What spectral class is Altair categorized under?

Altair is categorized as a spectral class A7 star. This classification indicates that it has a relatively high surface temperature ranging from about 7,500 to 10,000 Kelvin, which is typical for A-type stars. These stars often exhibit a white or bluish hue due to their temperature, and they are characterized by strong hydrogen absorption lines in their spectra.

Spectral class A stars, including A7, are known for having a significant presence of metallic lines, which reflect their relatively high luminosity and surface temperature. Altair, being a well-studied star and part of the Summer Triangle asterism, represents a classic example of this stellar classification, further distinguished by its rapid rotation, which affects its shape and brightness.

In contrast, the other spectral classes listed—K2, M5, and B3—represent different temperature and luminescence characteristics. K-type stars, like K2, are cooler and are known for their orange color. M-type stars, such as M5, are even cooler, appearing red and often being associated with red dwarfs. B-type stars, exemplified by B3, are much hotter and typically appear blue, having distinctively different spectral features compared to A-type stars. Thus,