Definition:

A celestial body resembling a small planet but lacking certain technical criteria that are required for it to be classified as such.

The difference between a dwarf planet and a planet is the area surrounding each celestial body. A dwarf planet has not cleared the area around its orbit, while a planet has.

A planet is an object that orbits the Sun in an elliptical orbit, has compounded its matter in a spherical shape, and has cleared its orbit of other debris. While, a dwarf planet also orbits the Sun, has compounded its matter in a spherical shape, but has not cleared its orbit of other debris.

Timeline:

1 Jan 1801 - Giuseppe Piazzi discovers the first and largest asteroid, Ceres, orbiting between Mars and Jupiter in the asteroid belt.

18 Feb 1930 - Discovered by American astronomer Clyde Tombaugh, Pluto was long considered our solar system's ninth planet.

8 Jan 2005 - Scientists using images from ground-based telescopes announce they have discovered a Pluto-sized world billions of miles beyond the orbit of Neptune. This discovery reignites a debate about the definition of a planet.

Timeline:

19 Jan 2006- NASA's New Horizon launches and is on its way to dwarf planet Pluto and the Kuiper Belt region of space. New Horizons is designed to make the first close-up study of dwarf planet pluto, its moons and other icy worlds in the distant Kuiper Belt.

24 Aug 2006 - After much debate, the International Astronomical Union announces a new definition for planets that changes Pluto from a planet to a dwarf planet.

Pluto is the largest dwarf planet in our solar system, and one of the largest members in the Kuiper Belt. Until 2006, Pluto was once considered the planet furthest away from the Sun. Now, Pluto is considered a dwarf planet. This dwarf planet has a rocky core that is surrounded by a mantle of water ice and other ices that cover the surface. Pluto is also considered a double- planet system because its moon, Charon, is very large and it orbits close to its parent planet. 

Ceres is the largest object in the Asteroid Belt, which is located between Mars and Jupiter. It’s the only dwarf planet in the inner solar system. Ceres is the first Dwarf Planet to have a spacecraft visit. The one characteristic that allows Ceres to stand out from the others is that it has water. Ceres has a radius of 476 kilometers, which is about the size of Texas. 

The other Dwarf Planets:

Eris: This dwarf planet was first discovered in 2003. It takes Eris 557 Earth years to complete a single orbit around our sun. It's so far away from the sun that its atmosphere collapses and freezes. Scientists have found that the temperature varies from -359 to -405 degrees Fahrenheit.

Continued:



Haumea: This dwarf planet was first discovered in 2003. Haumea is the fastest rotating object in our solar system. It completes a turn on its axis every four hours. Astronomers believe that Haumea is made of rocks with a coating of ice.

Makemake: This dwarf planet was first discovered in 2005. It takes Makemake 310 Earth years to make one orbit around the Sun. It's unofficial name was Easterbunny.