Why Is the Sun Red-Orange?

Star Classification

The sun is a class G star, according to the current spectral classification used in modern astrophysics. With a surface temperature of about 5,000 to 6,000 K, it is certainly much hotter than any person on earth can withstand, but in comparison to other stars, it is actually relatively cool. The hottest stars in the universe burn blue and white, reaching up to 60,000 K in temperature. Conversely, the sun is more of a yellow or orange, the color of "cooler" stars, due to its composition of ionized and neutral metals, along with weak hydrogen lines.

The red and orange color that you see is the result of the light particles being diffused by the particles in this atmosphere, which is mostly composed of oxygen and nitrogen. These two elements scatter light wave photons in general but have a greater effect on light frequencies that are closer to the ultraviolet part of the spectrum. As such, red and orange, which are farthest from ultraviolet, are least affected by atmospheric particles. Therefore, when you see the sun, you are more likely to perceive it as either or both of these colors instead of as violet, blue or other colors closer to ultraviolet.

When the sun is setting, the side of the Earth that you are on is turned away from the sun's brilliance. Consequently, the mass of the air particles can be said to be denser than when the sun is shining, without the sun's rays to dissipate them. More particles means more light scattering, which translates into a more prominent red and orange hue for the sun when it goes down. This effect is enhanced further if there is plenty of cloud cover, creating more of an atmospheric shield for the sun's rays to penetrate.

The sun won't be a reddish orange forever; though, it will be a very, very long time before you will see any significant change in the color of this planet's most important star. Stars change color over time due to the presence or absence of certain gases and metals in their composition, which shifts as they burn towards their eventual demise. The sun has about 5.4 billion years to go, and towards the end of that time, it will swell into a giant red ball before leaving behind a shining white dwarf star.