Dwarf Planets

A dwarf planet is a celestial body that orbits the Sun and has some of the characteristics of a planet but doesn't meet all the criteria required to be classified as a full planet. According to the International Astronomical Union, a dwarf planet must meet the following criteria:

1. It Orbits the Sun: Like a planet, a dwarf planet must revolve around the Sun.

2. It Must have Sufficient Mass: It has enough mass for its gravity to pull it into a roughly spherical shape.

3. It Has not Cleared It's Own Orbit: Unlike full planets, a dwarf planet has not cleared the neighborhood around its orbit of other objects. This means it shares its orbital zone with space debris like asteroids and smaller space rocks.

4. Not a Moon: It is not a moon of another planet.

Some well-known examples of dwarf planets include Pluto, Ceres (in the asteroid belt), Haumea, Makemake, and Eris. Dwarf planets are often smaller than regular planets and can be found in places like the Kuiper Belt (beyond Neptune) or in the asteroid belt between Mars and Jupiter.

CERES

Ceres is the biggest object in the Asteroid Belt and makes up about 40% of its total mass. It was discovered in 1801 by Giuseppe Piazzi. Ceres is made of rock and ice, and scientists think it may have a hidden ocean beneath its surface which means it could possibly support tiny forms of life. It has a very thin atmosphere with water vapor, and one of its most famous features is the bright spots in the Occator Crater which are salt deposits left behind by evaporating water. In 2015, NASA’s Dawn spacecraft visited Ceres, taking detailed pictures and discovering water ice under its surface. Scientists also found signs of ice volcanoes that may have been active in the past. Because of its water and other important materials, Ceres is one of the best places in the solar system to look for signs of life. It has very weak gravity (only 3% of Earth's), and a day on Ceres lasts about 9 hours, while a year takes 4.6 Earth years. 

ERIS

Eris is one of the largest known dwarf planets in the Kuiper Belt and was discovered in 2005. It is about the same size as Pluto (roughly 2,326 km / 1,445 miles in diameter) and was initially thought to be larger, which led to the debate that resulted in Pluto’s reclassification as a dwarf planet in 2006. Eris has a highly elliptical orbit, taking it as far as 97 AU from the Sun, making it one of the most distant known objects in the solar system. It's surface is covered in frozen methane, giving it a bright and reflective appearance (Even brighter than Pluto). Eris has one known moon called Dysnomia. Because of its distant orbit, a year on Eris lasts about 558 Earth years!

Makemake

Makemake is a dwarf planet in the Kuiper Belt, discovered in 2005. It is about 1,430 km (890 miles) in diameter, making it the third-largest known Kuiper Belt Object (after Pluto and Eris). Unlike Pluto, it has no significant atmosphere and has a surface covered in methane and ethane ice, giving it a reddish appearance. Makemake has one known moon called MK2, discovered in 2016. 

Haumea 

Haumea is a rapidly rotating dwarf planet, discovered in 2004, it is unique because of its elongated, football-like shape. This unusual shape is due to its extremely fast rotation, spinning once every 3.9 hours making it one of the fastest-spinning large objects in the solar system. Haumea is about 1,960 km (1,218 miles) long and has a surface covered in crystalline water ice. It has two moons, Hiʻiaka and Namaka, and is surrounded by a thin ring, making it the only known dwarf planet with a ring system.