They originally thought the tiny object was an asteroid.
Moving on Up
The asteroid Hygiea just got a promotion.
Using European Southern Observatory's SPHERE instrument at the Very Large Telescope (VLT), astronomers were able to get their most detailed look yet at Hygiea, an object in the asteroid belt.
Four for Four
To be classified as a dwarf planet, an object must meet four requirements: it must be spherical, it must orbit the Sun, it can't be a moon — and it must not have cleared the neighborhood around itself, which would make it a proper planet.
Astronomers already knew that Hygiea met the latter three requirements, and the new VLT data allowed them to confirm the first.
"Thanks to the unique capability of the SPHERE instrument on the VLT, which is one of the most powerful imaging systems in the world, we could resolve Hygiea’s shape, which turns out to be nearly spherical," lead researcher Pierre Vernazza said in a news release. "Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the Solar System."
READ MORE: ESO Telescope Reveals What Could be the Smallest Dwarf Planet Yet in the Solar System [European Southern Observatory]
More on dwarf planets: Astronomers Just Found a Dwarf Planet Three Times As Far Away As Pluto