February 18 marks the discovery of Pluto by astronomer Clyde W. Tombaugh. The discovery reshaped the understanding of the solar system, as Pluto was long considered the ninth planet until the ...

Eighteen years ago today, Pluto lost its planetary status in a vote by International Astronomical Union (IAU) members on the final day of their 2006 general assembly meeting. The word "planet" comes ...

Twenty years after Pluto became a dwarf planet, people are still fighting over its status. Experts explain why the debate feels so personal.

Dwarf planet Pluto was discovered by American astronomer Clyde Tombaugh. Pluto was long considered the 9th planet in the solar system, but the International Astronomical Union reclassified Pluto as a ...