The Moon's orbit around the Earth is slightly elliptical, as is the Earth's orbit around the Sun. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure. The Sun's distance from Earth is about 400 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. An annular eclipse can occur when the Sun has a larger apparent size than the Moon, whereas a total eclipse can occur when the Moon has a larger apparent size. Ĭomparison of minimum and maximum apparent sizes of the Sun and Moon (and planets). Even at 99%, it would be no darker than civil twilight. Partial eclipses are virtually unnoticeable in terms of the Sun's brightness, as it takes well over 90% coverage to notice any darkening at all. However, some eclipses can be seen only as a partial eclipse, because the umbra passes above the Earth's polar regions and never intersects the Earth's surface. This phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. A partial eclipse occurs when the Sun and Moon are not exactly in line with the Earth and the Moon only partially obscures the Sun.At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse.Hence the Sun appears as a very bright ring, or annulus, surrounding the dark disk of the Moon. An annular eclipse occurs when the Sun and Moon are exactly in line with the Earth, but the apparent size of the Moon is smaller than that of the Sun.This narrow track is called the path of totality. During any one eclipse, totality occurs at best only in a narrow track on the surface of Earth. A total eclipse occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona to be visible.Partial and annular phases of the solar eclipse of May 20, 2012 Enthusiasts known as eclipse chasers or umbraphiles travel to remote locations to see solar eclipses. Only the total phase of a total solar eclipse is safe to view without protection. Looking directly at the Sun can lead to permanent eye damage, so special eye protection or indirect viewing techniques are used when viewing a solar eclipse. Astronomers' predictions of eclipses began in China as early as the 4th century BC eclipses hundreds of years into the future may now be predicted with high accuracy. In some ancient and modern cultures, solar eclipses were attributed to supernatural causes or regarded as bad omens. Total solar eclipses occur rarely at a given place on Earth, on average about every 360 to 410 years.Īn eclipse is a natural phenomenon. Total eclipses are more rare because they require a more precise alignment between the centers of the Sun and Moon, and because the Moon's apparent size in the sky is sometimes too small to fully cover the Sun. Solar (and lunar) eclipses therefore happen only during eclipse seasons, resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total. Instead, because the Moon's orbit is tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. If the Moon were in a perfectly circular orbit and in the same orbital plane as Earth, there would be total solar eclipses every new moon. In partial and annular eclipses, only part of the Sun is obscured. In a total eclipse, the disk of the Sun is fully obscured by the Moon. Such an alignment coincides with a new moon, indicating the Moon is closest to the plane of the Earth's orbit. During a partial solar eclipse (right), the Moon blocks only part of the Sun's disk ( October 23, 2014).Ī solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring Earth's view of the Sun, totally or partially. An annular solar eclipse (left) occurs when the Moon is too far away to completely cover the Sun's disk ( May 20, 2012).
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