People have been interested in the Earth, and the Universe around it, for a very long time. The Universe is an immeasurable space that is permeated by energy in various forms.
In ancient times, the prevailing view was that the Earth was stationary and all the surrounding planets revolved around it. This was the geocentric theory of the universe, which was disproved by Nicolaus Copernicus in 1543. Copernicus is the founder of the heliocentric system, according to which the Sun is at the center of the planetary system and the Earth is one of the planets orbiting the Sun.
Solar System
The Solar System is a collection of astronomical bodies under the dominant influence of the Sun’s gravitational field. The galaxy in which the Solar System is located is called the Milky Way. It is a cluster of more than 400 billion stars, and a huge amount of interstellar matter. It has a diameter of 100,000 light years in length. The Milky Way is a spiral galaxy, having the shape of a flattened disk. It concentrates. most of the galaxy’s mass. The galaxy circles its central density called the galactic nucleus. Stars circle the galactic nucleus. at different speeds. It is likely that there is a huge mass in the Milky Way’s nucleus, which, compressed to a small volume, may have formed a so-called black hole.
This is a formation that has so much mass concentrated in a small volume and such a strong attraction that nothing can leave it, not even light. Nowadays, the phenomenon of expansion of the Universe, that is, galaxies moving away from each other, is known. The farther away the galaxies in question are, the more rapidly they expand. The most distant galaxies are located at a distance of 10-12 billion light years, so they must have been moving away at the speed of light. It is assumed that at one time all galaxies were concentrated at one point, but about 15 billion years ago the Big Bang occurred. Since then, the Universe has been expanding at the same speed in all directions.
According to current knowledge, the planetary system in which Earth is located was formed about 4.6 billion years ago. The solar system consists of: The Sun, eight planets, natural satellites (moons) of the planets, planets, comets, meteoric bodies and interplanetary dust and gas. The Sun is a star and contains 99.9% of the mass contained in the bodies of the solar system. A star is a celestial body that shines with light of its own originating from thermonuclear transformations taking place inside it. In the night sky it is easiest to identify stars, which send out huge amounts of energy. Stars vary greatly in size. Giant stars are several hundred times larger in diameter than the Sun, while the size of dwarf stars is close to the size of the Earth. All stars except the Sun are visible in the sky as small luminous dots because they are very far from Earth.
The closest star besides the Sun, Proxima Centauri, is 4.3 light years away from Earth. A light year is the distance light travels in a vacuum in one year. The basic building blocks of stars are hydrogen, and helium. The most common chemical reaction that occurs in stars is just the synthesis of hydrogen into helium. Nuclear reactions in stars do not occur over the entire volume of the star, but only at certain central locations, in the nuclei. The energy that is produced by these reactions is radiated gradually, sometimes over millions of years. Stars are formed from interstellar matter, which under certain conditions can condense under the influence of gravity.
Sun
The Sun is the central star of the solar system. Around the Sun orbits the Earth, the other planets, and other celestial bodies. The Sun is the brightest object in the sky visible from Earth and the main source of energy that reaches our planet. The star is one of 120 billion stars in the Milky Way galaxy. The diameter of the Sun is 109 times larger than the diameter of the Earth. The Sun belongs to the small stars and is a ball of gas with a mass of about 2×1030 kg, of which 74% is hydrogen, 25% helium, and less than 1% heavier elements and occasional simple chemical compounds.
The sun is kept in equilibrium by the force of gravity on one side and the increasing pressure of the gas with depth, which balances the weight of the matter above. The thermonuclear transformations taking place inside the Sun ( the transformation of hydrogen into helium) release enormous energy. This energy is the source of the light with which the star shines. The Sun’s magnetic field is very strong (the strongest in the Solar System, but it seems to be rather average compared to other stars) and has a huge range, reaching far beyond Pluto’s orbit. The innermost layer of the Sun is the nucleus. The hydrogen content of the nucleus is
approx. 40 %.
The nucleus produces 95 % of all the energy produced by the Sun. The remaining 5% is produced in the layers directly above the nucleus. The solar atmosphere consists of several layers. The first of these is the photosphere. The photosphere is the visible, surface layer of a star that emits waves in the form of visible light. The next layer is the small chromosphere. The chromosphere is a thin layer of the solar atmosphere, extending up to 10,000 km above the photosphere. Above the chromosphere is the corona reaching millions of kilometers into space. The solar corona can also be observed during solar eclipses, or in obscuring the central part of the sun. The solar corona has a much higher temperature than the rest of the solar atmosphere. The temperature of the Sun’s surface is 5530°C. In contrast, the temperature of the core reaches 14 million°C.
