In a paper published on Earth Moon and Planets vol66 pp 2312

In a paper published on Earth, Moon, and Planets (vol.66, pp. 231-238, 1994), the author Mark R. Kidger states that the frequency of appearance of bright naked eye comets (magnitude 3.5) between 1750 and 1994 was one bright naked eye comet per 2.5 years.

(a) How large is the probability to observe no bright comets in a single year?

(b) How large is the probability to observe at least one bright comet in a decade (10 years)?

(c) How large is the probability to observe two comets in two consecutive years (as it happened in 1996 and 1997 with comet Hyakutake and comet Hale- Bopp)?

(d) What is the return period (recurrence interval) of the event described in the last point?

Solution