HD 123657
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 14h 07m 55.755s |
| Declination | +43° 51′ 16.03″ |
| Apparent magnitude (V) | 4.98–5.33 |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | M4.5III |
| U−B color index | 1.66 |
| B−V color index | 1.58 |
| R−I color index | 1.66 |
| Variable type | LB |
| Astrometry | |
| Radial velocity (Rv) | −36.24 km/s |
| Proper motion (μ) | RA: +11.443 mas/yr Dec.: −30.812 mas/yr |
| Parallax (π) | 6.0110±0.1554 mas |
| Distance | 540 ± 10 ly (166 ± 4 pc) |
| Absolute magnitude (MV) | −0.90 |
| Details | |
| Mass | 3.96 M☉ |
| Radius | 131.7+3.4 −3.5 R☉ |
| Luminosity | 1,600±130 L☉ |
| Surface gravity (log g) | 0.66 cgs |
| Temperature | 3,444±125 K |
| Metallicity [Fe/H] | −0.03 dex |
| Other designations | |
| BY Boötis, HD 123657, HIP 69038, HR 5299, GSC 03040-00969, TYC 3040-969-1, BD+44°2325, IRAS 14059+4405, IRC +40253, SAO 44901 | |
| Database references | |
| SIMBAD | data |
HD 123657 (BY Boötis) is a star in the northern constellation of Boötes, near the end of the handle of the Big Dipper. It is a fifth-magnitude star, and can be spotted to the unaided eye in sufficiently dark skies, far from light pollution. Based on stellar parallax measurements, it is about 540 light-years distant.
This is a slow irregular variable with an apparent magnitude varying between 4.98 and 5.33. The variability of the brightness of HD 123657 was announced by Joel Stebbins and Charles Morse Huffer in 1928, based on observations made at Washburn Observatory. The star was given its variable star designation, BY Boötis, in 1973.
HD 123657 has a spectral classification of M4.5III, placing it as a cool red giant that exhausted its hydrogen supply. It has expanded to over 132 times the size of the Sun, now radiating 1,600 times its luminosity at a cool photosphere that has an effective temperature of 3,400 K.