Even many years later, some astronomers want to revise the definition of a planet to clarify the parameters that set planets apart from other celestial objects. But why isn't Pluto considered a ...

Clyde Tombaugh discovered Pluto in 1930 at Lowell Observatory in Flagstaff. Here's how Pluto won - and lost - its planetary status.

Pluto is too far away from Earth to be seen with the naked eye. If you stood on Pluto's surface, the Sun would merely appear to be a very bright star. Although previous images showed that ...

Why it matters: Their new proposed definition wouldn't bring Pluto back into the planetary fold, but it could reclassify thousands of celestial bodies across the universe. How it works ...

Pluto was reclassified from a planet to a dwarf planet by the International Astronomical Union because it did not meet all three criteria of their updated definition of a planet. According to the ...

Why was Pluto reclassified as a dwarf planet? One might think that it’s purely a matter of size. Mercury, the smallest of the ...