1. Primordial helium: This is the helium that was formed during the Big Bang. It makes up about 24% of the mass of the universe.

2. Stellar nucleosynthesis: This is the process by which stars fuse hydrogen atoms into helium in their cores. As stars age, they produce helium as a byproduct of this process.

Here's a breakdown of each source:

Primordial helium:

* Formed during the first few minutes after the Big Bang.

* This helium is found in very low concentrations throughout the universe.

* It's a key element for studying the early universe and the Big Bang theory.

Stellar nucleosynthesis:

* Stars fuse hydrogen atoms into helium in their cores, releasing energy.

* This process is known as the proton-proton chain reaction.

* As stars evolve, they produce more and more helium.

* Some of this helium is released into space when stars die in supernova explosions.

* This helium can then be incorporated into new stars and planets.

Helium on Earth:

* Earth's helium is primarily derived from the radioactive decay of uranium and thorium in the Earth's crust.

* This decay process produces alpha particles, which are helium nuclei.

* These helium nuclei eventually combine with electrons to form helium atoms.

* Helium is found in natural gas deposits, where it is extracted as a byproduct.

Therefore, the helium we use on Earth comes from both primordial and stellar sources, making it a valuable and fascinating element with a rich cosmic history.