Many people don't realise that elements heavier than iron
are only made in neutron star mergers or supernovae explosions.
The sun or normal stars can't make them.
These elements formed the dust in our solar system
when it was very young.
As our solar system is about 4.5 billion years old
most of those elements have decayed into relatively safe elements.
When nuclear technology was invented it allowed humans to create dangerous elements that have not
been around for billions of years.
The radiation from them is too high for us to cope with if we're too close or consume them in our food.
This what we refer to as radioactive waste.
Ancient Neutron-Star Crash Made Enough Gold and Uranium to Fill Earth's Oceanshttps://www.space.com/neutron-star-crash-made-gold-uranium.htmlBy Charles Q. Choi May 08, 2019 Science & Astronomy
Enough gold, uranium and other heavy elements about equal in mass to all of Earth's oceans likely came to the solar system from the collision of two neutron stars billions of years ago, a new study finds.
If the same event were to happen today, the light from the explosion would outshine the entire night sky, and potentially prove disastrous for life on Earth, according to the new study's researchers.
Recent findings have suggested that much of the gold and other elements heavier than iron on the periodic table was born in the catastrophic aftermath of colliding neutron stars, which are the ultradense cores of stars left behind after supernova explosions.