The debate over Pluto’s planetary status has been ongoing since its reclassification as a “dwarf planet” in 2006 by the ...

With a diameter of 1,440 miles, Pluto is farthest from the sun. While major planets make roughly circular orbits, Pluto ...

Pluto was demoted from a planet to a dwarf planet in 2006. So why is its status still so controversial today?

Discover why Pluto is not a planet according to the IAU's latest resolutions on planets and dwarf planet definitions.

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 IAU, a dwarf planet is as related to a planet as an asteroid is -- not at all. This hard definition has been drawing criticism since the IAU demoted Pluto in a 9-8 vote in 2006.

Planet X or not, Pluto existed. Smaller than the Moon, but inhabiting the realm of the giant planets, it defied our notions regarding the architecture of the Solar System.

Two of Pluto's midsize moons may be made of the guts of its largest moon, Charon, new research suggests.

The US state of Arizona has taken the unusual step of naming a state planet. Even more unusually, they have chosen Pluto – which is not a planet – as their representative in the solar system.

Planet X or not, Pluto existed. Smaller than the Moon, but inhabiting the realm of the giant planets, it defied our notions regarding the architecture of the Solar System.

On January 17, 2006 the New Horizons mission will launch for Pluto, the last unexplored planet of the solar system — or is it? Some scientists now claim that Pluto does not deserve its planetary ...

The International Astronomical Union in Prague ruled today that the much-maligned Pluto no longer qualifies as a planet under historic new guidelines, thereby stripping Pluto of the planetary ...