Tau Canis Majoris Cluster, Mexican Jumping Star
|Right Ascension||07 : 18.8 (h:m)
|Declination||-24 : 57 (deg:m)
|Visual Brightness||4.1 (mag)
|Apparent Dimension||8 (arc min)|
Discovered by Hodierna before 1654.
Independently rediscovered by William Herschel in 1783.
The Tau Canis Majoris cluster, NGC 2362, was one of the discoveries of Giovanni Battista Hodierna, which he published in 1654. Nevertheless, as these observations were forgotten until their rediscovery in the early 1980s, this cluster escaped its rediscovery until it was eventually found by William Herschel on March 4, 1783 as his second discovery, and cataloged by him as H VII.17 based on his measurement of March 6, 1785.
Open cluster NGC 2362 contains about 60 stars, and with 25 million years, is quite young; it is still associated with nebulosity. The brightest star is Tau Canis Majoris, which is of magnitude 4.39 and spectral type O8 (Sky Catalog 2000). As it is the brighter component of a a spectroscopic binary, the mass of the system could be estimated at 40 to 50 solar masses. If, as it appears, this star is actually a member of this cluster at 5,000 light years distance, it is one of the most luminous supergiants known, at about absolute magnitude -7, or 50,000 solar luminosities.
The Sky Catalog 2000 classified this cluster as of Trumpler type I,3,p,n, taking into account that it is associated with a huge but faint diffuse nebula, which is 1.5 x 5 degrees in extension ! However, Burnham states that there's no nebulosity in the immediate neighborhood; this may be blown away by the enormous stellar wind of the young stars, above all Tau CMa.
The image in this page was obtained by Chris & Dawn Schur.
Caldwell 64 in Patrick Moore's list.
Last Modification: March 29, 1998