Yes, hydrogen is the most abundant gas in the universe. It is the primary element formed shortly after the Big Bang and is still being produced through various processes in stars.
Hydrogen is crucial for stellar fusion reactions, particularly in stars like our Sun. In the core of stars, the extreme pressure and temperature allow hydrogen atoms to undergo nuclear fusion, converting hydrogen nuclei (protons) into helium nuclei. This process, known as nuclear fusion, releases an enormous amount of energy and is the primary source of the Sun's energy output.
Additionally, hydrogen is present in vast quantities in interstellar space, in molecular clouds, and in the form of atomic hydrogen. These clouds of hydrogen gas are where stars are born. Gravity pulls these clouds together, and as they contract, they can become dense enough for the hydrogen to ignite and form a new star.
Due to its abundance and importance in stellar processes, hydrogen is often referred to as the "building block" of the universe. It plays a crucial role in the formation and evolution of stars and is fundamental to our understanding of cosmology and astrophysics.