A second prominent open star cluster to the north-west of the Great Carina Nebula (NGC 3372, G.C.N.) is
the Gem Cluster, or Little Jewel Box. This is a compact cluster of more than 100 stars, the dominant ones
being blue supergiants and a pulsating red supergiant, V361 Carinae.
At 8,400ly distant, it is obviously associated with the G.C.N. (at 8,500ly). It, also, is a young cluster, with an
estimated age of just 12 million years, like the other cluster in this region, NGC 3324. Also, like NGC 3324,
there is mass segregation within the cluster, the larger and more massive stars accumulating near the core.
A recent spectroscopic study of this cluster puts doubt on some of the above (
https://phys.org/news/2022-08-young-cluster-ngc.html). An age estimation of around 20My was determined, making this cluster
one of the oldest in the G.C.N. region. Also, this age relates to the dim, red stars within the cluster, the
obvious blue supergiants being of a much younger age.
The enveloping nebula is a prominent H-II region, catalogued as GUM 30 and RCW 51. I have used a
filter that emphasises the emission spectra of the nebula in order to display its complexity. This filter
also has the beneficial effect of reducing the First Quarter Moon’s detrimental sky glow.
Telescope: APM 152mm f/7.9 APO refractor, f=1200mm
Camera: ZWO ASI294MC Pro
Exposure: 45 x 300 sec, Optolong L-eNhance filter
Bortle 3-4 sky, 50% Moon waxing
Field of View: approx. 0º 55’ x 0º 37’
Image processed and prepared in PixInsight and Photoshop Elements
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