The final supermoon of 2019 will appear in the sky Wednesday night, aligning with the vernal equinox marking the end of winter.
Wednesday’s moon is the third supermoon of the year, following a super blood wolf moon on Jan. 21 and a super snow moon on Feb 19. A supermoon, also known by astronomers as a perigean full moon, occurs when a full moon reaches its closest point to the Earth in its elliptical orbit, making it appear unusually bright and large.
According to NASA, the moon already reached its closest point to earth—223,300 miles from the earth, or about 16,700 miles closer than usual—at about 3:45 p.m. on Tuesday, but it won’t be completely full until Wednesday at 9:43 p.m. EDT. The vernal equinox will have occurred roughly four hours earlier. The moon will appear largest and brightest to a viewer right after sunset, as it begins to rise. Those thwarted by cloudy skies can watch the supermoon via a livestream from the Virtual Telescope Project.
According to Earthsky.org, a full moon has not aligned with the spring equinox since 2000, and it will not come within a day of the equinox again until 2030. Twice a year, on the equinoxes, the northern and southern hemispheres receive equal amounts of sunlight, and night and day are about equal in length. The March equinox marks the first official day of spring in the Northern Hemisphere and the end of summer in the Southern Hemisphere.
According to folklore tradition, the March full moon is known as the worm moon because it coincides with the period when the earth thaws and earthworms begin to emerge. Native Americans dubbed the February full moon the snow moon and the January moon the wolf moon supposedly because of the howling from wolves unable to find food in the dead of winter.