Aludra (Eta Canis Majoris)

Aludra and Canis Major

Canis Minor and Aludra. Map © 2003 Torsten Bronger.

Aludra (Eta Canis Majoris) is a supergiant B star and the fifth brightest star in the constellation Canis Major. Its name refers to an Arabic group called "the Virgins," which consists of the stars of the Great Dog's lower portions. Some of the Virgins, including Aludra and Wezen, are in a loose stellar association known as Collinder 121.


Formed only about 12 million years ago, Aludra is already in old age, blowing a strong stellar wind from its surface at a speed of some 500 km/s. The material it has lost – about one-third of a solar mass – has gathered into a cloud that is detectable by its infrared emission. A seventh magnitude white star about 2' from Aludra, easily visible in a small telescope, is not a physical companion but lies a mere 600 light-years from the Sun – about five times closer than Aludra itself.

visual magnitude 2.45
absolute magnitude -7.51
spectral type B5Ia
surface temperature 13,500 K
luminosity 100,000 Lsun
distance 3,200 light-years (1,000 pc)
position RA 07h 24m 05.7s,
Dec -29° 18' 11"
other designations 31 Canis Majoris, HR 2827,
CD-29°4328, HD 58350,
SAO 173651, FK5 283,
HIP 35904, GC 9886,
CCDM 07240-2918