Formation of Stars

Question

What external factors are necessary to initiate/trigger the formation of a star, and as a consequence, a possible planetary system? Provide with pros and cons in regard to the necessity of each factor. What chemical elements are converted during thermonuclear reactions in the star's interior, releasing huge amount of energy? Give the supporting equations / formulae (the thermonuclear reaction equations).

Answer 1

The formation of a star does not happen isolated somewhere out in space. First, there has to be matter in the form of gigantic clouds of hydrogen gas. Star formation includes the formation of planets due to the "lumpiness" of the clouds of hydrogen that are spread throughout the universe. It used to be thought that "solar systems" were a rare occasion, however, after several years of modeling the formation of a star from a massive lumpy cloud of gas (hydrogen), models indicated that the concentration of hydrogen gas is not homogenous, rather, it is sort of "lumpy". The bigger the lump, the greater the sum of gravitational effects. Since gravity depends directly on the mass of the two attracting masses, and inversely on the distance squared between the masses the bigger the "lump" the stronger the gravitational pull on nearby gas.

This gravitational pull continues on until the size of the gas "lump" is so great, that the crushing forces of gravity on the atoms of hydrogen cause two forms of hydrogen nuclear isotopes called, "deuterium" and "tritium" to be crushed together under a process that is known as "fusion" to create a nucleus of helium. The mass of the products of this reaction weigh less than the products, which means some of the mass has been converted to energy following Albert Einstein's famous equation, "E = mc²".

H¹₂ (deuterium)+ H¹₃ (tritium) goes to He²₄ (helium) + n⁰ (neutron) + E

The star now shines brightly while continuing to create each atomic nuclei in the periodic table beginning with helium, then lithium, and so on until iron (element # 26) at which fusion stops since the formation of heavier nuclei requires energy, rather than releases energy.

Non of the above would happen without a "Big Bang" that created matter, space and time, along with the forces of gravity, and the much stronger "electro-weak force" that allows like charges to repel and opposite charges to attract. The "strong nuclear" force was also created that allows protons to exist within the confines of atomic nuclei.

Hope this helps.