Using NASA’s Hubble Space Telescope, a team of astronomers has spotted a star system that could have left behind a “zombie star” after an unusually weak supernova explosion.
Type Ia supernovae are events that happen in binary star systems consisting of a "compact object" (usually a white dwarf, the burned-out husk of a formerly sunlike star) and an "evolved star" such as a red giant. If the stars are sufficiently close to one another, the red giant may transfer gas from its outer envelope onto the white dwarf. When a sufficient amount of gas accumulates on the white dwarf, violently detonates, causing an explosion so catastrophic that it destroys the white dwarf entirely. Type Ia's are important cosmic "standard candles" because it is thought they all shine with the same amount of light, enabling us to estimate large distances throughout the Universe.
Theory predicts that sometimes, the explosion energy is right on the hairy edge of "destructive", and leaves behind a remnant in a rare event called a "Type Iax". New Hubble Space Telescope observations might just have seen one of these weak supernovae before it exploded, giving us new insights into the conditions that result in a Type Iax. The results are to be published in the 7 August issue of Nature.