What is a lunar eclipse? Three types of lunar eclipses.

The position of the sun, earth and moon during a lunar eclipse
There are three basic types of lunar eclipses

While the shadow of the moon falls on the earth in a solar eclipse, the reverse is true in a lunar eclipse. The shadow of the earth moves over the moon. Since the earth is larger than the moon, lunar eclipses are quite different from solar eclipses.

A lunar eclipse happens once every 29 and a half days, and the moon can be seen with the naked eye during a total lunar eclipse.

When the moon crosses earth’s orbit, earth casts its shadow and a lunar eclipse takes place. This is the case about twice a year. Since the orbit of the moon is inclined by 5.1 degrees compared to Earth’s Earth’s ecliptic plane, the moon can pass in orbit by up to 37,000 kilometers above or below the Earth’s shadow. Therefore, a lunar eclipse does not occur with every orbit.

Types of lunar eclipses

Seen from the moon, it would look as if the edge of the earth is glowing reddish. Since blue light is more scattered in earth’s atmosphere, red light in particular reaches the moon. Similar to the light effect at sunset. Seen from Earth, the moon shines in a dark copper red. In contrast to a solar eclipse, a lunar eclipse can be observed from the entire side of our planet facing the moon.

Overall, there are three types of lunar eclipses:

  1. Total eclipse
  2. Partial eclipse
  3. Penumbral eclipse

In the event of a partial lunar eclipse, the moon only partially enters Earth’s umbra (the fully shaded inner region of a shadow cast by an opaque object). The shadow edge cast by the earth is depicted on the surface of the moon and is visible as an arc. From this circular shape of the shadow, the ancient Greeks already concluded that the earth must be a sphere.

So-called penumbral eclipses are often barely noticeable. During these lunar eclipses, the moon only crosses the comparatively bright penumbra of the earth. The sun in such cases is only be partially covered by earth for an observer on the moon. So, a significant part of the sunlight still reaches the moon.

The part of the moon that is closest to the umbra appears noticeably darker when viewed from Earth. In addition, only part of the moon is usually in partial shade. Because the penumbra (partially shaded outer region of the shadow cast by an opaque object) lying in a ring around the umbra is only about as wide as the diameter of the moon.

On average, penumbral eclipses are about half as common as umbra eclipses. And about half of all umbra eclipses are total lunar eclipses.

2020 Lunar eclipses

Calendar DateEclipse TypeGeographic Region of Eclipse Visibility
2020 Jan 10PenumbralEurope, Africa, Asia, Aus.
2020 Jun 05PenumbralEurope, Africa, Asia, Aus.
2020 Jul 05PenumbralAmericas, sw Europe, Africa
2020 Nov 30PenumbralAsia, Aus., Pacific, Americas

source: NASA Eclipse website

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