HD 179821 or V1427 Aquilae is either a post-red supergiant yellow hypergiant or a post-AGB yellow supergiant star in the constellation of Aquila, surrounded by a detached dust shell. It is a semi-regular variable nearing the end of its life.
Quick Facts Observation data Epoch J2000 Equinox J2000, Constellation ...
HD 179821HD 179821 Credit: Hubble Legacy Archive |
Observation data Epoch J2000 Equinox J2000 |
Constellation |
Aquila |
Right ascension |
19h 13m 58.61s[1] |
Declination |
+00° 07′ 31.9″[1] |
Apparent magnitude (V) |
8.19[2] (7.83 - 8.23[3]) |
Characteristics |
Evolutionary stage |
YHG or post-AGB |
Spectral type |
G4 0-Ia[4] (G5Ia - K4I[3]) |
Apparent magnitude (U) |
10.81[5] |
Apparent magnitude (B) |
9.694[2] |
Apparent magnitude (R) |
8.2[6] |
Apparent magnitude (J) |
5.371[6] |
Apparent magnitude (H) |
4.998[6] |
Apparent magnitude (K) |
4.728[6] |
B−V color index |
+1.504[2] |
Variable type |
SRd[3] |
Astrometry |
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Radial velocity (Rv) | +81.8±3.7[7] km/s |
Proper motion (μ) | RA: −0.090[1] mas/yr Dec.: −3.494[1] mas/yr |
Parallax (π) | 0.1893 ± 0.0206 mas[1] |
Distance | approx. 17,000 ly (approx. 5,300 pc) |
Absolute magnitude (MV) | −8.9[8][9] or −5.7[7] |
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Details |
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if a hypergiant |
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Mass | 19 - 30[7][10] M☉ |
Radius | 400 - 450[11] R☉ |
Luminosity | 126,000[11] - 295,000[9] L☉ |
Surface gravity (log g) | 0.5[8] cgs |
Temperature | 4,898 - 6,761[11] K |
Metallicity [Fe/H] | 0.0[8] dex |
if post-AGB |
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Mass | 0.8[7] M☉ |
Radius | 147[7][lower-alpha 1] R☉ |
Luminosity | 20,000+12,000 −7,400[7] L☉ |
Surface gravity (log g) | 0.5[8] cgs |
Temperature | 5,660[7] K |
Metallicity [Fe/H] | 0.0[8] dex |
Other designations |
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Database references |
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SIMBAD | data |
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