Lunar Eclipses | Types & History

Megan Mathis, Artem Cheprasov
  • Author
    Megan Mathis

    Megan Smith is a high school science teacher who has taught Earth Science, Marine Biology, and other sciences for the past few years. Megan has a Bachelor of Science in Marine Biology from the University of New Haven, and a Master of Science in Biology Adolescent Education from the CUNY- College of Staten Island.

  • Instructor
    Artem Cheprasov

    Artem has a doctor of veterinary medicine degree.

Learn what a lunar eclipse is. Read the lunar eclipse definition. Study the types of lunar eclipse and when they occur. Explore the stages of a lunar eclipse. Updated: 01/19/2022

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What's a Lunar Eclipse?

If an observer peers at the moon, they may be lucky enough to catch a glimpse of something special. There are exclusive events that occur when the Earth, moon, and sun align in a straight line (Figure 1). These phenomena are collectively known as called eclipses. Eclipses are when an observer can see the light of one celestial object become obscured from another celestial object passing by. Obscuring is the concealing or darkening of an object.

There are 2 types of eclipses that can occur which are a solar eclipse and a lunar eclipse. During a solar eclipse, the moon passes in front of the sun temporarily blocking the light. During a lunar eclipse, the moon becomes darkened from it moving through Earth's shadow. The position of Earth is directly between the moon and the sun which results in the lunar eclipse (Figure 1). Lunar eclipses can only occur when the moon is in the full moon stage and are safe to observe with the human eye. On average, 3 lunar eclipses can be observed from Earth each year.

Figure 1: Alignment of the Earth, sun, and moon during a lunar eclipse.

Figure 1: Alignment of the Earth, sun, and moon during a lunar eclipse.

Seven Stages of Lunar Eclipse

When the moon darkens during a lunar eclipse, there are two parts to Earth's shadow that are involved. They are known as the umbra and penumbra. The umbra shadow is from the complete blockage of light creating a total darkest shadow on the moon. This often results in the moon having an orange or copper red appearance to it. The penumbra shadow is from partial blockage of light which creates a partial shadow on the moon. Both types of shadows are important as they are involved with the seven stages of lunar eclipses as the moon moves into and out of them (Figure 2).

The first stage occurs when the moon crosses into Earth's penumbra. Second, after crossing into the penumbra, the moon crosses into the umbra which begins a partial lunar eclipse. In stage three, the moon becomes completely wrapped up in the umbra shadow which starts the total eclipse. The moon continues to move through the umbra until it reaches the middle of the eclipse in stage four. This is when the center of the moon and the center of Earth are lineups meaning the moon is fully obscured. Totality occurs in this stage where the moon is fully inside Earth's shadow. It can last for almost two hours.

Stage five occurs when the total lunar eclipse ends. During this stage, the moon moves back out into the umbra. In stage six, the moon leaves the umbra completely which signifies the end of a partial lunar eclipse. In stage seven, the moon leaves the penumbra signifying the end of the eclipse (Figure 2).

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Figure 2: Diagram of the moon moving into and out of Earths shadows over time.

Figure 2: Diagram of the moon moving into and out of Earths shadows over time.

Types of Lunar Eclipse

There are different types of eclipses that can occur as it all depends on the angle of when the moon crosses into Earth's shadows: penumbral lunar eclipse, a partial lunar eclipse, a total lunar eclipse, and a central lunar eclipse. Each type deserves a spotlight.

Penumbral Lunar Eclipse

Penumbral lunar eclipses occur when the moon travels only through the penumbral shadow. This casts only a partial shadow on a portion of the moon, giving only a slightly faded appearance. Penumbral lunar eclipses are difficult to see as they occur ever so slightly. This is different from umbras which are shadows created by total blockage of light.

Partial Lunar Eclipse

Partial lunar eclipses are easier to observe with the human eye. Partial lunar eclipses are when part of the moon moves through Earth's umbra. This is different from the penumbral as a portion of the moon becomes covered in Earth's shadow (Figure 3). This event occurs when the moon is full.

Figure 3: Partial lunar eclipse observed from Earth.

Figure 3: Partial lunar eclipse.

Total Lunar Eclipse

Total lunar eclipses can also be viewed with the human eye and are often advertised in the news in advance. During total lunar eclipses, the moon is in between the sun and Earth which stops the sun from lighting up the moon. During total lunar eclipses, the moon is complete in Earth's umbra. All of these aspects result in an appearance that can be surprising to the viewer.

During total lunar eclipses, the moon is sometimes called a blood moon from the coppery red appearance to it. It can also appear to be a hue of browns and other warm colors from the sun's rays not refracting on the moon (Figure 4).

Figure 4: Orange or red copper moon observed during total lunar eclipses from Earth.

Figure 4: Orange or red copper moon observed during total lunar eclipses from Earth.

Central Lunar Eclipse

Another special type of eclipse that can occur during full moons are known as the central lunar eclipse. Central lunar eclipses occur when the center of the moon crosses over the center of the umbra shadow. Central lunar eclipses are rare as they are the longest possible pathway the moon can take crossing into and out of Earth's shadows.

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Frequently Asked Questions

What are the 4 types of lunar eclipses?

The 4 types of lunar eclipses are the total lunar eclipse, the partial lunar eclipse, the penumbral lunar eclipse, and the central lunar eclipse. The total and partial lunar eclipse can be viewed with the human eye as the penumbral and central are more rare or difficult to observe.

How often does a lunar eclipse occur?

The average of lunar eclipses that occurs in a year is 3. This includes total, partial, and penumbral lunar eclipses.

What is a simple description of a lunar eclipse?

A lunar eclipse is when a full moon becomes darkened from it moving through Earth's shadow. The position of Earth is directly between the moon and the sun which results in the lunar eclipse.

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