I know when supernovae explode they emit huge amounts of energy and these sort of energy bursts can be harmful to planet Earth because they can strip the ozone. Was the energy burst from Sn 1054 arrive at Earth in 1054 (when the light from the object did) or will it arrive when the Crab Nebula expands to the point where it becomes dangerously close to Earth? Also, will the Crab Nebular begin to retract sooner or later (it's currently expanding), if so when. Is this object any danger to those of us on Earth ever?
Any really harmful radiation in the form of gamma rays arrived at the same time as the light did. Any secondary radiation in the form of particles arriving at this point in time would have a maximum speed of 87% of the speed of light and would be really tame compared to the normal cosmic radiation background. The expansion of the nebula itself poses no threat as for one, it is just dust and gas, and two. by the time it expanded enough to reach Earth it would be so thin you wouldn't be able to tell it from the normal vacuum of space. SN1054 was 6500 ly from us. In order for a supernova to be a threat it needs to at most about 100 ly distant, and since raditation levels would fall off by the square of distance, radiation reaching us from SN1054 would be some 4225 times weaker than that.
