partial solar eclipse

Partial solar eclipse of 11 May 2040

At greatest eclipse the Moon's disc spans 0.5034° against the Sun's 0.5281° — a ratio of 0.9533. Because the Moon appears smaller, it cannot cover the Sun, and a ring of sunlight is left around it. That is what makes this eclipse annular rather than total.

Why eclipses come in seasons

The Moon's orbit is tilted about 5° to the ecliptic, so at most new and full moons it passes above or below the alignment. An eclipse needs the syzygy to coincide with the Moon being near one of the two nodes where the orbits cross. At this eclipse the Moon's ecliptic latitude was -1.149° — close enough to zero for the shadow to connect.

Times computed from VSOP87 and an ELP-derived lunar theory, validated against NOVAS and JPL Horizons to within one arcminute. See the alignment for yourself in the live simulation.