Planets of the solar system
Planets are celestial bodies orbiting a star, rotating on their own axis and shining with the reflected light of the star. Until August 24, 2006, the planets of the solar system included Pluto, however, by the decision of the International Astronomical Union, Pluto is no longer counted as a planet, but only as a transneptunian object, or in the category of objects called plutonic objects. The planetary system, therefore, is formed by the planets in the order closest to the Sun:
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
The planets of the solar system can be divided into inner planets such as Mercury, Venus, Earth, Mars. These planets have similar size, physical structure, chemical composition. They are often called rocky planets The next four outer planets, i.e. Jupiter, Saturn, Uranus Neptune, are so-called giant planets, or gas planets, as they are made of gases, mainly hydrogen, helium, methane, ammonia and water.
Mercury- counting from the Sun, the first planet of the Solar System. In terms of size in the Solar System, it ranks eighth. It is one of the brightest objects in the sky, however, its short distance from the Sun and relatively fast rotation make Mercury extremely difficult to observe. Mercury’s surface is very similar to that of the Moon – there are numerous and deep craters. The planet has no atmosphere; there are also no tectonic phenomena. In addition, many cliffs and canyons can be found on the surface. The temperature on the planet varies from -180° C to 430°C.
Venus- Venus is the third brightest celestial body after the Sun and the Moon visible from Earth. Since observations of this planet are only possible in the evening and morning, it is also called: Dawn, Morning Star or Evening Star. One of the characteristics of Venus is a very thick layer of clouds, preventing any observations of the planet’s surface. Venus’ atmosphere consists mainly of carbon dioxide (96.5 percent) and, to a much lesser extent, nitrogen (about 3.5 percent). Venus has a weak magnetic field, which is three orders of magnitude smaller than Earth’s. The temperature on the surface of the globe oscillates around 400°C, and in some places even 500°C. Despite the fact that Venus is almost twice as far from the Sun as Mercury, it is the hottest planet in the solar system. Such a high temperature is caused by the greenhouse effect.
Earth-This is the third in order (counting from the Sun). Around the Earth orbits one natural satellite-the Moon. The Earth’s internal structure consists of a nucleus, mantle, and crust. The chemical composition of the Earth is mainly iron, oxygen, silicon, magnesium. The average radius of the Earth is km 371.6, the volume is 1,083 x 1018 , the temperature of the surface averages 14°C, and the interior, about 5,000°C. In terms of density, the Earth ranks first among the planets of the solar system. 71% of Earth’s surface is occupied by water, only 29% is land. Earth is the only planet in the Solar System where water can commonly exist in the liquid state.
Mars-The fourth planet in the solar system by distance from the Sun. Mars has two small moons of irregular shape and is a planet half the size of Earth. Mars’ atmosphere is very thin and rarefied. The average atmospheric pressure hovers around 750 pascals. The red planet consists of a solid nucleus with a radius of about 1,700 kilometers, which consists mainly of nickel and iron. It is surrounded by a rocky mantle. The planet’s surface is a 30-kilometer-long crust consisting of two-thirds silicon, but also iron and its compounds, such as iron oxide and iron sulfide, which give the planet its red color.
The temperature on Mars fluctuates very rapidly over the course of the year. The reason for these fluctuations is the shape of the Martian orbit: it is strongly elliptical. The average temperature on the red planet ranges from -120°C to 22°C.
Mars is known in the Solar System for its highest mountain ranges and largest canyons. The highest mountain on Mars, and at the same time the largest in the Solar System – Olympus Mons – the cone of an extinct volcano, is more than24 kilometers high and has a base diameter of about 550 kilometers.
Jupiter-The largest planet in the solar system. Its mass is twice that of all other planets in our system. It has many moons (at least 63-most of all the solar system’s planets) and rings. Jupiter, along with Saturn, Uranus and Neptune, are gas planets, sometimes also called Jupiter planets. Jupiter is the fastest-rotating planet in the solar system, resulting in a large flattening of the planet at the poles. It takes about 12 years to circle the sun, and it takes about 10 hours to rotate around its axis. Jupiter’s atmosphere consists of about 86% hydrogen and about 14% helium.
Saturn-The second largest planet in the solar system after Jupiter. Saturn has the lowest density of all the planets in the entire solar system. Saturn is noticeably flattened at the poles. The period of the planet’s rotation around its axis at the equator is faster than at the poles and lasts 10h 14min. This is also approximately how long a day lasts.
Saturn impresses with the number (second only to Jupiter) of its moons – of the 60 discovered so far, 48 already have official names. A very characteristic feature of Saturn is the arrangement of more than 10000 separate rings around the planet. Speaking of Saturn’s rings, the seven largest rings are usually distinguished. They are made of millions of nuggets of ice, and rocks that combine according to their density. The formation of Saturn’s rings is explained by the fact that they may be the remnants of some natural satellite that disintegrated after a collision with some other body, perhaps a comet.
