Lunar Eclipse – What is a Lunar Eclipse


What is a lunar eclipse? A lunar eclipse occurs when the Moon lines up precisely behind the Earth so that the Earth blocks the Sun’s rays and the Earths shadow falls upon the Moon. This relatively rare occurrence only happens when the Moon, Earth and Sun are exactly or very closely aligned, with the Earth in the middle. The shadow cast can partially or totally cover the Moon, creating partial eclipses and total eclipses for our viewing pleasure. The type and length of a lunar eclipse depends upon the Moon’s location relative to its orbital nodes. A lunar eclipse lasts for a few hours and can be viewed from anyone on the night side of the Earth. Because lunar eclipses are no brighter than the full moon itself, they are safe to observe without any eye protection or special precautions.

You may notice that the moon looks spectacularly bright just before and after the eclipse. The Moon’s surface is rather reflective, and close to the time of a lunar eclipse you are seeing the most direct reflection possible from the Moon’s surface. If it is a very clear night, you will get a beautiful view of the moon. You will see various phases of illumination similar to those observed over the course of a lunar cycle.

Lunar Eclipse vs. Solar Eclipse

Unlike a solar eclipse, which can only be viewed from a certain relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of the Earth. A lunar eclipse lasts for a few hours, whereas a total solar eclipse lasts for only a few minutes at any given place, due to the smaller size of the moon’s shadow. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are no brighter (indeed dimmer) than the full moon itself.

Lunar Eclipse Types

Lunar Eclipse

Lunar Eclipse

The shadow of the Earth can be divided into two distinctive parts: the umbra and penumbra. Within the umbra, there is no direct solar radiation. However, as a result of the Sun’s large angular size, solar illumination is only partially blocked in the outer portion of the Earth’s shadow, which is given the name penumbra. A penumbral eclipse occurs when the Moon passes through the Earth’s penumbra. The penumbra causes a subtle darkening of the Moon’s surface. A special type of penumbral eclipse is a total penumbral eclipse, during which the Moon lies exclusively within the Earth’s penumbra. Total penumbral eclipses are rare, and when these occur, that portion of the Moon which is closest to the umbra can appear somewhat darker than the rest of the Moon.

A partial lunar eclipse occurs when only a portion of the Moon enters the umbra. When the Moon travels completely into the Earth’s umbra, one observes a total lunar eclipse. The Moon’s speed through the shadow is about one kilometer per second (2,300 mph), and totality may last up to nearly 107 minutes. Nevertheless, the total time between the Moon’s first and last contact with the shadow is much longer, and could last up to 4 hours. The relative distance of the Moon from the Earth at the time of an eclipse can affect the eclipse’s duration. In particular, when the Moon is near its apogee, the farthest point from the Earth in its orbit, its orbital speed is the slowest. The diameter of the umbra does not decrease appreciably within the changes in the orbital distance of the moon. Thus, a totally eclipsed Moon occurring near apogee will lengthen the duration of totality.

When is the next Lunar Eclipse?

The lunar eclipse calendar is a listing of all lunar eclipses from 2016 through 2018. Times are expressed in Coordinated Universal Time (UT), the international basis for other time zones. The type and length of a lunar eclipse depends upon the Moon’s location relative to its orbital nodes. A lunar eclipse lasts for a few hours and can be viewed from anyone on the night side of the Earth. For additional lunar eclipse dates, please see NASA’s lunar eclipse page.

ObjectTypeYearDate
Solar EclipseTotal2019July 2
Lunar EclipsePartial2019July 16-17
Solar EclipseAnnular2019December 26
Lunar EclipsePenumbral2020January 10-11
Lunar EclipsePenumbral2020June 5-6
Solar EclipseAnnular2020June 21
Lunar EclipsePenumbral2020July 4-5
Lunar EclipsePenumbral2020November 29-30
Solar EclipseTotal2020December 14
Lunar EclipseTotal2021Nay 26
Solar EclipseAnnular2021June 10
Lunar EclipsePartial2021November 18-19
Solar EclipseTotal2021December 4

Lunar Eclipse Cycle

Every year there are at least two lunar eclipses, although total lunar eclipses are significantly less common. If one knows the date and time of an eclipse, it is possible to predict the occurrence of other eclipses using an eclipse cycle like the saros.

Lunar Eclipse Mythology

Several cultures have myths related to the lunar eclipse. The Egyptians saw the eclipse as a sow swallowing the moon for a short time. Other cultures viewed the eclipse as the moon being swallowed by other animals, such as a jaguar in Mayan tradition, or a three legged toad in China. Some societies thought it was a demon swallowing the moon, and that they could chase it away by throwing stones and curses at it.

Popular Full Moon Calendars

Some popular full moon calendars, in addition to the 2016 Full Moon Calendar, include the following: Moon Calendar 2011, Moon Calendar 2012, Moon Calendar 2013, Moon Calendar 2014, Moon Calendar 2015, Moon Calendar 2016, Moon Calendar 2017, Moon Calendar 2018, Moon Calendar 2019, Moon Calendar 2020.

You can also check out our Full Moon Calendar, Lunar Calendar, Lunar Eclipse Calendar and Solar Eclipse Calendar!