Fact Check: Five dwarf planets and a new candidate — how is it decided?

Using observations made through the European Space Organisation’s SPHERE instrument at the Very Large Telescope (VLT), astronomers have now found Hygiea may possibly be a dwarf planet. They have reported their findings in the journal Nature Astronomy.

If it qualifies, Hygiea will be the smallest dwarf planet in the Solar System.

Dwarf planets

The International Astronomical Union sets four criteria for a dwarf planet, and Hygiea already satisfies three — it orbits around the Sun, it is not a moon, and it has not cleared the neighbourhood around its orbit. The fourth requirement is that it have enough mass that its own gravity pulls it into a roughly spherical shape.

According to the new study, VLT observations now show Hygiea satisfied that condition, too. This is the first time astronomers have observed Hygiea in high resolution to study its surface and determine its shape and size.