In 2015, the ultra-distant galaxy CR7 was measured to have hydrogen and helium, but no carbon or oxygen. With new ALMA observations, there’s carbon after all.
As brilliant as our Universe’s stars are today, they weren’t the first to arise in time and space.
A variety of heavy elements are found inside every star, star cluster, or galaxy ever observed.
The only way to create elements heavier than helium is through nuclear fusion, requiring the existence of previous generations of stars.
Yet according to the predictions of the Big Bang, the first stars should have been made of pristine material.
Over time, gravitation should pull this gas — made of hydrogen-and-helium only — together, forming unpolluted populations of stars.
In 2011, we found the first evidence for unpolluted, pristine gas, but it hadn’t yet collapsed to form stars.
But even bigger news came in 2015, when the galaxy COSMOS Redshift 7 (CR7) was discovered.
From 13 billion years ago, helium lines were observed, without any carbon or oxygen lines.
The hope was that CR7 contained stars made of hydrogen and helium alone.
But recent observations from ALMA have crushed those hopes.
By looking at the dust around the stars, they’ve found carbon after all, and it’s everywhere.
It’s an accreting, growing galaxy, but it’s not pristine.
We must look elsewhere to find the Universe’s first stars.
Mostly Mute Monday tells the scientific story of a picture, object, or phenomenon in the Universe in images, visuals, and no more than 200 words. Talk less, smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.