What is a solar eclipse? Undoubtedly, experiencing this celestial phenomenon will fill your mind with a galaxy full of questions.
Imagine a time long ago when these cosmic events could not be anticipated to the precise moment as we can now, thanks to science. The depth of mystery our ancestors must have felt.
Today, we have answers, and we’ll cover all the essential basics, from a simple explanation of “What is a solar eclipse?” to the more complicated aspects of this wondrous event.
What is a Solar Eclipse?
The Simple Explanation
A solar eclipse is when the Moon aligns precisely between the Earth and the Sun, blocking either part or all of the light from the Sun as viewed from a specific location on the Earth’s surface.
Shadow of the Eclipse
As the Moon obstructs the light of the Sun, a shadow is cast upon the Earth. An observer must be within one of the two distinct parts of this shadow to experience the eclipse.
Umbra
The innermost darkest part of the Moon’s shadow is the umbra. It is a result of the Moon completely covering the bright face of the Sun, creating a shadow in the shape of a circular cone where no direct sunlight penetrates, tapering to a small point as it reaches the surface of the Earth.
As this circular point of the umbral shadow moves across the planet, it creates a narrow path known as the path of totality. On average, this umbral shadow covers approximately 115 miles in diameter of the Earth’s surface, sometimes more, sometimes less. A viewer must be within the umbral shadow (path of totality) to experience a total solar eclipse.
Penumbra
The outer lighter area of the shadow is the Penumbra. This part of the shadow results from the Moon obscuring only a portion of the Sun’s light. Any observer viewing the eclipse within this area of the shadow would experience a partial eclipse.
What Causes a Solar Eclipse?
How it Happens
A solar eclipse occurs somewhere over our planet on average two times a year. The maximum is five, but very rare. It happens while the Moon is in its new moon phase, and its orbital position is close to where it intersects Earth’s ecliptic plane. This period is known as the eclipse season.
Eclipse Season
& Lunar Nodes
A lunar node is where the Moon’s orbit intersects with Earth’s elliptical orbit around the Sun. There are two, a descending and ascending lunar node. It’s near these two points the eclipse season begins approximately once every six months.
Since the axis of the Moon’s orbit is slightly tilted by 5˚ compared to the Earth’s ecliptic plane, this impedes the alignment required to create an eclipse during most lunar cycles, on average every 29.5 days.
During the eclipse season, the Moon is in a lower ecliptic latitude, creating a greater chance the of Lunar Nodes (where the Moon and Earth orbital planes intersect) aligning with the Earth and Sun, producing the correct conditions for a solar eclipse event to happen.
Lunar eclipses will also occur during an eclipse season if the Moon is in its full moon phase and positioned within its orbit on the dark side of Earth aligned with the Sun.
Different Types of a Solar Eclipse
Which type of solar eclipse depends on the alignment and the apparent sizes of the Moon and Sun as seen from the Earth’s surface. Their apparent size continuously changes from the varying distances in relation to one another, such as Earth to the Sun and the Moon to Earth.
The changing distance between celestial bodies results from their different positions within their elliptic orbits.
Total Solar Eclipse
A total solar eclipse occurs when the Moon completely covers the Sun, as seen from Earth.
The orbits and inclinations of the Earth, Sun, and Moon must perfectly align at the correct distance for the Moon’s apparent size to match the apparent size of the Sun, completely covering its entire solar disk.
This brief phase, one of the five stages of the solar eclipse, typically lasts only minutes at any given location.
The maximum duration of totality, how long totality lasts, depends from where in this path of the dark shadow you are observing the eclipse. It is longest when observed from the middle of the umbral shadow and shortest near its edge.
Seconds before totality happens, viewers may often witness two distinct events, “Bailey’s Beads” and the “diamond ring effect,” created by the same phenomenon.
Moments before the Moon has completely covered the Sun’s disk, the last rays of light shine along the edge of the curved surface of the lunar landscape, appearing as numerous tiny beads of light referred to as Bailey’s beads.
One by one, they are extinguished until the final bead appears to burst with a sparkle of light as a thin golden band encircles the Moon’s surface just before going dark. This event is known as the “diamond ring effect“.
Once the Sun’s light has been completely obscured, totality has begun. During this period of dusk-like darkness, the Sun’s outer atmosphere, the solar corona, is now visible. The whitish ionized mixture of matter and gas known as plasma extends beyond the darkened disk, much like white blossoms on a flower.
It’s a rare and memorable site to experience. At any other time, the Sun’s atmosphere is hidden from our naked eyes by the bright face of the Sun. Scientists take advantage of this opportunity during totality to capture images and perform tests.
Partial Solar Eclipse
A partial solar eclipse, the most widely seen, happens as the sphere of the Moon becomes visible within the solar disk. Unlike a total eclipse, this only obscures part of the Sun.
This type of eclipse may be seen leading into and exiting the phase of totality during a total solar eclipse or while viewing an eclipse outside the path of totality within the penumbral part of the shadow.
It may also be the main event with no possibility of totality if the Earth, Moon, and Sun are not perfectly aligned. A partial eclipse can last two or three hours, much longer than the other types of eclipse.
Annular Solar Eclipse
The word “annular” is taken from the Latin word “annulus,” meaning “ring.” Appropriately so, as this type of eclipse checks all of the requirements for totality, except the apparent size of the Moon does not match that of the Sun.
The alignment is correct, but because of the Moon’s proximity to Earth, positioned further out within its orbit, its does not completely cover the Sun’s disk of light.
