|Right Ascension||08 : 47.8 (h:m)
|Declination||-42 : 29 (deg:m)
|Visual Brightness||4.6 (mag)
|Apparent Dimension||(arc min)|
Possibly discovered by Lacaille 1751-52. Discovered by Dunlop 1826. Independently rediscovered by Trumpler 1930.
This bright cluster matches well in position with No. II.6 in Lacaille's catalog of 1751-52, although it was a missing Lacaille object for a long time. From Lacaille's list, it found its was into Johann Elert Bode's atlasses and catalogs, and e.g. listed as "f 396 Argus" in his Uranographia (Bode 1801), which were then used by James Dunlop, who found it to be a cluster and cataloged it as Dun 490 (Dunlop 1828). The identity of Lac II.6 and Dun 490 was noted by Arthur Auwers in 1862 when investigating Lacaille's catalog (Auwers 1862). It was independently found by R.J. Trumpler in 1930 and cataloged as Trumpler 10.
This cluster was classified as of Trumpler type II 3 m (Götz) or II 2 p (Sky Catalogue 2000.0). Its brightest star is given as of mag 6.42, and from the spectral type B3 of its bluest main sequence star, an age of 47 million years was derived. According to the WEBDA database (see below), Trumpler 10 is about 1100 light-years distant (the Sky Catalogue has 1400 ly) and somewhat younger, namely 38 million years old.
Last Modification: May 25, 2008