Actually, it's true that glass stops near UV... when you get to high energies, though, the photon passes through the glass, through the sensor, through the back of the camera, and through you. But it can leave a little energy in its wake and generate a blip on the image. If you take an extended image with the shutter closed, or with the cap on, if that's not possible, you'll see some bright pixels...there's lower level electrical noise, but the bright pixels are cosmic rays. The higher you turn up the ISO, the lower the excitation threshold is, and you get more of these bright pixels in a shorter period of time. That's the way I understand it, at least. When I was working in lasers...this kind of thing occasionally became a real nuisance.
But this is waaaay OT. We all agree that there really isn't noise, per se, in this photo, and there are other issues which have to do with optimizing the light into the camera, that would make a picture like this better.