Iota Carinae

For i Carinae, see HD 79447.

ι Carinae

Location of ι Carinae (circled in red)
Observation data Epoch J2000      Equinox J2000
Constellation	Carina
Right ascension	09^h 17^m 05.40686^s[1]
Declination	−59° 16′ 30.8353″[1]
Apparent magnitude (V)	2.21[2]
Characteristics
Spectral type	A7 Ib[3]
U−B color index	+0.16[4]
B−V color index	+0.18[4]
Variable type	Suspected[5]
Astrometry
Radial velocity (Rv)	13.3[2] km/s
Proper motion (μ)	RA: −19.03[1] mas/yr Dec.: +13.11[1] mas/yr
Parallax (π)	4.26 ± 0.1 mas[1]
Distance	770 ± 20 ly (235 ± 6 pc)
Absolute magnitude (MV)	−5.1[6]
Details
Mass	6.9[7] M☉
Radius	46.4–50.1[7] R☉
Luminosity	4,900[8] L☉
Surface gravity (log g)	1.85±0.1[7] cgs
Temperature	7,500[7]–7,700[9] K
Metallicity [Fe/H]	−0.14[8] dex
Rotational velocity (v sin i)	10.0[8] km/s
Age	56[7] Myr
Other designations
iota Car, HR 3699, HD 80404, SAO 236808, FK5 351, CD−58°2529, CPD−58°1465, NSV 04444, HIP 45556.[10]
Database references
SIMBAD	data

Iota Carinae (ι Carinae, abbreviated Iota Car, ι Car), officially named Aspidiske /ˌæspɪˈdɪskiː/,[11] is a star in the southern constellation of Carina. With an apparent visual magnitude of 2.2,[2] it is one of the brighter stars in the night sky.

Appearance and location

The star and rest of southern Carina never sets on places from about 34° S southwards including Cape Town; its northernmost viewpoints are unobstructed southern horizons near to the 30th parallel north, once a day.[12]

The False Cross is an asterism formed from Iota Carinae, Delta Velorum, Kappa Velorum and Epsilon Carinae. It is so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation.[13]

The star appears 46.0' (0.7668°) WSW of V357 Carinae, a mid-third-magnitude star, also forming part of the asterism and leading to its long, narrow projection which culminates in Canopus.[14]

Nomenclature

ι Carinae (Latinised to Iota Carinae) is the star's Bayer designation.

It has the traditional cognate names Aspidiske (not be confused with Asmidiske, the proper name of Xi Puppis), Scutulum and Turais (or Tureis, a name shared with Rho Puppis). Turais is the Arabic تُرَيْس turais "small shield" (diminutive), while Aspidiske and Scutulum are Greek and Latin translations from ασπίδα and scūtum.[12] In 2016, the International Astronomical Union formed its Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[16] included a table of the first two batches of names it approved which included Aspidiske for this star.

In Chinese, 海石 (Hǎi Shí), meaning Sea Rock, refers to an asterism consisting of Iota Carinae, Epsilon Carinae, HD 83183, HD 84810 and Upsilon Carinae.[17] Consequently, Iota Carinae itself is known as 海石二 (Hǎi Shí èr, English: the Second Star of Sea Rock).[18]

Properties

Based on parallax measurements this star is about 770 light-years (240 parsecs) from the Earth. It has a stellar classification of A7 Ib,[3] with the luminosity class of 'Ib' indicating it has reached the stage of its evolution where it has expanded to become a lower-luminosity supergiant. It is just entering the Hertzsprung gap of the Hertzsprung–Russell diagram, and is evolving towards a red supergiant phase.[19]

Iota Carinae has around seven times the Sun's mass and has expanded to roughly 50 times the Sun's radius.[7] It is radiating about 4,900 times the luminosity of the Sun.[8] However, this luminosity appears to vary, causing the star's apparent magnitude to range between 2.23–2.28.[5] This energy is being radiated into space from the star's outer envelope at an effective temperature of 7,500 K,[7] giving Iota Carinae the white hue typical of an A-type star.[20] Being short of the rough initial mass limit above which stars collapse and explode as supernovae, Iota Carinae will likely end its life as a white dwarf with roughly the current mass of the Sun, similar to Sirius B today[21] (which was also estimated to have an initial mass of up to 7 solar masses).[22]

