HYGIEA

Nov. 3, 2019

Astronomers using ESO’s SPHERE instrument at the Very Large Telescope (VLT) have revealed that the asteroid Hygiea could be classified as a dwarf planet.

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As of today, there are officially five dwarf planets in our Solar System. The most famous is Pluto, downgraded from the status of a planet in 2006. The other four, in order of size, are Eris, Makemake, Haumea and Ceres.
Now, there is a claimant for a sixth dwarf planet. Called Hygiea, it has so far been taken to be an asteroid. It lies in the asteroid belt between Mars and Jupiter.
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. If it qualifies, Hygiea will be the smallest dwarf planet in the Solar System.
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.