Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Many Americans grew up with this as the definitive planetary lineup and created clever mnemonic devices to memorize them in ...

NASA's New Horizons spacecraft captured this high-resolution enhanced color view of Pluto that is inserted beneath the Short Wave logo. The image combines blue, red and infrared images taken by the ...

The debate over Pluto’s planetary status has been ongoing since its reclassification as a “dwarf planet” in 2006 by the International Astronomical Union (IAU). Recent discussions and new scientific ...

For many people, the definition of a planet was only made clear in 2006, when the spunky world Pluto was demoted from a planet to a dwarf planet. Now, a team of astronomers is pushing for “planet” ...

Once the quirky underdog of our solar system, Pluto held planetary status until 2006, when it got a cosmic demotion that still stings space fans. Discovered in 1930, Pluto was the ninth planet for ...

It has now been 15 years since ex-planet Pluto was re-classified as a dwarf planet by the International Astronomical Union (IAU). On August 24, 2006, the IAU convened at its 26th general assembly ...

Editor’s note: A version of this story originally appeared in Astronomy’s 2007 special issue 50 Greatest Mysteries of the Universe. For a more recent discussion of Pluto’s planethood, see “An ...

When the International Astronomical Union (IAU) demoted Pluto from a planet to a dwarf planet in 2006, it surprised a lot of people, including some scientists. Even many years later, some astronomers ...

In the cold, distant reaches of the Solar System, far beyond Pluto, astronomers have just identified what could be a new dwarf planet. It's called 2017 OF 201, a rock that appears to be some 700 ...

Pluto hasn't been a planet for almost 20 years. In the early 2000s, scientists discovered several objects of a similar size to Pluto. So, during the summer of 2006, members of the International ...