Practise IB Physics SL B.1.15 by comparing apparent brightness and combined stellar light, using distance and intensity evidence to explain what observers see.
Alpha Centauri A and B form the closest binary star system to the Earth. This binary star system is the third brightest stellar object in the night sky.
Arcturus is the fourth brightest star in the night sky. Its apparent brightness is slightly greater than that of the star Alpha Centauri A.
Outline why the binary star system Alpha Centauri appears brighter than Arcturus.
addition of Alpha Centauri B to the luminosity/brightness of the binary star system
OR
combined luminosity/brightness of the binary stars
OWTTE