Iota Cancri

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ι Cancri
Cancer constellation map.svg
Red circle.svg
Location of ι Cancri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cancer
ι Cnc A
Right ascension  08h 46m 41.81988s[1]
Declination +28° 45′ 35.6190″[1]
Apparent magnitude (V) 4.02[2]
ι Cnc B
Right ascension  08h 46m 39.98118s[1]
Declination +28° 45′ 54.1932″[1]
Apparent magnitude (V) 6.57[3]
Spectral type G8IIIa Ba0.2[4] + A2V[5]
ι Cnc A
Radial velocity (Rv)15.74 ± 0.13[6] km/s
Proper motion (μ) RA: -21.58 ± 0.75[1] mas/yr
Dec.: -45.69 ± 0.56[1] mas/yr
Parallax (π)9.85 ± 0.61[1] mas
Distance330 ± 20 ly
(102 ± 6 pc)
Absolute magnitude (MV)−0.79[7]
ι Cnc B
Radial velocity (Rv)25.00 ± 1.5[8] km/s
Proper motion (μ) RA: -22.74 ± 3.45[1] mas/yr
Dec.: -46.36 ± 2.56[1] mas/yr
Parallax (π)11.69 ± 2.75[1] mas
Distanceapprox. 280 ly
(approx. 90 pc)
ι Cnc A
Mass3.43[9] M
Radius21[6] R
Luminosity204[6] L
Surface gravity (log g)2.5[6] cgs
Temperature4,954[7] K
Metallicity [Fe/H]−0.14[6] dex
Rotational velocity (v sin i)170[10] km/s
ι Cnc B
Luminosity14.39[11] L
Temperature8,786[11] K
Age263[9] Myr
Other designations
48 Cancri
Iota Cancri A: HR 3475, HD 74739, BD+29°1824, HIP 43103, SAO 80416
Iota Cancri B: HR 3474, HD 74738, BD+29°1823, HIP 43100, SAO 80415
Database references
ι Cancri A and B (Jeffrey Fisher)

Iota Cancri (ι Cnc, ι Cancri) is a double star in the constellation Cancer approximately 300 light years from Earth. According to, it also has the name Decapoda.

The two stars of ι Cancri are separated by 30 arcseconds, changing only slowly. Although no orbit has been derived, the two stars show a large common proper motion and are assumed to be gravitationally related.[12]

The brighter star, ι Cancri A, is a yellow G-type giant with an apparent magnitude of +4.02. It is a mild barium star, thought to be formed by mass transfer of enriched material from an asymptotic giant branch star onto a less evolved companion. No such donor has been detected in the ι Cancri system, but it is assumed that there is an unseen white dwarf.[13]

The fainter of the two stars, ι Cancri B, is a white A-type main sequence dwarf with an apparent magnitude of +6.57. It is a shell star, surrounded by material expelled by its rapid rotation.[14]


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  2. ^ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV data. Bibcode:1986EgUBV........0M.
  3. ^ Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
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  6. ^ a b c d e Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal. 135: 209. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
  7. ^ a b Kovtyukh, V. V.; Chekhonadskikh, F. A.; Luck, R. E.; Soubiran, C.; Yasinskaya, M. P.; Belik, S. I. (2010). "Accurate luminosities for F-G supergiants from FeII/FeI line depth ratios". Monthly Notices of the Royal Astronomical Society. 408 (3): 1568. Bibcode:2010MNRAS.408.1568K. doi:10.1111/j.1365-2966.2010.17217.x.
  8. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  9. ^ a b Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (2008). "Stellar Parameters and Elemental Abundances of Late-G Giants". Publications of the Astronomical Society of Japan. 60 (4): 781. arXiv:0805.2434. Bibcode:2008PASJ...60..781T. doi:10.1093/pasj/60.4.781.
  10. ^ Royer, F.; Grenier, S.; Baylac, M.-O.; Gómez, A. E.; Zorec, J. (2002). "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i". Astronomy and Astrophysics. 393 (3): 897. arXiv:astro-ph/0205255. Bibcode:2002A&A...393..897R. doi:10.1051/0004-6361:20020943.
  11. ^ a b McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental parameters and infrared excesses of Hipparcos stars". Monthly Notices of the Royal Astronomical Society. 427: 343. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x.
  12. ^ Eggen, Olin J. (1994). "Photometry of F-K type bright giants and supergiants. 3: The luminosity, reddening, and heavy element abundance of GK stars". The Astronomical Journal. 107: 2184. Bibcode:1994AJ....107.2184E. doi:10.1086/117030.
  13. ^ Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x.
  14. ^ Hauck, B.; Jaschek, C. (2000). "A-shell stars in the Geneva system". Astronomy and Astrophysics. 354: 157. Bibcode:2000A&A...354..157H.