Researchers that study solar eclipses believe the sun is larger than we think. NASA scientists claim this year's historic solar eclipse will prove that our star is hundreds of miles larger. Computer models suggest that our Star, the Sun, could be a few hundred miles larger than believed. This year's solar eclipse, which falls on August 21, could prove these predictions are true. The size of the sun In 1891, a German astronomer known as Arthur Auwers was the first to estimate the size of the sun. Based on the star's photosphere, the body of the sun whose wavelengths are visible to the naked eye, he calculated that the sun had a radius of 432,470 miles (696,000km). This benchmark figure was widely used until 2015. In 2015, the International Astronomical Union updated this figure to 432,280 miles (695,700km) based on data from solar-observing satellites. But now a growing number of scientists have claimed that both of these estimates are too small. Is the sun bigger than we think? Xavier