IC 434

IC 434
Emission nebula
	IC 434 is found behind the Horsehead Nebula
Observation data: J2000 epoch
Subtype	H II region
Right ascension	05h 40.9m
Declination	−02° 27′
Distance	1,260 ly (385 pc) ly
Apparent magnitude (V)	4.5
Apparent dimensions (V)	60′ × 40′
Constellation	Orion
	See also: Lists of nebulae

IC 434 is a bright emission nebula in the equatorial constellation of Orion. It was discovered on February 1, 1786 by German-British astronomer William Herschel.^[2] The nebula is located at a distance of approximately 1,260 ly (385 pc) from the Sun and spans the interior of a neutral hydrogen shell with an angular size of 2° × 4°. At that distance, the dimensions correspond to a projected size of 42 ly × 85 ly (13 pc × 26 pc).^[2]

This is an H II region that is being ionized by ultraviolet radiation from the nearby Sigma Orionis (σ Ori) multi-star system. An additional half dozen stars provide further illumination of IC 434. This H II region is one of the youngest to form around members of the Orion OB1 association of hot stars. The region has a radius of about 13 ly (4 pc) and a mass of around ~ 100 M_☉ The mass displaced by the advancing ionization front of IC 434 is estimated at 10⁴ M_☉.^[3] The nebula includes dust with an estimated mass of 2.3 M_☉.^[2]

IC 434 is surrounded by a shell of neutral hydrogen gas with the identifier GS206-17+13. The primary driving energy behind this expanding shell was likely supplied by the blue supergiant Epsilon Orionis.^[2] The Horsehead Nebula is a dark nebula that is silouetted against the diffuse background of IC 434. It is protruding from the Orion B molecular cloud, which is part of the Orion molecular cloud complex.^[3]

References

^ ^a ^b ^c ^d Kier, Ruben (2009). The 100 Best Targets for Astrophotography: A Monthly Guide for CCD Imaging with Amateur Telescopes. Springer. p. 31. ISBN 978-1-4419-0603-8.
^ ^a ^b ^c ^d ^e Ochsendorf, B. B.; Tielens, A. G. G. M. (April 2015). "A bimodal dust grain distribution in the IC 434 H ii region". Astronomy & Astrophysics. 576. id. A2. arXiv:1501.02256. Bibcode:2015A&A...576A...2O. doi:10.1051/0004-6361/201424799.
^ ^a ^b Bally, John; et al. (February 2018). "Kinematics of the Horsehead Nebula and IC 434 Ionization Front in CO and C+". The Astronomical Journal. 155 (2). id. 80. Bibcode:2018AJ....155...80B. doi:10.3847/1538-3881/aaa248.

External links

Nemiroff, R.; Bonnell, J., eds. (21 February 2006). "Wisps Surrounding the Horsehead Nebula". Astronomy Picture of the Day. NASA.
IC 434
"IC 434". SIMBAD. Centre de données astronomiques de Strasbourg.

[Ruben_2009-1] Kier, Ruben (2009). The 100 Best Targets for Astrophotography: A Monthly Guide for CCD Imaging with Amateur Telescopes. Springer. p. 31. ISBN 978-1-4419-0603-8.

[Ochsendorf_Tielens_2015-2] Ochsendorf, B. B.; Tielens, A. G. G. M. (April 2015). "A bimodal dust grain distribution in the IC 434 H ii region". Astronomy & Astrophysics. 576. id. A2. arXiv:1501.02256. Bibcode:2015A&A...576A...2O. doi:10.1051/0004-6361/201424799.

[Bally_et_al_2018-3] Bally, John; et al. (February 2018). "Kinematics of the Horsehead Nebula and IC 434 Ionization Front in CO and C+". The Astronomical Journal. 155 (2). id. 80. Bibcode:2018AJ....155...80B. doi:10.3847/1538-3881/aaa248.

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