Zeta Geminorum - Properties

Properties

This star is a Classical Cepheid variable that undergoes regular, periodic variation in luminosity because of radial pulsations. In the V band, the apparent magnitude varies between a high of 3.68 and a low of 4.16 (with a mean of 3.93) over a period of 10.148 days. This period of variation is decreasing at the rate of 3.1 seconds per year, or 0.085 seconds per cycle. It has a nominal stellar classification of G0 Ibv, with the luminosity class of Ib indicating that this is an intermediate luminous supergiant. The 'v' suffix means that it has variable spectral features, with the actual classification changing between F7Ib and G3Ib over the course of a pulsation cycle. Likewise the effective temperature of the outer envelope varies between 5,780 K and 5,260 K, while the radius varies from 61 to 69 times the Sun's radius. On average, it is radiating about 2,900 times the luminosity of the Sun.

There is no evidence of a stellar companion to Zeta Geminorum. However, the star was recently discovered to belong to a star cluster. Delta Cephei, the prototypical classical Cepheid variables, is also a member of a star cluster. The Cepheid's cluster membership, along with recent Hubble Space Telescope and Hipparcos parallaxes, place strong constraints on the star's distance: 363 ± 9(σ₂) ± 26(σ) parsecs. Zeta Geminorum is thus an important calibrator for establishing the cosmic distance ladder.