Introduction to Astrophysics PP 1 chain Calculate the numbe

Introduction to Astrophysics - PP 1 chain

Calculate the number of photospheric photons that are required to radiate away the energy from a single occurrence of the pp I chain in the Sun\'s core.

Solution

The core of the Sun is considered to extend from the center to about 0.2 to 0.25 solar radius.^[1] It is the hottest part of the Sun and of the Solar System. It has a density of 150 g/cm³ (150 times the density of liquid water) at the center, and a temperature of 15 million degrees Celsius.^[2] The core is made of hot, dense gas in the plasmic state (ions and electrons), at a pressure estimated at 265 billion bar (3.84 trillion psi or 26.5 petapascals (PPa)) at the center.

The core inside 0.20 of the solar radius, contains 34% of the Sun\'s mass, but only 0.8% of the Sun\'s volume. Inside 0.24 solar radius, the core generates 99% of the fusion power of the Sun. There are two distinct reactions in which four hydrogen nuclei may eventually result in one helium nucleus: the proton-proton chain reaction – which is responsible for most of the Sun\'s released energy – and the CNO cycle.

Approximately 3.6×10³⁸ protons (hydrogen nuclei), or roughly 299 million metric tons of hydrogen, are converted into helium nuclei every second releasing energy at a rate of 3.86×10²⁶ joules per second