Supernova in the Making: Twin Stars Will Meet Explosive Death in 700 Million Years

— -- At the center of a mysterious nebula are two white dwarf stars that astronomers say will meet an explosive death in 700 million years, igniting an incredible supernova.

Each white dwarf star has a weight similar to the sun, and they orbit around each other every 4.2 hours in a slow death spiral.

Their distance is slowly being erased to the extent that astronomers believe the stars will crash into each other in 700 million years in a most spectacular fashion -- the first observed candidates for a kind of supernova known as a "Type 1a," which until now has been posited only in theory.

Researchers said both stars are in the oddly shaped Henize 2-428 nebula. Before the explosive transformation into a supernova, the white dwarf will often fuse with a partner star to gain matter.

In this case, the fused white dwarf stars will have 1.8 times the mass of the sun before it collapses and explodes so brightly that the distant cosmic occurrence would be visible from Earth, according to researchers.

It's the first time researchers have observed a "Type 1a" supernova in the making, according to findings that were published Monday in the journal "Nature."

In the more well-known variety of supernova, a star that is massive enough -- at least several times the mass of our sun -- will collapse and explode after running out of all its nuclear fuel and the core fuses lighter elements into iron.