Astronomy:Z Canis Majoris

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Z Canis Majoris
Observation data
Equinox J2000.0]] (ICRS)
Constellation Canis Major
Right ascension  07h 03m 43.16434s[1]
Declination −11° 33′ 06.2209″[1]
Apparent magnitude (V) 9.95
Spectral type Bpe[1]
B−V color index 1.19[1]
Variable type INA[2]
Radial velocity (Rv)−27 ± 10[1] km/s
Proper motion (μ) RA: −4.44[1] mas/yr
Dec.: 2.00[1] mas/yr
Parallax (π)1.24 ± 2.25[1] mas
Distance3750 ly
(1150[3] pc)
Other designations
Z CMa, BD−11 1760, HD 53179, HIP 34042, PPM 218073, SAO 152302.[1]
Database references

Z Canis Majoris (Z CMa) is a B-type star in the constellation of Canis Major.[1] It has an average apparent visual magnitude of approximately 9.85, though has brightened by 1-2 magnitudes in irregular outbursts in 1987, 2000, 2004 and 2008.[4]

The star is a complex binary system only 300,000 years old with two main components separated by an estimated 100 astronomical units (AU) or 0.1" as seen from Earth. The southeast component is an FU Orionis star (a type of pre-main-sequence star in a phase of very high mass accretion resulting in an accretion disk which dominates the optical spectrum) that is 1300 times as luminous as the Sun, has 3 times its mass and 13 times its diameter and a surface temperature of 10,000 K. The northwest component is a Herbig Ae/Be star that has been calculated to be 12 times as massive as the Sun with 1690 times its diameter, and shining with 2400 times its luminosity,[5] though there is some uncertainty about its properties. It is enveloped in an irregular roughly spherical cocoon of dust that has an inner diameter of 20 and outer diameter of 50 AU. The cocoon has a hole in it through which light shines that covers an angle of 5 to 10 degrees of its circumference. Both stars are surrounded by a large envelope of in-falling material that left over from the original cloud that formed the system. Both stars are emitting jets of material, that of the Herbig Ae/Be star being much larger - up to 11.7 light-years (3.6 parsecs) long.[6]

It is unclear whether the most recent (and brightest) brightening in 2008 was due to the Herbig Ae/Be star increasing in luminosity or a hole appearing in the cocoon.[6]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 "V* Z CMa". SIMBAD. Centre de données astronomiques de Strasbourg. 
  2. Z CMa, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 9, 2009.
  3. p. 2075, An infrared companion to Z Canis Majoris, Chris D. Koresko, Steven V. W. Beckwith, Andrea M. Ghez, Keith Matthews, and Gerry Neugebauer, in Astronomical Journal 102 (December 1991), pp. 2073–2078, 2127, 2128, doi:10.1086/116031, Bibcode1991AJ....102.2073K.
  4. Whelan, E.T.; Dougados, C.; Perrin, M. D.; Bonnefoy, M. et al. (2010). "The 2008 Outburst in the Young Stellar System Z CMa: The First Detection of Twin Jets". The Astrophysical Journal Letters 720 (1): L119-24. doi:10.1088/2041-8205/720/1/L119. Bibcode2010ApJ...720L.119W. 
  5. Szeifert, T.; Hubrig, S.; Schöller, M.; Schütz, O. et al. (2010). "The Nature of the Recent Extreme Outburst of the Herbig Be/FU Orionis Binary Z Canis Majoris". Astronomy and Astrophysics 509 (L7): 5 pp.. doi:10.1051/0004-6361/200913704. Bibcode2010A&A...509L...7S. 
  6. 6.0 6.1 Canovas, H.; Min, M.; Jeffers, S.V.; Rodenhuis, M. et al. (2012). "Constraining the Circumbinary envelope of Z Canis Majoris via Imaging Polarimetry". Astronomy & Astrophysics 543 (A70): 8 pp.. doi:10.1051/0004-6361/201117762. Bibcode2012A&A...543A..70C.