The second X-ray source to be discovered, during a 1963 sounding-rocket flight, and the first to be identified optically. The X-ray emission originates from the pulsar at the heart of the Crab Nebula supernova remnant.
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。