What Are Dwarf Planets?
Are you looking for an easy way to teach your child about space? We’ve put together a set of free materials that parents and teachers can use right away. In this lesson, your child will dive into the fascinating world of dwarf planets.
We’ll explore the criteria for a celestial body to be considered a dwarf planet. Explore science in a more engaging way with captivating 3D videos and interactive quizzes. Download our app to get started!
Table of Contents
What You Will Learn From This Lesson
- The IAU set three criteria for a planet.
- Dwarf planets meet two of the IAU’s criteria.
Understanding what dwarf planets are requires first knowing the rules for a full-fledged planet. The International Astronomical Union (IAU) established three criteria in 2006 for a celestial body to be considered a planet. First, it must orbit the Sun. Second, its shape must be nearly spherical. Third, the object must have cleared the neighborhood around its orbit, meaning there are no other similarly sized objects in its path. Only the eight major planets meet all three of these requirements.
Dwarf planets are celestial bodies that meet only the first two of the IAU’s criteria for a planet: orbiting the Sun and having a spherical shape. The primary reason objects like Pluto were reclassified as a dwarf planet is that they fail to satisfy the third condition of clearing their orbital path. For example, astronomers found other similar celestial bodies near Pluto’s orbit in the Kuiper Belt. As it only met the first two criteria, Pluto was reclassified from a planet to a dwarf planet.
Fun Fact
- Pluto, a dwarf planet, is located far out in the Kuiper Belt, even past Neptune.
- Pluto is the largest celestial body in the Kuiper Belt.
- Pluto takes about six Earth days to complete one full rotation.
Vocabulary
- Dwarf planet: A celestial body that orbits the Sun and is nearly spherical but has not cleared the neighborhood around its orbit.
- Orbit: The curved path, usually elliptical, that a celestial body follows around a star, such as the Sun.
- Kuiper Belt: A region of the solar system beyond Neptune where Pluto and other similar celestial bodies are located.
- Celestial body: A natural object that is located outside of Earth’s atmosphere, such as a planet or a dwarf planet.