A team of astronomers peered deep into the cosmos and discovered the brightest galaxy ever found in the early universe. Lying in this far away galaxy is evidence of the universe’s first generation of stars.
The astronomers observed deep into our universe’s past, to just 800 million years after the Big Bang. During a period known as reionization.
Instead of studying a small area of the sky, the astronomers widened their search. Several telescopes were used including ESA’s Very Large Telescope, W.M. Keck Observatory, Subaru Telescope and the Hubble Space Telescope.
The wider search area paid off with the discovery of CR7, an incredibly rare galaxy during this stage of the universe. CR7 shines three times brighter than the previous known brightest galaxy.
“We confirmed that the galaxy is more than 12 billion light years from us,” said Bahram Mobasher, a physics and astronomy professor at UC Riverside. “Combining these with other observations, the UCR team successfully identified the presence of ions from elements that could only be produced through intense radiation.”
Why is CR7 significant?
Astronomers believe there was a different type of star during the early years of the universe. Today’s stars contain all kinds of elements including oxygen, nitrogen, carbon, iron and more. But, what about the first stars? These stars, known as Population III stars, would have only been able to form from elements that existed before stars – hydrogen, helium and trace amounts lithium.
That brings us to CR7. VLT detected strong ionized helium emission in CR7. It’s what VLT didn’t detect that’s the big news. There were no signs of heavier elements in a bright pocket in the galaxy. That could mean stars with no heavy elements are in this area.
“The discovery challenged our expectations from the start,” said David Sobral from the University of Lisbon, Portugal.
“As we didn’t expect to find such a bright galaxy. Then, by unveiling the nature of CR7 piece by piece, we understood that not only had we found by far the most luminous distant galaxy, but also started to realize that it had every single characteristic expected of Population III stars. Those stars were the ones that formed the first heavy atoms that ultimately allowed us to be here. It doesn’t really get any more exciting than this.”
The next step for Sobral and his team is to conduct further observations to confirm what they observed are Population III stars. They will also be on the lookout more examples of Population III stars.
Having fun with the galaxy’s name
How many times have we seen scientists adopt boring names? ESA’s Very Large Telescope? Really? The team of astronomers had some fun coming up with CR7.
CR7 is an abbreviation of COSMOS Redshift 7. But, the name’s inspiration came from Portuguese soccer player Cristiano Ronaldo.
While inspired by Ronaldo, COSMOS Redshift 7 does have meaning – it’s a measure of the galaxy in terms of cosmic time. The higher the redshift, in this case 7, the more distant the galaxy and the farther back we are looking in time.
Read the full paper here.
Image: Artist impression of CR7. Credit: ESA