36 Ursae Majoris

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36 Ursae Majoris
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 10h 30m 37.5798s[1]
Declination +55° 58′ 49.931″[1]
Apparent magnitude (V) 4.82[2]
Spectral type F8 V[3]
U−B color index –0.01[2]
B−V color index +0.52[2]
Radial velocity (Rv) +8.5[4] km/s
Proper motion (μ) RA: –176.71[1] mas/yr
Dec.: –33.21[1] mas/yr
Parallax (π) 78.25 ± 0.28[1] mas
Distance 41.7 ± 0.1 ly
(12.78 ± 0.05 pc)
Absolute magnitude (MV) 4.29[4]
Mass 1.121[5] M
Radius 1.091 ± 0.020[6] R
Luminosity 1.605 ± 0.042[6] L
Surface gravity (log g) 4.36[7] cgs
Temperature 6,233 ± 68[6] K
Metallicity [Fe/H] –0.18[7] dex
Rotational velocity (v sin i) 5.5[8] km/s
Age 2.7[4] Gyr
Other designations
36 Ursae Majoris, BD+56 1459, FK5 394, HD 90839, HIP 51459, HR 4112, SAO 27670.[3]

36 Ursae Majoris is a double star[3] in the northern constellation of Ursa Major. With an apparent visual magnitude of 4.82,[2] it can be seen with the naked eye in suitable dark skies. Based upon parallax measurements, this star lies at a distance of 41.7 light-years (12.8 parsecs) from Earth.[1]

This star is a solar analog—meaning it has physical properties that make it similar to the Sun. It has 12% more mass and a radius 15% larger than the Sun,[5] with an estimated age of 2.7 billion years.[4] The spectrum of this star matches a stellar classification of F8 V, which indicates this is a main sequence star that is generating energy at its core through the nuclear fusion of hydrogen. The energy is being radiated into space from its outer envelope at an effective temperature of 6,126 K.[9] This gives the star the characteristic yellow-white hue of an F-type star.[10]

36 Ursae Majoris is thought[weasel words] to have a stellar companion B of spectral type K7V at wide separation (1500 AUs). An optical companion C (spectral type K2V) is located at 49,000 AUs, but is probably not bound to the system.

Hunt for substellar objects[edit]

According to Nelson & Angel (1998),[11] 36 Ursae Majoris could host one or two (or at least three) jovian planets (or even brown dwarfs) at wide separations from the host star, with orbital periods of 10–15, 25 and 50 years respectively. The authors have set upper limits of 1.1–2, 5.3 and 24 Jupiter masses for the putative planetary objects. Also Lippincott (1983)[12] had previously noticed the possible presence of a massive unseen companion (with nearly 70 times the mass of Jupiter, just below the stellar regime, thus a brown dwarf). Putative parameters for the substellar object show an orbital period of 18 years and quite a high eccentricity (e=0.8). Even Campbell et al. 1988[13] inferred the existence of planetary objects or even brown dwarfs less massive than 14 Jupiter masses around 36 Ursae Majoris.

Nevertheless no certain planetary companion has yet been detected or confirmed. The McDonald Observatory team has set limits to the presence of one or more planets[14] with masses between 0.13 and 2.5 Jupiter masses and average separations spanning between 0.05 and 5.2 AU.

An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of 38.6 AU. The temperature of this dust is 50 K.[15]


  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, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode:1966CoLPL...4...99J 
  3. ^ a b c "HR 4112 -- Star in double system", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-30 
  4. ^ a b c d Nordström, B. et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics 418 (3): 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959 
  5. ^ a b Takeda, Genya et al. (February 2007), "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog", The Astrophysical Journal Supplement Series 168 (2): 297–318, arXiv:astro-ph/0607235, Bibcode:2007ApJS..168..297T, doi:10.1086/509763 
  6. ^ a b c Boyajian, Tabetha S. et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101 . See Table 10.
  7. ^ a b Chen, Y. Q. et al. (February 2000), "Chemical composition of 90 F and G disk dwarfs", Astronomy and Astrophysics Supplement 141: 491–506, arXiv:astro-ph/9912342, Bibcode:2000A&AS..141..491C, doi:10.1051/aas:2000124 
  8. ^ Schröder, C.; Reiners, A.; Schmitt, J. H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377 
  9. ^ Valenti, Jeff A.; Fischer, Debra A. (July 2005), "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs", The Astrophysical Journal Supplement Series 159 (1): 141–166, Bibcode:2005ApJS..159..141V, doi:10.1086/430500 
  10. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  11. ^ The Range of Masses and Periods Explored by Radial Velocity Searches for Planetary Companions
  12. ^ An unseen companion to 36 Ursae Majoris A from analysis of plates taken with the Sproul 61-CM refractor
  13. ^ A search for substellar companions to southern solar-type stars
  14. ^ Detection Limits from the McDonald Observatory Planet Search Program
  15. ^ Eiroa, C. et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics 555: A11. arXiv:1305.0155. Bibcode:2013A&A...555A..11E. doi:10.1051/0004-6361/201321050. 

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