The Milky Way Is 2 Billion Years Older Than Believed

The Milky Way was formed 13 billion years ago ― 2 billion years earlier than previously believed, according to an analysis from the European Space Agency’s Gaia mission, performed by scientists from the Max-Planck Institute for Astronomy, Heidelberg, Germany.

What to know:

  • Astronomers studying data from the European Space Agency’s Gaia mission discovered that the early part of the Milky Way, known as the “thick disc,” began forming 13 billion years ago, around 2 billion years earlier than previously thought.

  • The universe was born almost exclusively with hydrogen and helium; other chemical elements (known collectively as metals) are made inside stars and explode back into space at the end of a star’s life.

  • Scientists assessing the universe’s age focused on sub-giant stars because at that specific point in the stars’ evolution, energy has stopped being generated in their core, and the stars are transforming into red giant stars.

  • Looking at roughly 250,000 sub-giant stars, scientists used brightness and positional data collected from Gaia and combined them with measurements of the stars’ chemical compositions to derive their ages.

  • Astronomers were able to determine the ages of sub-giant stars in different regions of the galaxy to a few percent, discovering that the Milky Way formed 2 billion years earlier than previously believed.

This is a summary of the article, “Gaia Mission Finds Parts of the Milky Way Much Older Than Expected,” published in Nature on March 23, 2022. The full article can be found on

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