A형 주계열성, or A-type main sequence stars, are a category of stars that are characterized by their blue-white color and high temperatures, typically ranging from 7,500 to 10,000 Kelvin. These stars are more massive than the Sun and have a spectral classification of A. They are known for their strong hydrogen absorption lines in their spectra, indicating that they are in a stable phase of hydrogen fusion in their cores. These stars are often found in open clusters and can be quite luminous, with luminosities up to 100 times that of the Sun. Examples of A-type stars include Sirius A and Altair. A-type main sequence stars have relatively short lifespans, usually lasting around 1 billion years before evolving into giant stars.