A classification of hot, luminous and
massive stars like Altair or Thuban.
The surface temperature of such stars can reach 10,000 Kelvin or more, twice
the surface temperature of the Earth's Sun.
Sirius, the brightest star in the sky, belongs to the A-type white classification. Specifically, the primary star of this binary system (the star visible to the naked eye) is classified as A1Vm. The 'V' here denotes that it is a main sequence or dwarf star, and the 'm' suffix relates to its unusual metallicity, with Sirius A showing unusually high levels of iron in its surface layers. Imagery provided by Aladin sky atlas
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