We present imaging and spectroscopic observations of 6478 Gault , a \sim 6 km diameter inner main-belt asteroid currently exhibiting strong , comet-like characteristics . Three distinct tails indicate that ultra-slow dust ( ejection speed 0.15 \pm 0.05 m s ^ { -1 } ) was emitted from Gault in separate episodes beginning UT 2018 October 28 \pm 5 ( Tail A ) , UT 2018 December 31 \pm 5 ( Tail B ) , and UT 2019 February 10 \pm 7 ( Tail C ) , with durations of \Delta T \sim 10 to 20 days . With a mean particle radius \overline { a } \sim 200 \mu m , the estimated masses of the tails are M _ { A } \sim 4 \times 10 ^ { 7 } kg , M _ { B } \sim 6 \times 10 ^ { 6 } kg and M _ { C } \sim 6 \times 10 ^ { 5 } kg , respectively , and the mass loss rates from the nucleus are 20 to 40 kg s ^ { -1 } for Tail A , 4 to 6 kg s ^ { -1 } for Tail B and \sim 0.4 kg s ^ { -1 } for Tail C. In its optical colors Gault is more similar to C-type asteroids than to S-types , even though the latter are numerically dominant in the inner asteroid belt . A spectroscopic upper limit to the production of gas is set at 1 kg s ^ { -1 } . Discrete emission in three protracted episodes effectively rules out an impact origin for the observed activity . Sublimation driven activity is unlikely given the inner belt orbit and the absence of detectable gas . In any case , sublimation would not easily account for the observed multiple ejections . The closest similarity is between Gault and active asteroid 311P/ ( 2013 P5 ) , an object showing repeated but aperiodic ejections of dust over a 9 month period . While Gault is 10 times larger than 311P/ ( 2013 P5 ) , and the relevant timescale for spin-up by radiation torques is \sim 100 times longer , its properties are likewise most consistent with episodic emission from a body rotating near breakup .