There’s a star that blew up 125 years ago that’s still glowing because the gas is basically taking its sweet time 'forgetting' the explosion.
arXiv · March 16, 2026 · 2603.12991
Why it matters
Usually, we expect the light from an explosion to fade quickly. Researchers found that this nova created a massive shell of gas that is currently recombining so slowly that we can still see the 1901 eruption as if it were happening much more recently.
From the abstract
The eruption of Nova Persei 1901 (GK Per) occurred 125 yrs ago; remarkably it still holds major surprises. Using data from the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), we find it has a bipolar molecular hydrogen shell. This shell, which has dimensions 18'x10', is co-spatial with the Halpha nebulosity surrounding the nova, which is purported to be an ancient planetary nebula (PN). The shell is detected most strongly in the 0--0 S(9) 4