Alnilam (Epsilon Orionis / ε Ori / 46 Orionis / HIP 26311) is the fourth brightest star in the constellation Orion. It is part of the so-called Belt of Orion (“The Three Marys”) along with Mintaka (δ Orionis) and Alnitak (ζ Orionis), being the brightest of the three, although it is the farthest in light years. Its name comes from the Arabic النظام An-niżām which means “pearl necklace.”
Summary
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- 1 Description
- 2 Observation data
- 3 Physical characteristics
- 4 Astrometry
- 5 Other densities
- 6 Sources
Description
Alnilam is a bluish-white supergiant of the spectral type B0Iab, very massive (about 40 solar masses), and extraordinarily luminous: including the large amount of ultraviolet radiation emitted by the star. Its surface temperature is 25,000 K, so hot that it illuminates the reflection nebula NGC 1990. A strong stellar wind blowing from its surface at 2,000 km / s causes it to lose mass at a rate 20 million times faster than the Sun. an irregular pulsating variable star of the Alpha Cygni type, with a fluctuation in brightness of 0.1 magnitudes. With an approximate age of only 4 million years, in the future it will become a red supergiant before exploding as a supernova and leaving a neutron star as a remnant.
Observation data
Epoch J2000 Constellation Orion
Right ascension (α) 05 h 36 m 12.81 s Declination (δ) -01 ° 12′06.9 ″ Apparent mag. (V) +1.70 (1.64—1.74) Color B0Iab
Physical characteristics
Stellar classification O9Ib / O9 / B2III Solar mass 30-64.5 M☉ Diameter (31☉) Radius (42.0 R☉) Color index −0.18 (BV) −1.03 (UB) Absolute magnitude -6.95 Surface gravity 3.0 (log g) Luminosity 832,000 L☉ Surface temperature 25,000 K
Rotation period – α Cygni variability
Astrometry
Mov. own in α 1.49 more / year
Mov. own in δ −1.06 more / year
Radial speed +25.90 km / s
Distance 1340 light years (600 pc)
Parallax 1.65 ± 0.45 more
Other densities
Alnilam, ε Ori, 46 Orionis, 112 G Orionis, HR 1903, BD -01 ° 969, HD 37128, SAO 132346, FK5 210, HIP 26311, TD1 4963, 参 宿 二
