All objects in the asteroid belt are assigned a sequential number. For Hygea, this number is 10, since Hygea became the tenth object discovered in the main belt. The first four were discovered in 1801-1807. Then the era of the Napoleonic wars and subsequent hard times interrupted the activity of scientists to search for new objects in this area of the Cosmos.
And only in 1845 the fifth asteroid was discovered – Astrea, a little later – Hebe, Iris, Flora, Metis. And in 1849, the Italian astronomer Annibale de Gasparis discovered the asteroid Hygea, named after the ancient Greek goddess of health. Despite the fact that Hygea is one of the four largest bodies in the asteroid belt, when viewed from Earth, it is barely visible due to its dark surface and large distance from the Sun, therefore it was discovered later than several smaller asteroids.
Until recently, it was believed that this asteroid has an irregular shape. In 2017, observations of Hygea with the VLT telescope in Chile made it possible to determine that it is spherical with a diameter of 434 km and belongs to spectral type C. It is the largest asteroid of this class, which dominates in the outer belt at a distance of about 3 AU.
Spectral analysis data suggest that Hygea’s surface is composed of carbonaceous materials, similar to carbonaceous chondrites falling to Earth. Hygea has a relatively low density of about 2 g / cm³, which is more comparable to the icy moons of Jupiter or Saturn than to the terrestrial planets.
Hygea is the main representative of the asteroids of the Hygea family, which was formed as a result of the collision of Hygea with a cosmic body 100 km in diameter about 2 billion years ago. As a result, many small fragments were knocked out of Hygea, which then formed this family. According to some researchers, the shape of the asteroid was not correct before the collision. After the collision, Hygea was completely destroyed. Then, as a result of repeated accretion, a spherical object was formed from most of the debris.