Nuclear astrophysics

As Nuclear Astrophysics , the transition area between is nuclear physics and astrophysics called. Research topics are related to phenomena and interactions

Energy conversion ( nucleosynthesis ) inside stars
Processes in giant stars (e.g. shell burning, variable stars)
Supernovae and theories of star collapse (neutron stars, black holes)
Cosmology , emergence of the first elements after the big bang .

These research areas also include the development of technologies to observe and study these interactions, for example neutrino oscillation , the detection of particles or the nuclear age determination of meteorites - and last but not least the development of theories for the interpretation of the observations and phenomena.

Traditionally, astrophysics is divided on the one hand according to the spectral range of the incoming radiation ( radio and infrared astronomy , spectroscopy , UV , X-ray and gamma astronomy ), and on the other hand according to the celestial objects examined ( e.g. planetology , solar physics , stellar physics and stellar evolution, interstellar matter , galaxy research and cosmology) ). In contrast, nuclear astrophysics has a more integrative approach and is not a predominantly observational science, but also has strong theoretical elements and experimental methods in connection with nuclear physics.

Nucleosynthesis in Stars

Nuclear astrophysics is researching this fundamental process of energy generation in all sun-like and heavier stars in the following areas:

Types of nucleosynthesis in astrophysics
Standard values for the nuclear reaction rates used in astrophysics

Main sequence stars and the relationship between the two fusion processes proton-proton cycle and carbon-nitrogen cycle

Nuclear cross sections in stars, helium fusion reactions

Processes of weak interaction with the stellar evolution

Neutrinos and high energy physics , solar neutrino problem

Theory of giant star stages and shell burning

Formation of unstable elements in the core of red giants (e.g. technetium )
AGB stars and asymptotic giant branches
Variable stars , core processes and oscillations

Star collapse, compact stars

The formation of very compact celestial bodies is a relatively new field of research. a. With:

Star collapse and theory of compact stars using equations of state from nuclear physics
White dwarfs and neutron stars
Simulations of gravitational collapse ,
X-ray bursters , Collapsar model for gamma ray bursters
Jet formation, collapse of rotating magnetars
Development of black holes
Origin of gamma-ray bursts

Theory of supernovae

The explosion in the final stage of very massive stars is only supported by little measurement data because the supernovae observed so far were too far away for precise spectroscopy with two exceptions . Therefore, astrophysical theories in particular contribute to this research area:

Theoretical models for supernovae and neutron stars
Nucleosynthesis in supernovae
the development of massive stars (8 to 50 solar masses ) in the pre-supernova stage
the role of neutrinos in the creation of heavy elements , heating mechanisms
Double stars with compact stars as partners
Merger of neutron stars
the question of neutrino mixing in supernovae

Planetology

For bodies in our solar system are u. a. the following nuclear topics are relevant:

Age determination of meteorites
original (primordial) composition and isotope ratios of comets , interplanetary dust and meteorites
Interaction between solar wind and the magnetosphere of planets
Excitation states, ions and isotopes in planetary atmospheres
Traces of cosmic rays in the soil of the moon and Mars
... ...

Nuclear physics and cosmology

When researching the beginnings of the universe, the questions about the formation of elements and very high-energy phenomena (gravitational wave, gamma-ray bursts) in the evolution of galaxies and the large structure of the universe are particularly topical:

Creation of the first elements after the Big Bang
- especially the primordial ratio of hydrogen to helium
- Frequency of lithium and other elements and implications for cosmology
- Evolution of chemical elements in galaxies
Detection and research of gravitational waves and gamma-ray bursts
electromagnetic and gravitational radiation during the fusion of two neutron stars
Nucleosynthesis in homogeneous big bang models
Models of inhomogeneous cosmologies

Combination of astro and nuclear physics

The two subject areas increasingly overlap, for example in

Equations of state for high density matter, also beyond the density of atomic nuclei
Properties of unstable nuclei , quark and nuclear matter of high density
Monte Carlo method for the quantum mechanical shell model (nuclear physics)
Modeling of cross sections, e.g. B. for the helium-3 fusion reaction
r-process and novel experiments in the study of the decay of nuclei

The ISOLDE (Isotope Separator On Line DEvice) project at the Proton Synchrotron Booster at CERN in Geneva has long contributed to the cooperation between nuclear and astrophysics . It is used to generate radioactive ion beams and can generate radioactive nuclides of 70 chemical elements in specially heated materials , ionize and analyze them in various ways . Primarily designed for atomic physics , materials and life sciences , it can also be used for nuclear astrophysics, for example with halo nuclei.

These very unstable nuclei near the drip line ('drip edge') during spontaneous decay through the emission of neutrons (neutron drip line) or protons (proton drip line) are important for understanding the rapid proton capture in stellar nucleosynthesis . For example, ISOLDE investigated the relevant processes of the three-alpha process and the r-process with mass numbers of around 130. The solar neutrino deficit is also determined by measurements at ⁷Be , because the beryllium isotope is a source of solar neutrinos during proton capture.

Experiments

Of many relevant experiments the following should be mentioned:

Fermi Gamma-ray Space Telescope
Neutrino detectors Super-Kamiokande and GALLEX
Laboratori Nazionali del Gran Sasso
Laboratory experiments of the HEPHY (Institute for High Energy Physics)

Literature and web links

Albrecht Unsöld , Bodo Baschek: The new cosmos. Introduction to astronomy and astrophysics , 7th edition, Springer-Verlag Berlin-Heidelberg 2005
J.Bennett, M.Donahue et al .: Astronomy. The cosmic perspective (Ed. Harald Lesch ), 5th, updated edition (1170 pages); Pearson Studium Verlag, Munich 2011, ISBN 978-3-8273-7360-1
Rudolf Kippenhahn: cosmology in the back pocket . Piper-Verlag, Munich-Zurich 2003

Individual evidence

↑ E. Dreisigacker: r process brought to the waiting point: New findings on nucleosynthesis. In: Physical sheets. Volume 42, No. 12, 1986, p. 412. doi : 10.1002 / phbl.19860421206 (free full text)

[1] E. Dreisigacker: r process brought to the waiting point: New findings on nucleosynthesis. In: Physical sheets. Volume 42, No. 12, 1986, p. 412. doi : 10.1002 / phbl.19860421206 (free full text)