[KayEyeDoubleDee]

Remember the speed of sound is far less than the speed of light. The size of the ripples are about 30,000 light-years.

It seems to me that if some process occurs once every 10 million years, then a byproduct travelling at the speed of light will be 10 million light years away at the next occurence.

[RadioAstronomer]

It seems to me that if some process occurs once every 10 million years, then a byproduct travelling at the speed of light will be 10 million light years away at the next occurence.

Indeed if the sound waves were traveling at c, they would be. The waves heat up the gas, which then emit X-rays.