Do astronauts age while traveling in space?

Yes they do. There is a common belief that astronauts do not age in space, or they age much more slowly than people on Earth, and this is true because of relativity, as time runs slowly the faster an object is moving. However, for relativistic effects to be visible, one must be travelling close to the speed of light, and the highest speed achieved by humans in space is nowhere near that speed. Even if we were able to achieve such high velocities, astronauts would still age, but because on this fast moving spaceship time runs more slowly, when the astronauts returned to Earth, it would appear as if they didn’t age much compared to people on Earth. This effect is called “time dilation” and is one of the fundamental ideas discussed in Einstein’s Theory of Relativity.