An Etymological Dictionary of Astronomy and Astrophysics
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The state, process, or effect of being on fire, burned, or subjected to intense heat. → helium burning; → neon burning; → oxygen burning; → shell burning.

Verbal noun of → burn.

A piece of glass of roundish shape, possibly made of rock crystals or a globular container filled with water, whose use is attested in ancient civilizations. In his comedy The Clouds, the Greek playwright Aristophanes (448-380 BC) mentions globules of glass that were known as burning spheres. Several Roman writers (Pliny, Seneca, Plutarch) speak of burning glasses. In particular, Seneca specifies that small and indistinct written characters appear larger and clearer when viewed through a globular glass filled with water. See also → magnifying glass.

→ burning; → sphere.

Guy, → globe; suzân "burning," → burning.

The stage in the evolution of a star after → helium burning when the core of the star consists mainly of carbon and oxygen. In stars of mass greater than about 8 solar masses, whose cores reach a temperature above 5 × 10⁸ K and density above 3 × 10⁹ kg m^-3, carbon burning can begin via reactions such as the following:
¹²C + ¹²C → ²⁰Ne + ⁴He
¹²C + ¹²C → ²³Na + p
¹²C + ¹²C → ²³Mg + n.
The time-scale for this phase of → nucleosynthesis is of order of five hundred years.

→ carbon; → burning.

The fusion of a deuterium nucleus with a proton which produces the lightest isotope of helium: D + H → ³He + γ. Deuterium burning occurs in stellar cores at a temperature exceeding 10⁶ K. The onset of deuterium burning marks the end of the → protostellar collapse. It is the only → nuclear reaction that occurs in → brown dwarfs. In normal stars, it is the second step in the → proton-proton chain which leads to the formation of ⁴He, allowing stars to arrive on the → main sequence.

→ deuterium; → burning.

A situation in the evolution of an → asymptotic giant branch star whereby both hydrogen and helium shells provide energy alternatively. As the burning → helium shell approaches the hydrogen-helium discontinuity, its luminosity decreases because it runs out of the fuel. As a consequence, the layers above contract in response, thus heating the extinguished → hydrogen shell until it is re-ignited. However, the shells do not burn at the same rate: the He burning shell becomes thermally unstable and undergoes periodic → thermal pulses.

→ double; → shell; → burning.

The stage in the evolution of a star, after the exhaustion of hydrogen, when the star produces its energy by the fusion of helium into carbon and oxygen.

→ helium; → burning.

A stage in the evolution of an → asymptotic giant branch star, when all the helium in the core is fused into carbon and oxygen. No more fusion takes place in the core, and as a result the core contracts. The core contraction generates a sufficient temperature for fusing the surrounding layers of helium. Since helium shell burning is unstable, it causes → helium shell flashes.

→ helium; → shell; → burning.

→ proton-proton chain.

→ hydrogen; → burning.

A phase in the life of a star that has left the → main sequence. When no more hydrogen is available in the core, the core will start to contract as it is no longer releasing the necessary energy whose pressure supports the surrounding layers. As a result of this contraction, gravitational energy is converted into thermal energy and the temperature will rise. Therefore a shell of unprocessed material surrounding the original core will be heated sufficiently for hydrogen burning to start. During the evolution of → asymptotic giant branch stars hydrogen shell burning occurs alternatively with helium shell burning. → double shell burning.

→ hydrogen; → shell; → burning.

A → nuclear fusion process that takes place in → massive stars and leads to the → production of → oxygen and → magnesium. It requires high temperatures and densities (around 1.2 × 10⁹ K and 4 × 10⁹ kg/m³).

→ neon; → burning.

A → nuclear reaction inside a star that produces the energy to make the star shine and also transform chemical elements into others.

→ nuclear; → burning.

The stage when a star fuses → oxygen into → silicon and → sulfur. It occurs only in → massive stars, with a mass over eight → solar masses.

→ oxygen; → burning.

The nuclear reactions in a shell around a star's core that continue after the fuel in the core itself has been exhausted. As the fuel is progressively exhausted, the shell moves outward until it enters regions too cool for the reactions to continue. For example, after the exhaustion of hydrogen in the core, helium burning might take place in the core with a shell of hydrogen burning surrounding it. Stars may have more than one region of shell burning during their stellar evolution, each shell with its own nuclear reactions. → hydrogen shell burning; → helium shell burning.

→ shell; → burning.

The → nucleosynthetic process taking place in the interior of → massive stars whereby → silicon is transmuted into iron, nickel, and neighboring nuclei collectively called the → iron peak elements.

→ silicon; → burning.