Alnilam
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Star Alnilam (ε Orionis) |
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| The belt stars of Orion: ε Ori is the middle star | |||||||||||||||||||||
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| AladinLite | |||||||||||||||||||||
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | Orion | ||||||||||||||||||||
| Right ascension | 05 h 36 m 12.81 s | ||||||||||||||||||||
| declination | -01 ° 12 ′ 6.9 ″ | ||||||||||||||||||||
| Apparent brightness | 1.69 (1.64 to 1.74) mag | ||||||||||||||||||||
| Typing | |||||||||||||||||||||
| B − V color index | −0.19 | ||||||||||||||||||||
| U − B color index | −1.04 | ||||||||||||||||||||
| R − I index | −0.17 | ||||||||||||||||||||
| Spectral class | B0 Ia | ||||||||||||||||||||
| Variable star type | ACYG | ||||||||||||||||||||
| Astrometry | |||||||||||||||||||||
| Radial velocity | (+27.3 ± 0.8) km / s | ||||||||||||||||||||
| parallax | (1.65 ± 0.45) mas | ||||||||||||||||||||
| distance | approx. 1500 ly approx. 600 pc |
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| Visual absolute brightness M vis | approx. −7 mag | ||||||||||||||||||||
| Proper movement | |||||||||||||||||||||
| Rec. Share: | (+1.44 ± 0.42) mas / a | ||||||||||||||||||||
| Dec. portion: | (−0.78 ± 0.19) mas / a | ||||||||||||||||||||
| Physical Properties | |||||||||||||||||||||
| Dimensions | 31.8 M ☉ | ||||||||||||||||||||
| radius | 26 R ☉ | ||||||||||||||||||||
| Luminosity |
375 000 L ☉ |
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| Effective temperature | 25,000 K | ||||||||||||||||||||
| Age | approx. 4 mill. a | ||||||||||||||||||||
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Other names and catalog entries |
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Alnilam is the name of the star ε Orionis (Epsilon Orionis). In the conspicuous winter constellation Orion , he stands in the middle of the Orion belt , to which the stars Alnitak and Mintaka belong to the left and right . The three giant stars are the most luminous in the large, bright open star cluster Collinder 70 .
According to more recent data , however, it can be assumed that ε Orionis, which is about 1500 light years away, is not itself a member of this star cluster Cr 70, but is far behind it. In the FK4 fundamental catalog , the main star has the number 210.
meaning
The name Al Nilam is derived from Arabic النظام, DMG an-Niẓām 'arrangement (of pearls, belt center)'. Also closely related to Arabic نظم, DMG Nazm , pearl necklace '. Other variants are also Alnihan and Alnitam , but all three variants are obviously incorrect transcriptions of the original Arabic name.
description
Alnilam is a blue supergiant and belongs to the spectral class B0. The temperature is approx. 25,000 Kelvin . It is one of the brightest stars we know. The bolometric luminosity exceeds that of our sun by 375,000 times. With a diameter of around 36 million kilometers, it is around 26 times larger than our sun.
Its distance, calculated using classical methods, is usually given as 1320 to 1350 light years, while the parallax measured by the astrometry satellite Hipparcos in 1995 is 2000 ± 500 light years.
Reflection fog
Alnilam is surrounded by a reflection nebula. This was discovered in February 1, 1786 by William Herschel using his 18.7 inch reflector telescope. It is listed under NGC 1990 in the New General Catalog .
See also
Web links
Individual evidence
- ↑ a b c Hipparcos catalog (ESA 1997)
- ↑ a b eps Ori. In: VSX. AAVSO , accessed May 12, 2019 .
- ↑ a b c Bright Star Catalog
- ↑ Pulkovo radial velocities for 35493 HIP stars
- ^ A b Hipparcos, the New Reduction (van Leeuwen, 2007)
- ↑ a b approximate mean value (see text)
- ↑ a b c Alnilam. Jim Kaler, accessed May 12, 2019 .
- ^ Richard Hinckley Allen: Star-names and their meanings. 1936, pp. 314-315.
- ↑ https://cseligman.com/text/atlas/ngc19a.htm#1990