What's a lunar eclipse and how many different kinds are there?
Different kinds of lunar eclipses
- Penumbral eclipse - This type of eclipse happens when the Moon passes through only the outer area of the Earth's shadow. This area is called the penumbra.
There is a special kind of penumbral eclipse called a total penumbral eclipse. During a tatal penumbral eclipse the Moon is totally in the Earth's penumbra, but not the umbra. During an eclipse of this kind, the areas of the Moon that are close to the umbra are darker than the rest of the Moon. These types of eclipses are very rare.
- Total lunar eclipse - This type of eclipse happens when the Moon passes totally into the umbra of the Earth. The umbra is the darkest part of the Earth's shadow. The Moon travels at about 1 kilometer per second through the umbra so an eclipse of this type could last nearly 107 minutes.
The Earth's atmosphere causes the Sun's light to be refracted into the Earth's shadow, so the Moon may not completely disappear as it travels through the umbra. The refracted light varies based on the amount of dust and clouds in the atmosphere blocking the light. The refracted light from the Sun causes the Moon to turn a copper red color that varies in intensity from one eclipse to the next.
How often do they occur?There are at least 2 eclipses of the Moon every year. They happen in cycles, so if you know what day and time one will occur you can predict future eclipses.
Unlike a solar eclipse, the lunar kind can be seen anywhere on the dark side of the Earth.