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E-vlbi science.jpg
MERLIN and e-VLBI observations of the OH masers in IRC+10420
Observation data
Epoch 2000      Equinox
Constellation Aquila
Right ascension 19 26 48.095
Declination +11 21 16.74
Apparent magnitude (V) 11.66
Evolutionary stage YHG
Spectral type F8I-G0I
B−V color index 2.32
Distance 3-5k pc
Mass 10 M
Other designations
IRC+10420, V1302 Aql, IRAS 19244+1115
Database references

IRC+10420 (also known as V1302 Aql) is a yellow hypergiant star (once mis-classified as a protoplanetary nebula) located in the constellation of Aquila at a distance of 4-6 kiloparsecs of the Sun.[1]

Physical properties[edit]

Despite being one of the most luminous stars known, 500,000 times brighter than the Sun,[1] IRC+10420 cannot be seen with the naked eye and needs a telescope to be observed.

IRC+10420's spectrum has changed from late F to A during last decades without experiencing changes in its luminosity. This suggests IRC+10420 is a former red supergiant that is evolving blueward on the Hertzsprung-Russell diagram to become a Luminous Blue Variable, a Wolf-Rayet star, or even a pre-supernova. Models suggest it started its life as a 40-50 solar masses star that lost most of its mass due to strong stellar winds leaving it with just 10 solar masses and that the star - which actually has a high surface temperature - is totally enshrouded in the matter it has expelled appearing as a fake photosphere, so IRC+10420 appears with a later spectral type as we see just the expelled dust and gas it has blown out during its life and not the star itself.

Surrounding nebula[edit]

IRC+10420 is surrounded by a reflection nebula with a mass of 30-40 solar masses that has been made by the material expelled by the strong stellar winds of its central star. This nebula has been studied with the help of the Hubble Space Telescope, showing a complex structure that includes arcs, rays, and condensations and that has been compared by the one surrounding the red hypergiant VY Canis Majoris.

See also[edit]

IRAS 17163-3907


  1. ^ a b Tiffany, C.; Humphreys, R. M.; Jones, T. J.; Davidson, K. (2010). "THE MORPHOLOGY OF IRC+10420's CIRCUMSTELLAR EJECTA". The Astronomical Journal 140 (2): 339. doi:10.1088/0004-6256/140/2/339.  edit
  • Volk, Bruce J.; Kwok, Sun; Volk, Kevin M. (1989). "A study of several F and G supergiant-like stars with infrared excesses as candidates for proto-planetary nebulae". Astrophysical Journal 346: 265. Bibcode:1989ApJ...346..265H. doi:10.1086/168007. 
  • Nieuwenhuijzen, H.; De Jager, H. (2000). "Checking the yellow evolutionary void. Three evolutionary critical Hypergiants: HD 33579, HR 8752 & IRC +10420". Astronomy and Astrophysics 353: 163. Bibcode:2000A&A...353..163N. 
  • Humphreys, Roberta M.; Smith, Nathan; Davidson, Kris; Jones, Terry Jay; Gehrz, Robert T.; Mason, Christopher G.; Hayward, Thomas L.; Houck, James R.; Krautter, Joachim (1997). "HST and Infrared Images of the Circumstellar Environment of the Cool Hypergiant IRC + 10420". Astronomical Journal 114: 2778. Bibcode:1997AJ....114.2778H. doi:10.1086/118686.