Astronomers have discovered a rare Type Ia supernova precursor in our cosmic neighborhood—though it won't explode for millions of years, if humans are still around to witness it.
Supernovae mark the explosive deaths of massive stars, at least eight times the Sun's mass. Two primary types exist: core-collapse supernovae from the implosion of massive stars, and Type Ia thermonuclear explosions triggered when a white dwarf accretes material from a companion, reaching critical mass in a binary system.
While core-collapse precursors are relatively common, spotting Type Ia candidates before detonation is challenging due to white dwarfs' faintness—unless they're nearby and actively accreting. In a new Nature Astronomy study, University of Warwick researchers describe such a system: HD 265435.
Located about 1,500 light-years from Earth, HD 265435 features a hot subdwarf star (roughly 60% solar mass) orbiting a white dwarf (about 1% solar mass) every 100 minutes. The white dwarf's gravity distorts the subdwarf into a teardrop shape as it steadily donates material.
For a Type Ia supernova, the white dwarf must reach 1.4 solar masses. Orbital dynamics suggest this merger won't occur for at least 72 million years, by which time the subdwarf may exhaust its fuel without fully merging.
Beyond their spectacle, Type Ia supernovae act as "standard candles" for measuring cosmic distances—key to discovering dark energy's role in accelerating universal expansion.
Today, these events help map the local Universe, but discrepancies arise with other methods, fueling the Hubble tension. "The more we understand supernova mechanics, the better we calibrate our standard candles," says lead author Dr. Ingrid Pelisoli. "This is crucial now, given the tensions between Type Ia results and other techniques."
