Lunar Eclipses: What They Are and When To See Them

~4 min
Lunar Eclipses: What They Are and When To See Them

A lunar eclipse is one of the most breathtaking astronomical events — our natural satellite gets engulfed by the Earth’s shadow and changes its color to red. Learn what types of lunar eclipses there are, why they occur, and when the next lunar eclipse happens.

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What is a lunar eclipse?

A lunar eclipse occurs when the Earth fully or partially blocks the Sun’s light from reaching the Moon. This can only happen during the Full Moon phase. If the Earth, the Moon, and the Sun form a straight line, a total lunar eclipse occurs. If their alignment is not exact enough, observers will see a partial or penumbral lunar eclipse — or no eclipse at all.

Watch our short explanatory video to better understand how lunar eclipses work.

Types of lunar eclipses

There are three types of lunar eclipses: total, partial, and penumbral.

A total lunar eclipse is the most spectacular of the three types. It happens when the Sun, the Earth, and the Moon are precisely aligned in space. The Earth comes between the Moon and the Sun and covers the entire Moon with the inner part of its shadow, called the umbra. Interestingly, our natural satellite doesn’t completely disappear during a total eclipse but turns dark red. Why does it happen?

Although the Earth blocks all direct sunlight, a small portion of the light gets refracted by the Earth’s atmosphere and reaches the Moon’s surface. Our planet’s atmosphere scatters the blue-colored light but lets the red-colored light through. That’s why the lunar disk becomes red. Because of the distinctive reddish hue, a total lunar eclipse is often called a Blood Moon.

A partial lunar eclipse occurs when only a part of the Moon gets covered by the Earth’s umbral shadow. This happens when the Sun, the Earth, and the Moon are not perfectly aligned. During this type of eclipse, only a portion of the Moon gets dark and reddish.

A penumbral lunar eclipse occurs when the Moon passes through the penumbra — the outer part of the Earth’s shadow. It’s the least noticeable type of eclipse: for a keen-eyed observer, the Moon will look only slightly darker than usual.

Lunar eclipse vs. solar eclipse

What’s the difference between a lunar eclipse and a solar eclipse? Both events involve three celestial bodies: the Sun, the Earth, and the Moon. During a lunar eclipse, which happens at night, the Moon gets covered by the Earth’s shadow. During a solar eclipse, which happens in the daytime, the Sun gets covered by the Moon’s disk. Lunar eclipses occur only at a Full Moon, and solar eclipses — only at a New Moon.

A lunar eclipse can be observed from wherever the Moon is above the horizon — anywhere on the night side of the Earth. This is due to the fact that the Earth’s shadow is very large compared to the Moon. A solar eclipse is much more challenging to see, as the Moon’s shadow is much smaller than the Earth’s. Therefore, solar eclipses are visible only from specific locations where the Moon’s shadow falls.

Interesting fact: eclipses always come in pairs. A solar eclipse occurs approximately two weeks before or after a lunar eclipse.

If you tend to confuse solar and lunar eclipses, remember this: when the Sun gets dark, we call it a solar eclipse, and when the Moon gets dark, we call it a lunar eclipse.

When is the next lunar eclipse?

The next lunar eclipse will occur on May 16, 2022 — it will be a total lunar eclipse. The eclipse will be visible from North and South America, Europe, Africa, and parts of Asia. The totality phase will begin at 03:29 GMT (on May 15 at 11:29 p.m. EDT) and reach its maximum at 04:11 GMT (on May 16 at 12:11 a.m. EDT). You can learn more about this eclipse from our article.

If you want to learn about all lunar eclipses that will occur in the upcoming decade, use the eclipse calendar made by NASA. You can also check our infographic, where we list five future eclipses with their timelines and visibility maps.

List of 5 upcoming lunar and solar eclipses, their dates, timelines, and visibility maps. Find out whether you can see them from your location!
See Infographic

How often do lunar eclipses happen?

As we’ve already mentioned, a lunar eclipse always happens at a Full Moon. However, not every Full Moon comes with a lunar eclipse. Here’s why: the Moon’s orbit is tilted at about five degrees to the Earth’s orbit, so our natural satellite usually passes above or below the Earth’s shadow at a Full Moon. On average, two lunar eclipses occur every year. The maximum number of lunar eclipses in a year is five, though it happens quite rarely. The last time five lunar eclipses occurred in one calendar year was in 1879; the next time it will happen in 2132.

How to watch a lunar eclipse?

You don’t need any special equipment to observe a lunar eclipse — though you can use binoculars to see more details on the red-shaded lunar surface. All you need to enjoy this astronomical event is a clear sky and an unobstructed horizon. To learn when the eclipse begins in your location, use the Eclipse Guide app.

F.A.Q.

How rare is a total lunar eclipse?

Total lunar eclipses account for about 29% of all lunar eclipses. On average, a total lunar eclipse occurs every 2.5 years in any given location.

Why is the Moon red during a lunar eclipse?

The eclipsed Moon looks red because sunlight gets refracted and scattered by the Earth’s atmosphere, with only red-colored light reaching the lunar surface.

Is a lunar eclipse safe to look at?

Unlike watching a solar eclipse (for which you need special solar filters), observing a lunar eclipse is absolutely safe for your eyes. That’s because the Moon doesn’t emit its own light but only reflects sunlight.

How do lunar eclipses affect humans?

You might hear that lunar eclipses can increase the risk of skin disease, badly affect pregnant women, or be harmful to digestion. However, there is no scientific evidence that lunar eclipses have any physical effect on people.

We hope you’ve learned something new about lunar eclipses from our article. Don’t hesitate to share it with your friends if you like it. You can also test your knowledge about solar and lunar eclipses with our challenging quiz. We wish you clear skies and happy stargazing!

Complete the following quiz and see how much you really know about solar and lunar eclipses. By the end of it, you should gain a better understanding of these astronomical phenomena and learn some interesting historical facts that you probably didn't know. Decide whether the following statements are true or false.
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