(6478) Gault is a main-belt asteroid discovered on May, 12 1988 by C. S. Shoemaker and E. M. Shoemaker at Mount Palomar. It was named after the astronomer Donald Gault. It is a small “rock” with a diameter of about 3.7-5 km. Its orbit has a perihelion at 1.86 AU and an aphelion at 2.75 AU, it will be at its perihelion in January, 2020.
Rotation period and spectral class are now unknow.
In firsts days of 2019, many astronomers has detected a strange behavior in their images: the asteroid (6478) Gault, from (about) the January, 7 2019 has a tail! This is reported in CBET 4594 from K. W. Smith, Queen’s University, Belfast; and L. Denneau, University of Hawaii, on behalf of the “Asteroid Terrestrial-Impact Last Alert System” (ATLAS) team. In first instance it was clear that this tail should be a result of an impact with another asteroid. But with the time, everything is changed, again: the apparition of a second tail gave to this rock a behavior similarly to comets (Main Belt Comet). If an impact has happen, it will be clear after time, with astrometric observations: if they check an orbital variation, this will be clear.
Me, Riccardo Papini, Massimo Banfi observed on 2019, march 8 6478 Gault with the WBRO (K49) with a 18 frames (with an exposure of 300 seconds) stacked, full calibrated, that revealed the follow measures for the tails:
1. 4′ 46″ for the principal tail;
2. 22.4 ” for the secondary tail.
Of course, our telescope is quite small (just 9.25 inches), other larger telescopes seen a principal tail longer than 6′. But the result is resonable.
Finally, let’s see in next future what this strange object will reserve for astronomers. Main Belt Comets are rare, but there are some. May be, 6478 Gault, had a transiction to this class probably because of an impact or for other reasons.