Supermassive stars have been proposed as the progenitors of the massive ( \sim 10 ^ { 9 } \mathrm { M } _ { \odot } ) quasars observed at z \sim 7 .
Prospects for directly detecting supermassive stars with next-generation facilities depend critically on their intrinsic lifetimes , as well as their formation rates .
We use the 1D stellar evolution code Kepler to explore the theoretical limiting case of zero-metallicity , non-rotating stars , formed monolithically with initial masses between 10 \mathrm { kM } _ { \odot } and 190 \mathrm { kM } _ { \odot } .
We find that stars born with masses between \sim 60 \mathrm { kM } _ { \odot } and \sim 150 \mathrm { kM } _ { \odot } collapse at the end of the main sequence , burning stably for \sim 1.5 \mathrm { Myr } .
More massive stars collapse directly through the general relativistic instability after only a thermal timescale of \sim 3 \mathrm { kyr } – 4 \mathrm { kyr } .
The expected difficulty in producing such massive , thermally-relaxed objects , together with recent results for currently preferred rapidly-accreting formation models , suggests that such ‘ ‘ truly direct ’ ’ or ‘ ‘ dark ’ ’ collapses may not be typical for supermassive objects in the early Universe .
We close by discussing the evolution of supermassive stars in the broader context of massive primordial stellar evolution and the possibility of supermassive stellar explosions .