While Planet X was estimated to be about six times more massive than Earth, Pluto’s mass is only 20% that of the Moon, itself 1% of the Earth’s mass. Pluto is much too small to gravitationally ...

Pluto had been considered the ninth planet since its discovery in 1930, but the IAU — which names astronomical objects — decided in 2006 that a planet must be spherical, orbit the sun and have ...

Pluto's discovery was widely celebrated, especially in the U.S. After all, it was the first planet discovered in the new world, and America needed the win in 1930.

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 ...

While Planet X was estimated to be about six times more massive than Earth, Pluto’s mass is only 20% that of the Moon, itself 1% of the Earth’s mass. Pluto is much too small to gravitationally ...

It would eventually be named Pluto after the Roman god of the underworld. Despite being smaller than several known moons, it was deemed large enough to be considered a planet.

Pluto was discovered in 1930 in Arizona, but in 2006 scientists decided to cut Pluto from the planetary line up. Here is why Pluto isn't a planet.

Though Pluto has formally been considered a dwarf planet for almost two decades, it still has many lessons left for planetary scientists — including hints about how the solar system formed.

Pluto's status has been a heated debate for decades with arguing over a dwarf planet classification. Here's what international standards say in 2023.

But Pluto’s heritage aside, let’s look at the facts. In 2006, at a meeting of the International Astronomical Union in Prague, astronomers voted to “demote” Pluto to dwarf planet status.

If you answered "Pluto's planethood," your grasp of the astronomical is excellent. Feb. 18 marks the 95th anniversary of the discovery of our outermost planet-not-planet.