planetary nebula
planetary-nebula的词性:n.(名词)
1. A nebula, such as the Ring Nebula, consisting of a hot, blue-white, central star surrounded by an envelope of expanding gas.行星状星云:由一颗炽热的、蓝白色的中心恒星和包围它的一层向外膨胀的气体组成的星云,如环状星云