According to research, the universe is approximately 13.8 billion years old. How did scientists determine how many candles to put on the universe’s birthday cake? They can determine the age of the universe using two different methods: by studying the oldest objects within the universe and measuring how fast it is expanding.
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 mass will last more than 20 billion years. The mass also affects the brightness, or luminosity, of a star; more massive stars are brighter.
Known as Population III stars, the first stars were massive and short-lived. They contained only hydrogen and helium, but through fusion began to create the elements that would help to build the next generation of stars.
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