l Carinae

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This article is about ℓ Carinae (HD 84810). For L Carinae, see HD 90264. For I Carinae, see HD 90589. For ι Carinae, see Iota Carinae.
ℓ Carinae[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension 09h 45m 14.81122s[2]
Declination –62° 30′ 28.4519″[2]
Apparent magnitude (V) 3.39[3]
Spectral type G5 Iab/Ib[4]
U−B color index +0.76[3]
B−V color index +1.03[3]
Variable type Classical Cepheid
Radial velocity (Rv) +3.3[5] km/s
Proper motion (μ) RA: –12.88[2] mas/yr
Dec.: +8.19[2] mas/yr
Parallax (π) 2.09 ± 0.29[2] mas
Distance approx. 1,600 ly
(approx. 480 pc)
Mass 8.4[4] to 13[6] M
Radius 169±8[7] R
Surface gravity (log g) 1.5[8] cgs
Temperature 5,091[8] K
Metallicity [Fe/H] 0.30[8] dex
Age 33.3±5.9[4] Myr
Other designations
l Carinae, 2MASS J09451481-6230284, CD–61 2349, FK5 1254, HD 84810, HIP 47854, HR 3884, IRAS 09438-6216, SAO 250683.

HD 84810, also known as l Carinae (l Car), is a star in the southern constellation of Carina. It has a mean apparent magnitude of +3.4,[3] making it readily visible to the naked eye and one of the brighter members of Carina. Based upon parallax measurements, it is approximately 1,600 light-years (490 parsecs) from Earth.[2]

From the characteristics of its spectrum, l Carinae has a stellar classification of G5 Iab/Ib.[4] This indicates the star has reached a stage in its evolution where it has expanded to become a supergiant with 169 times the radius of the Sun.[7] As this is a massive star with 8[4]–13[6] times the mass of the Sun, it rapidly burns through its supply of nuclear fuel and has become a supergiant in roughly 33 million years,[4] after spending 15–17 million years as a main sequence star.[6]

l Carinae is classified as a Cepheid variable star and its brightness varies over an amplitude range of 0.725 in magnitude with a long period of 35.560 days. The radial velocity of the star likewise varies by 39 km/s during each pulsation cycle.[9] It has a compact circumstellar envelope that can be discerned using interferometery. The envelope has been resolved at an infrared wavelength of 10μm, showing a radius of 10–100 AU at a mean temperature of 100 K. The material for this envelope was supplied by mass ejected from the central star.[6]


  1. ^ SIMBAD, "l Carinae", December 30, 2010
  3. ^ a b c d Madore, B. F. (June 1975), "Photoelectric UBV photometry of Cepheids in the Magellanic Clouds and in the southern Milky Way", Astrophysical Journal Supplement Series 29: 219–284, Bibcode:1975ApJS...29..219M, doi:10.1086/190342. 
  5. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E. 
  6. ^ a b c d Gallenne, A. (May 2009), "The circumstellar envelopes of the Cepheids ℓ Carinae and RS Puppis. Comparative study in the infrared with Spitzer, VLT/VISIR, and VLTI/MIDI", Astronomy and Astrophysics 498 (2): 425–443, arXiv:0902.1588, Bibcode:2009A&A...498..425K, doi:10.1051/0004-6361/200811307. 
  7. ^ a b Davis, J. et al. (April 2009), "Observations of the pulsation of the Cepheid l Car with the Sydney University Stellar Interferometer", Monthly Notices of the Royal Astronomical Society 394 (3): 1620–1630, arXiv:0812.4791, Bibcode:2009MNRAS.394.1620D, doi:10.1111/j.1365-2966.2009.14433.x. 
  9. ^ Klagyivik, P.; Szabados, L. (September 2009), "Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes", Astronomy and Astrophysics 504 (3): 959–972, arXiv:0908.3561, Bibcode:2009A&A...504..959K, doi:10.1051/0004-6361/200811464.