Why are Type Ia supernovae useful for measuring distances across the universe?
This nebula is the product of a supernova explosion; in this section, the blast wave has encountered an area of dense interstellar gas, creating turbulence in the wave and causing it to glow. The picture is a composite of three images taken by the Hubble Space Telescope.
Type Ia supernovae are essential tools for measuring distances across the universe because they function as "standard candles" with a uniform luminosity at their peak brightness.123
Because these supernovae all reach approximately the same intrinsic brightness, astronomers can determine their distance by comparing this known absolute magnitude to their observed apparent brightness. This consistency allows them to be used as distance indicators for galaxies far beyond the reach of other methods.132
The utility of Type Ia supernovae is further enhanced by the ability to calibrate their absolute magnitude at maximum light using data from their light curves, color measurements, and rates of dimming. By applying this technique, astronomers have been able to map the expansion of the universe over vast distances, a process that notably led to the discovery of dark energy and the realization that the expansion of the universe is accelerating.312