Waxing Crescent Moon reaches 27% illumination on May 21

On Thursday, May 21, the Moon is in a waxing crescent phase, with about 27% of its surface illuminated, according to NASA's Daily Moon Guide. At night observers can see the Mare Crisium and Mare Fecunditatis, and binoculars or a telescope will reveal the Endymion crater.

The Moon completes an orbit of Earth roughly every 29.5 days, moving through eight distinct phases: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The next full moon will occur on May 31, making May a month with two full moons.

These details follow the standard lunar cycle, where the same side of the Moon always faces Earth while sunlight creates the changing appearance.