Dimethylmercury ((CH3)2Hg) is an organomercury compound. This colorless liquid is one of the strongest known neurotoxins. It is described as having a slightly sweet smell, although inhaling enough vapor to detect its odor would be hazardous.
The formation of a star begins with gravitational instability within a molecular cloud, caused by regions of higher density-often triggered by shock-waves from nearby supernovae (massive stellar explosions), the collision of different molecular clouds, or the collision of galaxies (as in a starburst galaxy).
Figure 3: Interacting galaxies. Clockwise from top left: Arp 295, NGC 4676, Arp 299, NGC 7252, NGC 3921. (John Hibbard, NRAO). To understand the development of tidal tails, recall that tidal forces -- the differential gravitational forces from a nearby mass -- act to stretch an object radially. In this manner, our own Moon raises bulges on the surface of the Earth which give rise to our oceanic tides.