Brilliant and powerful supernova blasts usually herald the explosive “death” of a massive star that has burned up its necessary supply of nuclear-fusing fuel, and has collapsed either into a dense stellar corpse called a neutron star or–in the case of the most massive stars of all–into a stellar mass black hole. However, relatively small, solitary stars like our Sun die peacefully, “gently” tossing their outer gaseous layers into space, where they become beautiful multicolored objects called planetary nebulae that surround a dense little white dwarf star–which was the now-dead small star’s core. But, something very different happens when the white dwarf dwells in a binary system with a still-living companion star–and victim. In this case, the white dwarf may gravitationally sip up its sister star’s stellar material to the point that the white dwarf “goes critical”, and blasts itself to smithereens in a supernova explosion–just like the big guys. These terrible blasts, that herald the grand finale of a vampire-like white dwarf, are classified as Type Ia supernovae. In May 2019, an international team of astronomers announced that their discovery of a strange Type Ia supernova, with unusual chemical properties, may hold the elusive key to solving the nagging mystery of what triggers these violent explosions.
The discovery of the unusual supernova was made by a team of astronomers led by the Carnegie Institution’s Dr. Juna Kollmeier. The team also included Carnegie’s Dr. Nidia Morrell, Dr. Anthony Piro, Dr. Mark Phillips, and Dr. Josh Simon. Observations obtained by the Magellan Telescope, located at Carnegie’s Las Campanas Observatory in Chile, were crucial to detecting the emission of hydrogen that makes this strange supernova, named ASASSN-18tb, so distinctive.
All stars, regardless of their mass or temperature, “live” out their entire main-sequence (hydrogen-burning) “lives” by keeping a very precarious balance between two constantly warring forces–radiation pressure and gravity. The radiation pressure emitted by a star pushes all of the stellar material out and away from the star, and it keeps this enormous roiling, broiling ball of searing-hot gas bouncy against the opposing squeeze inward caused by the crush of the star’s own gravity–that relentlessly and mercilessly attempts to pull all of the stellar material inward. The radiation pressure of a star on the hydrogen-burning main sequence of the Hertzsprung-Russell Diagram of Stellar Evolution, is the result of the process of nuclear fusion, which commences with the burning of hydrogen, the lightest and most abundant atomic element in the Universe, into helium–which is the second-lightest atomic element. This process (stellar nucleosynthesis), progressively fuses increasingly heavier and heavier atomic elements out of lighter ones.
Many supernovae are triggered when a single, very massive star, has come to the end of that long stellar road after having fused its necessary supply of hydrogen fuel into heavier things. At this point, the massive star is doomed. Frequently, the supernova progenitor contains an extremely massive core that weighs-in at about 1.4 times that of our Sun (the Chandrasekhar Limit). These supernovae, that herald the death of a heavy star, are core-collapse supernovae (Type II).
Smaller, less generously endowed solitary stars, like our Sun, normally do not experience that sort of final blaze of glory. Our Sun, at this time, is a rather ordinary main-sequence star. There are eight major planets, myriad moons, and a significant number of other petite objects in orbit around our Star, which dwells in the outer suburbs of our large, star-splattered, spiral Milky Way Galaxy.