Acrux

This article is about the star. For the Christian college, see Alphacrucis. For research ship, see Alpha Crucis (research vessel).
Acrux

The position of Acrux
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Pronunciation /ˈeɪkrʌks/[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.


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).