Moon pesters the Pleiades – Astronomy Now

Some of the most spectacular observing events tale place when the Moon’s around, most gloriously when it lines us perfectly over the Sun, producing a total eclipse of the Sun. Unfortunately, a repeat the total eclipse of 11 August 1999 is not on the table, but we can watch as the Moon buzzes the wonderful Pleiades open cluster (Messier 45) 25 years on, on 26 August 2024. 

The Moon will fairly often approach and, more occasionally, occult bright deep sky objects which lie within around 5° north or south of the ecliptic, the apparent path of the Sun around the sky to which the planets and the Moon stick close. The Moon’s orbit is tilted by some 5° in respect to the plane of Earth’s orbit around the Sun, so our satellite can stray farther. The Pleiades, certainly, and the Beehive Cluster (M44 in Cancer) are likely the premium deep sky objects that can get in the Moon’s way.

On the night of 25/26 August, a last-quarter Moon and the Pleiades rise in the eastern sky at about 10pm BST, with their separation around 3° among the stars of Taurus. The Moon is closing fast though, so that by 1am, when the pair clear the horizon by over 20°, the distance between them is halved, with the Moon now 1.5° from Merope, one of the Seven Sisters. Watch through a pair of binoculars as the Moon slips the Pleiades southernmost extremities between 3am and 5am. 

Finally the Moon does more damage, when it moves in front of the magnitude +3.6 star Atlas (27 Tauri), the most easterly lying star of the Pleiades. Altas is occulted at the Moon’s bright limb at 4.52am BST, reappearing in strong twilight at about 5.30am. a telescope will give a great view of this event.