The age of the Geminids: a constraint from the spin-up time-scale

Interpreting fireball flickering in terms of the rotational modulation of the ablation process, the time since ejection into space of three Geminid meteoroids is determined. By estimating the time required to spin-up a meteoroid through non-isotropic photon scattering interactions with the solar radiation field, we find meteoroid ages consistent with ejection times some 1000-4000 yr ago. There appears to be some indication that the stream formation process lasted for at least similar to1000 yr. We also estimate the rotational bursting conditions for the three Geminid meteoroids and find tensile strengths of some 3 x 10(5) Pa. We interpret our results as being supportive of the argument that the parent body to the Geminid stream, (3200) Phaethon, is an aged cometary nucleus.