Epoch J2000 Equinox J2000
|Right ascension||08h 03m 35.1s|
|Declination||−40° 00′ 11.6″|
|Apparent magnitude (V)||2.21|
|U−B color index||−1|
|B−V color index||−0.27|
|Proper motion (μ)||RA: −30.82 mas/yr
Dec.: 16.77 mas/yr
|Parallax (π)||3.00 ± 0.10 mas|
|Distance||1,090 ± 40 ly
(330 ± 10 pc)
|Absolute magnitude (MV)||-5.5|
|Luminosity (bolometric)||550,000 L☉|
|Surface gravity (log g)||3.5 cgs|
|Metallicity [Fe/H]||0.34 dex|
|Rotational velocity (v sin i)||>220 km/s|
Zeta Puppis (Zeta Pup, ζ Puppis, ζ Pup) is a star in the constellation of Puppis. It is also known by the traditional names Naos (//, from the Greek ναύς "ship") and Suhail Hadar (سهيل هدار, possibly "roaring bright one") in Arabic.
Its spectral class is O4If, making it an exceptionally hot star, and it is one of the sky's few naked-eye class O-type stars as well as one of the closest to Earth. It had been assumed to be part of the Vela complex near the Gum nebula over 400 parsecs from Earth, but the 2008 reduction of Hipparcos data gave a distance of 335 parsecs (1,093 ly) ± 4%. Its surface temperature is 42,000 K . The current mass is calculated at 22.5 solar masses and the radius at 14 times the solar radius but these values are highly uncertain. Older derivations assumed the larger distance and were correspondingly larger, but some new calculations still give values up to twice these.
Zeta Puppis is an extreme blue supergiant, one of the most luminous stars in the Milky Way. Visually, it is 12,500 times more powerful than the Sun, but being an extreme blue star, most of its radiation is in the ultraviolet and hence its bolometric luminosity is over 500,000 times that of the sun. It is also the 62nd brightest star in terms of apparent magnitude from Earth
Zeta Puppis, being typical of O-type stars, is also notable for its extremely strong stellar wind, and it has garnered increasing attention for this over the past decade. Its stellar wind velocity has been estimated at 2,500 km/s, which sees the star shed more than a millionth of its mass each year, or about 10 million times that shed by our own Sun over a comparable time period. This mass ejection is highly evident in non-visible wavelengths such as radio and X-ray.
It was long thought that Zeta Puppis was associated with the Vela star-forming region about 1400 light years distant. However the parallax obtained in 2008 from the revision of Hipparcos data (see above) shows that the star is closer. The new distance combined with the known radial velocity show that it encountered the Trumpler 10 OB association around 2 million years ago. It appears not to have originated there since Trumpler 10 has a well established age in excess of 30 million years while Zeta Puppis is no more than a tenth that age. Others theories include the idea that Zeta Puppis was the companion of the star that went supernova and produced the Gum Nebula, but evidence supporting this is sparse. It also shows a common feature of runaways, an anomalously high rotational velocity of 220 km/s at the equator as well as an apparent enrichment in helium and nitrogen on the surface.
In 1896, Edward C. Pickering observed mysterious spectral lines from ζ Puppis, which fit the Rydberg formula if half-integers were used instead of whole integers. It was later found that these were due to ionized helium.
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