Word: vacuuming
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Dates: during 1970-1979
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...expedition will carry out three major experiments, all involving the outer corona. This is a tenuous gas, thinner than any man-made vacuum, and heated by two million degrees centigrade. Although the inner part of the corona can be seen through special narrow band filters without an eclipse, a total solar eclipse is essential to study the whole structure, including the outer portion, of the corona...