How Old Are Galaxies?

Illustration of our galaxy, the Milky Way.

This is an illustration of our galaxy, the Milky Way. The Milky Way is an ancient galaxy that was born only a few hundred million years after the Big Bang. Credit: NASA/JPL

Most galaxies are between 10 billion and 13.6 billion years old. Our universe is about 13.8 billion years old, so most galaxies formed when the universe was quite young!

Astronomers believe that our own Milky Way galaxy is approximately 13.6 billion years old. The newest galaxy we know of formed only about 500 million years ago.

Illustration that says the universe is 13.8 billion years old, the Milky Way is 13.6 billion years old, our Sun is 4.5 billion years old and Earth is 4.5 billion years old.

Credit: NASA/JPL-Caltech

How can astronomers study things that are so far away?

Astronomers use light to study things that are far away. In fact, light even gives us a way to look back in time!

Light always travels at a certain speed: nearly 186,000 miles (300,000 kilometers) per second. That means that light can travel about 6 trillion miles (about 10 trillion kilometers) in one Earth year. We call this distance a light-year.

This means that the farther away something is, the longer it takes for light from that object to reach us.

What is the most distant galaxy we know of?

In 2016, astronomers used NASA's Hubble Space Telescope to measure a galaxy called GN-z11 that is 13.4 billion light-years away. Because it is that far away, Hubble sees the light from the young galaxy as it was when the Universe was just 400 million years old.

This animation shows the location of the farthest galaxy ever seen, called GN-z11. Credit: NASA, ESA, and P. Oesch (Yale University), G. Brammer (STScI), P.van Dokkum (Yale University) and G. Illingworth (University of California, Santa Cruz)

What can we learn by studying distant galaxies?

Astronomers have observed lots of galaxies at different distances. By comparing them, we can begin to understand how galaxies and their stars are born, how they change and how they die over time.

article last updated January 24, 2019

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