An annular solar eclipse occurred at the Moon's ascending node of orbit on October 22, 2137 BC, with a magnitude of 0.9736. A solar eclipse occurs when the Moon passes between the Earth and Sun, completely or partially blocking the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than that of the Sun, blocking most of the Sun's light and causing it to appear as an annulus (ring). An annular eclipse also appears as a partial eclipse over a region thousands of kilometers wide.