Acrux

Acrux

The position of Acrux
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Pronunciation /ˈkrʌks/[citation needed]
Right ascension 12h 26m 35.89522s[1]
Declination −63° 05′ 56.7343″[1]
Apparent magnitude (V) 0.76[2] (1.33 + 1.75)[3]
Characteristics
Spectral type B0.5IV + B1V[4]
B−V color index −0.26[2]
Variable type β Cep[5]
Astrometry
Radial velocity (Rv)−11.2 / −0.6[6] km/s
Proper motion (μ) RA: −35.83[1] mas/yr
Dec.: −14.86[1] mas/yr
Parallax (π)10.13 ± 0.50 mas[1]
Distance320 ± 20 ly
(99 ± 5 pc)
Absolute magnitude (MV)−3.77[7] (−2.2 + −2.7[8])
Orbit[9]
Primaryα Crucis Aa
Companionα Crucis Ab
Period (P)75.7794±0.0037 d
Eccentricity (e)0.46±0.03
Periastron epoch (T)2,417,642.3±1.6 JD
Argument of periastron (ω)
(secondary)
21±6°
Semi-amplitude (K1)
(primary)
41.7±1.2 km/s
Details
α1
Mass17.80 + 6.05[3] M
Radius7.29 ± 0.34[5][a] R
Luminosity31,110+3,190
−2,910
[5] L
Temperature28,840[5] K
Rotational velocity (v sin i)124[5] km/s
α2
Mass15.52[3] M
Radius5.53[10] R
Luminosity16,000[11] L
Temperature28,000[12] K
Rotational velocity (v sin i)200[12] km/s
Age10.8[13] Myr
Other designations
α Crucis, CPD−62°2745, HIP 60718, CCDM J12266-6306, WDS J12266-6306
α1 Cru: Acrux, 26 G. Crucis, FK5 462, GC 16952, HD 108248, HR 4730
α2 Cru: 27 G. Crucis, GC 16953, HD 108249, HR 4731, 2MASS J12263615-6305571
Database references
SIMBADα Cru
α1 Cru
α2 Cru

Acrux is the brightest star in the southern constellation of Crux. It has the Bayer designation α Crucis, which is Latinised to Alpha Crucis and abbreviated Alpha Cru or α Cru. With a combined visual magnitude of +0.76, it is the 13th-brightest star in the night sky. It is the most southerly star of the asterism known as the Southern Cross and is the southernmost first-magnitude star, 2.3 degrees more southerly than Alpha Centauri.[14] This system is located at a distance of 321 light-years from the Sun.[1][15]

To the naked eye Acrux appears as a single star, but it is actually a multiple star system containing six components. Through optical telescopes, Acrux appears as a triple star, whose two brightest components are visually separated by about 4 arcseconds and are known as Acrux A and Acrux B, α1 Crucis and α2 Crucis, or α Crucis A and α Crucis B. Both components are B-type stars, and are many times more massive and luminous than the Sun. This system was the second ever to be recognized as a binary, in 1685 by a Jesuit priest.[16] α1 Crucis is itself a spectroscopic binary with components designated α Crucis Aa (officially named Acrux, historically the name of the entire system)[17][18] and α Crucis Ab. Its two component stars orbit every 76 days at a separation of about 1 astronomical unit (AU).[11] HR 4729, also known as Acrux C, is a more distant companion, forming a triple star through small telescopes. C is also a spectroscopic binary, which brings the total number of stars in the system to at least five.

  1. ^ a b c d e f Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b Corben, P. M. (1966). "Photoelectric magnitudes and colours for bright southern stars". Monthly Notes of the Astron. Soc. Southern Africa. 25: 44. Bibcode:1966MNSSA..25...44C.
  3. ^ a b c Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series. 124 (1): 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181. ISSN 0365-0138.
  4. ^ Cite error: The named reference houk1979 was invoked but never defined (see the help page).
  5. ^ a b c d e Sharma, Awshesh N.; Bedding, Timothy R.; Saio, Hideyuki; White, Timothy R. (2022). "Pulsating B stars in the Scorpius–Centaurus Association with TESS". Monthly Notices of the Royal Astronomical Society. 515 (1): 828–840. arXiv:2203.02582. Bibcode:2022MNRAS.515..828S. doi:10.1093/mnras/stac1816.
  6. ^ Cite error: The named reference gcsrv53 was invoked but never defined (see the help page).
  7. ^ Kaltcheva, N. T.; Golev, V. K.; Moran, K. (2014). "Massive stellar content of the Galactic supershell GSH 305+01-24". Astronomy & Astrophysics. 562: A69. arXiv:1312.5592. Bibcode:2014A&A...562A..69K. doi:10.1051/0004-6361/201321454. S2CID 54222753.
  8. ^ Van De Kamp, Peter (1953). "The Twenty Brightest Stars". Publications of the Astronomical Society of the Pacific. 65 (382): 30. Bibcode:1953PASP...65...30V. doi:10.1086/126523.
  9. ^ Thackeray, A. D.; Wegner, G. (April 1980), "An improved spectroscopic orbit for α1 Crucis", Monthly Notices of the Royal Astronomical Society, 191 (2): 217–220, Bibcode:1980MNRAS.191..217T, doi:10.1093/mnras/191.2.217
  10. ^ Cite error: The named reference lang2006 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference kaler was invoked but never defined (see the help page).
  12. ^ a b Dravins, Dainis; Jensen, Hannes; Lebohec, Stephan; Nuñez, Paul D. (2010). "Stellar intensity interferometry: Astrophysical targets for sub-milliarcsecond imaging". Optical and Infrared Interferometry II. Proceedings of the SPIE. Vol. 7734. pp. 77340A. arXiv:1009.5815. Bibcode:2010SPIE.7734E..0AD. doi:10.1117/12.856394. S2CID 55641060.
  13. ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.
  14. ^ Bordeleau, André G. (12 August 2013). "Federative Republic of Brazil: Constellations in the Breeze". Flags of the Night Sky. New York: Springer. pp. 1–72. doi:10.1007/978-1-4614-0929-8_1. ISBN 978-1-4614-0928-1.
  15. ^ Cite error: The named reference GSM was invoked but never defined (see the help page).
  16. ^ "A Story about Crux | Centre for Astronomical Heritage (CfAH)".
  17. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  18. ^ "IAU Catalog of Star Names". Retrieved 21 November 2016.


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