When We Discovered Pluto, It Changed How We Saw The Solar System

On the 23rd and 24th of January, 1930, a young astronomer working in Flagstaff, Arizona, scanned a small patch of the night sky. He was taking pictures of star positions, looking for anomalies that would signal movement somewhere at the edge of the solar system. He took the pictures then set them aside, not realizing… »7/12/15 3:00pm7/12/15 3:00pm

Pluto has regained its position as the ninth largest body to orbit the Sun. Probably.

When scientists first discovered the dwarf planet Eris back in 2005, they claimed that the icy body was actually larger than Pluto. But when Eris' orbit passed in front of a dim star late last year, astronomers got their first chance to take a good hard look at the dwarf planet's actual diameter. And as it turns out,… »10/28/11 2:40pm10/28/11 2:40pm