Why are Type Ia supernovae useful as standard candles for cosmology?

Answer

Peak intrinsic luminosity is remarkably uniform due to the Chandrasekhar limit threshold.

Type Ia supernovae are intrinsically valuable to cosmology because they originate from white dwarfs that have reached a critical mass threshold, specifically around $1.4 M_ ext{sun}$, known as the Chandrasekhar limit. When this limit is approached, often through accretion in a binary system or merger, the subsequent thermonuclear runaway reaction ignites carbon fusion throughout the white dwarf, causing a complete detonation. Because the initiating condition—reaching this specific mass limit—is so consistent, the total energy output, or peak intrinsic luminosity, of the resulting explosion is highly deterministic and remarkably uniform across different galaxies. This consistency allows astronomers to use them as reliable standard candles, meaning by comparing their apparent brightness to their known absolute brightness, precise intergalactic distances can be calculated.

Why are Type Ia supernovae useful as standard candles for cosmology?

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