The Solar System is our home, located in one arm of the Milky Way galaxy. The general picture is that it consists of the star called Sun with 8 orbiting planets. However, there are many more celestial bodies in the Solar System, the genuine richness of shapes, size and the structure of the bodies.
Firstly, the article addresses the way how the crucial discoveries about the Solar System are done. In 1609 Galileo Galilei built a telescope and found that Jupiter has satellites, Venus has phases and many more. This fundamental observation clarifies our understanding of the Solar System and its planets. Besides, we will give a general overview of planets as well as on so-called small bodies of the Solar System – with emphasizing facts about planetoids. Eventually, the discovery of the outer planets is presented.
Galileo Galilei’s observations
When Galilei heard that a lensmaker from the Netherlands had invented ‘glasses that magnify’, he started to make his own telescope. The first telescope has about 3x magnification, but soon Galilei made an improved version with 30x. His observations between 1609 and 1611 results with unbelievable discoveries for that time.
- Galilei saw that the Moon is not a perfect sphere but has hills, valleys, and other geographical forms. This finding was contrary to the idea that the celestial bodies are of perfectly spherical shape.
- Based on observations of sunspots he found that the Sun rotates around its own axis with a period of approximately 27 days.
- With his telescope, Galilei saw four satellites of Jupiter, called Galilean satellites in his honor. These satellites are Io, Europa, Ganymede, and Callisto. This discovery has had the greatest impact since it was direct evidence against the theory that the Earth was the center of the universe and that other body orbiting the Earth.
- Galileo discovered that similar to the Moon, Venus has phases. This phenomenon indicates that Venus orbits the Sun.