Question

What is the orbital period of Halley's comet?
A) $66years$
B) $75years$
C) $86years$
D) $96years$

Answer 1

Hint:Recall that orbit is the path. Orbital period is the time taken by any astronomical object to complete one orbit around the other object. It depends on the mass of the body around which the orbit has to be completed and the distance from the centre.

Complete step by step answer:
Step I:
A comet is defined as a small body that is made up of dust particles, gas balls and ice. It rotates around the sun in a fixed orbit.
Halley’s comet is named after an astronomer Edmond Halley. He observed that a comet is approaching Earth in three different years. Then it was concluded that three different comets were actually the same, but it was approaching Earth in three different years.

Step II:
 It is the most famous comet ever. It is a periodic comet and repeats its rotation around the Earth after every $75years$. It is quite possible for human beings to see this comet twice in its lifetime. It was last seen in the year $1986$ and is expected to return in $2061$.
Therefore the orbital period of Halley’s comet is $75years$.

$\therefore$ Option B is the correct answer.

Note:It is to be remembered that the word comet has been taken from the Greek word ‘kometes’. It means that the body is long haired. It is made up of four parts. These are- nucleus, coma, ion tail and the dust tail. All the parts of the comet are visible and can appear from any direction in the sky.