A solar eclipse begins with a phase of partial eclipse, when the leading edge of the Moon makes first contact with the edge of the Sun. There is nothing to see at this moment. In fact, there is no way to see this anyway unless one is viewing the Sun through a properly-designed solar filter, such as our American Eclipse USA Eclipse Shades, which block out the blinding rays of the Sun.
ALWAYS view the Sun through a proper solar filter, or by using a projected image, during a partial eclipse and at all other times. Detailed information is provided on our Safe Eclipse Viewing page.
Soon after first contact, a “bite” appears along the edge of the Sun’s disc. This bite grows larger as the eclipse progresses, and the Moon covers more and more of the Sun’s face. This is the ingress of the Moon during a solar eclipse. For most total eclipses, the partial phase lasts for more than an hour.
As the partial eclipse becomes deeper, Sun’s light becomes more faint. The sky takes on a grey light, an eerie daytime twilight, and the colors of objects appear washed out. Also, the temperature drops considerably. Two-thirds of the Sun’s radiation is in the form of heat, and as more of the Sun’s disc is obscured by the Moon, more of the heat is blocked as well. Animals go to sleep during a deep solar eclipse, believing that night is falling.
During a total eclipse of the Sun, night falls at noon as the Moon’s dark shadow (or umbra) moves from west to east across the Earth. The umbra draws a narrow band along the surface, the path of totality, along which a total solar eclipse can be seen. This is an amazing thing in itself! But there are many interesting phenomena that occur before, during and after totality, if you have enough time to see them!
During the waning minutes of partial eclipse, as the Sun is being covered by the Moon up in the sky, the full shadow of the Moon is on the ground, racing toward your location! The Moon’s shadow moves very fast across the Earth, faster than the speed of sound, over a thousand miles per hour! Airplanes in flight cannot keep up with the Moon’s shadow! Looking “upstream” along the eclipse path, toward the west, the Moon’s shadow is visible as a dark beam, reaching down through the sky from space, extinguishing the blue glow of the daytime sky, darkening clouds and mountains off in the distance, and heading your way!
As the Sun is being finally enveloped by the Moon, the diamond ring can be seen, a dwindling patch of bright sunlight still visible as the Sun disappears and the ghostly shadow of the Moon makes its appearance. Prior to totality, the brightness of the sky dims to the point where the brightest stars can be seen. The bright planets Venus and Jupiter start to become visible.
Shadow bands are sometimes visible along light-colored surfaces just before and after totality. At this point, all that remains of the Sun is a tiny sliver of brilliant light that actually “twinkles” like a star through the windy layers of the Earth’s atmosphere. Sunlight passes through these rolling and boiling layers of turbulent air, producing these alternating dark and light bands on the ground, similar to the effect of undulating waves of sunlight dancing along on the bottom of a swimming pool. A large piece of white poster board can provide enough contrast for viewing shadow bands.
Baily’s beads are seen along the dwindling edge of the Sun. This happens because the limb of the Moon is not perfectly smooth, but has jagged mountains, and the bright sunlight pours through the valleys between these lunar mountains, which is visible as a broken ring of sunlight, with blazingly bright “beads” of the Sun’s surface blinking on and off as the Moon progresses over the Sun.
WARNING!!! The diamond ring and Baily’s beads are not safe to view directly! These are portions of the Sun’s bright photosphere and can damage your eyes! You need to practice safe eclipse viewing when observing these effects!
During totality, night falls at noon! The Sun is replaced by a black hole in the sky, where the Moon completely obscures the bright solar disc. The chromosphere of the Sun becomes briefly visible in the first few seconds following the onset of totality. This is a red-colored region of the Sun’s atmosphere, visible along the leading edge of the Moon’s motion. Many formations of the solar atmosphere are visible in the chromosphere, including prominences, gigantic eruptions from the Sun, many times larger than the Earth.
Most spectacular of all is the solar corona, the wispy outer layers of the atmosphere of the Sun, extending in all directions around the Sun’s position. This glorious solar feature is one of the rarest sights in nature, and is only naturally visible during a total eclipse.
The corona is the main source of light during totality, and is itself about as bright as the Full Moon normally appears. To compare the brightness levels, stand outside sometime at midnight under a Full Moon and look around at the landscape. Then do the same sometime at high noon, and notice the differences. Try to imagine a total eclipse in these terms, as the brightness of noon is quickly exchanged for that of a moonlit midnight.
During a total solar eclipse, the dark beam of the Moon’s umbra passes directly over the land, and the surrounding area is within that zone of totality. The brightness of the sky falls to a deep stage of twilight. The sunlit areas beyond the umbra can still be seen, in the distant places outside the region of totality. This results in a colorful daytime horizon visible off in the distance on all sides.
In the fleeting minutes of totality, the brightest stars can become visible. Venus and Jupiter are plainly seen, somewhere alongside the Sun along the plane of the solar system. It can also be possible to observe the Sun’s location among the constellations, which are invisibly hidden behind the bright glare at all other times. But these stars will not be readily seen, as our eyes will not have enough time to adapt to the darkness during the short minutes of totality.
