Night Skies

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?

January 4: Partial Solar Eclipse

A partial solar eclipse is visible across parts of Europe, Africa, and Asia today.

June 1: Partial Solar Eclipse

A partial solar eclipse is visible across northern Alaska and Canada. The lunar disk will obscure no more than a third of the Sun from these locations, however, so it won't be much of a show.

June 15: Total Lunar Eclipse

A total lunar eclipse will decorate the skies of most of the world tonight, but not North America.

November 25: Partial Solar Eclipse

A partial solar eclipse is visible across Antarctica and parts of the South Pacific today, but not North America.

December 10: Lunar Eclipse

A lunar eclipse will be visible across most of the United States, with the best view from the Pacific Northwest, Alaska, and Hawaii.

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.