Naos (Zeta Puppis)

Zeta Puppis

Naos (Zeta Puppis) is a blue supergiant and the second brightest O star in the sky in terms of apparent magnitude. It is embedded in the Gum Nebula and used to be the Zeta star of Argo Navis (Jason's vessel Argos) – the Greek naos meaning "ship" – before becoming Zeta in Puppis, the Stern, after the big constellation was broken up.


Typical of its breed, Naos is blowing a fierce stellar wind, averaging 2,300 kilometers per second and over a millionth of a solar mass a year (10 million times the rate lost by the Sun). This wind has been so well observed at wavelengths from radio wave to X-ray that it has become a major proving ground for stellar wind theorists.


Naos is a classic O-type runaway star, having been ejected at high speed (nearly 100 km/s) from its place of origin in the neighboring constellation Vela. Over the past 1 to 2 million years – much of its brief life – it has covered some 400 light-years. Such stars are invariably single and spin much faster than normal O stars: in Naos's case, at least 220 km/s at its equator (100 times the Sun's rotation speed).


visual magnitude 2.21
absolute magnitude -5.96
spectral type O5IAf
surface temperature 42,400 K
luminosity 790,000 Lsun
mass 59 Msun
radius 20 Rsun
distance 1,400 light-years (430 pc)
position R.A. 08h 03m 35.1s, Dec. -40 00' 12"
other designations Suhail Hadar, HR 3165,
HD 66811, SAO 198752, FK5 306,
CoD C-39 3939, CPD P-39 2011,
HIP 39429