Cosmos/Moon/Orbit/en

Moon Orbit

The Moon's path

According to NASA, the Moon orbits Earth in the prograde direction and completes one revolution relative to the Vernal Equinox and the stars in about 27.32 days (a tropical month and sidereal month) and one revolution relative to the Sun in about 29.53 days (a synodic month). Earth and the Moon orbit about their barycentre (common centre of mass), which lies about 4,670 km (2,900 mi) from Earth's centre (about 73% of its radius), forming a satellite system called the Earth–Moon system.

Tidal locked

Tidal locked: NASA's explanation of why the side of the moon we see never changes

The reason why the moon doesn't appear to rotate (Assuming NASA's statement that the moon is an orbiting body), the Moon is "Tidally locked", which is where a moon possesses a "synchronous rotation", and takes just as long to rotate around its own axis as it does to revolve around its the earth. Hence the same side of the Moon always faces the Earth, although there is some variability because the Moon's orbit is not perfectly circular.

Lunar Analemma

When making lunar analemma, we have to take pictures with a delay of 50 minutes and 29 seconds for each day for a lunar month. Because for the moon it takes 24 hours 50 minutes and 29 seconds to reach the same position after each day. This means that if we start today at 9:00 pm we should take the photograph of tomorrow at 9:50:29 pm. Also with the moon, we would capture both, it’s the position in the sky and its phases. Astronomer Gyorgy Soponyai captured the above image from March 26 to April 18.