Key Differences Between Dwarf Planets and Planets Explained
Dwarf Planet Meaning
So, what is a dwarf planet? As we all know that our universe seems infinitely large. Even trying to comprehend its size is profound in itself. Space is filled with a ton of fascinating objects known as heavenly bodies or celestial bodies. There are several types of heavenly bodies such as planets, stars, moons, asteroids, meteors, dwarf planets and many more. We are very tiny as compared to these objects. Some of the planets are way larger than our planet earth. We are on a continuous quest to discover these bodies based on our current technological capabilities. There are more than a billion stars in our milky way galaxy, and more than fifty such galaxies combine to form a local group. It is always fascinating to learn about these objects.
Due to the sheer size of these bodies, we have not even discovered a tiny fraction of our galaxy. There are several mnemonics available to remember the names of the planets in our solar system and you can also make your own as per your comfort. Today we will focus on dwarf planets and find out What is a dwarf planet? Our solar system also contains a dwarf planet named Pluto. We used to count it as one of the planets, but due to some complications now it falls under the category of dwarf planets. Below we will learn about Dwarf planets, dwarf planet meaning, and look at a dwarf planets list.
What is a Dwarf Planet?
So let us start by understanding the dwarf planet definition. Dwarf planets are celestial bodies or planetary-mass objects(having a mass equivalent to a planet) that are not satellites and also do not dominate their region, unlike the regular planets. These bodies are too large to be categorized in the smaller objects and too large to be called a full-fledged planet. According to the international astronomical unit, a planet needs to meet specific criteria to be called the dwarf planet. First, it should directly orbit around the sun like other planets. Second, it needs to have enough gravity so that it can pull its mass in a spherical or round shape. Lastly, its orbit needs to be clear of small objects.
The above criteria describe the dwarf planet’s meaning, and if a planet meets all these criteria, then it is categorized as a dwarf planet. However, the critical difference between planets and dwarf planets is in that last criteria. A regular planet has a substantial amount of mass or gravity to pull or push away the objects that obstruct its orbital path. In the case of dwarf planets, their gravity or mass is not adequate to perform this maneuver. It is challenging to pinpoint the total number of dwarf planets in the solar system(milky way). To classify or approve a celestial body as a dwarf planet, we need to observe it closely.
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( Dwarf Planets )
Alan Stern was the first person to introduce dwarf planets in his three-part categorization of planetary objects(having the mass equivalent to planets) in our solar system. He called them satellite planets, classical planets, and dwarf planets. Ultimately the international astronomical union accepted the term dwarf planet in 2006. There are several known or discovered dwarf planets such as Pluto, Eris, Ceres, Haumea, and Makemake. The scientific society believes that there are still more than a hundred dwarf planets that need to be discovered. So, you must be wondering which planet is known as Dwarf planet? Let us move on to a dwarf planets list and categorize which is the dwarf planet?.
Which is the Dwarf Planet?
Based on the dwarf planet meaning we will look at planets and determine which is the dwarf planet? Below is the discovered dwarf planets list and their discovery dates respectively.
Pluto:- It was previously in the category of planets, but since 2006 it is considered a dwarf planet.
Ceres:- This celestial body was also considered a planet until 2006. It was discovered in 1801.
Eres:- it was discovered in 2005.
Makemake:- We classified it as a dwarf planet in 2008.
Haumea:- discovered in 2004, announced in 2005 and classified as a dwarf planet in 2008.
How was Pluto Named a Dwarf Planet?
You must remember the mnemonic My Very Educated Mother Just Served Us Nine Pizzas for all the planets in the solar system. The last one pizzas use to represent pluto as it was considered as one of the nine planets in our solar system. It was discovered on February 18, 1930, and since then it was considered as a planet. But since 2006 the international astronomical union reclassified it as a dwarf planet. It used to come very close to the sun in its orbital path and considered an odd planet. An astronomer named Michael brown discovered a similar-sized object as pluto called Eris. Later, when the terminology dwarf planet came to being then both of these objects were reclassified into this category.
FAQs on What Is a Dwarf Planet?
1. What exactly defines a dwarf planet according to the International Astronomical Union (IAU)?
A dwarf planet is a celestial body that meets specific criteria set by the IAU in 2006. For an object to be classified as a dwarf planet, it must:
- Orbit the Sun directly, not another planet.
- Have enough mass and gravity to be pulled into a nearly round shape, a state known as hydrostatic equilibrium.
- Have not cleared its orbital neighbourhood of other objects and debris.
This third point is the key distinction that separates dwarf planets from planets.
2. What is the main difference between a planet and a dwarf planet?
The primary difference lies in their orbits. A planet, like Earth or Jupiter, has become gravitationally dominant in its orbital path, meaning it has either absorbed or ejected most other objects. A dwarf planet, while large enough to be round, shares its orbital space with other celestial bodies and has not 'cleared' this neighbourhood.
3. Why was Pluto reclassified from a planet to a dwarf planet?
Pluto was reclassified because while it meets the first two criteria for a planet (it orbits the Sun and is round), it fails on the third. Pluto's orbit is located in the Kuiper Belt, a region teeming with other icy objects. Because it has not cleared its orbital neighbourhood and shares its path with these other bodies, it fits the official definition of a dwarf planet.
4. Which celestial bodies are recognised as dwarf planets in our solar system?
As of now, the International Astronomical Union (IAU) officially recognises five dwarf planets. In order of their distance from the Sun, they are:
- Ceres: Located in the main asteroid belt between Mars and Jupiter.
- Pluto: The most famous dwarf planet, located in the Kuiper Belt.
- Haumea: An elongated dwarf planet in the Kuiper Belt.
- Makemake: Also found in the Kuiper Belt.
- Eris: One of the largest known dwarf planets, located even farther out than Pluto.
5. How are dwarf planets different from asteroids?
The key difference is shape and size. A dwarf planet has sufficient mass and self-gravity to overcome rigid body forces and assume a round shape (hydrostatic equilibrium). Most asteroids are much smaller and lack the gravitational pull to become spherical, resulting in irregular, potato-like shapes.
6. What does it mean for a celestial body to 'clear its orbital neighbourhood'?
'Clearing the neighbourhood' means a celestial body has become the gravitationally dominant object in its orbit. Over millions of years, its gravity has either pulled in (accreted) or flung away most other objects from its orbital path. Planets like Earth have cleared their orbits, whereas dwarf planets like Pluto share their orbit with a multitude of other objects.
7. Can a moon also be classified as a dwarf planet?
No, a moon cannot be a dwarf planet. The fundamental definition of both a planet and a dwarf planet requires the object to orbit the Sun directly. A moon, by definition, is a natural satellite that orbits a planet. Even if a moon is large and round, like Earth's Moon or Jupiter's Ganymede, it is disqualified because its primary orbit is around a planet, not the Sun.
8. Why is Earth considered a planet and not a dwarf planet?
Earth is considered a planet because it successfully meets all three criteria defined by the IAU. It orbits the Sun, it has enough mass to be nearly round, and most importantly, it has cleared its orbital neighbourhood of other large objects. Its gravitational influence is dominant in its path around the Sun, unlike a dwarf planet.
