Object of the Week, November 15th, 2020 – NGC 1624 + Sh 2-212
NGC 1624 (Cr 53) + Sh 2-212 (LBN 722)
[Open Star Cluster + Emission nebula]
Perseus
RA: 04 40 36.4
DEC: +50 27 42
Between the stars Capella and Mirphak we find a nice combination of an open cluster inside an emission nebula.
Discovered by William Herschel in 1790 he already described the cluster and the nebula: "6 or 7 small stars, with faint nebulosity between them, of considerable extent, and of an irregular form". From Steve's notes I learned that G.P. Bond rediscovered the object later in 1851.
The cluster itself seems to be very young with an age of less than 4 million years. Trumpler classify the 11.8mag bright and 3' large cluster as "l2pn". The special is the brightest single star "NGC 1624-2". This 11.7vmag star which is positioned right in the middle of the cluster is considered as the most magnetic massive star known. Despite the absorption of the field and the high extinction by dust, the massive star with its strong radiation seems to be one of the stars (the other is named ALS 18661, 13.1vmag, 30" SE) which ionized the nebula.
Although Herschel already mentioned the nebula around the cluster, Steward Sharpless cataloged it as a single object in his compilation of 313 nebula in 1959. The special is a YSO at the NW border of the nebula. Deharveng et al. [2008A&A...482..585D] described this object (IRAS 04366+5022) as a "massive star formed in isolation triggered via the collect and collapse process".
I've logged two observation. While the 20x125 binocular shows a small, unresolved but bright cluster, the 14.5" shows some stars and the nebular around. Challenging for big telescopes could be the resolution of the cluster and the observation of the YSO.
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