Due to precession of the Earth's axis of rotation, in the next 7,500 years the south celestial pole will pass close to this star and Upsilon Carinae and it will become the South Star around 8100 CE.[23]

References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600
2. Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
3. Gray, R. O.; Garrison, R. F. (1989-07-01). "The Late A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation". The Astrophysical Journal Supplement Series. 70: 623. Bibcode:1989ApJS...70..623G. doi:10.1086/191349. ISSN 0067-0049.
4. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
5. Ruban, E. V.; et al. (September 2006), "Spectrophotometric observations of variable stars", Astronomy Letters, 32 (9): 604–607, Bibcode:2006AstL...32..604R, doi:10.1134/S1063773706090052, S2CID 121747360
6. Tanrıverdi, T.; Baştürk, Ö. (2016). "Abundance analysis of the supergiant stars HD 80057 and HD 80404 based on their UVES Spectra". New Astronomy. 47: 46–56. arXiv:1512.03762. Bibcode:2016NewA...47...46T. doi:10.1016/j.newast.2016.02.006. S2CID 119220398.
7. Neiner, Coralie; Oksala, Mary E.; Georgy, Cyril; Przybilla, Norbert; Mathis, Stéphane; Wade, Gregg; Kondrak, Matthias; Fossati, Luca; Blazère, Aurore; Buysschaert, Bram; Grunhut, Jason (2017-10-01). "Discovery of magnetic A supergiants: the descendants of magnetic main-sequence B stars". Monthly Notices of the Royal Astronomical Society. 471 (2): 1926–1935. arXiv:1707.00560. Bibcode:2017MNRAS.471.1926N. doi:10.1093/mnras/stx1549. ISSN 0035-8711.
8. Smiljanic, R.; et al. (April 2006), "CNO in evolved intermediate mass stars", Astronomy and Astrophysics, 449 (2): 655–671, arXiv:astro-ph/0511329, Bibcode:2006A&A...449..655S, doi:10.1051/0004-6361:20054377, S2CID 3711409
9. Ayres, Thomas R. (2018-02-20). "Cracking the Conundrum of F-Supergiant Coronae". The Astrophysical Journal. 854 (2): 95. arXiv:1802.02552. Bibcode:2018ApJ...854...95A. doi:10.3847/1538-4357/aaa6d7. ISSN 0004-637X.
10. "iot Car -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-14
11. "IAU Catalog of Star Names". Retrieved 28 July 2016.
12. Allen, Richard Hinckley (1899), "Star-names and their meanings", New York, G. E. Stechert: 74, Bibcode:1899sntm.book.....A
13. Moore, Patrick (2010). Patrick Moore's Astronomy: Teach Yourself. Hachette. ISBN 978-1444129779.
14. In the Sky Map, Dominic Ford, 2011–2019.
15. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
16. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
17. (in 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.
18. (in Chinese) 香港太空館 – 研究資源 – 亮星中英對照表 Archived 2010-08-11 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
19. Neuhäuser, R; Torres, G; Mugrauer, M; Neuhäuser, D L; Chapman, J; Luge, D; Cosci, M (2022-07-29). "Colour evolution of Betelgeuse and Antares over two millennia, derived from historical records, as a new constraint on mass and age". Monthly Notices of the Royal Astronomical Society. 516 (1): 693–719. arXiv:2207.04702. Bibcode:2022MNRAS.516..693N. doi:10.1093/mnras/stac1969. ISSN 0035-8711.
20. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
21. Kaler, James B., "ASPIDISKE (Iota Carinae)", Stars, University of Illinois, retrieved 2012-01-14
22. Whittet, D. C. B. (1999-12-01). "A physical interpretation of the 'red Sirius' anomaly". Monthly Notices of the Royal Astronomical Society. 310 (2): 355–359. Bibcode:1999MNRAS.310..355W. doi:10.1046/j.1365-8711.1999.02975.x. ISSN 0035-8711.
23. "Precession".