Science

4,000 of the earliest galaxies in our universe mapped in 3D

Astrophysicists have produced a 3D map of 4,000 galaxies at a time when our universe was in its infancy.

Most of the galaxies are believed to be younger versions of our own Milky Way

A view of the field in the constellation of Sextans, seen in infrared light. This is roughly the same region of the sky studied to create the new 3D map. (ESO/UltraVISTA team)

Astrophysicists have produced the largest 3D map of our universe at a time when it was in just in its infancy.

Light from distant stars and galaxies can take hundreds of millions to billions of years to reach us — depending on how far away they are — which means when we look at galaxies now we're looking back in time. This new map is a picture of what can be seen from Earth today, but takes us back to almost the very beginning of our universe.

In the new study, astronomers were able to peer back between 11 to 13 billion years. Our universe is roughly 13.8 billion years old, meaning the researchers were able to see the universe when it was only seven to 20 per cent of its current age. This, in turn, allowed them to get a picture of the universe in its earliest stages.

A 3D map showing the distance to galaxies in billions of light-years. The positions of the 4,000 galaxies appear as circles: the bluer circles indicating galaxies nearer to the Earth, and green, yellow, orange and red circles illustrate galaxies that are progressively farther away from the Earth. (D. Sobral)

As the galaxies are so far away, they weren't seen in visible light. Instead, the scientists used two telescopes — the Subaru telescope in Hawaii and the Isaac Newton telescope in the Canary Islands — fitted with different filters that looked for very specific radiation. The results revealed 4,000 galaxies. 

"We see these 4,000 galaxies, and what is very interesting about them is that it tells us about the infancy of galaxies like our own Milky Way," David Sobral, lead author of the study published in the Monthly Notices of the Royal Astronomical Society and lecturer at Lancaster University in England, told CBC News.

"We can't really see our own galaxy in the past, but we can see what galaxies similar to our own looked like when they were very, very young."

This artist's concept depicts the most up-to-date information about the shape of our own Milky Way galaxy, classified as a barred spiral. According to NASA, roughly 60 per cent of galaxies fall into the spiral group. (NASA/JPL-Caltech/R. Hurt/SSC/Caltech)

These early galaxies are 30 times smaller than the Milky Way — which is about 100,000 light-years in diameter — and are very compact — roughly only 3,000 light-years across — and full of hot stars.

Eventually, astrophysicists believe they will grow to become spiral galaxies like our own galaxy.

What was particularly interesting to Sobral is that these young galaxies are much brighter compared to those that were born later.

As well, the galaxies underwent bursts of activity when forming stars rather than the way our galaxy currently seems to be forming them, which is at a steady rate.

Time travelling

While other telescopes, such as the Hubble space telescope, have also found young galaxies, they are only able to look at a small patch of sky. This map of the 4,000 galaxies has a wider view, the width of approximately three full moons as seen from Earth. 

This image shows the area around the Hubble eXtreme Deep Field, which imaged a small patch of sky in search of some of the earliest galaxies. The full moon is shown to scale for comparison. (NASA/ESA/Z. Levay/STScI )

The next step, Sobral said, is to discover more about these distant galaxies, including the distribution of various elements and the formation of different types of stars within them. And he hopes to see follow-up studies by other astronomers to help build on the knowledge of our early universe.

"It's exciting," he said. "We can time travel and start to see how our own galaxy may have looked like even before the sun formed. And it shows that the universe is really full of galaxies."

ABOUT THE AUTHOR

Nicole Mortillaro

Senior reporter, science

Based in Toronto, Nicole covers all things science for CBC News. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books. In 2021, she won the Kavli Science Journalism Award from the American Association for the Advancement of Science for a Quirks and Quarks audio special on the history and future of Black people in science. You can send her story ideas at Nicole.Mortillaro@cbc.ca.

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