Sh 2-46
H II region
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Sh 2-46 (also known as RCW 158), is an H II region, a glowing cloud of ionized hydrogen gas—located in the southern constellation of Serpens. Situated approximately 6,000 light-years from Earth, the nebula is notable for its red emission caused by the ionization of hydrogen atoms, energized by the central runaway star HD 165319 (O9.7Ib).[2] It is an isolated nebula positioned above the galactic plane and contains polycyclic aromatic hydrocarbons (PAHs).[3][4][5] It is located about 3° west of the Eagle Nebula (Messier 16) and is part of broader star-forming activity in the region.[6]
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| Nebula | |
|---|---|
Image of Sh 2-46 Nebula | |
| Observation data: epoch | |
| Right ascension | 18h 06m 6.00s[1] |
| Declination | −14° 08′ 60.0″[1] |
| Distance | 6,000 ly (2,000 pc) |
| Constellation | Serpens |
| Designations | Sh 2-46, RCW 158, Gum 80, LBN 58[1] |
Central star
The primary ionizing source for Sh 2-46 is the massive O-type supergiant star HD 165319, classified as O9.7Ib. This luminous blue star is a runaway star, believed to have originated in the nearby Eagle Nebula (NGC 6611) but was ejected due to gravitational interactions about 1.8 million years ago. As it travels through Sh 2-46 at high speed, it creates a dynamic environment, including the observed bow shock.[2][3][7][8]
