The sun in this photo framing the tower of the Golden Gate Bridge, and, for that matter, all suns in the photo other than the real sun, are caused by an optical phenomenon called double refraction. (Double refraction is also called birefringence).
In double refraction, each ray of light separates into two rays (the “ordinary” ray and the “extraordinary” ray) when the light heads through the lens. The extra suns are in my photo caused by the extraordinary rays. The birefringence effect is dependent on how the light is polarized.
Normally, you’d want to avoid something like double refraction in your photos (although, avoid as much as can, you’ll likely see some if you shoot directly into the sun with a long lens as I did in this photo).
But last night I was feeling bored, and I knew I had more than enough photos in my files for my Golden Gate project, so I amplified the effect by adding a polarizing filter in front of my lens, and rotating the outer ring of the filter to change the direction of polarization until the subsidiary “sun” was in position.
[375mm in 35mm terms, circular polarizer, 1/750 of a second at f/9 and ISO 100, tripod mounted.]