Alnilam
| catalogues and names | Alnilam, e Ori, eps Ori, 46 Ori, HR 1903, HD 37128, SAO 132346, FK5: 210, WDS 05362-0112 |
| other names | Alnihan, Alnitam |
| constellation | Orion |
data from The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991)
| note (category: star names): | ALNILAM; Alnihan; Alnitam. |
position, motion, parallax:
| position (J2000) | RA: 5h 36min 12,8sec | DEC: -1° 12' 7'' |
| position (J1900) | RA: 5h 31min 8,3sec | DEC: -1° 15' 57'' |
| proper motion (J2000) | RA: 0,001 arcsec/a | DEC: -0,002 arcsec/a |
| radial velocity | 26 km/s note: spectroscopic binaries |
|
| rotational velocity | 87 km/s (uncertain) (variable) | |
| trigonometric parallax | -0,002 arcsec | |
| note (category: radial and/or rotational velocities): | UV AEROBEE spectra indicate mass ejection at velocity up to 1800k/s. |
magnitude
| visual magnitude | 1,7 (V on UBV Johnson system) |
spectral / color information
| spectral class | B0Ia |
| B-V-magnitude | -0,19 |
| U-B-magnitude | -1,04 |
| R-I-magnitude | -0,17 |
| note (category: spectra): | Nitrogen deficient. Interstellar Lyman alpha absorption observed by AEROBEE rocket. Walborn declares "no e", but Merrill found H alpha emission. |
| note (category: colors): | In both infrared survey and UV CELESCOPE. Color excess E(B-V) = +0.08. |
variability information
| variable star identification | Eps Ori |
| note (category: variability): | Alpha Cyg 1.64 - 1.74V. |
double/multiple star system information
| separation | 179,9 arcsec |
| mag difference (of double or brightest multiple) | 8,7 |
| note | Worley (1978) update of the IDS |
miscellaneous information
| note (category: group membership): | Ori OB1b2; Orion belt; cluster NGC 1980; nebulosity. |
| note (category: stellar radii or diameters): | Diam. = 0.00067 - 0.00069". |
data from SKY2000 - Master Star Catalog (Myers+ 1997)
position, motion, parallax:
| position (J2000) | RA: 5h 36min 12,809sec | DEC: -1° 12' 7,02'' | ±0,06 arcsec | source: 15 |
| proper motion (J2000) | RA: 0,0001 arcsec/a | DEC: -0,002 arcsec/a | source: 25 | |
| radial velocity | 26 km/s | source: 25 | ||
| galactic coord. (B1950) | longitude: 205,22° | latitude: -17,24° | ||
| GCI unit vector (J2000) | X: 0,103579 | Y: 0,9944 | Z: -0,020976 | |
magnitude:
| visual | 1,6 (observed) | source: 31 |
| photovisual | 1,8 | source: 2 |
spectral information:
| spectral class | B0 | source: 96 | |
| Morgan-Keenan | B0Ia | source: 25 | |
| B-magnitude | 1,51 ±0,05 | B-V-magnitude | -0,19 |
| U-magnitude | 0,47 ±0,05 | U-B-magnitude | -1,04 |
variability information:
| variability type | 133 |
| var. amplitude | 0,1 |
double/multiple star system information:
| separation between brightest and second brightest component | 179,9 arcsec |
| magnitude difference between brightest and second brightest component | 8,8 |
| position angle | 57 ° |
sources:
| 2 | HD and HDE Catalogs |
| Cannon, A.J., and E.C. Pickering, Harvard Annals, Vols 91-99, 1918-24, Cambridge, Massachusetts: Harvard University; Cannon, A.J., Harvard Annals, Vol. 100, 1925-36, Cambridge, Massachusetts: Harvard University; and Cannon, A.J., and M. Walton Mayall, Harvard Annals, Vol. 112, 1949, Cambridge, Massachusetts: Harvard University | |
| 15 | FK5, FK5 Extension and FK5 Supplement |
| Fricke, W., H. Schwan and T. Lederle, "Fifth Fundamental Catalogue (FK5), Part I. The Basic Fundamental Stars," Veroff. Astronomisches Recheninstitut, No. 32, Heidelberg, Germany, 1988, and Fricke, W., H. Schwan, and T.E. Corbin, "Fifth Fundamental Catalogue (FK5), Part II. The FK5 Extension," Veröff. Astronomisches Recheninstitut, No. 33, Heidelberg, Germany, 1991 | |
