Originally Posted by Kwalish Kid

You have yet to provide one cosmological SNIa paper that relies upon this assumption. Why do you continue to make this claim?

Originally Posted by Riess et al

A Brief History of Supernova Cosmology

While this paper emphasizes new data and constraints for cosmology, a brief summary of the subject may help readers connect work on supernovae with other approaches to measuring cosmological parameters. Empirical evidence for SNe I presented by Kowal (1968) showed that these events had a well-defined Hubble diagram whose intercept could provide a good measurement of the Hubble constant. Subsequent evidence showed that the original spectroscopic class of Type I should be split (Doggett & Branch 1985;
Uomoto & Kirshner 1985; Wheeler & Levreault 1985; Wheeler & Harkness 1986; Porter & Filippenko 1987).

The remainder of the original group, now called Type Ia, had peak brightness dispersions of 0.4 mag to 0.6 mag (Tammann & Leibundgut 1990; Branch & Miller 1993; Miller & Branch 1990; Della Valle & Panagia 1992; Rood 1994; Sandage & Tammann 1993; Sandage et al. 1994). Theoretical models suggested that these “standard candles” arose from the thermonuclear explosion of a carbon-oxygen white dwarf that had grown to the Chandrasekhar mass (Hoyle & Fowler 1960; Arnett 1969; Colgate & McKee 1969). Because SNe Ia are so luminous (MB ~ −19.5 mag), Colgate (1979) suggested that observations of SNe Ia at z ~1 with the forthcoming Space Telescope could measure the deceleration parameter, q0.