How Old is the Universe?
The universe cannot be younger than the objects contained inside of it. By determining the ages of the oldest stars, scientists are able to put a limit on the age.
The life cycle of a star is based on its mass. More massive stars burn faster than their lower-mass siblings. A star 10 times as massive as the sun will burn through its fuel supply in 20 million years, while a star with half the sun’s masswill last more than 20 billion years.
Early stars aren’t the only way to place limits on the age of the universe. Dense collections of stars known as globular clusters have similar characteristics.