Pic 1 and 2, a night sky full of stars. Pic 3 and 4, no stars. Help me understand because I am Nescio.
'Nescio' is Latin for 'I don't know' ('ne' = not; 'scio' = know). There are a few reasons why there aren't stars in some pictures taken from space because of light from the sun, the camera and exposure used, etc. Basically, in space the sun is extremely bright and blocking out light from distant stars (not to mention light from the earth, reflected off the moon, etc.). Those stars are there, but their light is so dim that the camera isn't picking it up. Hubble, or the upcoming JWST telescope, does see this star light by contrast.
Those first two would be long exposure images. I suspect the hikers were superimposed in the first. As Ath said, the space walker is in full sun so the camera would be taking a hight speed shutter shot. Just take your camera out at night some where dark and take a picture of the sky. You might capture the bright ones. When I did some nightshots with an old 35mm SLR I would leave the shutter open for 10-12 seconds using 800 or 1000ASA film.
Yup. Make sense. A bit like the question why we can see the moon while we know from the moon landings it's a total dark place over there. Found some interesting examples of shutter speed. https://en.wikipedia.org/wiki/Shutter_speed