The International Astronomical Union (IAU) approved a new classification scheme for planets and smaller objects in our Solar System in 2006. According to it, there are 3 classes of objects: 1) Small solar system bodies (including most asteroids and comets) 2) The much larger planets (including Earth, Jupiter, and so on) 3) The new category of in-between sized "dwarf planets" A "dwarf planet" is a celestial body: (a) It is in orbit around the Sun, (b) It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) It has not cleared the neighborhood around its orbit, and (d) It is not a satellite. Presently, there are 5 dwarf planets: 2 of them Pluto and Ceres (Qualify as dwarf planet through direct observation), while other 3 Eris, Haumea and Makemake (Thought to be dwarf planets from mathematical modeling).

It is expected that at least 40 other known dwarf planets are present and estimate that other 200 dwarf planet may be found in future.

>  Pluto was discovered by American astronomer Clyde Tombaugh in Arizona in 1930.

> The planet is so far out it takes light from the sun about 5 hours and 30 minutes to reach Pluto, while 8 minutes it takes to reach Earth.

> The planet is only about two-thirds the size of our moon and was the biggest known object in the Kuiper Belt.

> Pluto is so cold that nitrogen and oxygen become frozen solid.

>  Pluto has a moon, Charon, about half the size of the planet.

Ceres:

> Ceres was the first asteroid to be discovered and it was discovered by Giuseppe Piazzi in January 1801.

> Ceres is the largest object in the asteroid belt.

> Ceres is the first and only asteroid promoted to dwarf planet status.

Eris:

> It has highly elongated orbit around Sun lasting 558 years

> Presently positioned approximately 14.5 billion km far from Earth

> Surface temperature of about -240°C

> Eris is named for the Greek mythological goddess personifying discord

> It was first seen in 2003 but finally recognized in 2005

Haumea:

>  Haumea is a dwarf planet in the Kuiper belt.

> On September 17, 2008, it was accepted as a dwarf planet by the International Astronomical Union (IAU) and named after Haumea, the Hawaiian goddess of childbirth

> Average solar distance is about 6.5 billion km.

> Its mass is approximately one-third of Pluto

> Revolution Period is about 285 Earth years

Makemake:

> This object was discovered by Mike Brown, Chad Trujillo and David Rainowitz on March 31, 2005, just before Easter that year.

> Makemake is now the fourth designated dwarf planet in the solar system, and the third plutoid.

> Makemake is currently visually the second brightest Kuiper belt object after Pluto.

> No satellites have been detected orbiting Makemake.