When Gustav Holst finished his iconic work "The Planets" in 1917, Pluto had yet to be discovered. Six years ago, British composer Colin Matthews was commissioned to round out the set. He called his ...

In 2006, astronomers gathered in Prague to consider a very basic question: How many planets are in our solar system? Was it nine, or was it actually eight, or perhaps as many as 12? By the end of the ...

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 ...