The smallest dwarf planet to be discovered

Smallest dwarf planet
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Using ESO’s SPHERE instrument at the Very Large Telescope (VLT), astronomers have revealed that the asteroid Hygiea could actually be a dwarf planet.

Hygiea is the fourth largest in its asteroid belt, after Ceres, Vesta and Pallas. For the first time, astronomers have observed Hygiea in order to determine its shape and size. The research found that Hygiea is spherical and could potentially take the place of Ceres as the smallest dwarf planet in the solar systems.

Hygiea satisfies three of the four requirements for a dwarf planet, the requirements being; the object orbits around the sun, it is not a moon and unlike a planet, and the final requirement is that it has enough mass to draw its own gravitational pull.

“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,” says lead researcher Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille in France. “Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the Solar System.”

Researchers have also used ESO’s technology in order to measure Hygiea’s size, measuring it up to just over 430km. The most famous dwarf planet, Pluto, has a diameter of almost 2400km, while the previous smallest dwarf planet, Ceres, was close to 950km in size.

Astronomers were surprised to see that Hygiea lacks the very large impact craters expected of an asteroid which originated from a parent body that split into 7000 member. “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.

The research team observed that 5% of its surface was covered by two unambiguous craters. “Neither of these two craters could have been caused by the impact that originated the Hygiea family of asteroids whose volume is comparable to that of a 100 km-sized object. They are too small,” explains study co-author Miroslav Brož of the Astronomical Institute of Charles University in Prague, Czech Republic.

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