This is an image of the very last test of the Pratt & Whitney J58, the engine that powered the legendary SR-71 Blackbird and A-12 Oxcart. It used to get so hot at full afterburner that it looked like it was about to melt. Those shock diamonds are beautiful.
I love this description excerpted by The Aviationist:
To experience a J58 in full burner close up and personal is hard to describe. Picture a gigantic blow torch, 40 inches in diameter, putting out a blue-yellow-orange flame over 50 feet long. Imagine standing 30 feet from this, feeling the vibration and heat. You wear both foam plugs and earmuffs. Your ears still ring afterward, because the sound is conducted through your body. The back half of the engine transforms from dull grey to bright orange, seemingly transparent. The flame has little three-dimensional diamond shaped shock patterns about every two feet. I lost count at 13. It is both frightening and beautiful, an amazing demonstration of perfectly controlled power. And to think — this was done with 1950s technology…