Annu. Rev. Astron. Astrophys. 1992. 30: 359-89 Copyright © 1992 by Annual Reviews. All rights reserved

5. CONCLUSIONS

SNe Ia appear to be photometrically quite homogeneous, generally following standard light-curve shapes to within 0.1 mag and having an absolute magnitude scatter of no more than 0.25 mag. The available data favors a low value of the ratio of extinction to color excess, R_B 1.5, which is unexpected and not understood. The spectral features closely follow a standard pattern of evolution, but real differences in the blueshifts of spectral features occur and their physical significance is not yet clear.

With advances in observation and modeling, SNe Ia are certain to become increasingly valuable as extragalactic distance indicators. Relatively nearby SNe Ia (z 0.1) will be used to probe departures from pure Hubble flow and to measure the value of the Hubble constant. More remote SNe Ia (z 1) will be used to test the reality of the universal expansion and measure the deceleration parameter.

AKNOWLEDGMENTS

It is a pleasure to thank Alex Filippenko for Figure 5 and for a critical reading of the manuscript, and Stefano Benetti, Bruno Leibundgut, and Doug Miller for informative discussions. One of the authors (G.A.T.) wishes to thank the Swiss National Science Foundation for financial support.