The solar system has eight planets. But it wasn't always the case. In 1930, when Pluto was first discovered by American astronomer Clyde Tombaugh, it was considered the ninth planet of the solar system. In fact, it continued to be known as a planet till 2006 when the International Astronomical Union (IAU) redefined the definition of a planet and reclassified Pluto as a "dwarf planet". While astronomers found an agreement over Pluto, it didn't last long. In recent years, questions have been raised on classification of…
