Because NASA images and those produced by major observatories do not show exactly what the human eye sees.
Most of these images are created using long exposures, ranging from several minutes to many hours. During that time, telescopes collect far more light than our eyes can perceive in a single glance.
In addition, many images combine photographs taken through different filters to reveal chemical elements, temperatures and physical processes that are invisible to human vision. They are then digitally processed to highlight scientific information.
One of the most important tools used by astrophysicists is spectroscopy. Rather than simply taking a picture, they analyse the light emitted by stars, galaxies and nebulae by splitting it into a spectrum, much like a prism separates white light into the colours of the rainbow. This allows scientists to determine the chemical composition of celestial objects, measure their temperature and motion, and even discover planets orbiting other stars. In many scientific images, the colours do not represent what the human eye would actually see, but rather scientific information that helps us better understand the Universe.
When you observe the night sky through a telescope with your own eyes, you see the Universe as human vision naturally perceives it. Although the colours are usually much more subtle than in photographs, the experience is extraordinary because you are looking directly at light that has travelled for thousands or even millions of years before reaching your eyes.
During our experiences, we also explain why celestial objects appear the way they do and how to interpret what you see through the telescope.