The smallest dwarf planet in our solar system was hiding in the asteroid belt

SPHERE image of HygieaESO

  • Hygiea, classified as an asteroid so far, might actually be a dwarf planet.
  • The European Southern Observatory has been able to confirm that Hygiea has a spherical shape.
  • But, Hygiea is missing a large impact crater normally found on asteroids after they have broken off from the parent asteroid.
The asteroid belt between Jupiter and Mars is home to many asteroids and planets. Now European Southern Observatory ( ESO) thinks one of the objects floating along the main belt might be the smallest dwarf planet in our solar system — an asteroid known as Hygiea.

Hygiea isn’t a new discovery but the fact that it meets the International Astronomical Union’s (IAU) requirements to be classified as a dwarf planet is new.

It orbits the Sun, and not another planet, so that rules it out from being a Moon. But unlike an actual planet, it hasn’t pushed away or pulled in any of the objects that are cluttering its orbit.
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ESO’s Very Large Telescope (VLT) was able to capture a third detail that puts Hygiea in the running for a dwarf planet — it has just enough mass for its gravity to pull it together in a spherical shape.

"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," said lead researcher Pierre Vernazza.

Dwarf planets in the universe’s remnants

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When the big bang first happened and planets were formed, the asteroid belt basically contained whatever was left over.

The clumps could have formed a planet but scientists believe that Jupiter’s gravity was so strong that the space objects continued to orbit the Sun instead, colliding every so often.

These collisions led to bigger parent bodies breaking into smaller asteroids. Hygiea is supposed to be a part of a 7000 member family and it’s separation from the parent space object should have left a large impact crater — but it’s nowhere to be found.

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"This result came as a real surprise as we were expecting the presence of a large impact basin, as is the case on Vesta," says Vernazza.

According to the team’s deductions, it’s possible that Hygiea’s parent asteroid collided into a large object between 75 to 150 kilometers wide and the resulting collision was so violent that it completely shattered it.

Their study states that as the left-over pieces of the collision reassembled, Hygiea got its round shape — fulfilling the third parameter to be be classified as a dwarf planet.

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