Solar Eclipse

photo courtesy The University of Tennessee Department of Physics and Astronomy

A solar eclipse occurs when the moon travels between the Earth and the Sun, casting a shadow on the Earth. There are four types of Solar Eclipses:

Total Solar Eclipse - The Sun is completely hidden by the Moon. The sky becomes almost completely dark, bright planets and stars can be seen, and some animals may behave as though it is night time. If the Sun is active, solar flares may be visible around the Moon.

Partial Solar Eclipse - Only part of the Sun is hidden by the Moon. Even if a large portion of the sun is blocked by the moon, it is not safe to look directly at the sun without proper eye protection.

Annular Solar Eclipse - A corona (ring of the Sun) can still be seen around the Moon. The Moon's umbra (darkest part of the shadow) fails to reach the Earth's surface, which can happen if the Moon is too far from the Earth.

Hybrid (Annular/Total) Solar Eclipse - The curvature of the Earth's surface causes a single solar eclipse to be observed as an annular solar eclipse from some locations but a total solar eclipse from other locations. A total eclipse is seen from places on Earth that are physically closer to the Moon and intersect the Moon's umbra. Other locations, further from the Moon, fall in the Moon's antumbra and the eclipse is annular.

Geometry of Solar Eclipses

photo courtesy The University of Tennessee Department of Physics and Astronomy

An eclipse of the Sun (solar eclipse) can only occur during a New Moon when the Moon passes between Earth and Sun. When the Moon's shadow falls upon the Earth's surface, some portion of the Sun is covered by the Moon. The Moon's shadow has two parts:

Penumbra - Faint outer shadow; partial eclipses are seen from within this shadow.

Umbra- Dark inner shadow; total eclipses are seen from within this shadow. The track of the Moon's shadow across Earth's surface is called the Path of Totality. It is typically 10,000 miles long and only 100 miles wide. In order to see the Sun totally eclipsed by the Moon, you must be in the path of totality.

Lunar Eclipse

photo courtesy The University of Tennessee Department of Physics and Astronomy

A lunar eclipse occurs when the Earth travels between the Moon and the Sun, casting a shadow on the Moon. There are three types of Lunar Eclipses:

Total (Umbral) Lunar Eclipse - The entire Moon passes through Earth's umbral shadow (the dark inner portion of the shadow) and the moon appears to completely disappear from the night sky.

Partial (Umbral) Lunar Eclipse - A portion of the Moon passes through Earth's umbral shadow. You will see a portion of the Earth's shadow projected onto the moon. These events are easy to see, even with the unaided eye.

Penumbral Lunar Eclipse - The Moon passes through Earth's penumbral shadow (the outer portion of the shadow). This does not cause a noticeable darkening of the Moon's surface. These events are of only academic interest since they are subtle and quite difficult to observe.

An eclipse of the Moon (lunar eclipse) can only occur during a Full Moon, and only if the Moon passes through some portion of the Earth's shadow. The shadow is composed of two cone-shaped components, one nested inside the other. The outer or penumbral shadow is a zone where the Earth blocks part but not all of the Sun's rays from reaching the Moon. In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon.