Is a sun a star or a planet? While science now agrees the sun is a star, new telescopes may soon challenge how we define solar objects.

Pluto has long been one of the most debated celestial bodies in our solar system. Once classified as the ninth planet, it was redefined in 2006 as a dwarf planet, a decision that still sparks ...

Pluto, discovered in 1930, was once considered the ninth planet in our solar system. In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet because it doesn't meet all the ...

In August 2006, the International Astronomical Union made the controversial, but correct, decision to demote Pluto from its status as the ninth planet in our Solar System. From that day forward, ...

The Sun, our nearest celestial neighbor, is undeniably a star, not a planet, as centuries of astronomical observations have ...

(Correction: An earlier version of this story misstated how far Pluto is from the sun. The correct number is 3.7 billion miles.) What was discovered in Flagstaff, Arizona, and killed off in Prague? If ...

The 95th anniversary of Pluto's official discovery by Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona is rapidly approaching and the historic location is gearing up to host a grand ...