In 1976, this was reported as a spectroscopic binary system by
Helmut A. Abt and Saul G. Levy, giving it an orbital period of 371 days.[8] However, this was brought into question by Christopher L. Morbey and Roger F. Griffin in 1987, who suggested that the data could be explained by random chance.[9] Further observations in 2009 with observations with the
Bok Telescope in Arizona did show changes of 180 m/s in
radial velocity, although there was not sufficient evidence to support a
Keplerian orbit.[10] There is a 14th-magnitude
common proper motion companion to Theta Ursae Majoris at an
angular separation of 4.1
arcseconds,[11] so this may potentially be a triple star system.[12]
The primary component of this putative system has a published
stellar classification of F6 IV,[3] indicating it is a
subgiant star that is
evolving away from the
main sequence. In 2009, Helmut A. Abt listed it with a stellar classification of F7 V, suggesting that it is still on the main sequence.[13] It is larger than the Sun with 141% of the Sun's mass and 250% of the Sun's radius.[2] Consequently, it is shining brighter and evolving more rapidly than the Sun, with a luminosity nearly eight[3] times the Sun's at an age of 2.2 billion years.[5] This energy is being radiated from the star's
outer atmosphere at an
effective temperature of 6,300 K.[6] At this heat, the star glows with the yellow-white hue of an
F-type star.[14]
The
McDonald Observatory team has set limits to the hypothetical presence of one or more planets around the primary with masses between 0.24 and 4.6
Jupiter masses and average separations spanning between 0.05 and 5.2
AU.[15]
Naming and etymology
With
τ,
h,
υ,
φ,
e, and
f, it composed the Arabic
asterismSarīr Banāt al-Na'sh, the Throne of the daughters of Na'sh, and Al-Haud, the Pond.[16] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al-Haud were the title for seven stars :
f as Alhaud I,
τ as Alhaud II,
e as Alhaud III,
h as Alhaud IV, this star (θ) as Alhaud V,
υ as Alhaud VI and
φ as Alhaud VII .[17]
^
abcdMallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507,
Bibcode:
1999A&A...352..495M
^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
^"tet UMa -- Spectroscopic binary", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-04
^Abt, H. A.; Levy, S. G. (March 1976), "Multiplicity among solar-type stars", Astrophysical Journal Supplement Series, 30: 273–306,
Bibcode:
1976ApJS...30..273A,
doi:10.1086/190363
^Morbey, C. L.; Griffin, R. F. (June 1987), "On the reality of certain spectroscopic orbits", Astrophysical Journal, Part 1, 317: 343–352,
Bibcode:
1987ApJ...317..343M,
doi:
10.1086/165281
^"The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from
the original on 2013-12-03, retrieved 2012-01-16