This results in a bright ring around the dark disk of the Moon known as the “ring of fire.” It’s an annular eclipse of the Sun.
Hybrid Solar Eclipse
A hybrid solar eclipse is quite rare. This hybrid eclipse morphs between two different types of eclipses, a total and annular eclipse, depending on where on Earth the eclipse is being viewed.
It happens as a result of the curvature of the Earth impacting the size of the Moon’s shadow because of the distance between different areas of the Earth from the Moon.
As a result, the eclipse casts its umbral shadow of totality in some locations, especially near the central path, and appears annular, not completely covering the Sun’s disk of light at others, particularly near the start and end points.
How to Safely View a Solar Eclipse
A solar eclipse is a spectacular event to witness but to prevent permanent eye damage, it should only be viewed through special-purpose safe solar filters manufactured in compliance with the ISO 12312-2 international safety standard.
Solar viewing can be very damaging to your eyesight if attempted without protective filters.
These filters can be solar eclipse glasses, handheld viewers, or filters attached to the front end of a binocular or a telescope refractor (tube), as long as they are certified to ISO safety standards.
Should Solar Filters Be Used During Totality?
The only time a total eclipse is safe to view without a protective filter is during the very short period of totality, lasting only seconds to minutes. It will vary between locations.
For eye safety, solar viewers or filters will need to be used once again as the Sun’s bright face reappears during the remainder of the eclipse.
Eye protection must be used 100% of the time while viewing the eclipse except during totality.
How to Create a Pinhole Projector (DIY)
An alternative to protective eye filters would be to construct a pinhole projector. They are easy to make as no special equipment is required, and ideal for group viewing with no risk to eyes.
A pinhole projector is a simple and safe way to observe a solar eclipse as it allows you to indirectly view the eclipse without the risk of damaging your eyes.
A Safe DIY Way to View the Solar Eclipse
- The best way to create a simple pinhole projector is by taking a sturdy piece of paper or cardboard and puncturing a small, round (smooth) hole in the center using a pin or thumbtack.
- Turn your back to the Sun and lift the paper with the hole over your shoulder, allowing sunlight to pass through it.
- Secure a second piece of paper as a projection screen. Position it some distance away to capture the inverted image of the Sun projected through the pinhole.
- Increase the size of the Sun’s image by moving the projection screen farther from the pinhole paper.
Past and Future
Solar Eclipses?
Solar eclipses have occurred over Earth since the Moon first formed and settled into an orbit around our planet. Many ancient cultures witnessed these rare events and used myths, symbolism and spirituality to understand how a solar eclipse fit into their cultural realm.
One such historic occurrence happened during a battle known as the Battle of the Eclipse. It was fought in the early 6th century BC in Anatolia (present-day Turkey) between the Medes and the Lydians. Once the eclipse was observed over the battlefield, both sides stopped fighting and took it as a sign for peace.
Although solar eclipses happen somewhere over Earth on average two or three times a year, they often don’t return to the exact same location for hundreds of years. It can be decades before a solar eclipse reoccurs over larger areas such as a continent or country.
The most recent span of time between observations of a total solar eclipse in the United States is eight years between the Great American Total Solar Eclipse of 2017 and the Great American Total Solar Eclipse of April 8, 2024.
In October of 2023, North America also experienced an annular solar eclipse, which was seen in the US states from Texas to Washington.
The next solar eclipse for the United States beyond 2024 will be partial eclipses on August 12, 2026, January 26, 2028, and January 14, 2029.
The lower 48 states of the US will have to wait until 2044 before another total solar eclipse returns, with totality only visible in two states, North Dakota and Montana.
Why Do Scientists Study
Solar Eclipses?
Scientists perform important research on solar eclipses for a variety of reasons.
Studying the corona, the outer atmosphere of the Sun, only visible during total solar eclipses, is critical to understanding key aspects of how the Sun transfers heat and energy into the solar wind.
This ongoing flow of particles from the Sun impacts both Earth’s technology and astronauts in space. Understanding how the solar wind accelerates at the Sun can help anticipate its effects on Earth.
Total solar eclipses also provide a unique opportunity to analyze Earth’s atmosphere under unusual conditions. Unlike the regular global shift in light during dawn and dusk, an eclipse causes a localized change in light over Earth and its atmosphere within the Moon’s shadow.
This specific blocking of the Sun’s energy helps study its influence on our atmosphere, especially the upper layers like the ionosphere.
This region, where the Sun’s energy forms a layer of charged particles, is important to understand because it hosts many low-Earth orbit satellites and communication signals, including radio waves and GPS. Changes in this area can significantly affect our technology and communication infrastructure.
Solar Eclipse vs. Lunar Eclipse?
Here are several interesting differences between a solar and lunar eclipse.
- A solar eclipse requires the Moon to be in its phase of a “New Moon,” while a lunar eclipse requires the opposite phase of a “Full Moon.”
- The Moon is between the Earth and the Sun during a solar eclipse, while it is the Earth’s blue disk passing between the Sun and the Moon during a lunar eclipse.
- A total solar eclipse is seen within a small location on Earth, while a total lunar eclipse can be seen from the entire “night side” of the Earth.
- During a solar eclipse, the Moon obscures light from the Sun reaching a portion of the Earth, while a lunar eclipse is created by the Earth, blocking the Sun’s light from illuminating the Moon.
- The darkest part of the Moon and Earth’s shadow are both called the “umbra.”
