He wouldn't have gotten this amount of light in the shot if he had.
He had to give the shot an enormous time of exposure to be able to see all of this. The trails are caused by the stars moving in the sky as the Earth spins, all during the time the camera is absorbing light for the shot.
Incorrect. This is a stacked series of 30sec exposures to give the trails as opposed to a single long exposure. A high iso 30sec shot would have rendered similar lighting without the trails in this instance.