Mu Sagittarii
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 13m 45.8s |
| Declination | −21° 03′ 32″ |
| Apparent magnitude (V) | +3.85 |
| Characteristics | |
| μ Sgr A | |
| Evolutionary stage | Blue supergiant (Aa) |
| Spectral type | B8Iap + B1.5V |
| U−B color index | −0.52 |
| B−V color index | +0.22 |
| Variable type | EA + α Cyg |
| μ Sgr B | |
| Spectral type | B9III |
| U−B color index | −0.11 |
| B−V color index | −0.04 |
| μ Sgr C | |
| U−B color index | −0.30 |
| B−V color index | +0.23 |
| μ Sgr D | |
| Spectral type | B2IV |
| U−B color index | −0.57 |
| B−V color index | +0.11 |
| μ Sgr E | |
| Spectral type | B2.5V |
| U−B color index | −0.67 |
| B−V color index | +0.04 |
| Astrometry | |
| Parallax (π) | 0.6437±0.038 mas |
| Distance | 5,100 ± 300 ly (1,550 ± 90 pc) |
| Absolute magnitude (MV) | A: −7.1 B: −1.2 D: −3.3 E: −2.1 |
| Details | |
| μ Sgr Aa | |
| Mass | 23 M☉ |
| Radius | 115 R☉ |
| Luminosity | 180,000 L☉ |
| Surface gravity (log g) | 1.75 cgs |
| Temperature | 12,200 K |
| μ Sgr Ab | |
| Mass | 9.8 - 15 M☉ |
| Radius | 12.2 R☉ |
| Surface gravity (log g) | 4.0 cgs |
| Temperature | 23,000 K |
| Age | 10 Myr |
| μ Sgr B | |
| Luminosity | 603 L☉ |
| Temperature | 18,200 K |
| μ Sgr D | |
| Mass | 5.940+0.269 −0.228 M☉ |
| Radius | 4.95+0.30 −0.45 R☉ |
| Luminosity | 1,764+398 −270 L☉ |
| Surface gravity (log g) | 3.82+0.07 −0.05 cgs |
| Temperature | 16,487+272 −200 K |
| μ Sgr E | |
| Mass | 6.47±0.21 M☉ |
| Radius | 6.36+0.36 −0.31 R☉ |
| Luminosity | 2,668+337 −298 L☉ |
| Surface gravity (log g) | 3.55±0.03 cgs |
| Temperature | 16,700+200 −300 K |
| Other designations | |
| Polis, μ Sagittarii, μ Sgr, Mu Sgr, 13 Sagittarii, CCDM J18210-2950, IDS 18078-2105, SAO 186497, WDS J18138-2104 | |
| μ Sgr A: HD 166937, HIP 89341, HR 6812, PPM 268080, BD−21°4908, FK5 682, GC 24856 | |
| μ Sgr D: HD 314059, BD−21°4907 | |
| μ Sgr E: HD 314057, BD−21°4909, 2MASS J18134906-2103528 | |
| Database references | |
| SIMBAD | μ Sgr AB |
| μ Sgr D | |
| μ Sgr E | |
Mu Sagittarii (μ Sagittarii, abbreviated Mu Sgr, μ Sgr) is a multiple star system in the constellation of Sagittarius. The brightest component, a blue supergiant designated Mu Sagittarii Aa, is formally named Polis /ˈpɒlɪs/. The system is 5,000 light-years from the Sun and is part of the Sgr OB1 stellar association.