The Hilda family (001) is an ancient collisional asteroid family of at least 409 known asteroids, named for its largest member, the -across asteroid 153 Hilda. It lies within the larger dynamical group of Hilda asteroids, a group of asteroids in the 3:2 orbital resonance with Jupiter. All members of the family are dark P-type asteroids with albedos of around 0.06. Another asteroid family in the Hilda dynamical group is the Schubart family, named for its largest member, 1911 Schubart.
An asteroid family is a group of physically related asteroids usually created by a collision with an original larger asteroid, with the fragments continuing on similar orbits to the original. This is distinct from a dynamical group in that the members of a dynamical group only share similar orbits because of gravitational interactions with planets, which concentrate asteroids in a particular orbital range. Members of the Hilda family are both part of the wider Hilda dynamical group, and fragments of 153 Hilda. The family is considered a non-catastrophic asteroid family because 153 Hilda, its largest member, makes up nearly 3/4 of the family's total mass, rather than simply being the largest of a number of fragments each making up a small fraction of the original destroyed asteroid.
The family is believed to be one of the oldest collisional families ever discovered, with an estimated age of likely 4 billion years. Models based on the modern Solar System indicate it being very unlikely for an asteroid as large as 153 Hilda to suffer a collision large enough to create its family, even over the course of billions of years of encounters with other asteroids, leading to a 2011 study to propose that the family-creating impact event happened during the Late Heavy Bombardment, when impact rates in the Solar System were briefly much higher.
Large members
+The 10 brightest Hilda family membersName Abs. Mag Size (km) propera (AU) propere properi153 Hilda 7.8 171 3.9653 0.174 8.9171212 Francette 9.6 76 3.9674 0.230 7.2371746 Brouwer 10.0 63 3.9631 0.141 9.2511529 Oterma 10.0 56 3.9643 0.154 7.8703134 Kostinsky 10.5 50 3.9658 0.184 8.9661038 Tuckia 10.7 58 3.9648 0.164 8.2393990 Heimdal 11.0 36 3.9651 0.168 9.6414317 Garibaldi 11.1 39 3.9670 0.213 9.1653571 Milanstefanik 11.3 35 3.9620 0.127 9.2103561 Devine 11.3 33 3.9623 0.133 8.581
References