Learn about the difference between a total solar eclipse, a partial solar eclipse, and an annular eclipse. Knowing the difference can help you plan for success and avoid disappointment.
Many folks have been disappointed in the past when the media told them to see an “amazing eclipse.” The main problem is the word “eclipse.” It can mean a variety of things. There are partial, total, lunar, annular, penumbral, and solar eclipses. See our Eclipse Calendar for the coming year.
Most English nouns don’t suffer such ambiguity. If someone says soul-mate, rainbow, waterfall, or wedding, a clear, positive meaning is communicated.
Case in point: According to a survey of experienced observers, a partial solar eclipse is barely 1% as spectacular as a total solar eclipse. Only a total solar eclipse has the magic. That’s because an avalanche of unique effects suddenly unfolds in totality. You will only see a partial solar eclipse if you’re not living right on the slim path of totality or planning to drive to the path.
What is a Total Solar Eclipse
A total solar eclipse—like the one that crossed the U.S. in August 2017—occurs when all three celestial objects—Earth, Moon, and Sun—are perfectly aligned. The Moon casts a shadow onto Earth, and the sky becomes very dark as if it were night. However, you can only see the totality from a very narrow path on Earth (about 100 miles wide). It’s only during the minutes of 100% totality that you see the Sun’s bright corona shine across the sky, pink prominences leaping, stars emerge from the inky black sky, and other phenomena.
If you don’t live in this path, you will see a partial solar eclipse …
What is a Partial Solar Eclipse
A partial eclipse occurs when the Moon only partially covers the disk of the Sun (as seen in the above sequence). The Earth, Moon, and Sun are not perfectly aligned. The Sun appears to have a dark shadow on only a small part of its surface. Partial solar eclipses are quite common. They occur every few years.
Frankly, you might not even notice if you didn’t know a partial eclipse was happening. While astronomically interesting, the partial eclipse can’t deliver that weird and rare total darkness that you experience in a total solar eclipse.
What is an Annular Solar Eclipse?
There is a third type of eclipse called an annular (ANN-you-ler) solar eclipse. This occurs when the Moon passes between the Sun and Earth but when the Moon is at or near its farthest point from Earth (apogee). Because the Moon is farther away, it appears smaller than the Sun and does not completely cover the Sun. As a result, the Moon appears as a dark disk on top of a larger, bright disk, creating what astronomers call a “ring of fire” around the Moon.
What is a Hybrid Solar Eclipse?
Some folks refer to a fourth type of solar eclipse called “hybrid.” It simply means that some folks will see a total eclipse, and others will see an annular eclipse based on where they live as the Moon moves across the curved globe. It’s extremely rare, so I won’t explore this one further.
What is an Umbra and Penumbra?
During a solar eclipse, the Moon casts two shadows on Earth. The first shadow is called the umbra (UM bruh). This shadow gets smaller as it reaches Earth. It is the dark center of the moon’s shadow. The second shadow is called the penumbra (pe NUM bruh). The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse. People standing in the umbra will see a total eclipse.
Seeing an Eclipse Safely
If you do want to check out a solar eclipse, do NOT look at the Sun without proper filters. Please don’t wear sunglasses. They will NOT protect your eyes! See how to safely view a solar eclipse.