| Rencently,with the profound study of cosmology,it is hope to accurately measure the cosmological parameters(H0,ΩM,ΩΛetc.),estimate the ultimate fate of universe.However, the measurament of the distance is the first but difficult problem to solve.Fortunately,a kind of special celestial body--supernova,provides us a good distance scaler.This is due to the following two characteristics of supernova:firstly,it is very bright,the luminosity from the explosion of a typical supernova can achieves that of a glaxy,106 times that of cepheid variable.Secondly,the peak luminosity of Ia supernova is associated with the light curve.The absolute peak luminosity of supernova can be deduced from corresponding correction,with the error within 11%.In 1998 and 1999,two seperate high-redshift supernova research group found that the mean actual distance of the supernovas is 10 - 15%further than the theoretical value that cauculated by standerd cosmological model,basing on their observation data,so they obtainedΩΛ≠0,q0(deceleration parameter)< 0,which means the accelerate expanding of universe.However,we know that the dust is everywhere in the universe,it's extinction makes the light through by obscured,so that star appears further.In this paper,we deduce some basic characteristics of dust,according to the current dust theory and some phenominon of dust.We obtain the basic dust model,on the basis of two priciples:at first,the birth probability of stars,in current universe.Second,the physical properties of dust particles.This dust model is different from ordinary dust particles,though it doesn't contain apparent phenominon of redden,it still has effect of strong extinction.So its shape is not of ordinary shpere,but needle-like.Because of this charateristic,its extinction can't be eliminated by multicolor light curve shape method.In this paper,we obtain the extinction and scattering charateristics as well as the spectral type of dust,and deduce for dust the extinction formular with some approximated condition.
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