The solar corona is the most elusive sight in nature. It’s widely agreed that no photo or videos can do it justice. There have historically been great difficulties in photographing this wonder, since the mere camera lens cannot capture the extraordinarily intricate detail visible to the human eye. However, in recent years, astounding photographs of the Sun’s corona have been revealed through the work of Professor Miroslav Druckmuller of the Czech Republic, who has perfected an innovative computer processing technique….
The chance to see the corona is the single greatest reason why every single American should plan on being along the path of totality on Eclipse Day, Monday, August 21, 2017. So far, the American press and public are completely unaware and unappreciative of the wonder that will pass over millions of people next August. This is not surprising since an entire generation has grown up without this experience, and more over, there has not been a coast-to-coast American eclipse in a century. It is important that the press and the public wake up and become aware of this unprecedented event, that as many people as possible can make their plans to participate. This is especially true of the children, who can hope to see five American total solar eclipses within the next 35 years.
* * * * *
You’ll know that the phase of totality is drawing to a close when the reddish flames of the chromosphere reappear along the receding edge, signaling the imminent end. The total eclipse comes to a quick end as the diamond ring reappears as a growing swell of bright sunlight, indicating that the party is over! At this moment, it is important to return to practicing safe eclipse viewing, and using a solar filter or other suitable eye protection.
The bright sliver of the Sun again appears, and the attendant phenomena now run in reverse, and Baily’s beads and shadow bands are seen again. The Moon’s shadow moves off from the landscape, and the dark beam that preceded totality can now be seen darkening the clouds and mountains beyond toward the east, downstream on the path of totality. This is the egress of the eclipse, and partial eclipse lasts for another hour as the Moon moves out of alignment with the face of the Sun.
Again, it is totally safe to look directly at the Sun during totality, since the entirety of the face of the Sun is completely obscured. But again, it is very important to practice proper eye safety immediately before and after totality, including Baily’s beads and the diamond ring, and shield your eyes from the Sun’s bright disc. Though it might not feel hard to stare at the sliver of the Sun, even this tiny portion of the solar disc is bright enough to cause permanent eye damage. But since the solar disc is 100% covered during totality, observing it is 100% safe.
THE IMPORTANCE OF TOTALITY: A total solar eclipse is widely regarded at the ultimate astronomy event, and the greatest natural phenomenon of any kind. It is described as a powerful, emotional experience. Even calm, level-headed individuals report being deeply moved by the experience of totality. A total eclipse of the Sun is considered a mystical, spiritual experience by many, the greatest spectacle that can be seen on the Earth. There is simply nothing else in the world like a total solar eclipse, and it is unlike any other type of experience one can have. For this reason, it is very important that everyone understands that you will NOT experience a total eclipse unless you are precisely within the path of the totality!
To get an idea of the experience of totality, watch this two-minute video by Fred Espenak, “Mr. Eclipse,” which shows how quickly the various phenomena occur leading into and out of totality.
It is a very common misconception that a deep partial solar eclipse is similar to a total eclipse. On an eclipse day, an entire continent can see at least a partial eclipse. Locations close to the path of totality experience a “deep” partial eclipse, while locations far away from the path observe a more “shallow” partial eclipse.
Please carefully consider… it cannot be emphasized strongly enough that you will NOT experience a total eclipse of the Sun unless you are directly along the narrow path of totality. If you observe a 99% obscured partial eclipse, you will definitely see a strange sky, but you will NOT experience totality! If you live right outside the path, driving even a few miles directly into the path of totality makes all the difference between observing a total eclipse and not. Everywhere else outside the path, everyone is just standing in the sunshine! Visit our Seeing The Eclipse From Home page for more info about what to expect from observing a partial solar eclipse on Eclipse Day.
Another important point to consider… the maximum duration of totality is experienced along the centerline of the path of totality. You can still see about 87% of maximum duration within about half the distance from the centerline, and about 50% duration at about 7/8 of that distance. But the length of totality drops off really quick as you get close to the northern and southern edges of the path of totality. And right on the edge, totality is momentary, lasting only a split-second, ending just as it begins.
But there are benefits to being closer to the edge of the path. Though totality itself is short, all the attendant phenomena last longer, including shadow bands, the diamond ring, Baily’s beads and the chromosphere. Some eclipse “connoisseurs” actually prefer being closer to the edge, to enjoy a longer show with these phenomena! But we recommend that you just don’t be on the edge!
The total solar eclipse of August 21, 2017 will be the shortest 160 seconds of your life! Total solar eclipses follow the first rule of show business, to “always leave the audience wanting more”! Veteran eclipse chasers report that there is a letdown at the end of the eclipse, since the long-awaited show is over so quickly. But there is also an eagerness to get back into the Moon’s shadow and experience it again, like a fun ride at an amusement park! So they anxiously await the next eclipse! Many people are hooked and become die-hard eclipse chasers themselves!
(The content of this page is adapted from the Understanding Eclipses ebook, coming soon!)
* * * * *
Continue reading about why eclipses occur, and what’s happening with the orbit of the Moon, at our Celestial Causes of Eclipses page.
To learn some basic eclipse information, including the differences between a lunar and a solar eclipse, visit our What is an Eclipse? page.