Anywhere from four to seven times a year, our Earth, Moon and Sun line up just right to create the cosmic-scale shadow show known as an eclipse. The Moon’s orbit around Earth is tilted relative to Earth’s orbit around the Sun. This tilt is the reason why we have occasional eclipses instead of eclipses every month.
There are two types of eclipses: lunar and solar. During a lunar eclipse, Earth’s shadow obscures the Moon. During a solar eclipse, the Moon blocks the Sun from view.
What is Lunar Eclipse?
Lunar eclipses occur at the full moon phase. When Earth is positioned precisely between the Moon and Sun, Earth’s shadow falls upon the surface of the Moon, dimming it and sometimes turning the lunar surface a striking red over the course of a few hours. Each lunar eclipse is visible from half of Earth.
What Causes a Lunar Eclipse?
An eclipse happens when one astronomical body blocks light from or to another. In a lunar eclipse, the Moon moves into the shadow of Earth cast by the Sun.
When the Moon passes through the outer part of Earth’s shadow the penumbra, where the light of the Sun is only partly extinguished the Moon dims only slightly in what is called a penumbral eclipse.
When the Moon passes through the central part of Earth’s shadow the umbra, where the direct light of the Sun is totally blocked the lunar eclipse is considered partial if the Moon is partly within the umbra or total if the Moon is completely within it.
Types of lunar eclipses?
#1. Total lunar eclipse.
The Moon moves into the inner part of Earth’s shadow, or the umbra. Some of the sunlight passing through Earth’s atmosphere reaches the Moon’s surface, lighting it dimly. Colors with shorter wavelengths the blues and violets scatter more easily than colors with longer wavelengths, like red and orange.
Because these longer wavelengths make it through Earth’s atmosphere, and the shorter wavelengths have scattered away, the Moon appears orangish or reddish during a lunar eclipse. The more dust or clouds in Earth’s atmosphere during the eclipse, the redder the Moon appears.
#2. Partial lunar eclipse.
An imperfect alignment of Sun, Earth and Moon results in the Moon passing through only part of Earth’s umbra. The shadow grows and then recedes without ever entirely covering the Moon.
#3. Penumbral eclipse.
If you don’t know this one is happening, you might miss it. The Moon travels through Earth’s penumbra, or the faint outer part of its shadow. The Moon dims so slightly that it can be difficult to notice.
Why Does The Moon Turn Red During An Eclipse?
During a total lunar eclipse, the lunar surface turns a rusty red color, earning the nickname “blood moon”. The eerie red appearance is caused by sunlight interacting with Earth’s atmosphere.
When sunlight reaches Earth, our atmosphere scatters and filters different wavelengths. Shorter wavelengths such as blue light are scattered outward, while longer wavelengths like red are bent or refracted into Earth’s umbra, according to the Natural History Museum.
When the moon passes through Earth’s umbra during a total lunar eclipse, the red light reflects off the lunar surface, giving the moon its blood-red appearance.
“How gold, orange, or red the moon appears during a total lunar eclipse depends on how much dust, water, and other particles are in Earth’s atmosphere” according to NASA scientists.
Other atmospheric factors such as temperature and humidity also affect the moon’s appearance during a lunar eclipse.
Upcoming Lunar Eclipses
We will not experience another total lunar eclipse until March 14, 2025. There will however be partial and penumbral lunar eclipses to keep us occupied in the meantime.
Upcoming lunar eclipses according to NASA:
| Year | Date | Type of eclipse | Visible locations |
| 2024 | Sept. 18 | Partial | Americas, Europe, Africa |
| 2025 | Mar. 13/14 | Total | Pacific, Americas, W. Europe, W. Africa |
| 2025 | Sept. 7 | Total | Europe, Africa, Asia, Australia |
| 2026 | Mar. 3 | Total | E. Asia, Australia, Pacific, Americas |
| 2026 | Aug. 28 | Partial | E. Pacific, Americas Europe, Africa |
How often does a lunar eclipse happen?
This depends on what type of lunar eclipse you are referring to. There are two shadows cast into space by the Earth. A faint outer shadow called the penumbra and a much darker central shadow called the umbra.
Penumbral lunar eclipses happen at least twice each year. However, in many cases, the penumbra is so faint that, more often than not, most people completely miss out on noticing it when it happens.
Umbral eclipses occur about every 2 or 3 years sometimes twice in a single year. Since the umbra is dark and well-defined people notice it when the moon moves either partially or completely within it.
How long do lunar eclipses last?
It depends on how deeply the moon penetrates into the Earth’s umbra and how far away the moon is from the Earth. When the moon is near its closest point to Earth (perigee) it is moving much faster in its orbit as compared to when it’s near its farthest point from Earth (apogee).
Generally speaking, in the case of a total eclipse, it can last about three hours: one hour for the moon to move completely into the umbra, one hour for the moon to be completely immersed in the umbra and one hour for the moon to move out of the umbra.
Totality can vary from just a few minutes to as long as 107 minutes. In the latter case, the moon moves directly through the center of the Earth’s shadow while moving at its slowest in its orbit (apogee).