41 Lyncis

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41 Lyncis
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings

Location of 41 Lyncis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 09h 28m 39.98840s[1]
Declination +45° 36′ 05.3344″[1]
Apparent magnitude (V) 5.413[2]
Spectral type K0 III-IV[3]
U−B color index 0.74
B−V color index 0.983[3]
Radial velocity (Rv) +38.44[3] km/s
Proper motion (μ) RA: -7.50[1] mas/yr
Dec.: -128.77[1] mas/yr
Parallax (π) 11.65 ± 0.39[1] mas
Distance 280 ± 9 ly
(86 ± 3 pc)
Absolute magnitude (MV) 0.675[3]
Mass 2.07+0.14
[4] M
Radius 11[5] R
Luminosity 55[5] L
Surface gravity (log g) 2.30[3] cgs
Temperature 4789[3] K
Metallicity [Fe/H] –0.23[3] dex
Rotational velocity (v sin i) [5] km/s
Age 4.07±2.24[3] Gyr
Other designations
Intercrus, BD+46° 1509, CCDM J09287+4536, GC 13051, HD 81688, HIP 46471, HR 3743, SAO 42876.[2]
Database references
SIMBAD The star
planet b

41 Lyncis (abbreviated 41 Lyn), also designated HD 81688 and named Intercrus,[6] is a fifth magnitude star located in the northern constellation of Ursa Major. An extrasolar planet (designated 41 Lyncis b or HD 81688 b, later named Arkas) is thought to be orbiting the star.

It is estimated using parallax measurements to be approximately 280 light-years (86 parsecs) from the Sun.[1] The spectrum of this star matches a stellar classification of K0 III-IV,[3] with the luminosity class of III-IV suggesting it is at an evolutionary stage part way between a subgiant star and a giant star. This star has about double the mass of the Sun, although Kunitomo et al. (2011) give a lower estimate of 1.1+0.3
solar masses.[4] It has expanded to 11 times the Sun's radius and is radiating 55 times as much as the Sun from its outer atmosphere at an effective temperature of 4,789 K.[5] This temperature gives it the orange-hued glow of a K-type star.[7]

This star is following an orbit through the Milky Way with an eccentricity of 0.21. This will take it as close to the Galactic Center as 18.5 kly (5.7 kpc) and as far as 28.2 kly (8.6 kpc). The inclination of this orbit will carry it as much as 1,800 ly (550 pc) away from the galactic plane. For this reason, it is uncertain whether this star is a member of the thin disk population.[3]


41 Lyncis is the Flamsteed designation.[8] Typically, 'Lyncis' is the genitive for a star found in the constellation of Lynx. However, when the constellation boundaries were officially established by the International Astronomical Union in 1930, this star was located within Ursa Major. HD 81688 is the entry in the Henry Draper Catalogue. Following its discovery the planet was designated 41 Lyncis b or alternatively HD 81688 b. In July 2014 the IAU launched a process for giving proper names to certain exoplanets and their host stars.[9] The process involved public nomination and voting for the new names.[10] In December 2015, the IAU announced the winning names were Intercrus for this star and Arkas for its planet.[11]

The winning names were those submitted by the Okayama Astro Club of Japan. Intercrus means "between the legs" in Latin style, referring to the star's position in the constellation Ursa Major. Arkas was the son of Callisto (Ursa Major) in Greek mythology.[12]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[14] the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.[6]

Planetary system[edit]

On 19 February 2008 a planet was announced orbiting the star. It has 2.7 times the mass of Jupiter and completes an orbit every 184 days.[15]

The 41 Lyncis planetary system[15]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (Arkas) 2.7 MJ 0.81 184.02 ± 0.18 0 (fixed)


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357 
  2. ^ a b "HR 3743 -- Star in double system", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-03-25 
  3. ^ a b c d e f g h i j Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, Bibcode:2008A&A...480...91S, arXiv:0712.1370Freely accessible, doi:10.1051/0004-6361:20078788 
  4. ^ a b Kunitomo, M.; et al. (August 2011), "Planet Engulfment by ~1.5-3 M sun Red Giants", The Astrophysical Journal, 737 (2): 66, Bibcode:2011ApJ...737...66K, arXiv:1106.2251Freely accessible, doi:10.1088/0004-637X/737/2/66 
  5. ^ a b c d Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209 
  6. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  7. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16 
  8. ^ Kostjuk, N. D. (April 2004), "HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)", VizieR On-line Data Catalog: IV/27A, Institute of Astronomy of Russian Academy of Sciences, Bibcode:2004yCat.4027....0K 
  9. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
  10. ^ NameExoWorlds The Process
  11. ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  12. ^ NameExoWorlds The Approved Names
  13. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  14. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016. 
  15. ^ a b Sato, Bun'ei; et al. (2008), "Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae and HD 81688", Publications of the Astronomical Society of Japan, 60 (3): 539–550, Bibcode:2008PASJ...60..539S, arXiv:0802.2590Freely accessible, doi:10.1093/pasj/60.3.539 

External links[edit]

Coordinates: Sky map 09h 28m 40s, +45° 36′ 05″