Quck answer
Pluto is no longer considered a planet because of its size and orbit. In 2006, the International Astronomical Union (IAU) redefined the definition of a planet, which resulted in Pluto being classified as a “dwarf planet.” According to the new definition, a planet must meet three criteria: it must orbit the Sun, it must be round in shape, and it must have cleared its orbit of other debris. While Pluto meets the first two criteria, it fails to clear its orbit, as it shares its orbit with other objects in the Kuiper Belt. Therefore, it is now classified as a dwarf planet.
You may have already heard that Pluto is no longer considered a planet. But why is that? What happened that made it lose its position as the smallest planet in our solar system?
Astronomer Clyde Tombaugh discovered Pluto in 1930. From 1930 to 2006, Pluto was classified as the ninth planet in our solar system, located beyond Neptune.
However, in 2006, changes were made. The truth is, nothing about Pluto changed, but the definition of a planet did. Once these changes became official, Pluto no longer met the criteria to be considered a planet.
According to the new rules set by the International Astronomical Union, a celestial body must meet the following criteria to be classified as a planet:
- The body must have a round shape.
- It must orbit the sun.
- It must have “cleared the neighborhood” of its orbit, meaning that its gravity has cleared the area around it of other objects. Some objects may collide with the planet, while others may become its moons.
Pluto meets the first two criteria: it has a round shape and orbits the sun. However, it does not meet the third criteria. It has not yet cleared its orbit of other objects. Therefore, Pluto is no longer considered a planet.
But don’t feel too sad for Pluto! It now holds the title of a “dwarf planet.” Dwarf planets are celestial bodies that meet only the first two criteria in the new definition of a planet.
Like Pluto, other dwarf planets have not cleared their orbits and still have some cleaning up to do if they want to be considered “true” planets. Currently, there are five known dwarf planets, but scientists believe more will be discovered in the future.
Four of these dwarf planets, including Pluto, Makemake, Haumea, and Eris, are located beyond Neptune. The fifth dwarf planet, Ceres, resides in the asteroid belt between Mars and Jupiter.
Interesting facts about Pluto:
- Pluto is approximately the same size as the moon.
- It takes about 248 Earth years for Pluto to complete one orbit around the sun. Since its discovery in 1930, Pluto has not completed a full orbit yet. It still has more than 150 Earth years to go!
- Pluto is so far away that it takes more than five hours for sunlight to reach it. In comparison, sunlight reaches Earth in just eight minutes!
Give it a try
Understanding the vastness of our solar system can be challenging for both children and adults. If you have some time, materials, and a bit of creativity, you can try the activity “How Big Are the Planets in Our Solar System.” It’s an interesting exercise that will leave a lasting impression!
Once you grasp the enormity of our universe, you can bring the solar system closer to home by creating a scaled-down mobile of the planets, arranging them from largest to smallest. Hang it in your bedroom and let it inspire dreams that are out of this world!
If the project seems overwhelming, you can try a simpler version of a solar system mobile.
FAQ
1. Why was Pluto considered a planet in the first place?
Pluto was considered a planet because it was discovered in 1930 and was initially thought to be the ninth planet in our solar system. It was classified as a planet based on the criteria that were used at the time.
2. Why did scientists change their classification of Pluto?
Scientists changed their classification of Pluto because new discoveries and advancements in technology allowed them to gain a better understanding of the objects in our solar system. It was found that Pluto did not meet the criteria set by the International Astronomical Union (IAU) to be considered a planet.
3. What are the criteria set by the IAU for a celestial body to be classified as a planet?
The criteria set by the IAU for a celestial body to be classified as a planet are as follows: it must orbit the Sun, it must be spherical in shape, and it must have cleared its orbit of other debris. Pluto failed to meet the third criterion as it shares its orbit with other objects in the Kuiper Belt.
4. What is the Kuiper Belt?
The Kuiper Belt is a region in our solar system that lies beyond the orbit of Neptune. It is a collection of small icy bodies, including dwarf planets, comets, and asteroids. Pluto is one of the largest objects in the Kuiper Belt.
5. How is Pluto classified now?
Pluto is now classified as a dwarf planet. A dwarf planet is a celestial body that orbits the Sun, is spherical in shape, but has not cleared its orbit of other debris. There are currently five recognized dwarf planets in our solar system.
6. Why is it important to reclassify Pluto?
Reclassifying Pluto is important because it helps us to have a more accurate understanding of our solar system. By using consistent criteria for classification, scientists can better study and categorize the various objects in our celestial neighborhood. It also helps to differentiate between different types of celestial bodies, such as planets and dwarf planets, based on their characteristics.
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