Dwarf Planets


Astrophysics is the branch of science that gives all information about the universe and our place. The surrounding that covers the total universe is called space. The universe contains all planets, stars, galaxies, and various forms of energy in the universe. Some of them have their illumination among the above. The solar system consists of the sun which is surrounded by the planets such as mercury, venus, earth, mars Jupiter Saturn, and uranium. They revolve around the sun in their path. The knowledge about celestial bodies such as the sun, planets, comets, stars, and galaxies is gathered from the electromagnetic radiation that is received from them.

What are Dwarf Planets?

Dwarf planets are small mass planets that revolve around the sun in an orbit. They are different from our eight planets because they are less in mass. It is neither a natural satellite nor a planet. Dwarf planets have their gravity.

In what condition is a planet called a Dwarf Planet?

IAU means Indian Astronomical Union. Dwarf planets are celestial bodies that are smaller in mass and are in the orbit around the sun. Due to its smaller mass, it is considered a planet. IAU defines some specific criteria for a celestial body to be a planet.

They are given below.

  • It should revolve around the sun in its orbit.

  • It should have sufficient gravitational force to reshape its total mass into a spherical shape.

  • It should have the ability to clear smaller objects in its orbit.

The eight planets in our solar system fulfill all three criteria. So they are accepted as the planets. But dwarf planets are a little different from this due to the third point. It does not satisfy the third criteria. Dwarf planets failed to attract or push away the smaller objects that obstruct their path. That means their orbits are shared by nearby bodies of the same size.

Characteristics of Dwarf Planets

All dwarf planets have some specific characteristics. Some of the characteristics of the dwarf planets are given below.

  • Dwarf planets have sufficient mass for hydrostatic equilibrium.

  • They are spherical or nearly spherical.

  • They cannot be a satellite for any other celestial bodies.

  • It has no orbital dominance. That is, it cannot clear its path.

  • There is no specific demand for their mass or size.

  • Dwarf planets have their atmosphere. They may also have a moon, rings, and water on their own.

Types of Dwarf planets in our solar system

There are five dwarf planets recognized by the Indian Astronomical Union in our solar system. They are located in different regions of the solar system with different mass and different characteristics. According to IAU the five types of dwarf planets in our solar system are Pluto, Eris, Ceres, Makemake, and Haumea. The specific characteristics of each dwarf planet are discussed below.


Pluto is the largest dwarf planet that occurs in our solar system. It was considered a planet till 2005 and it was reconsidered as a dwarf planet in 2006. It is named after the Roman god underwater. It has five moons around it. They are Nix, Charon, Hydra, Kerberos, and Styx. It has no rings around it. It is an elliptical with a diameter of about 2370km. One day on Pluto is equal to six days on earth. It has 6% of Earth’s gravity. It is the brightest Kuiper belt object.


The second-largest dwarf planet that is located in the Kuiper belt is Eris. It is the least known dwarf planet that was found in 2005. It was first named Xena and it was modified as Eris. It is the name of the Greek goddess of chaos. It has only one moon like our planet called Dysnomia. It revolves in an unusual orbit and its diameter is about 2326km. Its orbital eccentricity is 26 times that of our Earth. It also has no ring around it. Its atmosphere is frozen. One day in Eris is 25.9 hours on Earth.


Only one dwarf planet is located in the asteroid belt which is Ceres. It was detected first in 1801 and it came under an asteroid in 1863 till 2005. 2006 onwards it was denoted as a dwarf planet which comes under the name of the Roman goddess of agriculture. It has water. It has no moons and no rings. The diameter of Ceres is about 952km. It is the smallest dwarf planet. Its gravity is about only 3% of our Earth’s gravity. One day is equal to 9 hours on Earth.


Makemake is the second brightest dwarf planet that is located in the Kuiper belt. It was founded in 2005 and named an Easter bunny and changed to Makemake based on the god of fertility. The surface of Makemake contains frozen gases and frozen methane. It has no moon and its diameter is about 1430km. One day is equal to 22.5hours.


Haumea is a dwarf planet that was found in Spain and it came under dwarf planet status in 2008. Its name means the Hawaiian goddess of childbirth. The reason for its name is that the two moons of this dwarf planet are considered to have formed from Haumea. It has an oblong shape. It has a ring around it which is a specific feature among dwarf planets. One day here takes only four hours. It is composed of rock with ice at the top layer and its diameter is 1240km.


Astrophysics deals with the study of celestial bodies like planets, stars, galaxies, etc. in our solar system there are eight planets. The facts about dwarf planets are discussed in this article. What are the conditions that make the planet a dwarf planet is also discussed here. The basic characteristics of the dwarf planets are discussed here. Three types of dwarf planets were discussed in detail with their characteristics.


Q1. What is hydrostatic equilibrium?

Ans. Hydrostatic equilibrium is the force balance. It is the condition of balance between the gravitational force and the gas pressure force. If the balance happens means that the body is in hydrostatic equilibrium. It is a self-regulating force.

Q2. What is meant by the Kuiper belt?

Ans. It was found that there is a region beyond the orbit of Neptune. The region beyond the orbit of Neptune at 30 astronomical units to about 50 astronomical units from the sun is called the Kuiper belt. Pluto, Makemake, and Haumea are the three planets in this region.

Q3. What is an asteroid belt?

Ans. It is a circumstellar disc inside the solar system in between the planets Mars and Jupiter. There are more irregularly shaped bodies like asteroids and minor planets. The dwarf planet Ceres is located in this region.

Q4. What is eccentricity?

Ans. Eccentricity measures the shape of the orbit. The orbital eccentricity is the parameter that determines the amount by which the orbits deviate from the circular path. Mathematically it is zero for a circle.

Q5. Why was Pluto demoted to dwarf planet?

Ans. IAU modified the criteria for a planet in 2006. As per the changes in the definition of the planet Pluto failed to satisfy some criteria. So Pluto was demoted from planet to dwarf planet.

Updated on: 24-Jan-2023


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