| 19 | WDS Catalog |
| Worley, C.E., and G.G. Douglass, Washington Catalog of Visual Double Stars 1996.0, United States Naval Observatory, 1996 | |
| 25 | Bright Star Catalogue, 5th edition |
| Hoffleit, D. and Warren, W.H. Jr., The Bright Star Catalogue, 5th Revised Edition, Version 2, 1994 | |
| 30 | GCVS, 4th edition |
| Kholopov, P.N., et al., General Catalogue of Variable Stars, fourth edition, Moscow: Nauka Publishing House, 1985-88 | |
| 31 | CRM' (non-GCVS variable data) |
| Warren, W.H. Jr., Northern Hemisphere Catalog of Red Magnitudes, 1994 | |
| 96 | SAO or HD/HDE Catalog |
| Reference from Value 1 or Reference from Value 2 | |
data from Smithsonian Astrophysical Observatory Star Catalog (SAO Staff 1966; USNO, ADC 1990)
position and proper motion:
| position (J1950) | RA: 5h 33min 40,476sec | DEC: -1° 13' 56,3'' | ±0,004 arcsec |
| position (J2000) | RA: 5h 36min 12,812sec | DEC: -1° 12' 7,05'' | |
| proper motion J1950 (FK4) | RA: -0,0002 arcsec/a | DEC: -0,002 arcsec/a | ±0,001 arcsec/a in RA ±0,001 arcsec/a in DEC |
| proper motion J2000 (FK5) | RA: 0,0001 arcsec/a | DEC: -0,002 arcsec/a | |
| source of proper motion data | Determined by source catalog | ||
magnitude:
| visual | 1,8 (accuracy: 2 decimals) |
| source of visual magnitude data | Taken from the "Henry Draper Catalogue". |
spectral information:
| spectral class | B0 |
| source of spectral data | Taken from the Henry Draper Catalogue or no spectrum in source catalog. |
catalogues
| source catalogue | FK4, catalogue number: 210 |
| Durchmusterung | BD-01 969 |
| Boss General Catalogue | 6960 |
| Henry Draper Catalogue | 37128 |
data from The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996)
position and proper motion:
| position (J2000) | RA: 5h 36,2min | DEC: -1° 12' |
| proper motion (J2000) | RA: 0,001 arcsec/a | DEC: -0,002 arcsec/a |
double/multiple star system information:
| component | year | number of measures | position angle | angular separation | magnitude of 1st component | magnitude of 2nd component | spectral class(es) | discoverer code |
| - | 1879 | 2 | 57° | 179,9'' | 1,7 | 10,5 | B0Iae | BUP 81 |
discoverer information:
| discoverer code | discoverer | reference |
| BUP 81 | - | - |
notes:
| note | Epsilon Ori. Possibly variable. |
data from Combined General Catalogue of Variable Stars (Vol. I-III) (Kholopov+ 1998)
position:
| position (J1950) | RA: 5h 33min 40sec | DEC: -1° 13' 54'' | ± 1 sec / ± 0.1 arcmin |
variability informations:
| variability type | ACYG | pulsating variable star |
| magnitute at max. brightness | 1,64 | |
| magnitute at min. brightness | 1,74 | |
| photometric system | visual, photovisual or Johnson's V |
spectral information
| spectral class | B0.5Iabea |
references
| to a study | Vol. I GCVS (see Kholopov et al. 1985-1988) |
| to a chart/photograph | Vol. I GCVS (see Kholopov et al. 1985-1988) |
miscanellous
| ID in the GCVS catalogue | 60/9005 |
| constellation | Orion |
| notes on existence | The star is equivalent to '0609007 eta'. |
| There are notes in published catalog. | |
variability type description
| variability type | description |
| ACYG | Variables of the Alpha Cygni type, which are nonradially pulsating supergiants of Bep-AepIa spectral types. The light changes with amplitudes of the order of 0.1 mag often seem irregular, being caused by the superposition of many oscillations with close periods. Cycles from several days to several weeks are observed. |