* Work of reference " correlation between visual magnitudes and outgassing rate of CO in comets beyond 3 AU" ,Author : N.Biver , 1.999) The next law properly conforms to the equation of the graph and only for the comet 29p , for anothers comets this next equation is correct log Q (CO) = 30.0-0.29*mred .* The speed of ejection of CO gas escaping the nucleus is 450-500 m s-1 ( e.g. Gunnarsson et al. 2002 ) ,Carbon monoxide gas has been detected in the coma of SW-1 and is thought to be the primary driver gas ( Senay & Jewitt 1994 , Festou et al. 2001 ) , Gunnarsson et al. 2002 ) . The nucleus of SW-1 has been estimated to be 15-40 km in diameter ( e.g. based on analysis of its 20 um thermal emission and photometry visible .