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2017 Solar Eclipse Government Information: Addl Resources

Facts and useful information about the August 21 total solar eclipse from NASA and other government agencies.

Glossary

Some basic eclipse terms:

  • ANNULAR ECLIPSE

    A solar eclipse that occurs when the apparent size of the moon is not large enough to completely cover the sun. A thin ring of very bright sunlight remains around the black disk of the moon.  (Toledo was in the direct path of an annular solar eclipse on May 10, 1994)

  • HYBRID ECLIPSE

    A solar eclipse which appears annular or total along different sections of its path.

  • MAGNITUDE (of a solar eclipse)

    The fraction of the apparent diameter of the sun covered by the moon. By convention it is usually quoted at maximum phase.

  • OBSCURATION (of a solar eclipse)

    The fraction of the sun’s area covered by the moon.

  • PATH OF TOTALITY

    The path (up to about 270 km or 168 miles wide) that the moon’s shadow traces on Earth during a total solar eclipse.

  • PENUMBRA

    The part of a shadow -- as of the moon or Earth -- within which the source of light, such as the sun, is only partially blocked. Also, it refers to the lighter outer area of a sunspot.

  • PHOTOSPHERE

    The bright, visible surface of the sun.

  • SOLAR ECLIPSE

    The passage of the new moon directly between the sun and Earth when the moon’s shadow is cast upon Earth. The sun appears in the sky either partially or totally covered by the moon.

  • TOTAL SOLAR ECLIPSE

    A solar eclipse seen from within the moon’s umbra. The moon appears to completely block the sun’s photosphere. (Toledo will be in the direct path of a a total solar eclipse on April 8, 2024)

  • TOTALITY

    The period during a solar eclipse when the sun’s photosphere is completely covered by the moon and the period for a lunar eclipse when the moon is in the complete shadow of Earth.

  • UMBRA

    A complete shadow – such as that of the moon or Earth -- within which the source of light, such as the sun, is totally hidden from view. Also, it refers to the dark inner area of a sunspot.

 More from NASA's Eclipse Glossary

 

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