Why We Have Heavy Elements on Earth

[paweld]

Why we have (although very little) on Earth heavy elemnents such
as uranium, lead, ... if they weren't created in Big Bang or stellar nucleosynthesis
(these proceses don't produce elements heavier than iron and nickel).
Any guesses?

 

[phyzguy]

No need to guess - these processes are well understood. Elements heavier than iron are produced primarily in supernova explosions, where there is a flood of neutrons which builds up the heavier elements. Look up the "S-process" and the "R-process" in stellar nucleosynthesis.

 

[paweld]

But is there any supernove near Earth?

 

[phyzguy]

Supernovae create massive shock waves which blow material out into the host galaxy. A galaxy like the Milky Way has on the order of about 1 supernova per century. Since the Milky Way was in existence for billions of years before the sun formed, there were millions of prior supernovae within the Milky Way, all churning up the interstellar material. So, when the solar system formed, there was an ample supply of heavy elements from supernovae with which to build the planets. As the song goes, "...we are stardust..."

 

[paweld]

Yes, it's now clear.
Thanks.

 

[Chronos]

Numerous supernova contributed matter to the proto cloud from which the solar system formed. Mostly from 6-9 billion years ago.