A bow shock is a bow-shaped normal shock created around a blunt object flying supersonic.

[![enter image description here](https://i.stack.imgur.com/ujFks.png)](https://i.stack.imgur.com/ujFks.png)

The shock itself - mach = 1 - can be very hot at hypersonic speeds. But the subsonic air behind is cooler, which is why we use bow shocks on reentry capsules.

But why is this air cooler? Or, if it isn't, then **why** does the bow shock produce less heating?

**edit: a clarification**

[![enter image description here](https://i.stack.imgur.com/11C6f.png)](https://i.stack.imgur.com/11C6f.png)

**Is this correct?**