Mu Sagittarii (μ Sagittarii, abbreviated Mu Sgr, μ Sgr) is a multiple star system in the constellation of Sagittarius. The brightest component, designated Mu Sagittarii Aa, is formally named Polis .[11] The system is 3,000 light-years from the Sun and is part of the Sgr OB1 stellar association.
Quick Facts Constellation, Right ascension ...
μ Sagittarii
Location of μ Sgr(circled) |
Observation data Epoch J2000.0 Equinox J2000.0 |
Constellation |
Sagittarius |
Right ascension |
18h 13m 45.8s[1] |
Declination |
−21° 03′ 32″[1] |
Apparent magnitude (V) |
+3.85[2] |
Characteristics |
μ Sgr A |
Spectral type |
B8Iap[3] + B1.5V[4] |
U−B color index |
−0.52[5] |
B−V color index |
+0.22[5] |
Variable type |
EA + α Cyg[6] |
|
μ Sgr B |
Spectral type |
B9III[4] |
U−B color index |
−0.11[5] |
B−V color index |
−0.04[5] |
|
μ Sgr C |
U−B color index |
−0.30[5] |
B−V color index |
+0.23[5] |
|
μ Sgr D |
Spectral type |
B2IV[7] |
U−B color index |
−0.57[5] |
B−V color index |
+0.11[5] |
|
μ Sgr E |
Spectral type |
B2.5V[7] |
U−B color index |
−0.67[5] |
B−V color index |
+0.04[5] |
Astrometry |
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|
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Parallax (π) | A: 0.09 ± 0.28 mas[1] |
Distance | 920[8] pc |
Absolute magnitude (MV) | A: −7.1[7] B: −1.2[9] D: −3.3[7] E: −2.1[7] |
|
Details |
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μ Sgr Aa |
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Mass | 14.1 - 30[10] M☉ |
Radius | 67.9[10] R☉ |
Luminosity | 200 000 L☉ |
Surface gravity (log g) | 2.0[10] cgs |
Temperature | 12,000[10] K |
μ Sgr Ab |
---|
Mass | 9.8 - 15[10] M☉ |
Radius | 12.2[10] R☉ |
Surface gravity (log g) | 4.0[10] cgs |
Temperature | 23,000[10] K |
Age | 10[7] Myr |
|
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μ Sgr B |
---|
Luminosity | 603[8] L☉ |
Temperature | 18,200[8] K |
μ Sgr D |
---|
Luminosity | 1,660[8] L☉ |
Temperature | 20,400[8] K |
|
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μ Sgr E |
---|
Luminosity | 2,450[8] L☉ |
Temperature | 20,900[8] K |
|
Other designations |
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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 |
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SIMBAD | μ Sgr AB |
| μ Sgr D |
| μ Sgr E |
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