Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Lyra |
Right ascension | 19h 09m 04.35193s [1] |
Declination | +34° 36′ 01.2420″ [1] |
Apparent magnitude (V) | 6.70 [2] (6.89 + 8.96 + 7.88) [3] |
Characteristics | |
HD 178911 Aa/Ab | |
Evolutionary stage | Main sequence |
Spectral type | G1V + K1V [4] |
B−V color index | 0.643±0.007 [2] |
HD 178911 B | |
Spectral type | G5V [5] |
B−V color index | 0.750±0.015
[2]
... |
Astrometry | |
HD 178911 Aa/Ab | |
Radial velocity (Rv) | −38.09±1.01 [1] km/s |
Proper motion (μ) |
RA: 76.618
[1]
mas/
yr Dec.: 207.126 [1] mas/ yr |
Parallax (π) | 20.2306 ± 0.3846 mas [1] |
Distance | 161 ± 3
ly (49.4 ± 0.9 pc) |
Absolute magnitude (MV) | 3.28 [2] |
HD 178911 B | |
Radial velocity (Rv) | −40.324±0.0012 [6] km/s |
Proper motion (μ) |
RA: 57.177
[7]
mas/
yr Dec.: 195.900 [7] mas/ yr |
Parallax (π) | 24.3775 ± 0.0274 mas [7] |
Distance | 133.8 ± 0.2
ly (41.02 ± 0.05 pc) |
Absolute magnitude (MV) | 4.90 [2] |
Orbit [4] | |
Primary | HD 178911 Aa |
Companion | HD 178911 Ab |
Period (P) | 1,296.984±0.355 d yr |
Semi-major axis (a) | 0.074±0.002″ |
Eccentricity (e) | 0.597±0.003 |
Inclination (i) | 147.29±0.99° |
Longitude of the node (Ω) | 276.91±1.45° |
Argument of periastron (ω) (secondary) | 83.88±0.87° |
Semi-amplitude (K1) (primary) | 6.47±0.09 km/s |
Semi-amplitude (K2) (secondary) | 8.33±0.18 km/s |
Details | |
HD 178911 Aa | |
Mass | 0.802±0.055 M☉
[4] 1.234±0.027 [8] M☉ |
HD 178911 Ab | |
Mass | 0.622±0.053 M☉
[4] 0.942±0.021 [8] M☉ |
HD 178911 B | |
Mass | 1.03±0.02 M☉ [9] |
Radius | 1.05±0.02 R☉ [9] |
Luminosity | 1.00±0.02 L☉ [9] |
Surface gravity (log g) | 4.40±0.02 cgs [9] |
Temperature | 5,642±29 K [9] |
Metallicity [Fe/H] | 0.23 [10] |
Rotational velocity (v sin i) | 4.6 [10] |
Age | 4.8±1.3 Gyr [9] |
Other designations | |
HD 178911 A: BD+34 3439, HIP 94076, SAO 67879, PPM 82386, LTT 15608, NLTT 47474 [11] | |
HD 178911 B: BD+34 3438, HIP 94075, SAO 67875, PPM 82385, LTT 15608, NLTT 47473 [12] | |
Database references | |
SIMBAD | data |
HD 178911 is a triple star system with an exoplanetary companion in the northern constellation of Lyra. With a combined apparent visual magnitude of 6.70, [2] it is a challenge to view with the naked eye. The system is located at a distance of approximately 161 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −38 km/s. [1]
A companion star, designated component B, was first reported by F. G. W. Struve in 1823. As of 2019, the two have an angular separation of 16.0 ″ along a position angle of 263°. [3] Component B shares a common motion through space with the primary, and thus they form a wide binary. [13] This secondary is a magnitude 7.88 [3] G-type main-sequence star with a stellar classification of G5V. [5] The physical properties of this star are similar to the Sun, although it has a higher metallicity. [9] [10]
In 1985, the primary was determined to be a spectroscopic binary pair using the CHARA speckle interferometry program. [14] Designated components Aa and Ab, these have an orbital period of 3.55 yr and an eccentricity (ovalness) of 0.6. [4] They are magnitude 6.89 and 8.96. [3] Based on based on a combined class of G5V for the pair, [8] they have derived main sequence stellar classifications of G1V and K1V, respectively. [4] C. D. Farrington and associates (2014) found dynamic masses for the components of 0.80 and 0.62, respectively. [4] However, based on the classes, the expected masses should be around 1.0 and 0.8. Manuel Andrade (2019) derived higher dynamic masses of 1.20 and 0.94. [8]
An additional companion HD 178911 C is a chance optical alignment and is not part of the system. [4]
In 2001 an extrasolar planet was discovered in orbit around HD 178911 B. [15] [13]
Companion (in order from star) |
Mass |
Semimajor axis ( AU) |
Orbital period ( days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | >7.35 ± 0.60 MJ | 0.345 ± 0.20 | 71.511 ± 0.011 | 0.139 ± 0.014 | — | — |