The universe is about 13.8 billion years old.

The European Space Agency's Planck mission provided the most accurate age for the universe. Between 2009 and 2013, the Planck satellite mapped the Cosmic Microwave Background. This is the leftover light from the early universe. In 2015, researchers used this data to set the age at 13.787 billion years. The margin of error is only 20 million years.Scientists also use the Hubble Constant to find the age. This number describes the speed at which the universe expands. Currently, the rate is about 67.4 kilometers per second for every megaparsec of distance. By knowing the expansion speed, astronomers can calculate how long the universe has been growing.Astronomers check their work by looking at the oldest stars. Globular clusters are groups of stars that formed very early in history. The oldest stars found so far are about 13 billion years old. This fits the timeline because stars could not be older than the universe itself.