In Type Ia supernovae, a white dwarf in a binary system accretes material until it surpasses the critical Chandrasekhar limit of about 1.44 solar masses, triggering runaway nuclear fusion and a cataclysmic explosion. Typically, this obliterates the white dwarf entirely—but in rare cases, a stellar remnant survives as a 'zombie star.'
Type Ia supernovae, or thermonuclear supernovae, occur exclusively in binary systems featuring a carbon-oxygen white dwarf and a companion star, often a giant beyond the main sequence.
When the companion overflows its Roche lobe, it transfers gas to the white dwarf, steadily building its mass. This ignites carbon fusion, followed by oxygen, spiking the star's core temperature dramatically.
The white dwarf's electron degeneracy pressure, independent of temperature, makes it vulnerable to runaway reactions, amplified by Rayleigh-Taylor instabilities and turbulence.
Within seconds, core temperatures hit billions of degrees, unleashing 1–2×1044 J of energy—enough to disrupt the star completely.
A shockwave ejects outer layers at roughly 6% the speed of light, ending degeneracy and restoring temperature-dependent pressure, resulting in total disintegration. Peak luminosity rivals 5 billion Suns.
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Yet, models suggest 5–30% of events leave a remnant: a 'zombie star' from a Type Iax supernova, with lower velocity and luminosity than standard Type Ia blasts. Though hypothetical, candidates exist.
SN 2012Z in NGC 1309, spotted in January 2012 by the Katzman Automatic Imaging Telescope (KAIT), is a prime suspect for a Type Iax event.
Pre-explosion images enabled before-and-after analysis, bolstering the zombie star theory. Ongoing luminosity checks aim to confirm the remnant, with researchers estimating a 99% probability—versus a less likely second explosion of a 30–40 solar mass star.
