Measuring The Nuclear Reaction Pathway Of Novae
January 16, 2013

Astrophysicists Measure Nuclear Structure Of Radioactive Neon In Novae

April Flowers for - Your Universe Online

A multinational team of scientists has revealed new information about the explosive events known as novae.

Novae are dramatic stellar explosions driven by nuclear processes that make previously unseen stars visible for a short time. The team of astrophysicists measured the nuclear structure of the radioactive neon produced through this process in unprecedented detail.

The study, led by the University of York, UK, and Universitat Politècnica de Catalunya and the Institut d´Estudis Espacials de Catalunya, reveals that there is much less uncertainty in how quickly one of the key nuclear reactions will occur as well as in the final abundance of radioactive isotopes than has previously been assumed.

The findings, published in a recent issue of Physical Review Letters, will help with the interpretation of future data from satellites observing gamma rays.

Large stars end their lives with spectacular explosions called supernovae. Smaller stars — known as white dwarves — however, sometimes experience smaller, but still dramatic explosions called novae, the brightest of which are visible to the naked eye.

When a white dwarf is close enough to a companion star to drag matter — mostly hydrogen and helium — from the outer layers of that companion star onto itself, building up an envelope, then a nova occurs. A burst of nuclear fusion occurs when enough material has accumulated on the surface. This causes the white dwarf to brighten and expel the remaining material. The glow subsides within a few days to a few months and is expected to recur after typically 10,000 to 100,000 years.

Although novae are observed in the visible and nearby wavelengths, the emission only shows up about a week after the explosion. This means that scientists only get partial information about the event.

Dr Alison Laird, University of York´s Department of Physics, said, “The explosion is fundamentally driven by nuclear processes. The radiation related to the decay of isotopes - in particular that from an isotope of fluorine - is actively being sought by current and future gamma ray observing satellite missions as it provides direct insight into the explosion."

“However, to be interpreted correctly, the nuclear reaction rates involved in the production of the fluorine isotope must be known. We have demonstrated that previous assumptions about key nuclear properties are incorrect and have improved our knowledge of the nuclear reaction pathway.”

Scientists from the University of Edinburgh interpreted the data obtained from the experimental work done at the Maier-Leibnitz Laboratory in Germany. Scientists from Canada and the United States were also part of the team.

Dr Anuj Parikh, Departament de Fisica i Enginyeria Nuclear at the Universitat Politècnica de Catalunya, observed, "The observation of gamma-rays from novae would help to better determine exactly what chemical elements are synthesized in these astrophysical explosions. In this work, details required to calculate the production of the key radioactive fluorine isotope have been measured precisely. This will allow more detailed investigation of the processes and reactions behind the nova.”

This study is part of an ongoing investigation into the synthesis of elements in stars and stellar explosions.