A1 Thermonuclear Collapse

Topic

The central figure in this model is a white dwarf approaching its supporting mass limit.

A white dwarf within a binary system gains mass from its companion—or merges directly with another white dwarf—until it nears the Chandrasekhar limit, the mass threshold previously described as a fundamental aspect of this class of models.

At the moment when even the white dwarf's relativistic degeneracy pressure is no longer sufficient to support it, a runaway thermonuclear ignition is triggered; this consumes the entire star in seconds, releasing enough energy to completely disintegrate it. Unlike core-collapse events—which constitute a separate model—no compact remnant remains here: the white dwarf vanishes entirely in the explosion itself.

Because the mass threshold triggering the explosion is virtually identical in every instance, these explosions reach very similar peak brightnesses; it is precisely this similarity that makes them "standard candles" for measuring cosmic distances. Thus, from the white dwarf approaching its mass limit—where this document began—to the standard candles with which it concludes, and encompassing the accretion of matter from a companion and the remnant-free thermonuclear ignition, the thermonuclear collapse of white dwarfs ensures that crossing this same mass limit—repeatedly across different binary systems—produces explosions similar enough to serve as a fixed yardstick for measuring the scale of the universe itself.

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