New research suggests that a binary pair of Kuiper Belt objects, known as the Altjira system, is actually made up of three ...

Pluto and Charon’s unique characteristics make them the largest binary system in the trans-Neptunian region. Their shared orbital axis and comparable sizes—with Pluto’s diameter about 1,200 ...

(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?

Astronomers have discovered what they believed to be a rare stable trio of gravitationally bound Kuiper Belt objects, ...

Pluto was discovered at Lowell Observatory in Flagstaff, Arizona in 1930 and was considered our ninth planet until 2006. The International Astronomical Union reclassified Pluto as a dwarf planet ...

Pluto was discovered 95 years ago on Feb. 18, and even though it was demoted nearly two decades ago, it remains a fascinating part of our solar system. "Pluto is a complex and mysterious world ...

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 ...