NGC 1491 (LBN 704, LBN 706, Sh 2-206) - Emission nebula and HII region in Perseus

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© Velimir Popov & Emil Ivanov 2013
    Size: 1800 px      

NGC 1491 (also designated SH2-206 and LBN 704) is a bright emission nebula and HII region, located on the edge of a vast cloud region of neutral gas, about 10 700 light-years. HII regions are well known for being places where new stars are born, and are created when ultraviolet radiation from hot stars ionizes the surrounding gas, causing it to glow in visible light. The surrounding dust is also heated by this radiation, so we also see it glow in infrared light. The entire nebula is quite irregular.

The major source of ionizing radiation is the blue star BD +50 886, which has been classified either as O5V star (Crampton, D., Fisher, W.A. 1974 Publ. Dominion Astrophys. Obs. Victoria Vol. 14, No. 12, p. 296-297) or as O4 star (Hunter, D.A., Massey, P. 1990, Astronomical Journal (ISSN 0004-6256), vol. 99, March 1990) The ionizing star is located about 1' to the east of the brightest emission. The blue star is illuminating the nebula while its strong stellar wind is “blowing” a bubble in the gas that immediately surrounds it.

Image details (mosaic):


Center of field RA 04:03:15 (h:m:s)
Center of field DE +51:17:58 (deg:m:s)
Size 34.8 x 34.8 (arcmin)
Pixel scale: 1.04 (arcsec/pixel)
Orientation: Up is 179 degrees E of N
Charts and image details obtained from
Optic(s): RC 12" with Astro-Physics corrector @ f/5 (RC)
Mount: ASA DDM85 Premium
Camera: ATIK 4000 M
Filters: Astronomik HaLRGB filter set
Dates/Times: 5, 11 and 17.11.2012
Location: IRIDA Observatory, BG, longitude: E 24 44' 18", latitude: N 41 41' 42"
Exp. Details: L:10x10 min, R:7x10 min, G:7x10 min, B:7x10 min, Ha:5x20 min, OIII:7x20 min
  Bin 1, Total Exposure Time - 550 min (9:10 hrs)
More details: Dark and flat frames reduction
Processing: PixInsight / PS
Copyright: Velimir Popov and Emil Ivanov 2013. All Rights Reserved
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