The Sun illuminates the Earth in a full spectrum of light during the day, but at sunset much of the ordinary light is filtered out by the Earth’s atmosphere. This leaves mostly the red wavelength of light which is produced by hydrogen from the Sun. Beautiful sunsets are created by the hydrogen light painting clouds red/orange for a few brief moments of glory after the Sun disappears.
The light from the Sun’s hydrogen is always there, it is just drowned out by ordinary light most of the day. With a special filter on specially designed telescopes, however, it is possible to see the light from hydrogen during the day as noted in the lower two images. It is amazing what may be hidden in plain daylight, but we are given a brief glimpse every evening at sunset.
NOTE: NEVER LOOK AT THE SUN WITH ORDINARY TELESCOPES! SEVERE, PERMANENT EYE DAMAGE WILL OCCUR ALMOST INSTANTANEOUSLY. The photos of the sun above were taken through telescopes specifically designed to filter out harmful rays that would damage the eye.