Once again, vladtepesblog.com is delighted to present an original Fjordman essay, this time on one of my childhood passions, cosmology:

parts 1 and 2 are here: http://tundratabloid.blogspot.com/2010/05/fjordman-report-history-of-astrophysics.html , http://www.brusselsjournal.com/node/4424

The process of combining light elements into heavier ones – nuclear fusion – happens in the central region of stars. In their extremely hot cores, instead of individual atoms you have a mix of nuclei and free electrons, what we call plasma. The term “plasma” was first applied to ionized gas by Irving Langmuir (1881-1957), a physical chemist from the USA, in 1923. It is the fourth and by far the most common state of matter in the universe in addition to the three we are familiar with from everyday life on Earth: solid, liquid and gas. Extreme temperatures and pressure is needed to overcome the mutual electrostatic repulsion of positively charged atomic nuclei (ions), often called the Coulomb barrier after the French natural philosopher Charles de Coulomb, who formulated the laws of electrostatic attraction and repulsion.

While their work represented a huge conceptual breakthrough, the initial theories of Weizsäcker and Bethe did not explain the creation of elements heavier than helium. Edwin Ernest Salpeter (1924-2008) was anastrophysicist who emigrated from Austria to Australia, studied at the University of Sydney and finally ended up at Cornell University in the USA, where he worked in the fields of quantum electrodynamics and nuclear physics with Hans Bethe. In 1951 he explained how with the “triple-alpha” reaction, carbon nuclei could be produced from helium nuclei in the nuclear reactions within certain large and hot stars.

The fusion of hydrogen to helium by the proton-proton chain or CNO cycle requires temperatures in the order of 10 million degrees Celsius or Kelvin. Only at those temperatures will there be enough hydrogen ions in the plasma with high enough velocities to tunnel through the Coulomb barrier at sufficient rates. There are no stable isotopes of any element with atomic masses 5 or 8; beryllium-8 (4 protons and 4 neutrons) is highly unstable and short-lived. Only at extremely high temperatures of around 100 million K can the sequence called the triple-alpha process take place. It is so called because the net effect is to combine 3 alpha particles, which means standard helium-4 nuclei of two protons and two neutrons, to form a carbon-12 nucleus (6 protons and 6 neutrons). In main sequence stars, the central temperatures are too low for this process to take place, but not in stars in the red giant phase.

More advances were made by the English astrophysicist Fred Hoyle (1915-2001). He was born in Yorkshire in northern England and educated in mathematics and theoretical physics at the University of Cambridge by some of the leading scientists of his day, among them Arthur Eddington and Paul Dirac. During World War II he contributed to the development of radar. With the German American astronomer Martin Schwarzschild (1912-1997), son of the astrophysicist Karl Schwarzschild and a pioneer in the use of electronic computers and high-altitude balloons to carry scientific instruments, he developed a theory of the evolution of red giant stars. Hoylestayed at Cambridge from 1945 to 1973. In addition to his career in physics he is known for his popular science works and wrote novels, plays and short stories. He attributed life on Earth to an infall of organic matter from space. He remained controversial throughout his life for his support of many highly unorthodox ideas, yet he made indisputable contributions to our understanding of stellar nucleosynthesis and together with a few others convincingly showed how heavy elements are created during supernova explosions.

The English astrophysicist Margaret Burbidge (born 1919) was educated at the University of London. She worked in the USA for a long time, but also served as director of the Royal Greenwich Observatory in her native Britain. She studied spectra of galaxies, determining their masses and chemical composition and married fellow Englishman Geoff Burbidge (1925-2010), who was educated at the University of Bristol and atUniversity College, London, where he earned a Ph.D. in theoretical physics. The American astrophysicist William Alfred Fowler (1911-1995) earned his B.S. in engineering physics at Ohio State University and his Ph.D. in nuclear physics at the California Institute of Technology. He and his colleagues at Caltech measured the rates of nuclear reactions of astrophysical interest. After 1964, Fowler worked on problems involving supernovae and the formation of light elements.

Building on the work of Hans Bethe, Hoyle in 1957 co-authored with Fowler and the husband-and-wife team of Geoffrey and Margaret Burbidge the paper Synthesis of the Elements in Stars. They demonstrated how the cosmic abundances of all heavier elements from carbon to uranium could be explained as the result of nuclear reactions in stars. Out of the four, William Fowler alone shared the Nobel Prize in Physics in 1983 with Subrahmanyan Chandrasekhar for work on the evolution of the stars. By then Fred Hoyle was known for, among other things, attributing influenza epidemics to viruses carried in meteor streams.

The Canadian scientist Alastair G. W. Cameron (1925-2005) further aided our understanding of these stellar processes. Astrophysicists spent the 1960s and 70s establishing detailed descriptions of the internal workings of stars. Chushiro Hayashi (1920-2010), educated at the University of Tokyo, together with his students made valuable contributions to stellar models. He found that pre-main-sequence stars follow what are now called “Hayashi tracks” downward on the Hertzprung-Russell diagram until they reach the main sequence. He was a leader in building astrophysics as a discipline in Japan. The Armenian scientist Victor Ambartsumian (1908-1996) was a pioneer in astrophysics in the Soviet Union, studied stellar evolution and hosted international conferences to search for extraterrestrial civilizations. Continue Reading →