NGC4372 and the Doodad

NGC 4372, a globular cluster in the constellation of Musca (the fly). Located 18.9Kly (5.8Kpc) from the Solar System and 23Kly from the Galaxy's centre, the cluster is approx' 49.5ly in radius (99ly diameter) and weighs in at 3.29x10^5 solar masses. The cluster is one of the very metal poor (Fe-H = -1.88dex) and ancient (12.54Ga) clusters of the Galaxy and is categorised as a class XII globular cluster, meaning it is one of the less concentrated clusters by appearance. It's most likely in a relaxed state, having undergone core collapse and then rebound in the past. Two of its giant stars V1 and V2 have been shown to be unusually bright AGB (Asymptotic Giant Branch) stars, both with luminosities around 8000 solar. Normally, red giants along the AGB top out at around 5000-6000 L solar and it is believed that the conditions of their formation within such a metal poor cluster has contributed to their unusually high luminosity. Both stars are long period variables that appear to be undergoing the superwind stage that terminates their membership of the AGB and will finally, after a short period of time, turn them into planetary nebulae.

The bright blue star at the top of the picture is Gamma Muscae, a B5V star of the slowly pulsating B star variable type (SPB), varying between 3.84 and 3.86mag over a period of 2.7 days. The star weighs in at around 5 solar masses and is around 4 times the radius of the Sun. The dark, finger like projection just below ngc4372 is part of the dark nebula known as the Dark Doodad. The Doodad subtends a length upon the sky of some 3 degrees and is one of the closest star forming regions to the Solar System.

Pic was taken with t68 at the Bathurst Observatory (BAT-iTelescope Network), 15x120sec subs.
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