This at least accounts for the fact that a particular group of meteoroids shares with its parent comet more or less the same orbit , which can remain relatively unchanged over eons . an immediate consequence is that our earth makes periodic rendezvous with this meteoroid swarm , thereby culminating in a regular display of these celestial fireworks . to name a few , we have the lyrids in april and the geminids in december 流星雨的成因是地球遇上了一群密集的流星體,一般相信,流星群是由周期性彗星分解出來的物質(zhì)或由瓦解了的彗核所形成,所以流星群和其母體彗星有大致相同的軌道,由于流星群的軌道頗為固定,所以地球會(huì)周期性地穿越這些流星群,形成固定出現(xiàn)的流星雨,例如四月天琴座流星雨十二月雙子座流星雨等。