Thanks to new observations from the Atacama Large Millimeter / submillimeter Array (ALMA), astronomers have discovered water in the most massive galaxy in the early universe, SPT0311-58, located 12.8 billion light-years away from Earth.
Scientists studying SPT0311-58 found water, along with carbon monoxide, in the galaxy. The detection of these two molecules in abundance suggests that the molecular universe was getting stronger shortly after the elements were forged in the first stars.
“Using high-resolution ALMA observations of molecular gas in the galaxy pair known collectively as SPT0311-58, we detected water and carbon monoxide molecules in the larger of the two galaxies,” said Sreevani Jarugula, an astronomer at the University of Illinois. and principal investigator of the new study. “Oxygen and carbon, in particular, are first-generation elements and, in the molecular forms of carbon monoxide and water, they are fundamental to life as we know it.”
The most distant detection of water in a galaxy
Thus, several molecules (of water, made of hydrogen and oxygen atoms) were found in a massive galaxy that dates back to when the universe was only 780 million years old . This suggests that “the molecular universe got going very early,” moving from helium and hydrogen, or helium hydride, to more complex combinations rapidly, the researchers say.
Elements heavier than helium and hydrogen fuse together in a star’s core when it reaches the end of its life, so this study, published in The Astrophysical Journal , suggests that the first stars formed and died and that their deaths produced molecules in just 800 million years.
How is it possible to detect water at such a distance?
Scientists can detect H2O when cosmic dust absorbs ultraviolet radiation from stars in the galaxy and re-emits it in the form of far-infrared photons, which excite water molecules. This creates emissions that scientists can observe. Water molecules appear in blue, while carbon monoxide appears in violet. Water is the third most abundant molecule in the universe after molecular hydrogen and carbon monoxide, but scientists did not expect to see water molecules in this very early stage of the universe.
It takes a large number of stars to produce so much dust, as it is obtained from stars, which pulse and emit their outer layer of dust into the galaxy. Thus, although astronomers currently do not understand how such an enormous amount of gas and dust gathered in the young universe to form the first stars and the first galaxies, they do know that stars in young galaxies form at a speed of a thousand times. greater than in the Milky Way . This offers us a fabulous scenario to understand how many stars were forming in the early universe.
“This study not only provides answers about where and how far water can exist in the universe, it has also raised a big question: How has so much gas and dust come together to form stars and galaxies so early in the universe? ? “ explains astronomer Sreevani Jarugula of the University of Illinois. “The answer requires further study of these and other similar star-forming galaxies to better understand the structural formation and evolution of the early universe,” Jarugula explained.
Referencia: “Molecular Line Observations in Two Dusty Star-Forming Galaxies at z = 6.9,” S. Jarugula et al. 2021. The Astrophysical Journal, pre-print: arXiv:2108.11319v1 [astro-ph.GA], arxiv.org/abs/2108.11319
