The solar system has been a source of fascination for humans for centuries. We have looked up at the night sky and marveled at the stars, planets, and other celestial bodies for thousands of years. One of the most basic questions about the solar system is, “How many planets are there?”
For many years, the answer was simple: there were nine planets. These were Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. However, in 2006, the International Astronomical Union (IAU) changed the definition of a planet, which led to the reclassification of Pluto as a dwarf planet.
Under the new definition, a planet is defined as “a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.” This means that Pluto, which is part of the Kuiper Belt, a collection of icy bodies on the outer fringes of the solar system, does not meet the third criterion and is therefore not considered a planet.
So, how many planets are there in the solar system now? There are eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The four inner solar system planets (Mercury, Venus, Earth, and Mars) are classified as terrestrial planets because they are small, rocky, and close to the Sun. Jupiter and Saturn are gas giants, which means they are composed mostly of hydrogen and helium. Uranus and Neptune are the ice giants, containing mainly elements heavier than hydrogen and helium.
Pluto, while no longer considered a planet, is still a fascinating and important part of the solar system. With an atmosphere, stark surface features, and at least five moons, it is the most complex dwarf planet we know, and one of the most surprising solar system bodies. The New Horizons mission flew by Pluto in 2015, and scientists continue to uncover new and exciting details about this faraway world.
In conclusion, the answer to the question of how many planets are in the solar system is eight. While the reclassification of Pluto as a dwarf planet was a significant change, it did not diminish the wonder and beauty of the solar system. Each of the eight planets is unique and fascinating in its own way, and the ongoing exploration of our cosmic neighborhood continues to reveal new and exciting discoveries.
Source: https://skyandtelescope.org/astronomy-resources/solar-system-planets-how-many-are-there/
