Iota Ursae Majoris

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Iota Ursae Majoris
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 ι Ursae Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 08h 59m 12.45362s[1]
Declination +48° 02′ 30.5741″[1]
Apparent magnitude (V) 3.14[2]/10.1/10.3
Spectral type F0IV-V + M3V + M4V[3]
U−B color index +0.08[2]
B−V color index +0.19[2]
Variable type Suspected
Radial velocity (Rv)+9.0[4] km/s
Proper motion (μ) RA: -441.29[1] mas/yr
Dec.: -215.32[1] mas/yr
Parallax (π)68.92 ± 0.16[1] mas
Distance47.3 ± 0.1 ly
(14.51 ± 0.03 pc)
Absolute magnitude (MV)+2.31[5]
Primaryι UMa A
Companionι UMa BC
Period (P)2084 ± 15 yr
Semi-major axis (a)16.7 ± 0.3″
Eccentricity (e)0.90 ± 0.02
Inclination (i)54 ± 4°
Longitude of the node (Ω)134 ± 2°
Periastron epoch (T)B 2029 ± 1
Argument of periastron (ω)
23 ± 5°
ι UMa A
Mass1.7 ± 0.1 / 1.0 ± 0.3[3] M
Luminosity9.87[5] L
Surface gravity (log g)4.30 ± 0.07[3] cgs
Metallicity [Fe/H]7260 ± 70[3] dex
Rotational velocity (v sin i)154[7] km/s
Age620[8] Myr
ι UMa B
Mass0.35 ± 0.05[3] M
ι UMa C
Mass0.30 ± 0.05[3] M
Other designations
Talitha, Talitha Borealis, Alphikra Borealis, ι Ursae Majoris, ι UMa, Iota UMa, 9 Ursae Majoris, BD+48 1707, FK5 335, GJ 331, HD 76644, HIP 44127, HR 3569, SAO 42630, WDS J08592+4803A,BC.[9]
Database references
ι UMa A
ι UMa BC
ι UMa B
ι UMa C

Iota Ursae Majoris (ι Ursae Majoris, abbreviated Iota UMa, ι UMa), also named Talitha,[10] is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of 3.14,[2] making it visible to the naked eye and placing it among the brighter members of this constellation. Based upon parallax measurements, it is located at a distance of 47.3 light-years (14.5 parsecs) from the Sun.


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

The star bore the traditional names Talitha, Talitha Borealis and Alphikra Borealis. Talitha, which was shared with Kappa Ursae Majoris) comes from the Arabic phrase Al Fiḳrah al Thalitha "the third spring, or leap, of the ghazal".[11] The term Borealis meaning "the north side" in Latin. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[13] included a table of the first two batches of names approved by the WGSN; which included Talitha for this star.

In Chinese, 三台 (Sān Tái), meaning Three Steps, refers to an asterism consisting of ι Ursae Majoris, Kappa Ursae Majoris, Lambda Ursae Majoris, Mu Ursae Majoris, Nu Ursae Majoris and Xi Ursae Majoris. Consequently, ι Ursae Majoris itself is known as 上台一 (Shàng Tái yī, English: Star of First Upper Step).[14]

The star was also dubbed Dnoces ('Second,' backwards) after Edward H. White II, an Apollo 1 astronaut. The name was invented by his fellow astronaut Gus Grissom as a practical joke.[15]

Stellar system[edit]

The Iota Ursae Majoris system is composed of two sets of binary stars. The two binary systems orbit around each other once every 2,084 years.[3] The apparent separation between the two binaries is rapidly decreasing as they follow their orbits. In 1841 when the B component was first discovered, they had a separation of 10.7 arcseconds, or at least 156 AU. By 1971 their separation had decreased to 4.5 arcseconds, or at least 66 AU. This system appears to be dynamically unstable with a high likelihood and may become disrupted on a time scale on the order of 105 years.[16]

The brightest component is a white A-type subgiant. It is a member of a spectroscopic binary system whose components have an orbital period of 4,028 days. The companion, which has not been directly observed, is thought to be a white dwarf with a mass of 1.0 ± 0.3 M.[3]

The companion binary is composed of the 9th magnitude and 10th magnitude stars, both of which are red dwarfs.[3] These two red dwarfs, designated Iota Ursae Majoris B and C respectively, orbit around each other with a period of 39.7 years, and are separated by roughly 0.7 arcseconds, or at least 10 AU. This pair may be the source of the X-ray emission detected from this system.[17]

See also[edit]


  1. ^ a b c d e 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): 99. Bibcode:1966CoLPL...4...99J.
  3. ^ a b c d e f g h i Zhuchkov, R. Ya.; Malogolovets, E. V.; Kiyaeva, O. V.; Orlov, V. V.; Bikmaev, I. F.; Balega, Yu. Yu. (2012). "Physical parameters and dynamical properties of the multiple system ι UMa (ADS 7114)". Astronomy Reports. 56 (7): 512. Bibcode:2012ARep...56..512Z. doi:10.1134/S1063772912070074.
  4. ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, eds., "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, University of Toronto: International Astronomical Union, 30: 57, Bibcode:1967IAUS...30...57E
  5. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. ^ "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 16 May 2017.
  7. ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224
  8. ^ Su, K. Y. L.; et al. (December 2006), "Debris Disk Evolution around A Stars", The Astrophysical Journal, 653 (1): 675–689, arXiv:astro-ph/0608563, Bibcode:2006ApJ...653..675S, doi:10.1086/508649
  9. ^ "iot UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-02-25.
  10. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  11. ^ Richard Hinckley Allen :Star Names — Their Lore and Meaning - Ursa Major, the Greater Bear
  12. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  13. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  14. ^ (in Chinese) (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日
  15. ^ "Post-landing Activities", Apollo 15 Lunar Surface Journal, NASA. Commentary at 105:11:33.
  16. ^ Zhuchkov, R. Ya.; Orlov, V. V.; Rubinov, A. V. (January 2006), "Dynamical stability of the quadruple systems HD 68255/6/7 and HD 76644", Astronomy Reports, 50 (1): 62–67, Bibcode:2006ARep...50...62Z, doi:10.1134/S1063772906010070
  17. ^ De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society, 415 (1): 854–866, arXiv:1103.4363, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x

External links[edit]