克赫历程是天文学的事件，发生在恒星或行星表面冷却时。冷却的结果，造成恒星与行星的降压，并且以收缩来补偿。这种压缩，相对的加热了恒星/行星的核心。这种历程在木星和土星，还有核心温度不够高，不足以引发核融合的棕矮星上非常明显。估计木星就是通过这个机制才使他能释放出比从太阳吸收到更多的能量，但是土星可能没有。

这个机制最初是由开尔文和亥姆霍兹在1800年代晚期提出，用来解释太阳的能量来源。我们现在知道，克赫历程所能产生的总能量远低于太阳所释放出来的能量。

The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools. The cooling causes the pressure to drop, and the star or planet shrinks as a result. This compression, in turn, heats up the core of the star/planet. This mechanism is evident on Jupiter and Saturn and on brown dwarfs whose central temperatures are not high enough to undergo nuclear fusion. It is estimated that Jupiter radiates more energy through this mechanism than it receives from the Sun, but Saturn might not. The latter process causes Jupiter to shrink at a rate of two centimetres each year.