Question

why does sun appear reddish early in the morning ?will the phenomenon be observed by an astronaut on the moon?

Answer 1

In the morning, the sun is at the horizon. Sunlight has to travel a long distance through thick layers of air. The colloidal particles in the sky like molecules of air scatter away coulours of shorter wavelengths like blue. So colors of longer wavelengths enter our eye like red. Hence the sun appears reddish during morning.

In the noon, the sun is overhead and sunlight has to travel a relatively shorter distance. Here, the colloidal particles in the sky scatter very little of colors of shorter wavelengths like blue. Hence it appears white.

Answer 2

The sun appears reddish early in the morning due to atmospheric refraction.
No, the astronaut will not be able to observe atmospheric refraction as there is no atmosphere in outer space(moon).