The study, published in the journal Nature on October 28, observed (10) Hygiea with the SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument attached to the European Southern Observatory's Very Large Telescope (VLT) in 2017 and 2018.
New research shows that it also meets the fourth requirement, as well: a dwarf planet must have enough mass so that that gravity could pull it into a sphere.
What was thought to be an asteroid known as Hygiea was believed the be the fourth largest object in the asteroid belt, situated between Mars and Jupiter, behind asteroids Vesta, Pallas and dwarf planet Ceres. They found that Hygiea is spherical, potentially taking the crown from Ceres as the smallest dwarf planet in the Solar System. The main point of difference between the two though is that a planet has to have cleared other objects out of the neighborhood around its orbit - if it hasn't, it's a dwarf planet.
It orbits the Sun, and not another planet, so that rules it out from being a Moon. The instrument also measured the diameter of Hygiea, putting it at just over 430km.
There are now five dwarf planets - Pluto, Eris, Haumea, Makemake and Ceres.More news: Federer withdraws from Paris Masters
One surprising find was that Hygiea lacks any large impact craters on its surface. Observing Hygiea with ground-based equipment showed that the asteroid looks nearly as round as Ceres, with no sign of the mammoth impact craters that have deformed objects like Vesta.
As the main member of a collection of almost 7,000 objects classified under the Hygiea family, these hunks of space rocks are believed to have formed from a giant historic collision between a projectile and a larger asteroid that occurred some two billion years ago.
"Such a collision between two large bodies in the asteroid belt is unique in the last 3-4 billion years", says Pavel Ševeček, a PhD student at the Astronomical Institute of Charles University who also participated in the study.
The European Space Observatory's SPHERE instrument has spotted what may be the smallest small planet in our solar system.
Commenting on the potential reclassification of Hygiea, Robert Massey, from the U.K.'s Royal Astronomical Society, said the move would be "completely reasonable" given that it fits the criteria for a dwarf planet. Ceres and Pluto are 2400km and 950km in diameter, respectively, so a round Hygiea would be a significantly lower bar for the minimum size of any dwarf planet.More news: Sam Burgess poised to retire from NRL
According to this theory, a high velocity projectile measuring between 46 and 93 miles in diameter obliterated whatever the parent object was, creating Hygiea and its roughly 7,000 asteroid belt siblings.
Once the left-over pieces reassembled, they gave Hygiea its round shape and thousands of companion asteroids, the team said. "They are too small", explains study co-author Miroslav Bro of the Astronomical Institute of Charles University in Prague, Czech Republic. It was initially called Bourbon Hygieia, but in 1852 was simply changed to Hygiea, with a single "i".
With advances in numerical computation, and more powerful telescopes, scientists are now more able to rewind the clock and piece together cosmic conundrums such as these.
"Thanks to the VLT and the new generation adaptive-optics instrument SPHERE, we are now imaging main belt asteroids with unprecedented resolution, closing the gap between Earth-based and interplanetary mission observations".More news: DC Anthology Series STRANGE ADVENTURES Is Headed To HBO Max