Nunki (Sigma Sagittarii)

Nunki (Sigma Sagittarii) is the second brightest star in the constellation Sagittarius; its Babylonian name is of unknown origin. Blue-white Nunki is a B star and one of the hotter of the bright stars, radiating much of its light in the ultraviolet. Typical of its breed, it is a fast spinner, rotating with a speed of over 200 kilometers per second – 100 times that of our Sun. Although still on the main sequence, Nunki is much more massive than the Sun and will exhaust its internal fusion reserves in another 50 million years or so.


visual magnitude 2.05
absolute magnitude -2.14
spectral type B3V
surface temperature 20,000 K
luminosity 3,300 Lsun
radius 5 Rsun
mass 7 Msun
distance 224 light-years
position R.A. 18h 55m 15.9s,
Dec. -26° 17' 48"