How Solar Eclipses Occur

Buzz

Ngày cập nhật gần nhất: 15/4/2026

An image of the moon obscuring the sun during a solar eclipse.

During a total solar eclipse, the moon covers the sun's surface completely. Matt Anderson Photography / Getty Images

Solar eclipses are rare and captivating events. When you're in the right place at the right time for a total solar eclipse, the experience is truly remarkable.

This article explores what takes place during a solar eclipse and provides tips for safely observing this extraordinary phenomenon.

What Is a Solar Eclipse?

The positions of the sun, moon, and Earth during a solar eclipse. Umbra and penumbra are the regions within the moon's shadow. Photo courtesy NASA

A solar eclipse happens when the moon moves directly between the Earth and the sun, casting its shadow on Earth and blocking the sunlight from our perspective.

The moon orbits the Earth at an angle of about 5 degrees in relation to the Earth-sun plane. It crosses the Earth's orbital plane twice a year, during what we call eclipse seasons. This is when eclipses can happen. For a solar eclipse to occur, the moon must be in the proper moon phase during the eclipse season, specifically a new moon. This rarity contributes to the infrequency of solar eclipses.

Types of Solar Eclipses

Total Solar Eclipse Photo courtesy NASA

The moon's shadow consists of two parts: a central region (umbra) and an outer region (penumbra). Depending on which part of the shadow passes over you, you will experience one of three types of solar eclipses:

Total Solar Eclipse - The full central portion of the sun is obscured.
Partial Solar Eclipse - Only part of the sun's surface is hidden.
Annular Solar Eclipse - A narrow, ring-like band of sunlight is visible around the sun's disc.

Total Solar Eclipse

A total solar eclipse is a mesmerizing celestial event that happens when the Moon passes directly between the Earth and the Sun, completely covering the Sun's disk. As the Moon perfectly aligns, it briefly appears to entirely block the Sun's brilliant face, unveiling the solar corona—the Sun's outer atmosphere—as a glowing halo of light. The daylight significantly dims, and the surrounding atmosphere takes on an eerie, twilight-like glow.

Observers who find themselves within the path of totality of the eclipse are treated to the breathtaking spectacle of the Sun's brilliant disk transforming into a magnificent celestial ring, often referred to as the "diamond ring" effect, just before and after the total phase. To safely witness this mesmerizing occurrence, it is crucial to wear specially designed eclipse glasses to protect the eyes from the Sun's harmful rays. However, a total solar eclipse is the only type where it is safe to briefly remove the eclipse glasses when the Moon fully obscures the Sun.

Partial Solar Eclipse

A partial solar eclipse takes place when the Moon covers only a section of the Sun. Unlike the complete coverage seen in a total solar eclipse, during a partial eclipse, a part of the Sun’s disk remains visible, creating a striking crescent shape.

Although the overall daylight may not be drastically reduced, the environment adopts a softer, more subdued quality as the Moon's outline gently overlaps the Sun's brilliance. It’s essential to note that even during a partial solar eclipse, looking at the event directly without proper eye protection can result in eye damage. Thus, wearing eclipse glasses is critical.

Annular Solar Eclipse

An annular solar eclipse is a remarkable celestial phenomenon that occurs when the Moon passes between the Earth and the Sun, but the Moon's apparent size is slightly smaller than the Sun's, resulting in the Sun appearing as a bright ring, or "ring of fire," around the edges of the Moon's silhouette.

This unique event happens when the Moon is at a point in its orbit that is farther away from the Earth, causing it to appear smaller in the sky. As the Moon partially covers the Sun, the surrounding landscape takes on an otherworldly quality, and observers witness the striking visual spectacle of the Sun's radiant rim framing the Moon's dark center.

Hybrid Eclipse

It's also important to know what a hybrid eclipse is. A hybrid solar eclipse, also known as an "annular-total eclipse," is a rare and fascinating event that occurs once every decade. A hybrid eclipse transitions between an annular eclipse and a total eclipse along its path. Depending on an observer's location, a hybrid eclipse may appear as a total eclipse in some areas and an annular eclipse in others.

This intriguing phenomenon occurs when the curvature of the Earth's surface influences the alignment between the Sun, Moon, and observer, leading to an eclipse that shifts from one type to another, creating an unforgettable visual experience for those fortunate enough to witness it.

How to Watch a Solar Eclipse

Never look directly at the sun – this can damage your eyes. The safest way to view the sun is by projecting its image. Here's a simple method for projecting the Sun’s image:

Find two pieces of cardboard (such as flaps from a box or the backs of paper pads).
Use a pin or pencil to poke a small hole in the center of one piece (no larger than the point of the pin or pencil).
Hold both pieces in your hands.
Stand with your back to the Sun.
Hold the piece with the pinhole in one hand, and position the other piece (the screen) behind it.
The sunlight will pass through the pinhole and project an image onto the screen (see How does a pinhole camera work? for more details on the process).
Adjust the distance between the pieces to focus the image and modify its size.

Enjoy observing!

For more information about solar eclipses and related topics, be sure to explore the links provided below.