ISBN: | 978-5-5121-5950-7 |
High Quality Content by WIKIPEDIA articles! The Moon completes its orbit around the Earth in approximately 27.3 days (a sidereal month). The Earth and Moon orbit about their barycentre (common centre of mass), which lies about 4700 km from Earth`s centre (about three quarters of the Earth`s radius). On average, the Moon is at a distance of about 385000 km from the centre of the Earth, which corresponds to about 60 Earth radii. With a mean orbital velocity of 1.023 km/s, the Moon moves relative to the stars each hour by an amount roughly equal to its angular diameter, or by about 0.5°. The Moon differs from most satellites of other planets in that its orbit is close to the plane of the ecliptic, and not to the Earth`s equatorial plane. The lunar orbit plane is inclined to the ecliptic by about 5.1°, whereas the Moon`s spin axis is inclined by only 1.5°.