Whenever we see the photographs clicked in the space or taken by the astronauts, why are there no stars visible in them?
Let us find out the real reason behind it.
The reasons why stars are not seen in the space photographs are completely different. First, the visibility of stars in a photo depends on the sensitivity of the camera’s matrix, its resolution and exposure time.
The human eye also has its sensitivity and an analog of exposure, and we see stars whose apparent magnitude is up to +6m or +8m if the sky is perfectly dark.
If you try to take a picture of the starry sky on the phone’s camera, then on it, like on the space photographs, most or almost all stars will not be visible, their magnitude is just very low for the camera.
But if you take a special camera with long exposure and high resolution, then you can see many stars than the human eye sees.
So, the astronauts see more stars while being in the space than those that are taken in the photographs.
Secondly, the visibility of stars is affected by illumination from brighter objects. In a large metropolis at night, it is impossible to see a single star in the sky due to the fact that their light is blocked by the light of the city. This effect is known as light pollution.
Light pollution is one of the reasons why modern expensive telescopes operating in the optical range are placed away from cities high up in the mountains.
In orbit, the exposure is due to light from the Sun, as well as due to the light reflected by the Moon and the Earth. Onboard the ISS, most of the time, one of these bodies creates an intense light, and it cannot be filtered without special cameras.
As for observing stars in orbit with the naked eye, light pollution here, especially from the Sun, can greatly complicate observation.
So, for example, the astronauts of the Apollo missions while on the Moon could observe the stars with the naked eye only hiding from the Sun in the shadow of the landing module.