What is a planet and how many are there in our Solar System?

A planet is a celestial object that orbits a star and does not emit its own light. There are eight planets in our Solar System, which all revolve around the Sun. These are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

The classification of Pluto as a planet has been a subject of debate for many years. In 2006, the International Astronomical Union reclassified it as a dwarf planet due to its small size and irregular orbit. Despite this, many people still consider Pluto a planet and include it in their lists of the eight planets of the Solar System.

Our Solar System is unique in several ways. Firstly, all the planets orbit the Sun in almost the same plane, as they were formed from a flattened disk of dust and gas rotating around our star (protoplanetary disk).

Secondly, the planets can be divided into two distinct groups: the first four are terrestrial planets. They are roughly similar to Earth in size and composition. At the same time, the next four are much larger and are composed primarily of gas.
The terrestrial planets, Mercury, Venus, Earth, and Mars, are relatively small and have solid surfaces. They are composed of rock and metal and have relatively low atmospheric pressure. In contrast, the gas giants, Jupiter, Saturn, Uranus, and Neptune, are much larger and are composed primarily of hydrogen and helium gas. They have much thicker atmospheres and, like Jupiter and Saturn, have distinctive rings.

The study of our Solar System and the search for exoplanets (planets orbiting other stars) has been a major focus of astronomical research in recent years. Thanks to this research, scientists hope to find out more about the formation and evolution of planetary systems and to search for signs of life beyond our Solar System.

The discovery of exoplanets has been revolutionized by technological advances, allowing astronomers to detect planets that were previously too small or too distant to be seen. In recent years, hundreds of exoplanets have been discovered, many of which are similar in size and composition to the terrestrial planets in our Solar System.

That's why it's an exciting time for astronomers and planetary scientists as they continue to explore and learn more about the planets in our Solar System and beyond. The search for exoplanets is an essential part of this exploration, as it will help us understand more about the diversity of planetary systems and the conditions necessary for life to exist.