Complex sentence: Since, coronal holes are regions in the sun's corona that have much lower densities and temperatures than most of the corona, these regions are lacking luminous gas and thus are very thin, which contribute to the escape of solar wind.
Split into simpler sentences: Since, coronal holes are regions in the sun's corona that have much lower densities and temperatures than most of the corona. These regions are devoid of luminous gas and thus are very thin, which most likely contribute to the flow of solar wind.