Delta Crucis

Delta Crucis
Diagram showing star positions and boundaries of the Crux constellation and its surroundings


Location of δ Crucis (circled)

Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Right ascension 12h 15m 08.71673s[1]
Declination –58° 44′ 56.1369″[1]
Apparent magnitude (V) 2.79[2]
Characteristics
Spectral type B2 IV[3]
U−B color index –0.921[4]
B−V color index –0.235[4]
Variable type β Cep[5]
Astrometry
Radial velocity (Rv)+22.2[2] km/s
Proper motion (μ) RA: -35.81[1] mas/yr
Dec.: -10.36[1] mas/yr
Parallax (π)9.45 ± 0.15[1] mas
Distance345 ± 5 ly
(106 ± 2 pc)
Absolute magnitude (MV)–3.2[6]
Details
Mass8.9 ± 0.1[7] M☉
Radius8.0[8] R☉
Luminosity10,000[6] L☉
Surface gravity (log g)3.88[6] cgs
Temperature22,570 ± 1,840[9] K
Rotational velocity (v sin i)210[10] km/s
Age18.1 ± 3.2[7] Myr
Other designations
CD-58 4466, FK5 455, HD 106490, HIP 59747, HR 4656, SAO 239791.[11]

Delta Crucis (δ Cru, δ Crucis) is a star in the southern circumpolar constellation of Crux. It is sometimes called Pálida (Pale [one]) in Portuguese.[12] This star is of apparent magnitude 2.79 and is located at a distance of about 345 light-years (106 parsecs) from Earth, the faintest of the four bright stars that form the prominent asterism known as the Southern Cross. Delta Crucis is massive, hot and rapidly rotating star that is in the process of evolving into a giant.

Properties

This star has a stellar classification of B2 IV,[3] making it a subgiant star that is in the process of evolving away from the main sequence stage. It is now developing into a red giant and will one day end as a white dwarf. Presently it is radiating around 10,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 22,570 K,[6] causing it to glow with a blue-white hue.[13] Delta Crucis is a strong candidate Beta Cephei variable[5] and changes its brightness subtly with a period of 1.3 hours. Its rotation is very fast, with a projected rotational velocity of 210 km s−1.[10]

Delta Crucis is a member of the Lower Centaurus Crux (LCC) component of the Scorpius-Centaurus Association, which is an OB association of massive stars that share a common origin and motion through space.[6] This is the nearest OB association to the Sun, with the LCC component having an age in the range of 16–20 million years.[14]

In culture

In Chinese, 十字架 (Shí Zì Jià), meaning Cross, refers to an asterism consisting of δ Crucis, γ Crucis, α Crucis and β Crucis.[15] Consequently, δ Crucis itself is known as 十字架四 (Shí Zì Jià sì, English: the Fourth Star of Cross.).[16]

The people of Aranda and Luritja tribe around Hermannsburg, Central Australia named Iritjinga, "The Eagle-hawk", a quadrangular arrangement comprising this star, γ Cru (Gacrux), γ Cen (Muhilfain) and δ Cen (Ma Wei).[17]

The other three stars of the Southern Cross; Alpha Crucis, Beta Crucis, and Gamma Crucis all have proper names. Delta crucis is named only by its constellation and Greek letter. Some have proposed naming it Dante, since Dante's divine comedy, written before Europeans had seen the southern cross, features a cross visible in the night sky from the southern hemisphere.

δ Cru is represented in the flags of Australia, New Zealand and Papua New Guinea as one of the stars comprising the Southern Cross. It is also featured in the flag of Brazil, along with 26 other stars, each of which represents a state. δ Cru represents the State of Minas Gerais.[18]

References

  1. 1 2 3 4 5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. 1 2 Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W
  3. 1 2 Houk, Nancy; Cowley, A. P. (1978), Catalogue of two-dimensional spectral types for the HD stars: Declinations -90 to -53, 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H
  4. 1 2 Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168
  5. 1 2 Telting, J. H.; et al. (June 2006), "A high-resolution spectroscopy survey of β Cephei pulsations in bright stars", Astronomy and Astrophysics, 452 (3): 945–953, Bibcode:2006A&A...452..945T, doi:10.1051/0004-6361:20054730
  6. 1 2 3 4 5 de Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1-2): 44–61, Bibcode:1989A&A...216...44D
  7. 1 2 Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 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:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
  8. ↑ Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
  9. ↑ Sokolov, N. A. (May 1995), "The determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A", Astronomy and Astrophysics Supplement, 110: 553, Bibcode:1995A&AS..110..553S
  10. 1 2 Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1). Bibcode:1970CoAsi.239....1B.
  11. ↑ "HD 106490 – Variable Star of beta Cep type", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2005-11-05
  12. ↑ da Silva Oliveira, R., "Crux Australis: o Cruzeiro do Sul", Artigos: Planetario Movel Inflavel AsterDomus.
  13. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16
  14. ↑ Jilinski, E.; et al. (March 2006), "Radial velocity measurements of B stars in the Scorpius-Centaurus association", Astronomy and Astrophysics, 448 (3): 1001–1006, arXiv:astro-ph/0601643Freely accessible, Bibcode:2006A&A...448.1001J, doi:10.1051/0004-6361:20041614
  15. ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  16. ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
  17. ↑ p. 8, Explorers of the southern sky: a history of Australian astronomy, Raymond Haynes, Cambridge, Cambridge University Press, 1996.
  18. ↑ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website.

External links

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