A total solar eclipse is an awe-inspiring phenomenon where the Moon completely blocks the view of the Sun. Before and after totality, there is a partial solar eclipse. During totality, viewers are in the Moon’s shadow or umbra. But, the sky doesn’t go completely dark. Instead, you see parts of Sun that are not ordinarily visible, such as the corona and solar prominences. Here is a look at the stages of a total solar eclipse, what to look for during totality, and how to view the eclipse safely.
Stages of a Total Solar Eclipse
A total solar eclipse consists of several distinct stages:
- First Contact (Partial Eclipse Begins): The Moon begins to obscure the Sun’s disk, causing a small crescent of darkness to appear on the edge of the Sun. This marks the start of the partial eclipse phase. At first contact, the viewer enters the penumbra.
- Second Contact (Total Eclipse Begins): As the Moon continues to move in front of the Sun, the darkness increases. Eventually, the entire solar disk is obscured, and the total eclipse phase begins. Observers within the path of totality will witness a rapid decrease in brightness as day turns into night.
- Totality: During this stage, the Moon fully covers the Sun’s photosphere, leaving only the faint solar corona visible. Totality can last from a few seconds to several minutes, depending on the specific geometry of the Earth, Moon, and Sun at the time of the eclipse. Look around and notice that the view is different from dawn or sunset because the horizon is bright in all directions. You may hear birds start to sing and notice a distinct lowering in temperature. Some stars are visible during totality, too.
- Third Contact (Total Eclipse Ends): The Moon begins to move away from the Sun, and the edge of the solar disk becomes visible again. The total eclipse phase ends, and the partial eclipse phase resumes.
- Fourth Contact (Partial Eclipse Ends): The Moon continues to move away from the Sun until it no longer obscures any part of the solar disk. At this point, the eclipse is over, and daylight returns to normal.
Special Features of a Total Solar Eclipse
During a total solar eclipse, several unique phenomena can be observed:
- Diamond Ring Effect: Just before totality and right before it ends (second and third contact), the Moon almost fully covers the Sun and a final bright spot of sunlight called the “diamond” remains visible. This striking visual effect resembles a diamond ring, hence the name.
- Baily’s Beads: Named after the British astronomer Francis Baily, these beads of light appear around the edge of the Moon during the seconds leading up to totality and just after. Baily’s beads are caused by sunlight passing through valleys and between mountains on the Moon’s irregular surface. The the thin reddish edge is the Sun’s chromosphere.
- Solar Corona: The solar corona is the Sun’s outer atmosphere, composed of plasma and extending millions of kilometers into space. The Sun’s intense brightness hides it, but it is visible during totality. The corona appears as a halo of blue-white, wispy light surrounding the dark silhouette of the Moon. The shape of the corona changes over time, so you may recognize a specific eclipse based on the photos of its corona.
- Solar Prominences: These are large, bright loops of plasma that extend from the Sun’s surface into the corona. During totality, solar prominences appear as red or pink arches near the edge of the solar disk, sometimes extending out into the corona. Sometimes brighter solar flares are visible, too.
- Shadow Bands: Shadow bands or flying shadows resemble the bands of light and dark that you see on the bottom of a swimming pool. In the case of a solar eclipse, the fluid is air instead of water and the solar crescent acts as an anisotropic filter. These bands become visible on the ground just before and immediately after totality.
List of Total Solar Eclipses
While solar eclipses occurs approximately twice a year, total solar eclipses are relatively rare. Here is the list of total solar eclipses up to the year 2030:
- April 20, 2023
- April 8, 2024
- August 12, 2026
- August 2, 2027
- July 22, 2028
Safely Viewing a Total Solar Eclipse
You (and your camera) need protection during any solar eclipse. Totality is the only time a solar total eclipse is dim enough to view without filters. Otherwise, use special solar filters or eclipse glasses or else view the Moon’s shadow indirectly. One way is by looking at the ground below a leafy tree. The overlapping leaves act are natural pinholes that leave tiny eclipse shapes on the ground. Sunglass are not enough protection for a solar eclipse. Photography comes with its own special risks, but safety mainly involves not-looking through a viewfinder and protecting the camera with the right kind of filter.
Total solar eclipses are rare and captivating events that offer observers a chance to witness the beauty and power of the Sun. The stages of a total solar eclipse, along with unique features like the diamond ring effect, Baily’s beads, and the visibility of the solar corona and solar prominences, make these celestial spectacles unforgettable experiences. There is nothing quite like a total solar eclipse – just remember to protect your eyes (and your camera) with proper solar viewing equipment.
- Baily (1836). “I. On a remarkable phenomenon that occurs in total and annular eclipses of the sun”. Monthly Notices of the Royal Astronomical Society. 4 (2): 15–19. doi:10.1093/mnras/4.2.15
- Littmann, Mark; Willcox, Ken; Espenak, Fred (1999). Totality – Eclipses of the Sun. Oxford University Press. ISBN 978-0-19-513179-6.
- Mobberley, Martin (2007). Total Solar Eclipses and How to Observe Them. Astronomers’ Observing Guides. New York: Springer. ISBN 978-0-387-69827-4.