We have completed maintenance on DiscoverMagazine.com and action may be required on your account. Learn More

This Massive Galaxy was Done Forming Stars at Just 1.5 Billion Years Old

Most massive galaxies today aren't forming many stars. So when did these galaxies stop?

By Erika K. Carlson
Dec 20, 2019 7:00 PMDec 20, 2019 7:18 PM
The distant galaxy marked in this image from the Subaru/XMM-Newton Deep Field is now the earliest known example of a massive galaxy that has stopped forming stars. (Credit: NAOJ)


Sign up for our email newsletter for the latest science news

Astronomers have discovered a distant, massive galaxy, seen as it was at about 1.5 billion years after the Big Bang. And it seems to be done forming stars. It's the earliest known example of a massive galaxy that has finished forming stars. And it implies that other massive galaxies may have completed the first phase of their growth this early in the universe’s history as well. 

The researchers, led by Masayuki Tanaka of the National Astronomical Observatory of Japan, presented their findings in a recent paper in The Astrophysical Journal Letters

Stopping Star Formation

Astronomers have noticed that most massive galaxies in the nearby universe today aren’t forming many stars.

“When these galaxies stop forming stars is one of the outstanding issues in the field of galaxy formation and evolution,” Tanaka said via email.

Tanaka and his team were looking for distant, massive galaxies that had stopped forming stars when they noticed this particular one from just 1.5 billion years after the Big Bang.

Growing in Phases

The finding also adds to astronomers’ picture of how massive galaxies grow and change with time. 

When astronomers peer deep into space, seeing galaxies as they looked billions of years ago, they find that massive galaxies tend to be dense and compact. But massive galaxies near us today also have sprawling edges, making them much larger.

This makes astronomers think that these giant objects must grow in two phases. First, they birth lots of stars in their centers, forming dense cores. Then, they accumulate more stars around the edges when they merge with other galaxies. 

Finding this distant galaxy with a fully formed core implies that the first step of this two-phase galaxy growth picture could have been completed as early as just 1.5 billion years after the Big Bang. 

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!


Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Our List

Sign up for our weekly science updates.

To The Magazine

Save up to 40% off the cover price when you subscribe to Discover magazine.

Copyright © 2024 Kalmbach Media Co.