A-type stars are a class of stars characterized by their white to blue-white color and high surface temperatures, typically ranging from 7,500 to 10,000 Kelvin. They are known for their strong hydrogen absorption lines in their spectra, which indicates that they are in a stable phase of hydrogen burning. A-type stars are often more massive than the Sun and can be found in various stages of stellar evolution. These stars are usually brighter than many other types, making them prominent in the night sky. Examples of A-type stars include Sirius A, the brightest star in the night sky, and Altair, part of the Summer Triangle. A-type stars have relatively short lifespans, lasting only a few hundred million years before evolving into red giants or other stellar types.