Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Iron in the sun: a greenhouse gas for X-ray radiation

06.09.2013
Novel X-ray spectroscopic method provides valuable data on highly charged iron ions for astrophysics

Scientists from the Heidelberg Max Planck Institute for Nuclear Physics (MPIK) in cooperation with DESY (Hamburg) at the synchrotron PETRA III have investigated for the first time X-ray absorption of highly charged iron ions.


Illustration of the inner structure of the Sun: The energy released by nuclear fusion of hydrogen to helium in the Sun’s core is transported outwards via radiation. In the outer shell energy transfer is dominated by convection.

Graphics (modified by MPIK): Kelvinsong, Wikimedia Commons http://commons.wikimedia.org/wiki/File:Sun_poster.svg


Transportable trap for highly charged ions (EBIT) in operation at the X-ray laser LCLS (Stanford Linear Accelerator Center, Menlo Park, California, USA).

Photo: J. R. Crespo López-Urrutia, MPIK

A transportable ion trap developed at MPIK was used for generation and storage of the ions. The high-precision measurements provide important new insight into the role of highly charged ions in astrophysical plasmas, e. g. for radiation transport inside stars. [Physical Review Letters, September 5, 2013]

Highly charged ions - that is, atoms which have been stripped off most of their electrons - play an important role in astrophysics. Within the large accumulations of visible (luminous) matter in the universe, the highly charged state is the natural one. This is the case in stellar atmospheres as well as in the interior of stars, where temperatures of several million degrees Celsius rule. Highly charged ions also abound around exotic objects such as neutron stars or black holes. Before matter plunges into their cores, it delivers gravitational energy, heating up and emitting extremely intense X-rays, which can be observed.

X-rays also determine the energy transport inside the Sun. At its core temperature of 15 million degrees, a natural fusion power plant runs with a total capacity of about 4•10^26 watts. The power density of 200 watts per cubic meter is, however, modest, and corresponds to about that of a compost heap. In contrast to such, the Sun is very large. If the solar core would freely radiate X-rays at those temperatures, a power exceeding the fusion energy yield by 11 orders of magnitude would be lost. The sun works because the radiation transport to the outside is inhibited, thus maintaining the high core temperature. Convection, the heat transport by turbulent upstream flows of hot matter, only takes place further outward, starting at about 70% of the solar radius. This good insulation reduces hydrogen consumption and extends the duration of fusion in our central star to the billions of years that are needed for the formation of a stable planetary system, and ultimately for the development of life.

A measure of the inhibition of radiation transport is the ‘opacity’ of the solar matter, a term describing how efficiently radiation is absorbed by it. Although the Sun consists mainly of hydrogen and helium, these elements only play a secondary role for the opacity. Their share of it diminishes from about 50% in the outer core to below 20% in the radiation zone. Crucial there are the tiny impurities (about 1.6% by mass) of heavier elements, dubbed by astronomers ‘metals’. Besides oxygen, iron, with its mass fraction of only 0.14%, plays for X-rays the role of a greenhouse gas, and contributes about a quarter of the total opacity. To illustrate it: the total amount of iron in the sun would reach for a solid wall of about 100 km thickness at the edge of the radiation zone, at 500,000 km radius. As a dilute impurity in the solar plasma, iron takes a substantial role in the X-ray shielding.

In order to better understand the role of these stellar ‘trace gases’ and obtain reliable data for comparison with astronomical observations, physicists in the team of José R. Crespo López-Urrutia from the Heidelberg Max Planck Institute for Nuclear Physics (MPIK) have prepared, in cooperation with colleagues from DESY (Hamburg) and eight other institutions worldwide, highly charged iron ions in eight different charge states and studied them systematically. PhD student Jan Rudolph and his colleagues installed a mobile electron beam ion trap (EBIT) for the production and storage of highly charged ions at the PETRA III storage ring. This facility provides one of the world's most powerful X-ray beams, which was focused onto the trapped ions and tuned in its energy. In this way, the absorption of the X-ray radiation by the iron ions could be measured for the first time, and with high precision. This new laboratory astrophysical data show a good agreement with the latest theoretical calculations. In addition to the characteristic energies of the absorption lines found in the spectra, their natural line width (for the first time measured in this experiment) is also very important, because it determines the maximum radiant power which a single iron ion can handle. It amounts almost one watt per ion for the observed X-ray transitions. Even within the solar core, iron ions are not yet saturated with respect to radiation transport, because they can absorb and emit X-ray photons a million times faster than normal atoms can do with the much less energetic visible photons. This combination of high rates and high photon energy crucially determines the dominance of iron in the solar radiation balance.

The new data provide valuable insights for the opacity calculations that can be used as the basis of stellar models. In addition, they also help in the diagnostics of astrophysical plasmas, such as those surrounding active galactic nuclei, or in binary systems containing compact objects - such as neutron stars or black holes - accreting matter from the partner star. The iron X-ray lines studied here are usually the last spectroscopic witnesses of such processes.

Original publication:
X-Ray Resonant Photoexcitation: Linewidths and Energies of Kα Transitions in Highly Charged Fe Ions

J. K. Rudolph et al., Physical Review Letters 111, 103002 (2013) DOI: 10.1103/PhysRevLett.111.103002 http://link.aps.org/doi/10.1103/PhysRevLett.111.103002

Dr. Bernold Feuerstein | Max-Planck-Institut
Further information:
http://www.mpi-hd.mpg.de/ullrich/page.php?id=36

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>