Alnitak

from Wikipedia, the free encyclopedia
Double star
Alnitak (ζ Orionis)
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation Orion
Right ascension 05 h 40 m 46 s
declination -01 ° 56.6 ′
Apparent brightness  2.03 mag
Astrometry
Radial velocity 18.50 ± 1.30 / 13.0 km / s
parallax (3.99 ± 0.79) mas
distance  approx. 800 ly
(approx. 250 pc )
Absolute bolometric magnitude M bol approx. −4.95 mag
Proper movement :
Rec. Share: (3.99 ± 0.74) / ≈ +4 mas / a
Dec. portion: (2.54 ± 0.40) / ≈ −2 mas / a
Individual data
Names Aa, Ab; B.
Observation data:
Apparent brightness Aa, Ab 2.05 mag
B. 4.21 likes
Typing:
Spectral class Aa, Ab O9.7 Ib
B. B0 III
B − V color index Aa, Ab −1.07
U − B color index Aa, Ab −0.21
Physical Properties:
radius Aa, Ab 10 R ☉
B.
Luminosity Aa, Ab 10,000 L ☉
B.
Effective temperature Aa, Ab 25,000 K
B.
Other names
and catalog entries
Bayer name ζ Orionis
Flamsteed name 50 Orionis
Bonn survey BD −2 ° 1338
Hipparcos catalog HIP 26727 [1]
Bright Star Catalog HR 1948 HR 1949
Henry Draper Catalog HD 37742 HD 37743
SAO catalog SAO 132444 SAO
Further designations: CCDM J05408-0156
Triple system, consisting of Aa / Ab and B

Alnitak (also Al Nitak ) is the name for the star ζ Orionis (Zeta Orionis), the left (eastern) belt star in Orion. The name ( Arabic النطاق, DMG an-niṭāq ) means “belt”, according to other sources “string of pearls”. Alnitak is a triple star and has an apparent magnitude of 2.03 mag.

In the immediate vicinity are the Horsehead Nebula and the Flame Nebula as parts of the Orion Nebula complex.

Main star

The main star Alnitak Aa belongs to the spectral class O9, its surface temperature is approx. 25,000 Kelvin . Like Beta , Delta and Epsilon Orionis , Zeta Orionis is also a bright blue supergiant with 100,000 times the bolometric luminosity of our sun . In the visual field, its luminosity is about 10,000 times greater than that of the sun. Alnitak is about 20 times the diameter of our sun. The distance from Alnitak is about 800  light years .

Two companions

Alnitak Aa has a close companion named Alnitak Ab who was only discovered in 2000. It is probably a main sequence star of the spectral class O with about 23 times the solar mass. The apparent brightness is around 4 mag and the luminosity in the visual area is accordingly about 1,300 times the solar luminosity.

At an angular distance of 2.3 ″ at a position angle of 165 degrees there is a more easily observable companion Alnitak B. Its brightness is 4.2 mag with about 1,100 times the visual solar luminosity, the spectral type is B0 III, the mass is about 13 solar masses estimated.

Alnitak was included in the third fundamental catalog FK3 (around 1950), but was no longer included in the FK4 as a double star visible in telescopes .

  • Size comparison between Alnitak and the sun

  • Orion Belt: Alnitak is the bright star in the lower left

See also

Web links

Commons : Alnitak  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b Comp. A and Comp. B in "2nd Cat. Of Radial Velocities with Astrometric Data (Kharchenko +, 2007)"
  2. ↑ a b c d Bright Star Catalog (A) and Bright Star Catalog (B)
  3. ↑ a b Hipparcos catalog
  4. ↑ Remie and Lamers: Effective temperatures, and radii of luminous O and B stars - A test for the accuracy of the model atmospheres , A&A vol. 105, no. 1, Jan. 1982, p. 85-97.
  5. ^ Alnitak on the Solstation website