smáæðar

Smáæðar, also known as dwarf planets, are celestial bodies that orbit the Sun and are massive enough to be rounded by their own gravity, but have not cleared their neighboring region of planetesimals. The term "smáæðar" is derived from the Icelandic word for "dwarf," reflecting the smaller size of these objects compared to the eight classical planets. The International Astronomical Union (IAU) introduced the category of dwarf planets in 2006, following the discovery of Eris, an object in the scattered disc region of the Solar System that was initially thought to be larger than Pluto.

The IAU's definition of a dwarf planet includes three criteria: the object must orbit the Sun, be massive enough to be rounded by its own gravity, and not have cleared its neighboring region of planetesimals. This definition distinguishes dwarf planets from small Solar System bodies such as comets, asteroids, and meteoroids. As of my knowledge cutoff in 2023, there are five officially recognized dwarf planets in our Solar System: Pluto, Eris, Makemake, Haumea, and Ceres. Ceres is unique among these objects as it is located in the asteroid belt between Mars and Jupiter, while the others reside in the Kuiper belt beyond Neptune's orbit.

Dwarf planets are of significant scientific interest due to their unique characteristics and the insights they provide into the formation and evolution of the Solar System. They offer clues about the conditions that existed during the early stages of planetary formation and the processes that shaped the current architecture of the Solar System. Ongoing research and exploration, including missions to Pluto and other dwarf planets, continue to expand our understanding of these fascinating celestial bodies.