The First Generation of Stars in a Distant Galaxy

You know, this one just writes its own headline when astronomers use a very cool radio telescope to look at a distant galaxy for evidence of the first stars. Astronomers using the Atacama Large-Millimeter/Submillimeter Array (ALMA), spotted evidence of chemical elements created by the earliest stars, objects that lie 13.28 billion light-years away. That’s a long ways away, and since it takes light

time to travel all those light-years, it’s also a long, long, long time ago.

Early Star and Galaxy Elements

The early universe was a very different place from the cosmos we know today. It had few stars, no chemical elements beyond hydrogen, helium, and traces of lithium. What it needed was time…and the formation of the first stars. When enough time passed, they formed. These were giant, monster stars and inside their cores, they were busily turning hydrogen into helium, and then helium into carbon, and then oxygen. In very short order, on the order of tens of millions of years, these massive supergiant stars exploded as supernovae. At that point, they scattered their elements to space, mixing a rich stew of carbon, nitrogen, oxygen and heavy elements all the way to iron with the abundance of hydrogen that existed.

Once out into space, the atoms of such elements as oxygen were heated by nearby stars, which caused them to glow, giving off infrared radiation. As this light traveled across space, it became stretched by the expansion of the universe. That changed the light into the distinct millimeter-wavelength light that ALMA then detected earlier this year.

Oxygen in Early Galaxies

So, you might wonder, what’s the big deal about oxygen? It’s everywhere, right? Not really. As I mentioned above, it didn’t exist right after the Big Bang. It had to be created inside stars. So, if you start to see oxygen at an early time in the cosmos, it’s important. It helps astronomers put a date and time and distance on the earliest stars. And, it helps them pinpoint the earliest epochs of star formation in the universe. It turns out that star formation started up, stopped and then started up again some 500 million years after the Big Bang. The idea is that the first stars formed, and their stellar winds may have choked off or “quenched” the amount of gas available to form more stars. That only lasted a short time though, and eventually gas in the galaxy began a second burst of star formation.

The other implication here is one for galaxy formation and when the first ones began to exist. It appears to have been very early in the history of the universe. Now astronomers want to know “how early”, and will continue studying these most distant stars and the existence of oxygen from dying stars even earlier in time. Want to learn more about this discovery? Check out the NRAO website where it was announced.