Star
Nunki
Blue-white star · B2.5V
σ Sagittarii · Sagittarius
Shown in its true colour — like most stars, it is too far away to photograph as more than a point of light.
Sigma Sagittarii, Latinized from σ Sagittarii; formally named Nunki, is the second-brightest star in the constellation of Sagittarius. It is a binary star system, viewed as a single star of combined apparent magnitude +2.05, about the same brightness as Saiph in Orion. The distance to this system, determined using a dynamical parallax measurement, is 225 light-years.
Description from Wikipedia (CC BY-SA 4.0).
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Key facts
Distance
~228 light-years
Apparent mag.
+2.05
Spectral type
B2.5V
Luminosity
643 × Sun
Absolute mag.
−2.17
Catalogue
HIP 92855
Spectral type
B2.5V
True colour from its B–V index (-0.13): a surface around 12100 K.
Did you know
- Nunki is also known as σ Sagittarii.
- Its spectral type B2.5V marks it as a blue-white star.
- It lies in the constellation Sagittarius.
