A new class of supernova represents a miniature star explosion.
n 2002, researchers began noticing that many supernovas appeared to be similar to regular Type Ia supernovas, but were distinctly fainter. Some shone with only 1 percent of the peak luminosity of Type Ia supernovas. Now, based on past and new observations, Foley and his colleagues have identified 25 examples of what they call Type Iax supernovas.
The data the scientists gathered suggest that, like a Type Ia supernova, a Type Iax supernova comes from a binary star system containing a white dwarf and a companion star. In Type Iax supernovas, the companion star has apparently already lost its outer hydrogen, leaving it dominated by helium. The white dwarfs then go on to accumulate helium from their companion stars.
It remains unclear what precisely happens during a Type Iax supernova. The helium in the companion star's outer shell might undergo nuclear fusion, blasting a shock wave at the white dwarf that makes it detonate. On the other hand, all the helium the white dwarf accumulated from its companion star could alter the density and temperature of the white dwarf's interior, forcing carbon, oxygen and maybe helium within the star to fuse, triggering an explosion.
In any case, it appears that in many Type Iax supernovas, the white dwarf actually survives the explosion, unlike in Type Ia supernovas, in which the white dwarfs are completely destroyed.
Type Iax supernovas are about a third as common as Type Ia supernovas. The reason so few Type Iax supernovas have been detected so far is that the faintest are only one-hundredth as bright as a Type Ia.