Pluto was once considered a planet, much like Earth, but shortly after the start of the 21st century, astronomers seemingly changed their minds, instead opting to categorize Pluto as a dwarf planet. But have you ever wondered why?
Pluto was initially discovered in 1930 and classified as a planet because it was unusually large given its distance to Earth. Pluto wasn’t demoted from planet to dwarf planet because it shrunk, but rather because modern technology helped us to see Pluto for what it really was. It was quickly determined that Pluto didn’t quite fit the definition.
Astronomers learned in the 1970s that Pluto was smaller than initially anticipated, and advancements in space telescopes in the 1990s further supported the notion that Pluto wasn’t quite ‘planet’ material.
Since the introduction of such powerful observation tools, astronomers have found a plethora of different dwarf planets that meet similar criteria as Pluto, including Eris, Makemake, and Sedna, to name a few. A quick search online reveals an extensive list of others, which don’t have quite as catchy names.
The next time you wonder why Pluto isn’t still a planet, consider the details mentioned in this video.