Annular eclipse | NASA

Total Solar Eclipse Could Prove the Sun Is Bigger Than We Think

Making a precise measurement of the sun is difficult, but the August 21 eclipse will offer scientists an opportunity to refine their calculations.

Xavier Jubier simulated an annular eclipse that occurred March 29, 1987, matching his results to photos taken at the time of the eclipse. His results precisely match when he combines incredibly precise data about the moon's contours and Earth's topography with a slightly larger solar radius. | Xavier Jubier/Hugette Guertin
This flash spectrum was taken in Gabon during an eclipse Nov. 3, 2013. On the left, a photo of the eclipse is visible, and the right shows the varying spectra released by the eclipse at that moment — the sun's photosphere creates the smooth spectrum of color, and the chromosphere above it releases the distinct arcs of color. This setup can let researchers pinpoint the instant the photosphere is covered, and thus determine its size. | Constantine Emmanouilidi, used with permission