The moon’s orbit around Earth is elliptical rather than circular, which means that sometimes the Moon appears slightly smaller in the sky than the Sun. If this happens during an eclipse, then a ring of brilliant sunlight remains visible, like a circle of fire around the Moon. This is called an annular eclipse (the word annular means “ring-shaped”).
Traditionally, eclipses are divided into two major types: solar and lunar. Solar eclipses occur when the Moon passes between Earth and the Sun, leaving a moving region of shadow on Earth’s surface. Lunar eclipses occur when Earth passes between the Sun and the Moon, casting a shadow on the Moon.
Solar eclipses may be classified as either total, in which the Moon completely covers the Sun, or annular, in which the Moon obscures all but an outer ring of the Sun. Whether an eclipse is total or annular depends on the distance between these three objects. Earth travels in an elliptical orbit around the Sun, and the Moon travels in an elliptical orbit around Earth, so the distance between these celestial bodies changes. When the Sun is nearest to Earth and the Moon is at or near its greatest distance, the Moon appears smaller than the Sun in the sky. When an eclipse of the Sun happens in this situation, the Moon will not appear large enough to cover the disk of the Sun completely, and a rim or ring of light will remain visible in the sky. This is an annular eclipse.
There are no annular lunar eclipses because Earth is much bigger than the Moon, and its shadow will never be small enough to leave a ring. However, the Moon does experience total eclipses. If the eclipse is a total lunar eclipse, the Moon will pass through the umbra (area of total shadow) created by Earth over the course of about two hours. Viewers will notice that the Moon does not typically go completely dark; it often takes on a red color, because the redder parts of sunlight that penetrate Earth’s atmosphere are refracted into the umbra, and this light reaches the Moon.
Picture Credit : Google
