Alpha Centauri A, otherwise known as Rigel Kentaurus A, Toliman A, Bungula A, Gliese 559 A, HD 128620 and HIP 71683, is the principal member, or primary, of the binary system Alpha Centauri. It is a solar-like main-sequence star with a similar yellowish colour, whose stellar classification is spectral type G2 V; it is slightly larger and more luminous than Sol. From the determined mutual orbital parameters, Alpha Centauri A is about 10 percent more massive than the Sun, with a radius about 22 percent larger. When considered among the individual brightest stars in the sky (excluding Sol), Alpha Centauri A is the fourth brightest at an apparent magnitude of +0.01, being slightly fainter than Arcturus at an apparent magnitude of −0.04.
The type of magnetic activity on Alpha Centauri A is comparable to that of the Sun, showing coronal variability due to star spots, as modulated by the rotation of the star. However, since 2005 the activity level has fallen into a deep minimum that might be similar to the Sun's historical Maunder Minimum. Alternatively, it may have an over long stellar activity cycle and is slowly recovering from a minimum phase.