Space jellyfish, and occurs when sunlight reflects off of plumes of exhaust gases from recently launched rockets, particularly later in the evening or in the early morning.
The phenomenon has been observed more frequently as more launches occur, and with the advent of reusable rockets, exhaust gases are also present when a rocket fires its engines as it returns to the ground
Photographer David Johnston was capturing shots of the Milky Way on the night of June 19th when he noticed a large red spot in one of his photos (This Background Image)
Coincidentally, SpaceX had launched one of its Falcon 9 rockets, carrying a Globalstar satellite minutes before when Johnston first noticed the red appear in the sky