The smallest and farthest planet in our solar system is the small, icy Pluto. It is even smaller than our moon and was discovered only in 1930, the only planet discovered in the 20th century. Pluto is about one-fifth the diameter of the Earth.
Unlike other outer planets, Pluto is terrestrial. The atmosphere is mainly nitrogen and seems to expand unexpectedly. The heat that reaches the Pluto is not enough to heat the surface of the planet. Planetary temperatures vary between -235 ° and -170 ° Celsius, depending on altitude from the surface.
Pluto is a very dark and cold place, even darker since 1954. The Sun, which provides light and heat to Earth, is another light in the sky because Pluto is so far away. Pluto is so far away from the Sun that it takes 247.7 Earth years to orbit the Sun.
Pluto has been a little tricky since its discovery in 1930.
Reasons Why Pluto is No Longer Considered a Planet:
Here are some reasons Why Is Pluto No Longer Considered a Planet:
- It is smaller than any other planet and even smaller than the Earth’s moon.
- Like terrestrial planets (Mercury, Venus, Earth, Mars), it is dense and rocky. However, the closest neighbors are the gaseous planets (Jupiter, Saturn, Uranus, Neptune). For this reason, many scientists believe that Pluto originated in another part of the universe and was trapped in the gravity of the Sun. Some astronomers have previously theorized Pluto as one of Neptune’s moons.
- Pluto’s orbit is unstable. All planets in our solar system rotate around the sun on a relatively flat surface. However, Pluto orbits the Sun at an angle of 17 degrees to this level. In addition, its orbit is very elliptical and intersects Neptune’s orbit. One of the satellites, Charon, is about half the size of Pluto. Some astronomers recommend treating the two objects as a binary system rather than a planet and a satellite.
- Pluto is relatively round and orbits the Sun, but it does not meet the criteria because its orbit intersects Neptune’s orbit. Critics of the resolution argue that other planets in the solar system, including Earth, have not cleaned the environment around their orbits. For example, the Earth finds asteroids in or near its orbit.
Conclusion about Pluto:
These facts contribute to a long-standing debate about whether Pluto should be considered a planet. On August 24, 2006, the International Astronomical Union (IAU), an organization of professional astronomers, made two decisions to collectively revoke the status of Pluto’s planet. The first of these decisions was Resolution 5A, which defines the word “planet”. Many people take the definition of “planet” for granted, but in the field of astronomy, it is not clearly defined what a planet is and what it is not.
Here’s how Resolution 5A defines a planet:
Pluto is relatively round and orbits the Sun, but it does not meet the criteria because its orbit intersects Neptune’s orbit. Critics of the resolution claim that other planets in the solar system, including Earth, have not cleared near their orbits. For example, the Earth finds asteroids in or near its orbit.
Resolution 5A also introduced two new categories of objects that orbit the sun. It is a dwarf planet and a small body of the solar system.
According to the resolution, a dwarf planet is
Small bodies in the solar system are objects that orbit the sun, but they are not planets or dwarf planets. Another resolution, Resolution 6A, also specifically targets Pluto and is called a dwarf planet. Not all astronomers support resolutions 5A and 6A. Critics point out that using the term “dwarf planets” to describe objects that are not planets by definition can be confusing and even misleading.
Some astronomers also questioned the validity of the resolution, as relatively few professional astronomers had the ability and opportunity to vote (less than 4% of the world’s astronomers and planetary scientists voted).
Here’s how the two resolutions classified the objects in orbit around our sun:
- Planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
- Dwarf planets: Pluto, Ceres (an object in the asteroid belt between Mars and Jupiter), 2003 UB313 (an object farther from the sun than Pluto)
- Small solar-system bodies: Everything else, including asteroids and comets
Hence, The International Astronomical Union (IAU) requires certain standards that it does not meet. As of 2021, Pluto is a dwarf planet that has not cleared its neighboring areas. Also, we can say that Pluto might not be a planet like earth but it is considered Dwarf planet.