planets. It is the lowest numbered asteroid in such a resonance (the next lowest numbered being 70 Panopaea). Hygiea has a rotation period of about 13.8256 hours, determined from observations with the VLT in 2017 and 2018. Its single-peaked light curve has an amplitude of 0.27 mag, which is largely attributed to albedo variations. , the direction of Hygiea's rotation is not known, due to a twofold ambiguity in lightcurve data that is exacerbated by its long rotation period—which makes single-night telescope observations span at best only a fraction of a full rotation—but it is believed to be retrograde. Lightcurve analysis indicates that Hygiea's pole points towards either ecliptic coordinates (β, λ) = (30°, 115°) or (30°, 300°) with a 10° uncertainty. This gives an axial tilt of about 60° in both cases. Hygiea family Hygiea is the main member of the Hygiean asteroid family that constitutes about 1% of asteroids in the main belt. The family was formed when an object with a diameter of about 100 km collided with proto-Hygiea about 2 billion years ago. Because the impact craters on Hygiea today are too small to contain the volume of ejected material, it is thought that Hygiea was completely disrupted by the impact and that the majority of the debris recoalesced after the pieces that formed the rest of the family had escaped. Hygiea contains almost all the mass (over 98%) of the family. See also Former classification of planets Notes References External links A simulation of the orbit of Hygiea Stellar occultation of 11 August 2013 (video) (displays Elong from Sun and V mag for 2011) Hygiea asteroids Hygiea Hygiea Possible dwarf planets C-type asteroids (Tholen) C-type asteroids (SMASS) 18490412 18490412