(Press-News.org) An international team of nuclear astrophysicists has shed new light on the explosive stellar events known as novae.
These dramatic explosions are driven by nuclear processes and make previously unseen stars visible for a short time. The team of scientists measured the nuclear structure of the radioactive neon produced through this process in unprecedented detail.
Their findings, reported in the US journal Physical Review Letters, show 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 suggested.
Led by the University of York, UK, and Universitat Politècnica de Catalunya and the Institut d'Estudis Espacials de Catalunya, Spain, the findings will help with the interpretation of future data from gamma ray observing satellites.
While large stars end their lives with spectacular explosions called supernovae, smaller stars, known as white dwarf stars, sometimes experience smaller, but still dramatic explosions called novae. The brightest nova explosions are visible to the naked eye.
A nova occurs when a white dwarf is close enough to a companion star to drag matter – mostly hydrogen and helium – from the outer layers of that star onto itself, building up an envelope. When enough material has accumulated on the surface, a burst of nuclear fusion occurs, causing the white dwarf to brighten and expel the remaining material. Within a few days to months, the glow subsides. The phenomenon is expected to recur after typically 10,000 to 100,000 years.
Traditionally novae are observed in the visible and nearby wavelengths, but this emission only shows up about a week after the explosion and therefore only gives partial information on the event.
Dr Alison Laird, from the 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."
The experimental work was carried out at the Maier-Leibnitz Laboratory in Garching, Germany, and scientists from the University of Edinburgh played a key role in the interpretation of the data. The study also involved scientists from Canada and the United States.
Dr Anuj Parikh, from the Departament de Fisica i Enginyeria Nuclear at the Universitat Politècnica de Catalunya, said: "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."
INFORMATION:
This work is part of an ongoing programme of research studying how the elements are synthesised in stars and stellar explosions.
The UK researchers received funding from the Science Technology Funding Council (STFC), and the project received further support from the Spanish MICINN, the EU Feder funds and ESF EUROCORES Program EuroGENESIS.
Using graphene – either as an alternative to, or most likely as a complementary material with – silicon, offers the promise of much faster future electronics, along with several other advantages over the commonly used semiconductor. However, creating the one-atom thick sheets of carbon known as graphene in a way that could be easily integrated into mass production methods has proven difficult.
When graphene is grown, lattices of the carbon grains are formed randomly, linked together at different angles of orientation in a hexagonal network. However, when those orientations ...
Facebook posts resonate significantly more with human nature than books or even human faces, according to a new study by Laura Mickes and colleagues from the University of California San Diego in the US. The difference in memory between these microblogs and actual published words from a page is as striking as the difference in memory between amnesiacs and healthy controls. The work is published online in Springer's journal Memory & Cognition.
Online social networking is very popular, and allows people to post their thoughts as microblogs, an opportunity that people exploit ...
Football players display different muscle response parameters depending on the position that they hold on the pitch, according to a study conducted by a team of Spanish researchers which has been published in the 'Journal of electromyography and kinesiology'.
Scientists from the University of Vigo have analysed different muscle response parameters in 78 Spanish first division footballers who have been playing for between four and fifteen years. They found variations depending on the field position of the players.
Published in the 'Journal of Electromyography and Kinesiology', ...
Black carbon is the second largest man-made contributor to global warming and its influence on climate has been greatly underestimated, according to the first quantitative and comprehensive analysis of this issue.
The landmark study published in the Journal of Geophysical Research-Atmospheres today says the direct influence of black carbon, or soot, on warming the climate could be about twice previous estimates. Accounting for all of the ways it can affect climate, black carbon is believed to have a warming effect of about 1.1 Watts per square meter (W/m2), approximately ...
While Mexico and the United States have ramped up their efforts to control and perhaps defeat Mexico's increasingly violent drug cartels, the outcome of these efforts remains in doubt and no panaceas are in sight, but prohibition has once again proved to be a failure, according to a paper from Rice University's Baker Institute for Public Policy.
The paper by Rice sociologist William Martin, "Cartels, Corruption and Carnage in the Calderón Era," traces the origins and growth of Mexican drug cartels and the corruption, failed government policies and gruesome violence ...
The European Alps range span eight countries from France to Slovenia and harbour an extraordinary diversity of habitats, plants and animals, including many species found nowhere else. They are widely considered to be one of the most important regions for the preservation of biodiversity in Europe. But the Alps are not just a natural paradise: they are the home and workplace of up to 14 million people and the destination for more than 100 million tourists each year. The resulting changes to the landscape have led to an increasing fragmentation of the plant and animal ...
DENVER – Recent studies have demonstrated that molecular-targeted agents, such as epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI), may prolong survival of selected patients based on tumor biomarkers. The presence of mutation in the EGFR gene is known as a predictive marker for the response to treatment. However, whether or not these EGFR mutations are prognostic factors for non-small cell lung cancer (NSCLC) has not been known. A recent study published in the February 2013 issue of the International Association for the Study of Lung Cancer's (IASLC) ...
DENVER – Exon 20 insertions are the third most common family of epidermal growth factor receptor (EGFR) mutations found in non–small-cell lung cancer (NSCLC). Little is known about cancers harboring these mutations aside from their lack of response to EGFR tyrosine kinase inhibitors, impairing the development of effective targeted therapies. A recent study published in the February 2013 issue of the International Association for the Study of Lung Cancer's (IASLC) Journal of Thoracic Oncology, concludes that patients with EGFR exon 20 insertions have similar clinical characteristics ...
DENVER – For patients with medically operable clinical stage I non–small-cell lung cancer (NSCLC), lobectomy or pneumonectomy is the standard approach. For patients with medically inoperable stage I NSCLC, stereotactic body radiotherapy (SBRT) has become a standard of care. Researchers from the Washington University School of Medicine wanted to compare the patterns of failure (primary tumor control, local control, regional control, and distant control) between each method.
A recent study published in the February 2013 issue of the International Association for the Study ...
Materialistic consumers may derive more pleasure from desiring products than they do from actually owning them, and are willing to overspend and go into debt because they believe that future purchases will transform their lives, according to a new study in the Journal of Consumer Research.
"Thinking about acquisition provides momentary happiness boosts to materialistic people, and because they tend to think about acquisition a lot, such thoughts have the potential to provide frequent mood boosts. But the positive emotions associated with acquisition are short-lived. Although ...
