Hygiea is a major asteroid located in the main asteroid belt. With a mean diameter of between 425 and 440 km and a mass estimated to be 3% of the total mass of the belt, it is the fourth-largest asteroid in the Solar System by both volume and mass, and is the largest of the C-type asteroids in classifications that use G type for 1 Ceres. It is very close to spherical, apparently because it had re-accreted after the disruptive impact that produced the large Hygiean family of asteroids.
VLT-SPHERE image of Hygiea
Image of 10 Hygiea taken by the 2MASS survey
Relative sizes of the four largest asteroids. Hygiea is furthest right.
The IAU 2006 draft proposal listed Hygiea as a potential planet.
An asteroid is a minor planet—an object that is neither a true planet nor a comet—that orbits within the inner Solar System. They are rocky, metallic, or icy bodies with no atmosphere. The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres, a dwarf planet almost 1000 km in diameter.
2013 EC, shown here in radar images, has a provisional designation
A composite image, to the same scale, of the asteroids imaged at high resolution prior to 2012. They are, from largest to smallest: 4 Vesta, 21 Lutetia, 253 Mathilde, 243 Ida and its moon Dactyl, 433 Eros, 951 Gaspra, 2867 Šteins, 25143 Itokawa.
Vesta (left), with Ceres (center) and the Moon (right) shown to scale
Phobos
