What characterizes the photographs used to showcase breathtaking images of nebulae from space telescopes?

Answer

They are long-exposure composites

The stunning photographs are almost never what is seen through an eyepiece; they are typically long-exposure composites where the camera shutter is left open for minutes or hours to gather a massive cumulative amount of light.

What characterizes the photographs used to showcase breathtaking images of nebulae from space telescopes?
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