Zeta (ζ) Puppis

	z Puppis		Bayer designation (1603)
	HR 3165		Harvard Revised Photometry designation (1879+)
	HD 66811		Henry Draper Catalogue (1918+)
	SAO 198752		Smithsonian Astrophysical Observatory (1966+)
	39429		Hipparcos catalogue (1997)

Synopsis

Single star; early Of-type supergiant, MK type O4I(n)f; located in Puppis; R.A. 08:03:35.052, dec. -40:00:11.64; culmination early March; magnitude 2.25; distance 429 pc (approx 1400 light years).

Introduction

Zeta Puppis is one of the best studied O-type stars; several important parameters have been determined with good accuracy, including the distance 352 (429) 549 pc (~1400 light years); diameter 20 R_¤; effective temperature 42,000 ± 1500 K; and period of rotation ~4.8 – 5.2 days (Howarth et al. 1995, Schaerer et al. 1997).

Most books will say that the star is commonly known as “Naos” but I have never heard anyone, astronomer or layman, use the name.

Description

The spectral type is certainly early O: Ochsenbien et al. 1988 published a value of O5Iaf; the earlier value of O4I(n)f derived by Walborn 1972 is preferred by Howarth et al. 1995 (table 1) and also by Schaerer et al. 1997.

Mass loss is typical for hot luminous stars. For Zeta Puppis a mass loss rate was determined from radio data by Lamers and Leitherer and rescaled by Schaerer et al. (1997) to reflect their revised distance estimate, yielding log M-dot = -5.57 ± 0.15.

Zeta Puppis possibly belongs to the young Vela R2 association of stars (Sahu 1992, Schaerer et al. 1997).

Interpretation

Observing

Locating

z Puppis is located in Puppis, the largest of the four constellations established in the 1750s, when Nicolas Louis de Lacaille divided up the ancient constellation of Argo Navis. As a consequence of this history, there is no α, β, etc. Puppis; at magnitude ~2.3, z is the brightest star in the constellation, and easily found with any star chart. Alternatively, if you think about the “false cross” as an approximate mirror image of the real cross, z Puppis is the more distant of the two mirrored pointer stars.

Appearance

A brilliant blue-white star, easily seen with the naked eye or any optical aid.

References

Böhm-Vitense, E. 1989a: Introduction to Stellar Astrophysics. Volume 1 – Basic Stellar Observations and Data. Cambridge University Press.

Howarth, I.D.; Prinja, R.K.; Massa, D. 1995: The IUE MEGA Campaign: The Rotationally Modulated Wind of ζ Puppis. Astrophysical Journal 452: L65-L68.

Lamers, H.J.G.L.M.; Cassinelli, J.P. 1999: Introduction to stellar winds. Cambridge University Press.

Ochsenbein F.; Halbwachs J.L. 1987: Le Catalogue des Etoiles les Plus Brillantes (Catalogue of the Brightest Stars). Bull. Inform. CDS 32, 83. NASA Astronomical Data Centre, catalogue 5053A.

Ochsenbien, F.; Acker, A.; Legrand, E.; Poncelet, J.M.; Thuet-Fleck, E. 1988: Le catalogue des etoiles les plus brilliantes. NASA Astronomical Data Centre, catalogue 5053.

Sahu M.S. 1992: A Study of the ISM in Puppis-Vela Including the Gum Nebula. PhD thesis, University of Groningen, The Netherlands.

Schaerer, D.; Schmutz, W.; Grenon, M. 1997: Fundamental Stellar Parameters of ζ Pup and γ² Vel from HIPPARCOS Data. Astrophysical Journal Letters 484: L153-L156.

Walborn, N.R. 1972: Spectral classification of OB stars in both hemispheres and the absolute-magnitude calibration. Astrophysical Journal 77 (4): 312-318.