What is the 'God of Age' Star (Tai Sui)?
Tai Sui doesn't actually exist as a real star! (It roughly corresponds to Jupiter, which takes 11.86 years to orbit earth, and is probably where the idea for the star came from). It's an imaginary star that changes position exactly 30 degrees of direction each year, i.e. orbiting Earth every 12 years exactly.
The star Tai Sui is said to bring misfortune to people in zodiac years matching their year of birth.
Later, during the course of history, Tai Sui evolved into the God of Age, and has been worshipped by Chinese people from one generation to another. People offer sacrifices to the God of Age to get rid of misfortune and pray for blessings in a zodiac year.