英语翻译
More precise data came from some good luck in timing:From 1985 to 1990,Pluto and Charon happened to be aligned in a way that made them eclipse each other every few days as seen from Earth—something that won’t happen again for more than 100 years.Detailed analysis of brightness variations during these eclipses allowed the calculation of accurate sizes,masses,and densities for both Pluto and Charon.These measurements confirmed that Pluto and Charon are both made of ice mixed with rock—just like comets.The eclipse data even allowed astronomers to construct rough maps of Pluto’s surface markings,which have not yet been explained (Figure 9.17b).