In 2006, the International Astronomical Union came up with a new way to classify planets that famously saw Pluto downgraded. Now a new row has started as astronomers try to define exoplanets
25 March 2022
What is a planet? Despite decades of trying, astronomers still haven’t found a definition that everyone can agree on – and the problem only gets harder when considering worlds outside our solar system. The latest attempt to define an exoplanet has sparked fresh controversy.
The International Astronomical Union (IAU), arbiter of all things cosmic, set out a final definition for planets in our solar system in 2006, famously demoting Pluto to a dwarf planet in the process. Its first requirement is that a …