Once it takes in material equivalent to about 1.44 times the mass of our Sun, it gets hot enough to ignite carbon fusion and trigger a thermonuclear runaway process. That leads to a violent explosion that can eject matter at up to 6 percent the speed of light and cause a peak brightness of 5 billion times that of the Sun.

Scientists know fairly precisely how much light a type Ia supernova produces, so they can use them as a “standard candle” to gauge distance. By comparing the theoretical with the observed brightness, they can accurately calculate the distance to the