Evidence of the Cometary Nature of Asteroid Don Quixote Provided by Observations at the Sanglokh Observatory

We report the results of multicolor optical observations of asteroid (3552) Don Quixote carried out at the Zeiss-1000 telescope of the Sanglokh International Astronomical Observatory of the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan in July 2018. The apparent and absolute magnitudes of the asteroid were determined in the VRI bands. The analysis of the light curves of the asteroid showed that the brightness substantially varied during the observations—from 11.50 ± 0.10 to 13.10 ± 0.18 of absolute it magnitudes. Such a considerable change in the magnitude is indicative of an outburst the asteroid, which means that we detected activity typical for comets. According to our observations, the color index (V‒R) corresponds to the values for nuclei of extinct short-period comets and D-type asteroids. The comet-like orbit, the low albedo, the color index, and detected activity suggest that the asteroid is very likely the nucleus of an extinct comet. According to the observations performed ten days after the outburst, the mean value of the effective diameter of the asteroid is 18.5 ± 2.5 km; and this estimate agrees well with the data available, which means that the outburst had terminated by that time. We suppose that the dust ejection and, consequently, the outburst resulted from a collision of asteroid 3552 with a small object or from the micrometeoroids bombardment of its surface.