Question

Which spectrum class does a star fit into if it has a surface temperature of 20,000 K

Answer 1

A star with a surface temperature of 20,000 K fits into the O spectral class. The O class consists of the hottest stars, with surface temperatures typically ranging from about 30,000 K down to about 10,000 K. Thus, a star at 20,000 K would be classified as an O star, specifically one of the cooler O-type stars.