An artist's impression of Sirius A and Sirius B. Sirius A is the larger of the two stars.
Sirius A has a mass of 2 M☉.[12][94] The radius of this star has been measured by an astronomical interferometer, giving an estimated angular diameter of 5.936±0.016 mas. The projected rotational velocity is a relatively low 16 km/s,[15] which does not produce any significant flattening of its disk.[95] This is at marked variance with the similar-sized Vega, which rotates at a much faster 274 km/s and bulges prominently around its equator.[96] A weak magnetic field has been detected on the surface of Sirius A.[97]