What Are the Three Types of Solar Eclipses?
Not all solar eclipses are created equal. How much of the Sun is covered by the moon determines if you can see a partial, annular, or total eclipse.
There are three types of solar eclipses - partial, annular, and total. Not all solar eclipses are created equal. How much of the Sun is covered by the moon determines if you can see a partial, annular, or total eclipse. A solar eclipse occurs when the moon passes between the Sun and Earth, completely or partially blocking our view of the Sun and casting a shadow on Earth. A solar eclipse can only occur during the day, if you have seen an eclipse at night then you have seen a lunar eclipse.
A partial eclipse occurs when the moon only covers part of the Sun. During a partial solar eclipse, the darkest shadow of the moon, the umbra, misses Earth. Only a partial shadow, the penumbra, lands on Earth.
Quick facts about partial solar eclipses:
- Partial solar eclipses occur, on average, two times per year.
- All solar eclipses begin and end with a period of partial eclipse.
- You must always wear eye protection during any partial phases of a solar eclipse.
An annular eclipse occurs when the moon doesn’t completely cover the Sun, leaving a “ring of fire” around the moon. During an annular eclipse, the Sun, moon, and Earth are perfectly aligned, but the moon is at its farthest point away from Earth. (The moon has an elliptical orbit, which varies its distance from Earth by 30,000 miles.) This larger distance prevents the moon from entirely blocking out our view of the Sun. Instead, we still see a ring of light around the edge of the moon. This is why annular eclipses are often called “ring of fire” eclipses. Annular eclipses are intriguing, but don't offer the same overwhelming spectacle as total solar eclipses: sunlight dims, but the sky does not go dark; the Sun’s outer atmosphere (solar corona) does not become visible; and you must wear your eclipse glasses throughout the entire event.
Quick facts about annular solar eclipses:
- The maximum phase of an annular eclipse is called annularity, and the area on Earth where you can see it is called the path of annularity.
- The path of annularity is small, averaging only 93 miles wide.
- An annular eclipse occurs every one to two years.
- Annularity can last anywhere from a few seconds to over 12 minutes.
Total Solar Eclipse
A total solar eclipse is when the moon completely blocks our view of the Sun, revealing the Sun’s outer atmosphere—the corona. A total solar eclipse occurs when the moon is precisely positioned between the Sun and Earth, causing the shadow of the moon to fall on Earth. If you are standing in the middle of this shadow (the umbra), then the view of the Sun will be completely blocked by the moon, allowing you to see the outer atmosphere of the Sun (the corona). If you’re anywhere within the significantly larger partial shadow (the penumbra), you will see a partial eclipse.
Quick facts about total solar eclipses:
- They occur on average, every 18 months. From the same place on Earth, you could see one about every 300 to 400 years.
- The period of time when the Sun is completely obscured by the moon is called totality. It can last anywhere from a few seconds to over seven minutes. During this phase, you can safely remove your eclipse glasses and look at the Sun’s corona, which is only as bright as the full moon!
- The area where the umbra hits Earth is called the path of totality. It is only about 100 miles wide and 10,000 miles long. You must be within this path to see the eclipse.
- The shadow from the moon travels across Earth at over 1,000 miles per hour during the eclipse.
- If you were standing on the moon (or orbiting Earth on a space station), you could see a dark shadow passing over Earth.
This image was taken from the International Space Station during the 2017 eclipse. It shows the shadow of the moon on Earth. (NASA/ISS)
What’s a hybrid eclipse?
Once in a while, an eclipse will be total along parts of its path and annular or partial along other parts. But the plane of the moon's orbit around Earth is tilted by about five degrees with respect to the Earth's orbit around the Sun. This causes the moon's shadow to often pass above or below the Earth. This is the least frequent type of solar eclipse.
Why isn’t there an eclipse every month?
The moon orbits Earth every month, so common sense would tell us that there should be an eclipse every month. But the moon’s orbit around Earth is not in a flat plane; it’s angled at about five degrees, so the moon’s shadow often goes above or below Earth. Check out this video to learn more.
How can the tiny moon block our view of the giant Sun?
When the moon passes in front of the Sun during a total solar eclipse, it exactly covers the Sun’s disk, while letting the corona shine out around it in a spectacular display. The two bodies aren’t really the same size, of course: the Sun is 400 times the diameter of the moon. But it’s also 400 times farther away from us, and this relationship between size and distance makes the Sun and the moon appear the same size. It’s a wonderful coincidence, and should not be taken for granted. Earth is the only planet in our solar system with a moon the proper size and distance to cause the striking solar eclipses we see.