Tracing the Origins of Stardust in the Nuclear Physics Laboratory
A team of researchers working at NSCL have discovered a short-lived nuclear state that boosts the destruction rate of phosphorus-30 via proton capture in a stellar explosion called a classical nova. This nuclear reaction, where a free proton combines with a phosphorus-30 nucleus, is critical to determining the origins of stardust in the form of presolar grains: microscopic rocks found inside of meteorites that predate our solar system and originate in the outflows of various stellar sources throughout the Milky Way. Some presolar grains rich in silicon-30 may come from classical novae − thermonuclear explosions on the surfaces of white dwarf stars − but in order to determine their origin, the rate of phosphorus-30 destruction via proton capture must be known precisely and compared to the rate of destruction via beta decay into silicon-30. To date, this rate has been difficult to quantify experimentally because the properties of the nuclear states potentially enhancing the proton capture have been uncertain. To cast light on this 5-billion-year-old question, the team carried out an experiment in which they observed and characterized a new short-lived state involved in the reaction. They found that the new state might in fact dominate the destruction rate of phosphorus-30. This is an important step toward determining whether “presolar nova grains” indeed come from novae.
A paper on this research was accepted for publication in Physical Review Letters on 29 January, 2016. It will be featured as an “Editor’s Suggestion”: http://journals.aps.org/prl/accepted/e907cY11Z061405db1f309e9595e76275d6e36dc8