from each other by huge distances and are thus isolated from each other. This means that the stars practically do not collide, although the motion of each of them is determined by the gravitational force created by all the stars of the Galaxy. The number of stars in the Galaxy is on the order of a trillion. The most numerous of them are dwarfs, whose masses are about 10 times less than the mass of the Sun. Depending on the mass, stars in the process of evolution become either "white dwarfs", or neutron stars, or "black holes".
A "white dwarf" is an electronic post—star formed when a star at the last stage of its evolution has a mass less than 1.2 solar masses. The diameter of the "white dwarf" is equal to the diameter of our Earth, the temperature reaches about a billion degrees, and the density is 10 t / cm3, i.e. hundreds of times more than the earth's density.
Neutron stars arise at the final stage of the evolution of stars with a mass of 1.2 to 2 solar masses. The high temperature and pressure in them create conditions for the formation of a large number of neutrons. In this case, a very rapid compression of the star occurs, during which a rapid development of nuclear reactions begins in its outer layers. At the same time, so much energy is released that an explosion occurs with the scattering of the outer layer of the star, the inner regions of the star are rapidly shrinking. The remaining object is called a neutron star, because it consists of protons and neutrons (they also have the name "pulsars"),
"Black holes" are stars at the final stage of their development, whose mass exceeds 2 solar masses, having a diameter of 10 to 20 km. Theoretical calculations have shown that they have a gigantic mass (1015 g) with an abnormally strong gravitational field. "Black holes" got this name because they do not have a glow, but due to their gravitational field, they capture all cosmic bodies from space and radiation that cannot come back out, "fall" into them as into a hole. Due to the strong gravity, no captured material body can go beyond the gravitational radius of the object, and therefore they appear "black" to the observer.
Star systems (star clusters) are groups of stars connected by gravitational forces, having a common origin, similar chemical composition and including up to hundreds of thousands of individual stars. There are scattered star systems, such as the Pleiades in the constellation Taurus. Such systems do not have the correct form. More than a thousand star systems are known. In addition, the star systems include globular star clusters, consisting of hundreds of thousands of stars. Gravitational forces keep stars in such clusters for billions of years. Scientists know about 150 globular clusters.
Galaxies are aggregations of star clusters. The concept of "galaxy" in modern interpretation means huge star systems. This term comes from the Greek word "milk, milky" and was coined to refer to our star system, which is a light strip with a milky hue stretching across the sky and therefore called the "Milky Way".
Conventionally, the appearance of the galaxy can be divided into three types. Spiral galaxies belong to the first (about 80%). In this species, the nucleus and spiral "sleeves" are clearly observed. The second type (about 17%) includes elliptical galaxies, i.e. those that have the shape of an ellipse. The third type (about 3%) includes irregular-shaped galaxies that do not have a distinct nucleus. In addition, galaxies differ in size, the number of stars included in them, and luminosity. All galaxies are in a state of motion, and the distance between them is constantly increasing, i.e. there is a mutual removal (scattering) of galaxies from each other.
The solar system belongs to the Milky Way Galaxy, which includes at least 100 billion stars, and therefore belongs to the category of giant galaxies. It has a flattened shape, in the center of which there is a core with spiral "sleeves" extending from it. The diameter of our Galaxy is about 100 thousand light—years, the thickness is 10 thousand light-years. Next to us is the Andromeda Nebula galaxy.
Metagalaxy is a system of galaxies that includes all known space objects.
Since the mega world deals with large distances, the following special units have been developed to measure these distances.
1. Light year is the distance that a ray of light travels during one year at a speed of 300,000 km/sec, i.e. it is 10 trillion km.
2. The astronomical unit is the average distance from the Earth to the Sun, equal to 8.3 light minutes. This means that the sun's rays, breaking away from the Sun, reach the Earth in 8.3 minutes.
3. Parsec is a unit of measurement of cosmic distances within and between star systems. 1pc is equal to 206,265 AU, i.e. approximately 30 trillion km, or 3.3 light years.
Features of the solar system device.
The solar system is a part of the Milky Way, and it, in turn, is a spiral galaxy, around the center of which the Sun rotates – the largest and heaviest object of the Solar System, which is its heart. The sun, in its system, has eight planets with their satellites, many asteroids, comets and an incredible number of meteor bodies. The planets of the Solar System are divided into two types: the first is the terrestrial group, and the second is the giant planets.
The structure of the Solar System has a significant impact not only on the planets, but also on their satellites, asteroids, comets and countless meteor elements that are also part of it.
Planets of the Earth group. This includes Mercury, Venus, Earth and Mars. Their characteristic features are small size and weight. As a rule, they include metals and rocks, due to which they differ in significant density. The planets of the Earth group are located closer to the Sun than other cosmic bodies.
Giant planets. Jupiter, Saturn, Uranus and Neptune. They are characterized by a large size and a small density due to their predominantly gaseous composition. Despite this, the giant planets have strong gravity and have a considerable number of satellites, only Jupiter has 63 of them. These huge cosmic bodies are located at a distance from the Sun.
Asteroid rings. The first asteroid ring is located on the border of two groups of celestial bodies – in the region of Mars and Jupiter and is considered the main one, and the second is the final element of the Solar System, it is located behind Pluto, in the recent past the ninth major planet, it is called the Kuiper belt. These asteroids are also called minor planets, currently about 10,000 asteroids in the main ring have been studied, presumably their number is 300,000.
Dwarf planets. This is Pluto, which received this status in 2006, the brightest representative of the main asteroid ring – Ceres and distant – Eris. Dwarf planets include those that have a diameter of about 1000 km.
Objects of the Solar system consisting of ice and dust. They exist outside the second asteroid ring, practically in interstellar space, and only some of them fall into the gravitational attraction of the Sun, collapsing, forming a trail of steam and dust.
The main pattern is the movement of the planets. They move in one direction relative to the Sun, namely against the movement of the hands of the clock. Venus and Uranus, which moves almost on its side, as well as some satellites of the planets have a different direction of rotation. Cosmic bodies rotate in an orbit whose shape is close to a circle, however, the orbits of Mercury and Pluto have an elongated trajectory, and comets move along such orbits.
The most common objects in the Solar System are small asteroids (several hundred thousand). They have no atmosphere, have an irregular shape and small size. But they also, like planets, revolve around the Sun and may have satellites (previously they were called small planets).
Comets are small bodies of the system (usually a couple of kilometers). For the most part, they consist of volatile substances (ice), which evaporate when sufficiently close to the Sun. It is thanks to this effect that we can enjoy their beauty.
Now there are more than three thousand of them. But over time, volatile substances from