What is the Sun's spectral classification?

What is the Sun’s spectral classification? The Sun’s spectral classification is G2V. This compact label combines a temperature-based spectral class with a luminosity class describing its evolutionary state.

The letter G places the Sun among yellow stars with surface temperatures broadly between those of hotter F-type stars and cooler K-type stars. The number 2 identifies its position within the G sequence: lower numbers are hotter and higher numbers are cooler. The Sun’s effective surface temperature is about 5,800 kelvin, though its color appears nearly white when viewed from space.

The Roman numeral V means luminosity class five, or a main-sequence star. Main-sequence stars are supported by a balance between inward gravity and outward pressure generated by hydrogen fusion in their cores. The Sun is therefore a G-type main-sequence star, often informally called a yellow dwarf.

Spectral classification is determined from a star’s spectrum, especially its absorption lines, rather than from color alone. The Sun is sometimes called an “average star,” but that is only partly true: most stars in the Milky Way are smaller, cooler red dwarfs. The Sun is currently about halfway through its roughly 10-billion-year main-sequence lifetime.