Triple star system in the constellation Lyra
! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000.0      Equinox J2000.0
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:center" colspan="2" | HD 178911 Aa/Ab
! style="text-align:left" | Evolutionary stage
! style="text-align:left" | Spectral type
! style="text-align:left" | B−V 
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| 
! style="text-align:center" colspan="2" | HD 178911 B
! style="text-align:left" | Spectral type
! style="text-align:left" | B−V 
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! colspan="2" style="text-align: center;" | HD 178911 B
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, 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.
Stellar system.
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 along a position angle of 263°. Component B shares a common motion through space with the primary, and thus they form a wide binary. This secondary is a magnitude 7.88 G-type main-sequence star with a stellar classification of G5V. The physical properties of this star are similar to the Sun, although it has a higher metallicity.
In 1985, the primary was determined to be a spectroscopic binary pair using the CHARA speckle interferometry program. Designated components Aa and Ab, these have an orbital period of and an eccentricity (ovalness) of 0.6. They are magnitude 6.89 and 8.96. Based on based on a combined class of G5V for the pair, they have derived main sequence stellar classifications of G1V and K1V, respectively. C. D. Farrington and associates (2014) found dynamic masses for the components of 0.80 and 0.62, respectively. 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.
An additional companion HD 178911 C is a chance optical alignment and is not part of the system.
Planetary system.
In 2001 an extrasolar planet was discovered in orbit around HD 178911 B.
! align=center| Companion
! align=center| Mass
! align=center| Semimajor axis
! align=center| Orbital period
! align=center| Eccentricity
! align=center| Inclination
! align=center| Radius
References.
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External links.
 ;indicator name="01-sky-coordinates" ; ;templatestyles src="Template:Sky/styles.css" / ;Coordinates: &amp;de=34.60045138888889&amp;zoom=&amp;show_grid=1&amp;show_constellation_lines=1&amp;show_constellation_boundaries=1&amp;show_const_names=1&amp;show_galaxies=1&amp;img_source=IMG_all 19h 09m 04.3838s, +34° 36′ 01.625″ ;/indicator ;