Dynamical study of Geminid formation assuming a rotational instability scenario

Abstract

Context. Various ideas have been proposed to explain the formation of the Geminid meteoroid stream from the asteroid (3200) Phaethon. However, little has been studied regarding whether the Geminid formation could be the result of mass ejection via rotational instability of this asteroid. Aims. In this work, we present the first dynamical study of the Geminid formation taking into account low-velocity mass ejection caused by Phaethon’s rotational instability. Methods. We conducted numerical simulations for 1-mm and 1-cm particles ejected in a wide range of ejection epochs (103–105 yr ago). We computed the minimum orbital intersecting distance (MOID) of the dust particles as the realistic condition, that is, the Earth’s radius and the Earth–Moon distance to be observed as the Geminid meteoroid stream. Results. We found that the low-velocity ejection model produced the Geminid-like meteoroid stream when the dust particles were ejected more than ~2000 yr ago. In this case, close encounters with terrestrial planets would transport some dust particles from the Phaethon orbit (the current MOID is as large as ~460 Earth radii) to the Earth-intersecting orbits. The optimal ejection epoch and the estimated mass were 18 000 yr ago and ~1010–1014 g (<0.1% of the Phaethon mass). Conclusions. Our results suggest that the JAXA DESTINY+ mission has the potential to find evidence of recent rotational instability recorded on the surface of Phaethon.