Free Astronomy Magazine May-June 2015

T his spectacular sequence of images shows the activity of 67P/Chu- ryumov-Gerasimen- ko viewed from different angles, in a period between 31 January and 25 March 2015 (left to right and top to and subsurface properties. But none of all that was detected, because the changes in the intensity of the magnetic field mea- sured by Philae in its brief period of activity were equally and simultaneously recorded also by the magnetometer aboard Rosetta which at that stage of the mission was trav- elling at 17 km from the surface. This leads to the conclusion that the source of the mag- netism found is not the cometary nucleus, but the Sun, which through its wind pushes that force as far as the comet. This does not, though, mean that 67P/Churyumov- Gerasimenko is totally free of magnetized material, but if there is any it is gathered in rocky structures less than 1 metre across, corresponding to the spatial resolution rea- ched by ROMAP during its measurements. It follows that if that comet is representa- tive of the entire class (and there is no rea-