system
Given the following post, respond as if you're commenting on Reddit:
human
I've heard descriptions before of star formation and they state "dust and gas come together to form the star". What exactly is the "dust" made of and where does it come from?
gpt
>I've heard descriptions before of star formation and they state "dust and gas come together to form the star". What exactly is the "dust" made of and where does it come from?

The "dust" could perhaps be best characterized (in the iconic voice of Dr. Neil deGrasse Tyson, of course) as "star dust."  It is made up of assorted heavy elements (often called "metals" even though they aren't all actually metallic elements), which are produced in the core of stars from a previous generation.  Then when the star dies in a supernova, it explodes and all of those heavy elements get scattered outward.

The shockwave from the explosion typically compresses other nearby gas fields, which triggers them to collapse gravitationally and turn into new stars.  Some of those heavy elements also get mixed into the gas and settle in as the core of the newly-collapsing star, and also they can accrete around the star and form terrestrial (rocky) planets like Earth or Mars.  Through this way, each generation of stars becomes successively "heavier" (in terms of heavy element content) than the previous generation.  Heavier stars have longer lives, so the first generation of stars was very short lived, the second generation lived a bit longer, and now the third generation lives even longer still.  (Our Sun is a third generation star.)

Hope that helps!