How do astronomers use Type Ia supernovae to measure distances to galaxies?

Astronomers use Type Ia supernovae as "standard candles" to measure distances to galaxies because these objects exhibit a high degree of uniformity in their maximum luminosity.21

Because Type Ia supernovae all reach approximately the same intrinsic brightness at their peak, astronomers can determine the distance to a galaxy by comparing this known absolute magnitude with the object's observed apparent brightness. Specifically, the absolute magnitude at maximum light can be further refined by analyzing the rate of dimming after the peak, the shape of the light curve, and specific color measurements.23

This method is particularly valuable because Type Ia supernovae are among the most luminous standard candles available, allowing astronomers to gauge distances to galaxies much farther away than is possible with other indicators. By applying this technique, researchers have been able to map the structure of the universe and measure its expansion rate, which led to the discovery of dark energy and the realization that the expansion of the universe is accelerating.132