Comet 73P/Schwassmannâ€-Wachmann 3 has been observed to fragment on several occasions , yet the cause of its fragmentation remains poorly understood .
We use previously unpublished archival Hubble Space Telescope data taken in 2006 to study the properties of the primary fragment , 73P-C , in order to constrain the potential fragmentation mechanisms .
Currently the literature presents a wide range of measured rotational periods , some of which suggest that the nucleus might have split due to rotational instability .
However , we find the most likely value of the rotation period to be 10.38 \pm 0.04 hours ( 20.76 \pm 0.08 hours if double-peaked ) , much longer than the critical period for rotational instability for any reasonable nucleus density and shape , even in the absence of tensile strength .
We also find strong , cyclic photometric variations of about 0.31 \pm 0.01 magnitudes in the central light from this object , while similar variations with a smaller range are apparent in the surrounding dust coma .
These observations are compatible with rotational modulation of the mass loss rate and with dust having a mean outflow speed of 107 \pm 9 m s ^ { -1 } .
Finally , we also estimate the radius of the nucleus to be 0.4 \pm 0.1 km accounting for dust contamination and assuming a geometric albedo of 0.04 .