"Natural Science 4" is an interactive encyclopedia that includes scientific information in the understanding of fourth grade students, wonderfully illustrated and animated.
.
www.edituraedu.ro
.
* Chapter 3 Lesson 15 *
* The Solar System *
The Solar System is represented by the Sun, the eight planets and many other smaller cosmic bodies. The sun is the central star and holds everything bound to it by a force called gravity. All these celestial bodies therefore move in the gravitational field of the Sun. Even the Solar System is not static in the Universe. It moves along with the Orion Arm, one of the outer arms of our Milky Way galaxy. Its speed is 220 kilometers per second.
In the beginning, it was believed that our planet is at the center of the Universe, and the Sun, together with the stars, revolve around it. Astronomer Copernicus, born in 1473, was the first to demonstrate that the Earth, along with the rest of the planets, revolves around the Sun. Thus, the Sun is located in the center of the Solar System and represents 99.86% of its mass. It was formed approx. 4.6 billion years and still has energy reserves for that long.
The Solar System includes the eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), together with their satellites. Natural satellites are celestial bodies that orbit a planet in its gravitational field. The most famous is the Moon, the natural satellite of the Earth.
Along with planets and natural satellites, other celestial bodies are asteroids. They are boulders, smaller or larger, made of rock and metals. There is a zone situated between Mars and Jupiter where multitudes are gathered. This is the asteroid belt.
Then there are broken pieces of cosmic bodies, called meteoroids, which fall from the cosmos to earth in the form of meteorites.
Let's not forget comets, made up mostly of ice and dust. They are also called comets, due to the dust and gas they release when they approach the Sun. Comets follow a well-defined path through space. One of the most famous is Halley's Comet. It has been observed several times from Earth. The last time was in 1986 and will be visible again on July 28, 2061.
Although the Solar System, viewed in isolation, is a huge assembly of celestial bodies, it is a tiny part of the Universe: the size of a glass of water in the planetary ocean.