Observations over the decades have shown that its colour slightly changes and it exhibits variation in light that indicate the star is actually an ellipsoidal binary with a period of seven days.[14] The system is more luminous than expected, given the spectrum and distance of the primary star, indicating that the companion star must be contributing a good proportion of its light. Stellar evolution modelling has concluded that the system likely begun as a binary system, with one star about double the Sun's mass and the other roughly equivalent to that of the sun. The larger star eventually aged and expanded as it used up its core hydrogen, and begun having its mass siphoned off by the smaller star; the system is likely to have been an Algol-type eclipsing binary at this stage. This star appears now to be an aged star composed mostly of helium with very little hydrogen and with a mass of 0.2 solar masses and around 37 times the luminosity of the Sun and surface temperature of 7000 K, while the once-smaller star is the Delta Scuti variable that is now around two solar masses.[15] Around 0.8 solar masses has been lost from the system over time.[15]
^Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
^Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
^ abJohnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
^Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
^ abTempleton, Matthew (16 July 2010). "Delta Scuti and the Delta Scuti Variables". Variable Star of the Season. AAVSO (American Association of Variable Star Observers). Retrieved 2 February 2014.
^Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. pp. 305–07. ISBN978-0-939923-78-6.
^Sterken, C. (1997). "The δ Scuti star θ Tucanae. II. UVBY colour variations and pulsational/orbital properties". Astronomy and Astrophysics. 325: 563–68. Bibcode:1997A&A...325..563S.