* Big Bang Nucleosynthesis: The very early universe, after the Big Bang, was incredibly hot and dense. During this period, only hydrogen and helium (along with trace amounts of lithium) were formed in a process called Big Bang nucleosynthesis.
* Stellar Evolution: Stars are formed from massive clouds of gas and dust, primarily composed of hydrogen and helium. These elements are the fuel that powers stars through nuclear fusion, where hydrogen is converted into helium, releasing enormous amounts of energy.
* Recycling of Elements: When stars die, they release elements heavier than hydrogen and helium back into the interstellar medium. However, hydrogen and helium still represent the majority of the matter ejected, ensuring their continued abundance in the universe.
Therefore, new stars are constantly born from clouds of gas and dust containing primarily hydrogen and helium, making these elements the fundamental building blocks of stars.
