A disk of gas and dust orbiting a young star from which a planetary system may form; the word is a contraction of protoplanetary disk. The first proplyds were photographed in the Orion Nebula in 1992 by the Hubble Space Telescope.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。