Just wondering… I believe the sun is following what is known as the “Main Sequence”. If this is correct, would the sun have been a blue star in its youth? - Jinx
Huh?
Yes, the sun is a yellow main sequence star. That means it will continue to be a yellow star until it becomes a red giant. It won’t change into another colour, and was never another. The colour of a star, determined by its surface temperature, is a function of its mass.
Stars do not follow the Main Sequence. They spend most of their lifetime at a single point along it. So, for its entire MS existence, the sun, or any other star, remains the same color (more or less). You are right, though, that at different points along the main sequence, a star’s color would be different.
Anyone got a link to a good, color, H-R diagram?