Thursday 25 May 2017

Closest Lunar Perigee of 2017.

At 1.24 am GMT on Friday 26 May 2017 the Moon will be at its closest point to the Earth in 2017, at a distance of 357 209 km. his will fall five hours and forty minutes after the New Moon, at 7.644 pm on Thursday 25 May, making it effectively invisible. The Moon completes one orbit about the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. These cycles mean that the Moon reached its furthest point from the Earth (apogee) of the year in the same lunar cycle, 406 401 km at 7.52 pm GMT on Thursday 8 June, which will be the second most distant Lunar Apogee of 2017.

 Simplified diagram of the Moon's orbit. NASA.

Although this is the closest point to the Earth that the Moon has reached this year, it is not exceptional. The Moon reached 356 511 km from the Earth on 14 November 2016, and will reach 357 122 km from the Earth on 10 March 2020.

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