质心

zhè xiē xì tǒng zhōng suǒ yǒu héng xīng dōu wéi rào yī gè gòng tóng de zhì xīn miáo shù tā men de guǐ dào

这些系统中，所有恒星都围绕一个共同的质心描述它们的轨道。

In these systems, all stars describe their orbits around a common centre of mass.