HD 157661
Star in the constellation Ara
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HD 157661 is the Henry Draper Catalogue designation for a likely triple star[3] in the southern constellation of Ara. With a measured annual parallax of 5.13 mas,[2] 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,[6] which means it is faintly visible to the naked eye.
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Ara[1] |
| HD 157661 | |
| Right ascension | 17h 26m 51.97802s[2] |
| Declination | −45° 50′ 34.9096″[2] |
| Apparent magnitude (V) | 5.70/6.46[3] |
| HD 157649 | |
| Right ascension | 17h 26m 44.66241s[4] |
| Declination | −45° 49′ 26.0995″[4] |
| Apparent magnitude (V) | 7.11[5] |
| Characteristics | |
| HD 157661 | |
| Spectral type | B7V + B9.5V[3] |
| U−B color index | −0.34[6] |
| B−V color index | −0.07[6] |
| HD 157649 | |
| Spectral type | B9.5V[7] |
| Astrometry | |
| HD 157661 | |
| Radial velocity (Rv) | +8[8] km/s |
| Proper motion (μ) | RA: −6.46[2] mas/yr Dec.: −27.91[2] mas/yr |
| Parallax (π) | 5.13±0.72 mas[2] |
| Distance | approx. 640 ly (approx. 190 pc) |
| Absolute magnitude (MV) | −1.12[1] |
| HD 157649 | |
| Proper motion (μ) | RA: −5.818[4] mas/yr Dec.: −28.942[4] mas/yr |
| Parallax (π) | 5.2246±0.0657 mas[4] |
| Distance | 624 ± 8 ly (191 ± 2 pc) |
| Details | |
| A | |
| Mass | 3.03[9] M☉ |
| Radius | 4.49[9] R☉ |
| Luminosity | 317[9] L☉ |
| Surface gravity (log g) | 3.61[9] cgs |
| Temperature | 11,493[9] K |
| B | |
| Mass | 3.31[10] M☉ |
| HD 157649 | |
| Mass | 2.65[4] M☉ |
| Radius | 2.88[4] R☉ |
| Luminosity | 69[4] L☉ |
| Surface gravity (log g) | 3.85[4] cgs |
| Temperature | 10,189[4] K |
| Rotation | 27.152 days[11] |
| Age | 327[4] Myr |
| Other designations | |
| HD 157661: CD−45 11531, HD 157661, HIP 85389, HR 6477[12] | |
| HD 157649: CD−45 11527, HD 157649 | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
| HD 157649 | |
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.[3]