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 Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

nachricht New functional principle to generate the „third harmonic“
16.02.2017 | Laser Zentrum Hannover e.V.

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>