Abstract: The relation between the stellar oscillation frequency and the average density is obtained by a semi-qualitative consideration of the equilibrium between gravity and pressure. It is explained to measure a stellar distance according to a period-luminosity relation.

Key words: stars, gravitational equilibrium, Cepheid variables

摘要： 根据球对称恒星引力与压力间的平衡，用半定量方法得到了恒星振动周期与其平均密度的关系。简要地说明了周光关系方法测量恒星距离的原理。

关键词: 恒星, 引力平衡, 造父变星