You can't be Sirius! Globular cluster hidden in glare of brightest star
Posted: Thu Feb 23, 2017 6:14 am
Globular cluster found in the background of Sirius
AnnSergey E. Koposov, V. Belokurov and G. Torrealba wrote:
(W)e report the discovery of two new star clusters, Gaia 1 and Gaia 2. Gaia 1 is particularly curious, as it is a massive (1.4×104 M), large (∼9 pc) and nearby (4.6 kpc) cluster, situated 10´away from the brightest star on the sky, Sirius!
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Based on the size typical for globular clusters in the MW, we conclude that Gaia 1 is a star cluster, most likely of globular variety given its age and metallicity. It also could be an old open cluster similar to e.g. Berkeley 25 located only ∼1 degree away on the sky from Gaia 1. From the density profile fit we also determine the total number of the satellite’s stars with G<19, N ∼ 1200±120. Assuming the Chabrier IMF and the best-fit isochrone, we deduce the total stellar mass of 14000 M and the V -band luminosity of MV ∼ −4. Note please that these numbers are only the ball-park estimates due to the uncertain age and metallicity of the stellar population.
