noun
periodic comet
A comet with a known orbital period, such as Halley's Comet. Used in astronomy.
ハレー彗星は有名な周期彗星です。
Halley's Comet is a famous periodic comet.
彗星 is the general term for comet, while 周期彗星 specifically refers to a periodic comet.
Compound of 周期 (period, cycle) and 彗星 (comet).