Mu Sagittarii information

μ Sagittarii
	Location of μ Sgr(circled)
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
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)	A: 0.09 ± 0.28 mas
Distance	920 pc
Absolute magnitude (MV)	A: −7.1; B: −1.2; D: −3.3; E: −2.1
Details
μ Sgr Aa
Mass	14.1 - 30 M☉
Radius	67.9 R☉
Luminosity	200 000 L☉
Surface gravity (log g)	2.0 cgs
Temperature	12,000 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
Luminosity	1,660 L☉
Temperature	20,400 K
μ Sgr E
Luminosity	2,450 L☉
Temperature	20,900 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, designated Mu Sagittarii Aa, is formally named Polis /ˈpɒlɪs/.^[11] The system is 3,000 light-years from the Sun and is part of the Sgr OB1 stellar association.

^ ^a ^b ^c Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
^ Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
^ Fraser, M.; Dufton, P. L.; Hunter, I.; Ryans, R. S. I. (2010). "Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants". Monthly Notices of the Royal Astronomical Society. 404 (3): 1306. arXiv:1001.3337. Bibcode:2010MNRAS.404.1306F. doi:10.1111/j.1365-2966.2010.16392.x. S2CID 118674151.
^ ^a ^b Cite error: The named reference zasche was invoked but never defined (see the help page).
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Echevarria, J.; Roth, M.; Warman, J. (1979). "Photometric Study of Trapezium-Type Systems". Revista Mexicana de Astronomía y Astrofísica. 4: 287. Bibcode:1979RMxAA...4..287E.
^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
^ ^a ^b ^c ^d ^e ^f Abt, H. A.; Cardona, O. (1983). "Confirmation among visual multiples of an increase of AP stars with age". Astrophysical Journal. 272: 182. Bibcode:1983ApJ...272..182A. doi:10.1086/161276.
^ ^a ^b ^c ^d ^e ^f ^g Lindroos, K. P. (1986). "A study of visual double stars with early-type primaries. V - Post-T Tauri secondaries". Astronomy and Astrophysics. 156: 223. Bibcode:1986A&A...156..223L.
^ Cite error: The named reference lindroos1985 was invoked but never defined (see the help page).
^ ^a ^b ^c ^d ^e ^f ^g ^h Cite error: The named reference polidan was invoked but never defined (see the help page).
^ "Naming Stars". IAU.org. Retrieved 16 December 2017.

[hipparcos-1] Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.

[ducati-2] Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.

[fraser-3] Fraser, M.; Dufton, P. L.; Hunter, I.; Ryans, R. S. I. (2010). "Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants". Monthly Notices of the Royal Astronomical Society. 404 (3): 1306. arXiv:1001.3337. Bibcode:2010MNRAS.404.1306F. doi:10.1111/j.1365-2966.2010.16392.x. S2CID 118674151.

[zasche-4] Cite error: The named reference zasche was invoked but never defined (see the help page).

[echevarria-5] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Echevarria, J.; Roth, M.; Warman, J. (1979). "Photometric Study of Trapezium-Type Systems". Revista Mexicana de Astronomía y Astrofísica. 4: 287. Bibcode:1979RMxAA...4..287E.

[gcvs-6] Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.

[abt1983-7] ^ ^a ^b ^c ^d ^e ^f Abt, H. A.; Cardona, O. (1983). "Confirmation among visual multiples of an increase of AP stars with age". Astrophysical Journal. 272: 182. Bibcode:1983ApJ...272..182A. doi:10.1086/161276.

[lindroos1986-8] ^ ^a ^b ^c ^d ^e ^f ^g Lindroos, K. P. (1986). "A study of visual double stars with early-type primaries. V - Post-T Tauri secondaries". Astronomy and Astrophysics. 156: 223. Bibcode:1986A&A...156..223L.

[lindroos1985-9] Cite error: The named reference lindroos1985 was invoked but never defined (see the help page).

[polidan-10] ^ ^a ^b ^c ^d ^e ^f ^g ^h Cite error: The named reference polidan was invoked but never defined (see the help page).

[IAU-LSN-11] "Naming Stars". IAU.org. Retrieved 16 December 2017.

Observation data Epoch J2000.0 Equinox J2000.0
Location of μ Sgr(circled)
Constellation	Sagittarius
Right ascension	18^h 13^m 45.8^s^[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

Parallax (π)	A: 0.09 ± 0.28 mas^[1]
Distance	920^[8] pc
Absolute magnitude (M_V)	A: −7.1^[7] B: −1.2^[9] D: −3.3^[7] E: −2.1^[7]

Details
μ Sgr Aa
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

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

μ Sgr E
Luminosity	2,450^[8] `L`_☉
Temperature	20,900^[8] 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

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