Most objects in space, including stars and planets, are formed by a process called accretion. Accretion occurs when small particles in space attract each other due to gravity, and begin colliding and clumping into larger particles. After a long, long time, enough particles merge together to become the size of a planet or star.

Within the core of the star, high pressures and temperatures develop. These temperatures and pressures are sufficient to cause nuclear fusion to occur, in which two lighter atoms combine to form a heavier atom, releasing energy. This process is known as stellar nucleosynthesis. At the end of a star’s lifetime, it mostly consists of phosphorus and sulfur.

Due to gravity, the star contracts further, reaching even higher temperatures and pressures, which causes a process called silicon burning to occur. Silicon burning creates even heavier elements, which are eventually ejected into the universe as the star explodes.

So, the dust that was incorporated into the star is eventually ejected into space, most likely as silicon or a heavier element.

Just like most organisms on Earth, stars have life cycles. Smaller stars have more peaceful deaths and what used to be the star turns into planetary nebula, which are beautiful and if you've never seen a picture of one, they're worth looking up! Larger, more massive stars on the other hand, have violent deaths. They undergo a supernova and explode, scattering their star dust, called supernova remnant, far into space around them. This star dust may eventually be used to create new stars, completing the cycle!

Depending on which state the star is and how far away the dust is from the star, the dust may be pulled to form the star, or they could become planets, comets, or remain as dust.

They get ionized into a plasma that makes up the star. There are differences in the nuclear physics of what happens inside stars depending on how much of the elements that make up dust (mainly carbon, oxygen, and silicon) that went into the star.