Is Our Universe Accelerating Symmetrically?

1. Is Our Universe Accelerating Symmetrically? Joseph M. Fedrow, The Evergreen State College, Olympia WA 98505 I. Introduction II. Theory III. Method IV. Results V. Conclusions •A type Ia supernova reaches maximum brightness in about a day, followed by a gradual decline in brightness. A Type II supernova reaches a maximum brightness only about one-fourth that of a Type Ia supernova and usually has alternating intervals of steep and gradual declines. http://cfa-www.harvard.edu/cfa/oir/Research/supernova/HighZ.html Figure 22.21 from Universe 6e, Freedman/Kaufmann, pub. Freeman, 2002 Sources of error • Possible sources of error include gray dust along our observed line of sight and metallicity present the explosion. • Gray dust could cause further reddening of the SN Ia and thereby deceive us into thinking that we are looking back at a further redshift then we really are. However, c2 is significantly worse for a gray dust model as opposed to one without gray dust (Riess et. al 2004). As a result we can reject a gray dust model as a possible source of error. • Metallicity, the ratio of metals to hydrogen and helium, present during the explosion of a SN Ia could affect the light curves we observe, thus making SN Ia not exactly uniform and as a result unreliable standard candles. However, it has been shown that although metallicty does effect the observed light curve of a SN Ia, it is primarily in the UV part of the spectrum (Nugent et. al 2000). Fortunately, because these observations were made in visible light this does not effect the results obtained by using SN Ia as standard candles.