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Basic Astronomy Concepts


coronagraph, solar corona, solar eclipse, celestial body, gravitational field

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Eclipse, in astronomy, the obscuring of one celestial body by another, particularly that of the sun or a planetary satellite. Two kinds of eclipses involve the earth: those of the moon, or lunar eclipses; and those of the sun, or solar eclipses . A lunar eclipse occurs when the earth is between the sun and the moon and its shadow darkens the moon. A solar eclipse occurs when the moon is between the sun and the earth and its shadow moves across the face of the earth. Transits and occultations are similar astronomical phenomena but are not as spectacular as eclipses because of the small size of these bodies as seen from earth.

Observation of Eclipses

Many problems of astronomy can be studied only during a total eclipse of the sun. Among these problems are the size and composition of the solar corona and the bending of light rays passing close to the sun because of the sunís gravitational field . The great brilliance of the solar disk and the sun-induced brightening of the earthís atmosphere make observations of the corona and nearby stars impossible except during a solar eclipse. The coronagraph, a photographic telescope, permits direct observation of the edge of the solar disk at all times. Today, scientific solar eclipse observations are extremely valuable, particularly when the path of the eclipse traverses large land areas. An elaborate network of special observatories may provide enough data for months of analysis by scientists. Such data may provide information on how minute variations in the sun affect weather on earth, and how scientists can improve predictions of solar flares.


Hess, Fred, M.A., Ed.D.

Professor of Chemistry, New York Maritime College, State University of New York. Author of "Chemistry Made Simple".

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