Its intensity can be modulated at very high speeds, and it can be switched off at very high speeds.

Photosynthesis is modulated by oxygen, and we have an oxygen insensitive hydrogenase that we think will totally change this process.

So, if you can see a signal that is modulated in such a way, that we see more encounters when earth's velocity vector is alligned with solar velocity vector relative to the galactic center then, and then you see the exact opposite six month later.