| Observation data EpochJ2000 EquinoxJ2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19h 17m 08.97863s[2] |
| Declination | +41° 15′ 53.3103″[2] |
| Apparent magnitude (V) | 7.09[3] |
| Characteristics | |
| Spectral type | G8III / G8V / K1V[1] |
| Variable type | Eclipsing binary |
| Astrometry | |
| Radial velocity (Rv) | 5.83 km/s |
| Proper motion (μ) | RA: 0.60[2]mas/yr Dec.: -8.07[2]mas/yr |
| Parallax (π) | 4.02±0.40 mas[2] |
| Distance | 810 ± 80 ly (250 ± 20 pc) |
| Absolute magnitude (MV) | –0.3 / 5.6 / 6.1[1] |
| Orbit[4] | |
| Primary | HD 181068 A |
| Companion | HD 181068 B |
| Period (P) | 45.4711 ± 0.0002 d |
| Semi-major axis (a) | 90.31 ± 0.72 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | 87.5 ± 2° |
| Periastronepoch (T) | Tmin = 2455499.9962 |
| Orbit[4] | |
| Primary | HD 181068 Ba |
| Companion | HD 181068 Bb |
| Period (P) | 0.9056768 ± 0.0000002 d |
| Semi-major axis (a) | 4.777 ± 0.039 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | 87.6 ± 1.4° |
| Periastronepoch (T) | Tmin = 2455051.23623 |
| Details[5] | |
| HD 181068 A | |
| Mass | 3 ± 0.1 M☉ |
| Radius | 12.46 ± 0.15 R☉ |
| Luminosity (bolometric) | 92.8 ± 7.6 L☉ |
| Surface gravity (log g) | 2.73 cgs |
| Temperature | 5100 ± 100 K |
| HD 181068 Ba | |
| Mass | 0.915 ± 0.034 M☉ |
| Radius | 0.865 ± 0.01 R☉ |
| Luminosity (bolometric) | 0.447 ± 0.037 L☉ |
| Surface gravity (log g) | 4.53 cgs |
| Temperature | 5100 ± 100 K |
| HD 181068 Bb | |
| Mass | 0.870 ± 0.043 M☉ |
| Radius | 0.8 ± 0.02 R☉ |
| Luminosity (bolometric) | 0.27 ± 0.027 L☉ |
| Surface gravity (log g) | 4.58 cgs |
| Temperature | 4675 ± 100 K |
| Other designations | |
| HD 181068,BD+41° 3292,HIP 94780,SAO 48282,KIC 5952403[6] | |
| Database references | |
| SIMBAD | data |
| KIC | data |
HD 181068 is astar system in theconstellation ofLyra. With an apparent magnitude of 7.09,[3] the system is not visible to the naked eye but may be viewed with a pair of binoculars. Based onparallax measurements made by theHipparcosspacecraft, the system is some 810light years (250parsecs) away fromEarth.[2]
HD 181068 is in theKepler spacecraft's field of view, and its unique properties were first observed by the satellite'sphotometer. It consists of ared giant, designated HD 181068 A, along with twomain-sequence stars, designated HD 181068 Ba and HD 181068 Bb, respectively. Normaleclipsing binaries have two components that pass in front of each other while eclipsing. However, all three components of HD 181068 orbit each other in such a way that theyeclipse each other, forming a rare triply eclipsing system.[7]
The primary, HD 181068 A, has aspectral type of G8III,[1] meaning it is ared giant that has used up its corehydrogen and has expanded to a radius of 12.46 R☉.[5] The primary star is also unusual in that it does not exhibitinternal seismic oscillations as have been detected in other red giants, althoughtidal forces from the closer pair may possibly be causing othervariability in thelight curve of the system.[7]
HD 181068 Ba and Bb have spectral types of G8V and K1V respectively, indicating their location on themain sequence, slightly later than the Sun. They are in a close orbit and complete an orbit once every 0.906days (about 21.7hours), while they orbit HD 181068 A every 45.5 days.[4] All three stars have similarsurface brightnesses and colors, so when the two companions eclipse the red giant, the change in brightness is very slight and hard to detect.[7]
