Elements in stars

E. M. Burbidge, G. R. Burbidge, W. A. Fowler and F. Hoyle, Synthesis of the elements in stars. Rev. Mod. Rhys. 29, 547-650 (1957). This is the definitive review on which all later work has been based. 

The matter that made up the solar nebula from which the solar system was formed already was the product of stellar birth, aging and death, yet the Sun is 4.5 billion years old and will perhaps live to be 8 billion years but the Universe is thought to be 15 billion years old (15 Gyr) suggesting that perhaps we are only in the second cycle of star evolution. It is possible, however, that the massive clouds of H atoms, formed in the close proximity of the early Universe, rapidly formed super-heavy stars that had much shorter lifetimes and entered the supernova phase quickly. Too much speculation becomes worrying but the presence of different elements in stars and the subsequent understanding of stellar evolution is supported by the observations of atomic and molecular spectra within the light coming from the photosphere of stars. 

C. Jaschek and M. Jaschek, The Behavior of Chemical Elements in Stars, Cambridge University Press 1995. 

Another important deviation from constancy in the abundance ratio of elements supposed to be primary is displayed by the ratios Fe/O and [Tc/a-elements in stars, which increase systematically with [Fe/H] (Figs. 8.5,8.6). This is usually attributed to the existence of a substantial contribution to the production of iron found in the younger, more metal-rich stars (like the Sun) by SN la, which take times of the order of a Gyr to complete their evolution and therefore cannot be treated... 

This equation (with a characteristic peak value at z = 1 or Z = p) is expected to apply primarily to oxygen and a-elements in stars that have lived long enough since the origin of the Galaxy to be still observable today, but may also apply approximately to iron in cases where O, a/Fe — const. 

Burbidge EM, Burbidge GR, Fowler WA, Hoyle F (1957) Synthesis of the elements in stars. Rev Mod Phys 29 547-630... 

So Norman Loclg er and William Crookes (see pages 74, 86) were right in a way, if not in the details there is an evolution of elements in stars. The creation of elements in stars is called nucleosynthesis, and it is responsible for the Earth and almost everything we see on it. Only hydrogen, plus some helium and a mere smattering of... 

Pu may be considered as an ideal tracer nuclide for these studies because of its decay characteristics. Its existence or absence in the early solar system can be considered as a crucial test for or against the theories of the synthesis of chemical elements in stars. 

The interpretation of the Li abundance gap using a diffusion model has been questioned because of the observed absence of abundance anomalies of heavy elements in F stars (Boesgaard and Lavery 1986 Thevenin, Vauclair and Vauclair 1986 Tomkin, Lambert and Balachandran 1985) where Be has been observed to be underabundant. Such anomalies had been predicted on account of the diffusion calculations in the absence of any mass loss (Michaud et al. 1976, Vauclair et al. 1978b). It has recently been shown that even a very small mass loss was sufficient to reduce considerably any expected overabundance in F stars. On Fig. 2c of Michaud and Charland (1986), it is shown that a mass loss rate of 10 15 Mo yr-1 is sufficient to keep the Sr overabundance, below a factor of 1.5 while Sr would be expected to be more than 100 times overabundant in the absence of mass loss (Michaud et al. 1976). The presence of even a very small mass loss rate considerably limits any overabundance when the radiative acceleration and gravity are close to each other as is the case for heavy elements in stars cooler than Teff = 7000 K. The same small mass loss rate reduces the Li overabundance in stars of Teff = 7000 K or more where Li is supported. As shown in Fig. 4 of Michaud (1986), the same mass loss rate of 10 15 Mo yr 1 eliminates the Li overabundance of a factor of 10 expected in the absence of mass loss at Teff = 7000 K. It has now been verified that the presence of mass loss cannot increase the Li underabundance that diffusion leads to beyond a total factor of 30 underabundance. 

Only one combination of four nucleons is bound, 4He, with two protons and two neutrons. All other combinations of four nucleons are unbound. Moreover, 4He, or the a particle, is especially stable (very strongly bound), and the nucleons are paired to give a total spin 5=0. Interestingly, if we add a nucleon of either type to the a particle, we produce an unbound nucleus Thus, there are no stable nuclei with A = 5 as both 5He and 5Li break apart very rapidly after formation. This creates a gap in the stable masses and poses a problem for the building up of the elements in stars, which is discussed in Chapter 12. There are two bound nuclei with A = 6, 6He and 6Li, with the helium isotope decaying into the lithium isotope, the others are unbound. Continuing on, between mass 6 and 209, all mass numbers... 

In the third part of the conference, on the Evolution of Galaxies and Stars, Hoyle presented the then recent and still important work by the Burbidges, Fowler, and himself on the origin of elements in stars.102... 

Wallerstein, G., Iben, I. Jr., Parker, P. et al. (1997) Synthesis of the elements in stars forty years of progress. Reviews... 

Bob nods. Mr. Plex, today I want to tell you how we find out what stars are made of. It is amazing that we know about the elements in stars even though they... 

Bob pauses and looks at Miss Muxdroozol, Let me list some facts. Scientists have observed around 74 different elements in stars. We re sure other natural elements exist in stars, but their quantities may be too low to make their lines visible. The majority of stars have similar compositions, with hydrogen making up about 90 percent of the number of atoms, followed by helium at 9.9 percent. All the other chemical elements are in the remaining 0.1 percent. Generally, the more complex the atom, the less you ll find of it in stars. Incidentally, the stellar spectra help scientists measure the radial velocities of stars because the wavelengths of the lines are shifted slightly by the Doppler effect. We ll talk about that later. ... 

Miss Muxdroozol is staring at the complicated looking Rydberg-Ritz equations. Bob, helium is the second most common element in stars. Is it also the second most common element in the Universe ... 

And so Hoyle decided to make heavy elements in stars, and to spread them around by means of supernova explosions. But in doing so, Hoyle had to follow the blueprint of abundances which God prepared earlier when He had planned to make the elements from Ylem [the primordial soup of high-energy photons]. 

Thus, with the help of God, Hoyle made all heavy elements in stars, but it was so complicated that neither Hoyle, nor God, nor anybody else can now figure out exactly how it was done. 

AIK warmly thanks the organisers of the Kodai School on Synthesis of the Elements in Stars for the hospitality and the opportunity to attend and give lectures at the school. AIK also thanks John Lattanzio, Maria Lugaro, Simon Campbell, Peter Wood, Pilar Gil-Pons, Lionel Siess, and Mark van Raai for discussions and/or material that helped in the preparation of the lecture notes given at the School. She thanks Robin Humble, Ross Church, and Maria Lugaro for help with proof-reading her lecture notes. 

Cosmochemistry is the chemistry of the cosmos. This is a broad topic that ranges from the nucleosynthesis of elements in stars to their chemistry on the Earth today. In this chapter, we describe chemical equilibrium (or condensation) calculations of the cosmochemical behavior of the elements. 

Lecture Notes of the Kodai School on "Synthesis of Elements in Stars" held at Kodaikanal Observatory, India, April 29-May 13,2008... 

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