A Star Is Reborn

As they grow old, stars with approximately the mass of our Sun experience explosive flashes just before their nuclear furnaces shut down. These flashes expel the stars’ outer shells and leave behind hot dense remnants called white dwarfs. Most of these remnants simply cool down, but some can experience a late explosion that restarts nuclear burning and expands them into giant stars again.

Hadjuk et al. (p.231;see the Perspective by Asplund) report observations and a stellar model of V4334 Sgr, a “born again” giant that reignited in 1992 and that was discovered by amateur astronomer Sakurai. The subsequent temperature drop of V4334 Sgr is 100 times faster than had been expected. The calculated mass ejection rates suggest that reignition events contribute unexpectedly large amounts of carbon and carbonaceous dust to the interstellar medium.