annularity

Annularity is the phase of an annular solar eclipse during which the Moon covers a smaller portion of the Sun than its apparent size, so the Sun remains visible as a bright ring around the Moon. This occurs when the Moon is near apogee in its elliptical orbit, making its apparent diameter smaller than the Sun’s as viewed from Earth. The effect is most pronounced when the Sun is near perihelion, increasing its apparent size and the contrast of the ring.

During annularity, the Moon’s umbra does not reach Earth; observers lie within the antumbra and see the Sun as an annulus around the Moon. The duration of annularity at a given location ranges from a few seconds to several minutes, depending on the exact distances and relative motion of the bodies. The annular phase is preceded and followed by partial phases as the alignment shifts.

Observing notes: viewing the Sun during any solar eclipse requires proper eye protection. The ring is often visually striking and can vary in appearance due to the Moon’s limb topography, introducing slight irregularities in the ring. Unlike a total solar eclipse, the corona is not visible during annularity, since the Sun’s disk remains at least partially uncovered.

Occurrences and context: annular eclipses occur when the alignment among the Sun, Moon, and Earth is right and the Moon is sufficiently far from Earth. They travel along a narrow path on Earth’s surface, typically spanning thousands of kilometers, with the ring visible only within that path.