FIGURE 1-3. A total solar eclipse photographed in perfect conditions. The large bright areas are coronal streamers. Close to the solar disk, bright prominences are visible, in particular on the left; these appear pink in real life.

various mechanisms. Around the circumference of the Moon is the corona, the term derived from the Latin and thence Spanish word meaning "crown" or "garland." This is a solar structure, far beyond the Moon, made visible only during an eclipse. Basically it is the tenuous glowing atmosphere of the Sun. The corona appears white to the eye. Vividly seen here are various coronal streamers.

Another distinct phenomenon that may be glimpsed during a total solar eclipse is the existence of transitory prominences, huge red clouds of glowing gas thrown up above the solar surface. These are also apparent in Figure 1-3, as bright spots close to the edge of the Moon. These prominences are often more obvious to the naked eye than in a photograph, and old-time eclipse-watchers were very familiar with them, terming them the "red flames." An example of this is the nineteenth-century sketch of totality shown in Figure 1-4. Before the advent of photography, this was the only way to record what was seen.

FIGURE 1-4. A total solar eclipse sketched by a nineteenth-century astronomer. To the naked eye the prominences jutting above the solar surface often appear more noticeable than they are in a photograph.

Figure 1-5 shows an eruptive prominence on a grand scale, without the benefit of an eclipse. This blob of superheated gas, 80,000 miles long, was thrown off the Sun in 1996 and its behavior was captured in ultraviolet light with a sensor on board the SOHO (Solar and Heliospheric Observatory) satellite. This series of images stretches over five hours, the prominence moving outwards at more than 15,000 miles per hour.

If the profiles of both the Moon and the Sun were perfectly circular, then as totality was reached the area of the solar disk visible would diminish until finally there was just one spot left in the line of sight, and then that would be abruptly blanked out. The effect would be that a dim corona would surround the dark Moon, with a single bright spot momentarily witnessed before it, too, disappeared. This so-called diamond ring effect is shown in Figure 1-6.

In reality neither the Sun nor the Moon is precisely circular,

FIGURE 1-5. A five-hour sequence of ultraviolet images of the Sun obtained with the SOHO satellite show a developing eruptive prominence at upper right.

FIGURE 1-6. The diamond ring effect is seen just as totality starts and ends. This shows an example, but it's a bit of a cheat. This was an artificial eclipse of the Sun by the Earth, photographed by the Apollo 12 astronauts on their way back from the Moon late in 1969, produced when their spacecraft slipped into the terrestrial shadow.

and under some circumstances a series of bright spots may also be seen around the limb. These are due to light squeezing through the valleys between craters and mountains at the edge of the Moon. These spots are called Baily's beads after the nineteenth-century British astronomer Francis Baily, who first described their form and origin in 1836. Baily's sketch is shown in Figure 1-7. The edge of the Moon is certainly crinkled, as one can see in Figure 1-8; during an eclipse the mountains of the Moon are cast in sharp relief, as seen in Figure 1-9.

We have seen how the basic aspects of solar eclipses appear in the sky; let us now return to our discussion of how humans have reacted to such events over the eons.

FIGURE 1-7. Baily's beads, from his original description in 1836.
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