HD 211073
Triple star system in the constellation Lacerta
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HD 211073 is a triple star[8] system in the northern constellation Lacerta, located around 570[2] light years from the Sun. It is visible to the naked eye as a faint orange-hued star with a baseline apparent visual magnitude of 4.50.[1] The system is moving closer to the Earth with a heliocentric radial velocity of −11.7 km/s.[6]
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Lacerta[1] |
| Right ascension | 22h 13m 52.72751s[2] |
| Declination | +39° 42′ 53.7288″[2] |
| Apparent magnitude (V) | 4.50[1] (4.49–4.55)[3] |
| Characteristics | |
| Evolutionary stage | horizontal branch[4] |
| Spectral type | K2.5 III[5] |
| B−V color index | 1.39[6] |
| Variable type | suspected[3] |
| Astrometry | |
| Radial velocity (Rv) | −11.69±0.13[6] km/s |
| Proper motion (μ) | RA: +38.941±0.104[2] mas/yr Dec.: +19.342±0.125[2] mas/yr |
| Parallax (π) | 5.7181±0.1508 mas[2] |
| Distance | 570 ± 20 ly (175 ± 5 pc) |
| Absolute magnitude (MV) | −1.34[1] |
| Details[4] | |
| HD 211073 Aa | |
| Mass | 2.23+0.22 −0.26 M☉ |
| Radius | 45.69+2.17 −2.39 R☉ |
| Luminosity | 573.50+51.88 −61.58 L☉ |
| Surface gravity (log g) | 1.46+0.05 −0.04 cgs |
| Temperature | 4,180+12 −14 K |
| Rotational velocity (v sin i) | 2.9±1.0[6] km/s |
| Age | 1.00+0.38 −0.19 Gyr |
| Other designations | |
| NSV 14076, BD+38°4711, FK5 1583, HD 211073, HIP 109754, HR 8485, SAO 72155, WDS J22139+3943[7] | |
| Database references | |
| SIMBAD | data |
The primary member, designated component Aa, is an evolved giant star with a stellar classification of K2.5 III[5] that is most likely (98% chance) on the horizontal branch.[4] It is a suspected variable star that ranges in magnitude from 4.49 down to 4.55.[3] This star is around a billion years old with 2.2 times the mass of the Sun and has expanded to 46 times the Sun's radius. It is radiating about 574 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,180 K.[4]
As of 2005, the inner pair of stars (Aa + Ab) in this system had an angular separation of 0.20″ along a position angle (PA) of 170°. The magnitude 8.15 component Ac was separated from Aa by 0.30″ with a PA of 27°, as of 2010. As of 2015, the magnitude 10.60 visual companion, designated component B, was separated from the primary by 30.50″ along a PA of 190°.[9]