Hygiea family

The Hygiea or Hygiean family of asteroids is a grouping of dark, carbonaceous C-type and B-type asteroids in outer asteroid belt, the largest member of which is 10 Hygiea. About 1% of all known asteroids in the asteroid belt belong to this family.

By far the largest member is 10 Hygiea, a 400 km diameter C-type asteroid that is the fourth largest in the belt. The remaining members are much smaller so Hygiea contains about 94–98% of the mass in the family (depending on the exact criteria for inclusion). The two next largest members are 333 Badenia, and 538 Friederike, both just over 70 km in diameter. After that, the remaining members have diameters of less than 30 km.

The Hygiea family is thought to be of the cratering type, implying that it was formed as a result of a giant impact that excavated the much smaller family members from Hygiea (Zappala 1995, Farinella 1996). However, the two 70-kilometer-diameter bodies are still surprisingly large to have been excavated in an impact that did not disrupt the parent body (compare e.g. to the Vesta family, which contains no members above around 10 km in diameter). They may be interlopers (see below) despite having a similar spectral type to Hygiea, because dark carbonaceous asteroids dominate the outer asteroid belt.

The family contains a significant number of objects of the otherwise rare B spectral type (Mothé-Diniz 2001). The largest of these is the previously mentioned 538 Friederike.

There are some indications that this family is relatively quite old (Tanga 1999).

A HCM numerical analysis by (Zappala 1995) found a 'core' group of family members, whose proper orbital elements lie in the approximate ranges

At the present epoch, the range of osculating orbital elements of these core members is

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