Mercury is bigger than Pluto, but it’s still considered the smallest planet because of Pluto’s designation as a dwarf planet. In 2006, the IAU determined Pluto did not meet the qualifications ...

For decades, our solar system was thought to have nine planets, with Pluto considered the smallest and farthest. But in 2006, ...

But Earth isn't the smallest planet in the solar system; that title went to Mercury after Pluto was relegated to a dwarf planet in 2006. But are there even smaller planets out there? And ...

Here's what to know about the short life of what was, for a single human lifetime, the solar system's smallest planet ... to reclassify Pluto as a dwarf planet. The reasoning was that it didn ...

In fact, Ceres makes up 25% of the total mass of the asteroid belt. Still, Ceres remains a dwarf planet. Perhaps as it should, given Pluto's relegation to dwarf planet — Pluto is 14 times larger ...

Feb. 18 marks the 95th anniversary of the discovery of our outermost planet-not-planet. Here's what to know about the short life of what was, for a single human lifetime, the solar system's smallest ...