Evidence for Active Asteroid 288P Being Triple

The main-belt object 288P/(300163) 2006 VW139 is remarkable for both being a binary system with unusual orbital properties (wide separation of the nearly equal-mass binary) and comet-like activity. We present new Hubble Space Telescope observations of 288P, taken in May 2020 when the system was inactive and the components were at maximum separation (142 km). The two known components were spatially resolved in our high-resolution images. We find that the light curve of the brighter component can be explained by the sum of two components with different periods, P1=16.0 h and P2=3.2 h, and the fainter component has a period of P3=3.6 h. These periods are considerably shorter than the reported orbital period of >100 days. Here we suggest that 288P is a triple active asteroid. Possible formation mechanisms are discussed.