How many planets are in our solar system ?

The question of how many planets there are in our solar system may seem like a simple one, but it has been the subject of much debate and controversy over the years. For many years, the answer was considered to be nine, including the well-known planet Pluto. However, in 2006, the International Astronomical Union (IAU) redefined the definition of a planet, leading to the reclassification of Pluto as a “dwarf planet.” So, the answer to the question of how many planets there are in our solar system is now eight.

In this article, we will explore the history of our understanding of the solar system and the different definitions of a planet that have been used over the years. We will also discuss the controversy surrounding the reclassification of Pluto and the current state of our understanding of the planets in our solar system.

  • History of the Solar System

Humans have been observing the skies and studying the stars for thousands of years. However, it wasn’t until the invention of the telescope in the 17th century that astronomers were able to make significant advances in our understanding of the solar system. In 1609, Galileo Galilei became the first person to use a telescope to observe the planets, discovering the four largest moons of Jupiter and making observations of Saturn, Venus, and Mars.

Over the next several centuries, astronomers continued to make discoveries and refine their understanding of the solar system. In the 19th century, French mathematician Urbain Le Verrier used mathematical calculations to predict the existence of a new planet, Neptune. The planet was subsequently discovered in 1846.

In the early 20th century, American astronomer Percival Lowell became convinced that there was another planet beyond Neptune, which he called “Planet X.” Lowell spent years searching for the elusive planet, but it was not until 1930 that Clyde Tombaugh, a young astronomer working at Lowell Observatory, finally discovered Pluto.

For many years, Pluto was considered the ninth planet in our solar system. However, as we will discuss in the next section, this classification was eventually called into question.

  • The Definition of a Planet

The question of what constitutes a planet has been a subject of debate among astronomers for centuries. For much of human history, planets were simply defined as bright objects that moved across the sky. However, as our understanding of the solar system grew, so too did the need for a more precise definition of a planet.

In the 19th century, the German astronomer Johann Bode proposed a definition of a planet as a celestial body that orbits the sun and has sufficient mass to assume a nearly spherical shape. This definition remained in use for many years, but it was not without its problems.

One of the biggest challenges with Bode’s definition was that it did not take into account the fact that many smaller objects in the solar system also orbit the sun and are nearly spherical. In the 20th century, as telescopes and other tools for observing the solar system improved, astronomers began to discover more and more of these smaller bodies, leading to calls for a new definition of a planet.

In 2006, the IAU officially redefined the definition of a planet, leading to the reclassification of Pluto as a dwarf planet. Under the new definition, a planet is defined as a celestial body that orbits the sun is nearly spherical, and has “cleared” its orbit of other debris. This last criterion is the key difference between a planet and a dwarf planet. A dwarf planet is a celestial body that orbits the sun and is nearly spherical but has not cleared its orbit of other debris.

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