Spectral type A refers to a classification of stars that have a surface temperature between 7,500 and 10,000 Kelvin. These stars are characterized by their strong hydrogen absorption lines in their spectra, which makes them appear white or bluish in color. They are often more luminous than the Sun and can be found in various stages of stellar evolution. Stars of spectral type A are typically young and can be found in open clusters. Examples include Sirius A, the brightest star in the night sky, and Altair, which is part of the Aquila constellation. These stars play a crucial role in the study of stellar formation and evolution.