The time taken by the Moon to complete one revolution around the Earth (with respect to the stars) is about:

The Moon takes about 27 days, 7 hours and 43 minutes (27.3 days) to complete one revolution around the Earth with respect to the distant stars. This period is called the sidereal month.

Sidereal month and synodic month:

• Sidereal month (about 27.3 days): the time the Moon takes to return to the same position relative to the stars.
• Synodic month (about 29.5 days): the time taken for the Moon to complete one full cycle of phases.

Why the synodic month is longer:

• While the Moon goes around the Earth, the Earth also moves along its orbit around the Sun.
• So the Moon has to travel a little more than one full orbit, about two more days, to return to the same position relative to the Sun and show the same phase again.

Rotation of the Moon:

• The Moon also rotates on its axis once in about 27.3 days, the same time it takes to revolve around the Earth.
• This is called synchronous rotation or tidal locking.

Because of this, the same side of the Moon always faces the Earth. The side we never see from Earth is called the far side.

Facts about the Moon:

• It is the Earth's only natural satellite and the fifth-largest moon in the solar system.
• Its average distance from the Earth is about 3,84,400 km.
• Its gravity is about one-sixth of the Earth's.

Indian missions to the Moon:

Chandrayaan-3's lander Vikram landed near the lunar south pole on 23 August 2023. India became the first country to land near the south pole and the fourth to soft-land on the Moon. 23 August is now celebrated as National Space Day.

Why not the other options?

• ✗24 hours is the length of an Earth day.
• ✗29.5 is the number of days (not hours) in a synodic month.
• ✗365 days is the time the Earth takes to revolve around the Sun.