10 Hygiea

10 Hygiea is the fourth-largest asteroid in the asteroid belt that lies between the orbits of Mars and Jupiter. Discovered by Annibale de Gasparis on April 12, 1849, it was named after Hygieia, the Greek goddess of health, cleanliness, and hygiene. Hygiea is unique among the large asteroids in that it appears to have a nearly round shape and may qualify as a dwarf planet under the criteria set by the International Astronomical Union (IAU).

Discovery and Naming

Hygiea was discovered by Italian astronomer Annibale de Gasparis from the Observatory of Capodimonte in Naples. It was the tenth asteroid to be discovered, which is reflected in its name. The naming convention of asteroids during the time followed a tradition of selecting names from classical mythology, with Hygiea being named after the goddess of health, which is fitting given the asteroid's numerical designation.

Physical Characteristics

Hygiea is primarily characterized by its nearly spherical shape, a trait that is not common among asteroids, especially in the asteroid belt. Its diameter is roughly 430 kilometers, making it one of the largest asteroids. Observations and studies suggest that Hygiea has a dark surface, with a low albedo indicating that it is composed of primitive carbonaceous materials. Its rotation period is relatively slow, taking about 27.63 hours to complete a rotation.

Spectroscopic studies have placed Hygiea in the C-type (carbonaceous) asteroid category, suggesting a composition rich in carbon and possibly water ice beneath its surface. This composition is indicative of the primordial matter from which the Solar System formed.

Orbit and Classification

Hygiea orbits the Sun at a distance that ranges from 2.78 to 3.50 astronomical units (AU) and completes an orbit every 5.57 years. Its orbit is moderately inclined at about 3.8 degrees to the plane of the ecliptic and has an eccentricity of 0.12, which is typical for asteroids in the main belt.

Given its size and spherical shape, there has been discussion among astronomers about reclassifying Hygiea as a dwarf planet. The IAU's definition of a dwarf planet includes the requirement that the body has sufficient mass for its self-gravity to overcome rigid body forces and assume a hydrostatic equilibrium (nearly round) shape. Hygiea meets this criterion based on observations from the Very Large Telescope (VLT) and other facilities.

Exploration

As of now, there have been no spacecraft missions to Hygiea. However, its large size, nearly spherical shape, and the potential for it to be classified as a dwarf planet make it an intriguing target for future exploration missions. Such missions could provide valuable insights into the early Solar System and the conditions that led to the formation of planets.

See Also

• Asteroid belt
• Dwarf planet
• C-type asteroid
• List of Solar System objects by size