Uranus-is the first planet to be discovered in modern times. The planet has been observed many times before, but each time it was considered a star. It is also the third largest and fourth most massive planet in our system. the structure and chemical composition of Uranus largely distinguish it from Jupiter and Saturn. First of all, Uranus contains relatively little hydrogen – 15% by mass, and only a small admixture of helium. Uranus has very thin and faintly visible rings, which cannot be directly observed from Earth. Uranus has 27 known moons. Almost all of them orbit in extremely circular and regular orbits. The temperature difference between the equator and the pole is only a few degrees. The mechanism of the heat flow occurring here remains unknown.
Neptune-The eighth and last planet of the Solar System. It is the farthest orbiting gaseous planet in the Solar System from the Sun. The structure of the planet is very similar to that of Uranus except that it is slightly smaller than it but heavier. Due to its great distance from the Sun, Neptune receives very little heat. The temperature of the outer layers of the atmosphere is -218°C. As it seems, there is some heat source inside the planet, which may be a remnant of Neptune’s formation period. The internal structure of Neptune is very similar to that of Uranus. The rocky core is surrounded by a layer of water ice, ammonia and methane, covered by a layer of molecular hydrogen.
Natural satellites
A natural satellite (moon) is a celestial body of natural origin, orbiting a planet (or asteroid). Regular moons, orbit in the same direction as the planet orbits the sun, in almost circular orbits, located (with slight deviations) in the plane of rotation of the planet. The prevailing view is that they were formed by the condensation of dust and gases from which the planet formed. Since most of the moons are known only from long-distance observations, theories about their formation tend to be tentative. The largest moons in our planetary system are: Jupiter’s Galilean moons Io, Europa, Ganymede (the largest natural satellite in the solar system) and Kallisto, Saturn’s satellite Titan, Neptune’s moon Triton, and Earth’s satellite: Moon all of them are over 3,000 km in diameter. Other celestial bodies are also observed in the solar system, such as asteroids (orbiting between the orbits of the planets), and comets (orbiting the Sun along elliptical, parabolic, or hyperbolic paths. Orbiting Jupiter are some of the largest moons in the Solar System called Jupiter’s Galilean moons.
The only permanent natural satellite of the Earth is the Moon. It is the fifth largest moon in the solar system. The average distance from the center of the Earth to the center of the Moon is 400 km.384 Without much difficulty, the length of the synodic and stellar months can be determined based on your own observations. Variations in the Moon’s phases are due to differences in its mutual position relative to the Sun and Earth, and the fact that the Moon does not shine with its own light, but with reflected light. It is illuminated by the Sun. When the moon in its movement around the Earth is in opposition, then it is visible from the Earth in its phase of maximum illumination, i.e. full. When the moon faces the Earth with its unlit side, then it is completely invisible to an observer on Earth. It is in the new moon phase.
Soon after the new moon, a narrow sickle of the moon can be observed, facing west with its convexity. A week after the new moon, for the observer, the moon takes the shape of a semicircle facing west with its convexity. It is then located in the first quarter. The larger part of the moon’s disk is visible, the longer it can be observed in the night sky. After the full moon, a gradual disappearance of the illuminated part of the Moon is observed. The loss is visible on the western side of the disc, which will be directed convexly towards the east. Three weeks after the new moon, only half of the Moon’s disc will again be visible. It will then be in its final quarter. For an observer on the Moon, the Earth is in a phase of illumination that is complementary to the phase of the Moon visible from Earth.
An observer from the Moon would see the Earth as a glowing disc of sizable size. The moon makes a circular motion around the Earth, and a rotational motion around its own axis. The period of rotation for the Moon is equal to a stellar month (27.3 days). The plane of the Moon’s orbit does not coincide with the plane of the ecliptic (the path on the celestial sphere along which the Sun, observed from Earth, apparently moves during the year), but is inclined to it at an angle of 5°,9′. The intersection of these two planes is called the line of nodes. The node, on the other hand, is the point of intersection of the ecliptic, and the Moon’s orbit. When the Moon in its orbital motion is in close proximity to either of the nodes, and it is full, then a lunar eclipse will occur. A lunar eclipse occurs, so when the Earth is between the Sun and the Moon and the Moon is in the cone of the Earth’s shadow. The length of a lunar eclipse depends on the distance of the Earth from the Sun, and the distance of the Moon from the Sun. The longest possible lunar eclipse can last
1 hour and 42 minutes.
A solar eclipse, on the other hand, occurs when the Moon comes between the Sun and Earth and thus obscures the sunlight. A solar eclipse can last for a maximum of 7 minutes and 40 seconds, and is only visible over a small area of the Earth’s surface. The most likely theory about the Moon’s formation is that the Moon formed simultaneously with the planets during the formation of the Sun about 5 billion years ago.
