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View Full Version : Object of the Week, November 15th, 2020 – NGC 1624 + Sh 2-212



Uwe Glahn
November 16th, 2020, 09:36 PM
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.

PanStarrs (with marked YSO)
4098

Sketch: 14.5", 142x, UHC, Seeing V, NELM 6m5+
4099
home (http://www.deepsky-visuell.de/Zeichnungen/NGC1624.htm)

As always, give it a go and let us know.

lamperti
November 17th, 2020, 07:11 PM
With a 22" at 77x: "The UHC filter showed it better than the O-III. Higher magnification did not show it as well. Looks like a small cluster with an emission glow around it. Very small and no sharp edges.

Raul Leon
November 17th, 2020, 08:31 PM
Hi here's my observation from 12/20/2011 : Ngc 1624 cluster with nebulosity ; magnitude: 11.8 ; size:5'x5' ; no filter used, the nebula is fairly faint and is more evident using averted vision. I used a 10mm Radian at 158x with my 14.5 Starstructure Dob f/4.34101

Robin
November 27th, 2020, 02:59 PM
Hi Uwe,

Recently I had a chance to observe this nebula and star cluster with my 12" Dobsonian. At 168x magnification, using a UHC filter, I saw a faint and diffuse glow centered around the brightest star of the cluster. I did not see the nebula witout filter.

Clear skies,

Robin

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