The first stars were made of only hydrogen and helium

That means that the gas it arose from had itself been enriched with many elements from supernova explosions since the universe began. So that's how the sun wound up with all the elements.It's still mostly hydrogen at 71 percent,with most of the rest being helium at 27 percent.But bear in mind that while the first stars were made up of hydrogen and helium alone,the remaining elements in the periodic table make up two percent of the sun.And what about Earth?Planets form as an incidental process to star formation out of the same gas cloud as the star itself.