Since ancient times, mankind has been interested in the visible movements of celestial bodies: the sun, moon and stars. It is hard to imagine the size of the universe. Our own solar system seems too large, stretching over 4 trillion miles from the sun. Meanwhile, the Sun is just one hundredth of a billion from the other stars that make up the Milky Way galaxy.
Milky Way
The galaxy itself is a huge wheel that rotates from gas, dust and more than 200 billion stars. Between them stretches trillions of miles of empty space. The sun has fixed on the outskirts of the galaxy, in a shape resembling a spiral: from above the Milky Way looks like a huge rotating hurricane of stars. Compared to the size of the galaxy, the solar system is extremely small. If you imagine that the Milky Way is the size of Europe, then the solar system will be no larger than a walnut.
solar system
The sun and its 9 satellite planets are scattered in one direction from the center of the galaxy. Just as planets rotate around their stars, so do stars around galaxies.
The sun will need about 200 million years at a speed of 588,000 miles per hour in order to make a complete revolution around this galactic carousel. Our Sun is no different from other stars, except that it has a satellite, a planet called Earth, inhabited by life. Around the Sun, planets and smaller celestial bodies, called asteroids, rotate in their orbits.
The first observations of the stars
Man has been observing the visible movements of celestial bodies and cosmic phenomena for at least 10,000 years. For the first time records in the annals of celestial bodies appeared in ancient Egypt and Sumer. The Egyptians were able to distinguish three types of bodies in the sky: stars, planets and "stars with tails." Then the celestial bodies were discovered: Saturn, Jupiter, Mars, Venus, Mercury and, of course, the Sun and the Moon. The visible movement of celestial bodies is the movement of these objects contemplated from the Earth relative to the coordinate system, regardless of the daily rotation. The real motion of cosmic bodies is their movement in outer space, determined by the forces acting on these bodies.
Visible galaxies
Looking into the night sky, you can see our nearest neighbor - the Andromeda Galaxy - in the form of a spiral. The Milky Way, despite its size, is just one of 100 billion galaxies in space. Without using a telescope, you can see three galaxies and part of ours. Two of them are called the Big and Small Magellanic Cloud. They were first seen in southern waters in 1519 by the expedition of the Portuguese explorer Magellan. These small galaxies rotate around the Milky Way, therefore, are our closest cosmic neighbors.
The third galaxy visible from Earth, Andromeda, is about 2 million light-years distant from us. This means that the starlight of Andromeda passes millions of years to get closer to our Earth. Thus, we contemplate this galaxy as it was 2 million years ago.
In addition to these three galaxies at night, you can see part of the Milky Way, represented by many stars. According to the ancient Greeks, this group of stars is milk from the breast of the goddess Hera, hence the name comes from.
Visible planets from Earth
Planets are celestial bodies orbiting the sun. When we observe Venus glowing in the sky, this comes from the fact that it is illuminated by the Sun and repels part of the sunlight. Venus is an Evening Star or Morning Star. People call her differently because in the evening and in the morning she is in different places.
As the planet Venus revolves around the Sun and changes its location. During the day there is a visible movement of celestial bodies. The celestial coordinate system not only helps to understand the location of the stars, but also allows you to compile star maps, navigate in the night sky by constellations and study the behavior of celestial objects.
The laws of planetary motion
Combining observations and theories about the motion of celestial bodies, people deduced the laws of our galaxy. The discoveries of scientists helped to decipher the visible movements of celestial bodies. The laws of planetary motion, discovered by Johannes Kepler, were one of the first astronomical laws.
The German mathematician and astronomer became the pioneer of this topic. Kepler, having studied the work of Copernicus, calculated for the orbits the best form explaining the visible movements of celestial bodies - the ellipse, and brought the laws of planetary movement, known in the scientific world as the laws of Kepler. Two of them characterize the movement of the planet in orbit. They read:
Any planet rotates in an ellipse. The Sun is present in one of his tricks.
Each of them moves in a plane passing through the middle of the Sun, while for equal periods the radius vector between the Sun and the planet, outlines equal areas.
The third law connects the orbital data of the planets within the system.
Lower and upper planets
Studying the visible movements of celestial bodies, physics divides them into two groups: the lower ones, which include Venus, Mercury, and the upper ones, Saturn, Mars, Jupiter, Neptune, Uranus and Pluto. The movement of these celestial bodies in the sphere takes place in different ways. In the process of the observed movement of the lower planets, they have a phase change like that of the Moon. When moving the upper planets, you can notice that the phase change does not occur in them, they are constantly turned to people with their bright side.
Earth, along with Mercury, Venus and Mars, belongs to the group of so-called inner planets. They revolve around the Sun in their internal orbits, in contrast to large planets that rotate in their outer orbits. For example, Mercury, which is 20 times smaller than the Earth, rotates around the Sun in its extreme inner orbit.
Comets and meteorites
Around the Sun, besides the planets, there are billions of ice blocks, consisting of frozen solid gas, fine stone and dust, comets that fill the solar system. The visible movements of celestial bodies represented by comets can only be seen when they approach the Sun. Then their tail begins to burn and glows in the sky.
The most famous of them is Halley's comet. Every 76 years, it leaves its orbit and approaches the Sun. At this time, it can be observed from Earth. Even in the night sky, you can contemplate meteorites in the form of flying stars - these are clumps of matter that move around the universe at great speed. When they fall into the gravitational field of the Earth, they almost always burn out. Due to the extreme speed and friction with the air shell of the Earth, meteorites are heated and decay into small particles. The process of their combustion can be observed in the night sky in the form of a luminous ribbon.
The astronomy curriculum describes the visible movements of celestial bodies. Grade 11 is already familiar with the laws by which the complex motion of the planets occurs, the change of the moon phases and the laws of eclipses.