2012 Lunar and Solar Eclipses
This illustration shows the Moon passing through Earth's shadow during a typical lunar eclipse. The Moon is slightly tinted when it passes through the light outer portion of the shadow, the penumbra, but turns dark red as it passes through the central portion of the shadow, called the umbra. [Tim Jones]An eclipse is the result of the total or partial masking of a celestial body by another along an observer's line of sight. Solar eclipses result from the Moon blocking the Sun relative to the Earth; thus Earth, Moon and Sun all lie on a line. Lunar eclipses work the same way in a different order: Moon, Earth and Sun all on a line. In this case the Earth's shadow hides the Moon from view.
When are this year's solar and lunar eclipses?
May 20: Annular Solar Eclipse
An annular eclipse of the Sun is visible from western North America. The eclipse occurs because the Moon passes directly between Earth and the Sun. The Moon will be near its farthest point from Earth, however, so it won't be big enough to cover the entire disk. Instead, a thin ring of sunlight will encircle the Moon, known as an annulus. From the United States, annularity will be visible during the late afternoon across a narrow strip from northern California to the plains of northwestern Texas.
June 4: Partial Lunar Eclipse
A slight lunar eclipse is visible before sunrise today from most of the United States. Earth’s dark inner shadow will take a small “bite” from the bottom of the Moon.
November 13: Total Solar Eclipse
A total solar eclipse is visible across the northern tip of Australia and a long path across the southern Pacific Ocean during the afternoon hours on American clocks.
November 28: Penumbral Lunar Eclipse
A faint eclipse of the Moon will take place. The Moon will pass through the hazy outer portion of Earth’s shadow, known as the penumbra, so the eclipse is barely noticeable. The lunar disk will look slightly darker than normal, but not by much, so most skywatchers won’t see any difference.
What is the difference between a lunar and a solar eclipse?
From our perspective on Earth, two types of eclipses occur: lunar, the blocking of the Moon by Earth's shadow, and solar, the obstruction of the Sun by the Moon.
When the Moon passes between Sun and Earth, the lunar shadow is seen as a solar eclipse on Earth. When Earth passes directly between Sun and Moon, its shadow creates a lunar eclipse.
Lunar eclipses can only happen when the Moon is opposite the Sun in the sky, a monthly occurrence we know as a full Moon. But lunar eclipses do not occur every month because the Moon's orbit is tilted five degrees from Earth's orbit around the Sun. Without the tilt, lunar eclipses would occur every month.
Lunar and solar eclipses occur with about equal frequency. Lunar eclipses are more widely visible because Earth casts a much larger shadow on the Moon during a lunar eclipse than the Moon casts on Earth during a solar eclipse. As a result, you are more likely to see a lunar eclipse than a solar eclipse.
The full Moon casts its shadow on Earth's surface during a total solar eclipse. [Tim Jones]
