HD 157661
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ara |
| HD 157661 | |
| Right ascension | 17h 26m 51.97802s |
| Declination | −45° 50′ 34.9096″ |
| Apparent magnitude (V) | 5.70/6.46 |
| HD 157649 | |
| Right ascension | 17h 26m 44.66241s |
| Declination | −45° 49′ 26.0995″ |
| Apparent magnitude (V) | 7.11 |
| Characteristics | |
| HD 157661 | |
| Spectral type | B7V + B9.5V |
| U−B color index | −0.34 |
| B−V color index | −0.07 |
| HD 157649 | |
| Spectral type | B9.5V |
| Astrometry | |
| HD 157661 | |
| Radial velocity (Rv) | +8 km/s |
| Proper motion (μ) | RA: −6.46 mas/yr Dec.: −27.91 mas/yr |
| Parallax (π) | 5.13±0.72 mas |
| Distance | approx. 640 ly (approx. 190 pc) |
| Absolute magnitude (MV) | −1.12 |
| HD 157649 | |
| Proper motion (μ) | RA: −5.818 mas/yr Dec.: −28.942 mas/yr |
| Parallax (π) | 5.2246 ± 0.0657 mas |
| Distance | 624 ± 8 ly (191 ± 2 pc) |
| Details | |
| A | |
| Mass | 3.03 M☉ |
| Radius | 4.49 R☉ |
| Luminosity | 317 L☉ |
| Surface gravity (log g) | 3.61 cgs |
| Temperature | 11,493 K |
| B | |
| Mass | 3.31 M☉ |
| HD 157649 | |
| Mass | 2.65 M☉ |
| Radius | 2.88 R☉ |
| Luminosity | 69 L☉ |
| Surface gravity (log g) | 3.85 cgs |
| Temperature | 10,189 K |
| Rotation | 27.152 days |
| Age | 327 Myr |
| Other designations | |
| HD 157661: CD−45 11531, HD 157661, HIP 85389, HR 6477 | |
| HD 157649: CD−45 11527, HD 157649 | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
| HD 157649 | |
HD 157661 is the Henry Draper Catalogue designation for a likely triple star in the southern constellation of Ara. With a measured annual parallax of 5.13 mas, is located at a distance of approximately 640 light-years (200 parsecs) from Earth. The combined apparent visual magnitude of the stars is 5.29, which means it is faintly visible to the naked eye.
The inner components of this system consist of a pair of B-type main sequence stars. The brighter star has a magnitude of 5.70 and a stellar classification of B7 V. At an angular separation of 2.115 arcseconds is the magnitude 6.46 secondary component, which has a classification of B9.5 V. The third member of the system is HD 157649, a 7.6 magnitude A-type star at a separation of 103 arcseconds.