Thorium

Thorium is relatively abundant in the universe, particularly in the Earth's crust. It is a naturally occurring, radioactive metal belonging to the actinide series, like uranium and plutonium. From an astronomical viewpoint, thorium's presence extends beyond Earth, and it's believed to exist in varying degrees within stars and planetary bodies. Its radioactive decay plays a significant role in the internal heat generation of planets, contributing to their geothermal activity. While thorium is not typically observed directly in astronomical observations, its isotopes and decay products have been detected in certain celestial bodies and stellar spectra, offering insights into their composition, formation processes, and age.