Do you know your eclipses?
From “blood moon” and “ring of fire” eclipses to total eclipses and deep or shallow partials, eclipses come in various types. However, one key question forms the basis of the conversation: What’s the difference between a solar eclipse and a lunar eclipse?
Here’s everything you need to know about how the positions of Earth, the moon and the sun combine to create some of the sky’s most spectacular events.
What causes a solar eclipse?
A solar eclipse happens when the moon moves between the sun and Earth, blocking the sun’s light and casting a shadow on Earth. This can occur only during a new moon, when the moon is positioned in front of the sun. However, the moon’s orbit is tilted by about 5 degrees, so it usually misses the sun from our perspective. Only when it aligns perfectly do we witness a solar eclipse. How can that happen when the moon is 400 times smaller than the sun? As luck would have it, the sun is 400 times farther from Earth than the moon is, causing them to appear almost the same size in our sky.
The next total solar eclipse will occur on Aug. 12, 2026, and will be visible from Greenland, Iceland and Spain.
What causes a lunar eclipse?
A lunar eclipse occurs when Earth gets between the sun and the moon, causing Earth’s shadow to be projected onto the lunar surface. By definition, this can happen only during a full moon. Although full moons occur roughly every 29 days, lunar eclipses are relatively rare because the moon’s orbit is slightly tilted relative to Earth’s orbit around the sun. As a result, the moon usually passes above or below Earth’s shadow instead of through it.
The next total lunar eclipse will take place on March 13-14, 2025, and will be best seen from North and South America, and glimpsed from parts of Europe and New Zealand.
How often do eclipses occur?
Every calendar year, there are two “eclipse seasons,” each of which lasts between 31 and 37 days, that can create between four and seven eclipses, according to NASA. These eclipse seasons are periods when the alignments of Earth, the moon and the sun cause either a full moon to move through Earth’s shadow or a new moon to appear to pass across the sun’s disk.
Eclipses don’t happen every month because the moon orbits Earth on an orbital path that’s slightly different from the ecliptic (the sun’s path through our daytime sky). Although that orbital path is tilted by 5 degrees to the ecliptic, it intersects it twice each month. The moon usually crosses the ecliptic when the sun is positioned elsewhere along it. When a new moon crosses the ecliptic, a solar eclipse occurs. When a full moon crosses the ecliptic, it results in a lunar eclipse. When one happens, the other follows, which is why there are typically two eclipses within an eclipse season, separated by two weeks.
Types of solar eclipse
There are three main solar eclipse types. During a partial solar eclipse, a new moon appears to move across part of the sun, blocking it from view. This event must be viewed through solar eclipse glasses, and solar filters must be used on cameras, binoculars and telescopes.
Related: Best solar viewing gear 2025: Observe partial and total eclipses in safety
During an annular solar eclipse, the moon covers only the center of the sun’s disk, leaving a bright “ring of fire” around its edges. This is also dangerous to look at without eye protection. The entire event is a kind of partial solar eclipse.
In contrast, during a total solar eclipse — which is preceded by a partial eclipse — the moon completely covers the sun, revealing the sun’s outer atmosphere, called the corona, during totality. That’s the only time it’s safe to look at a solar eclipse with the naked eye, since all of the sun’s light is blocked.
The existence of annular and total solar eclipses is explained by the moon’s slightly elliptical orbit, which means its apparent size waxes and wanes over the course of a month.
Types of lunar eclipse
A lunar eclipse has between one and five phases. During a penumbral lunar eclipse, the moon passes only through Earth’s outer, lighter penumbral shadow, with a slight dimming as the only visual effect. If it moves through Earth’s penumbra and then part of it goes through its umbra — the darkest part of the shadow — that part of the moon goes dark in a partial lunar eclipse.
When these phases are followed by the moon fully entering the umbra, there is a “blood moon” total lunar eclipse, when the entire lunar surface turns red during totality. The effect happens when sunlight is filtered by Earth’s atmosphere. As the moon leaves the umbra, a partial — and then penumbral — eclipse is visible.
Therefore, a total lunar eclipse has five distinct phases. Unlike with a solar eclipse, all phases of a total lunar eclipse are safe to look at with the naked eye.
How often do solar and lunar eclipses happen?
Total solar eclipses and “blood moon” total lunar eclipses tend to be the crowd-pleasing eclipse types. Most solar eclipses are partial, and most lunar eclipses are penumbral or partial. A total solar eclipse is visible from somewhere on Earth roughly every 18 months, but it is a rare event for any given location on Earth, occurring about once every 366 years, on average, according to NASA.
A total lunar eclipse can be seen from any given location about once every 2.5 years, according to Time and Date.
Additional resources
Read more about solar and lunar eclipses on Eclipse Wise — a website dedicated to predictions of eclipses. Learn about eclipses on other planets with this short article from Cornell University’s astronomy department. Watch a mini-documentary on the topic, titled “Lunar and Solar Eclipse Explained: A Beginner’s Guide to Eclipses,” from Science ABC.
Bibliography
NASA, “What is the Difference between a Solar Eclipse and a Lunar Eclipse?” accessed Feb. 25, 2025. https://mynasadata.larc.nasa.gov/mini-lessonactivity/what-difference-between-solar-eclipse-and-lunar-eclipse
NASA, “The Moon & Eclipses,” accessed Feb. 25, 2025. https://science.nasa.gov/moon/eclipses/
American Astronomical Society, “Shapes of the Sun & Moon In & Out of Eclipse,” accessed Feb. 25, 2025. https://eclipse.aas.org/eclipse-america/sun-moon-shapes
Vigdis Hocken and Aparna Kher. “What Is a Total Lunar Eclipse? – Sun, Moon & Space.” Time and Date, 20 February 2025, https://www.timeanddate.com/eclipse/total-lunar-eclipse.html Accessed 6 March 2025.
