SIMBAD references

The secular evolution of solar-type atmospheres may be studied through comparisons of the current Sun with old solar-type stars of known age. Among the few such stars in the solar Galactic neighborhood, β Hydri (G2 IV) stands out as a normal single star with an advanced age. Previous age determinations (≃9.5 Gy) were based on the old ground-based parallax of 153mas. The new Hipparcos value of 133.78±0.51mas implies an absolute magnitude M_V=3.43±0.01, 0.3mag brighter than previously believed. New evolutionary calculations produce best-fit models with ages around 6.7Gy. Although the Hipparcos data thus lead to a significant reduction of its estimated age, β Hyi remains an old star.