Water, Vital Ingredient for Life, Found in Galaxy 13 Billion Light-Years Away

Astronomers have detected water in a massive galaxy in the early Universe.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) scientists have spotted an abundance of water molecules in SPT0311-58, made up of two early galaxies located almost 13 billion light-years away from Earth.

The discovery suggests that molecules like this and carbon monoxide, which was also detected by the team, were forming in the early Universe shortly after the first elements were forged in the earliest generation of stars.

The discovery, detailed in research published in The Astrophysical Journal, represents the most distant detection of water in a star-forming galaxy, and the most in-depth study of molecular gas in the early Universe to date.

"Using high-resolution ALMA observations of molecular gas in the pair of galaxies known collectively as SPT0311-58 we detected both water and carbon monoxide molecules in the larger of the two galaxies," astronomer at the University of Illinois and the principal investigator on the new research, Sreevani Jarugula explained.

Jarugula continued by explaining the significance of the discovery: "Oxygen and carbon, in particular, are first-generation elements, and in the molecular forms of carbon monoxide and water, they are critical to life as we know it."

Researchers believe that the two galaxies that comprise SPT0311-58 are actually in the process of merging, as we see them billion of years ago.

Because of their distance and the time that the light from these galaxies has taken to reach us, we see these galaxies as they existed when the Universe was just 780 million years old, just 5 percent of its current age of around 13.8 billion years.

As we see them, the galaxies, which were first spotted by ALMA in 2017, are consuming their molecular gas to rapidly create new stars.

Researchers believe they could have eventually formed an elliptical galaxy, a galaxy with a stretched circular shape lacking features like the spiral arms or central bulge possessed by the Milky Way.

Jarugula also explained why these galaxies, in particular, were chosen by the team to investigate molecular gas in the early Universe: "This galaxy is the most massive galaxy currently known at the time when the Universe was still very young.

"It has more gas and dust compared to other galaxies in the early Universe, which gives us plenty of potential opportunities to observe abundant molecules and to better understand how these life-creating elements impacted the development of the early Universe."

A view of SPT0311-58 in emissions made by molecules and dust. On the right: The dust continuum seen in red (top), molecular line for H20 shown in blue (2nd from top), molecular line transitions for carbon monoxide, CO(6-5) shown in purple (middle), CO(7-6) shown in magenta (second from bottom), and CO(10-9) shown in pinks and deep blue (bottom). ALMA ESO/NAOJ/NRAO)/S. Dagnello (NRAO/ESO

Astronomers are able to spot water molecules, the third most common molecule in the universe after molecular hydrogen and carbon monoxide, when far-infrared radiation from dust in galaxies excites them and causes them to make characteristic emissions.

Jarugula said: "In this case, it helped us to detect water emission in this massive galaxy. This correlation could be used to develop water as a tracer of star formation, which could then be applied to galaxies on a cosmological scale."

Studying early galaxies like those in SPT0311-58 helps researchers to investigate the conditions in the early Universe. This in turn leads to a better understanding of how galaxies, stars, and eventually planets like our own, form and evolve.

"Early galaxies are forming stars at a rate thousands of times that of the Milky Way," said Jarugula. "Studying the gas and dust content of these early galaxies informs us of their properties, such as how many stars are being formed, the rate at which gas is converted into stars, how galaxies interact with each other and with the interstellar medium, and more."

Despite arriving at this important detection of water molecules in the largest galaxy of SPT0311-58, Jarugula believes that his team and ALMA, comprised of 66 radio telescopes spread across the Atacama Desert region of northern Chile, are far from done with this duo of galaxies.

"This study not only provides answers about where, and how far away, water can exist in the Universe but also has given rise to a big question, how has so much gas and dust assembled to form stars and galaxies so early in the Universe?" Jarugula concludes.

"The answer requires further study of these and similar star-forming galaxies to get a better understanding of the structural formation and evolution of the early Universe."

Astrophysicist and ALMA Program Director at the National Science Foundation, Joe Pesce was not involved in the current research. He said: "This exciting result, which shows the power of ALMA, adds to a growing collection of observations of the early Universe.

"These molecules, important to life on Earth, are forming as soon as they can, and their observation is giving us insight into the fundamental processes of a Universe very much different from today's."

The Galaxies of SPT0311-58
An illustration of the pair of galaxies that make up SPT0311-58. New observations have revealed abundant carbon monoxide and water in the larger of the two galaxies showing molecules were forming shortly after the elements were forged. ALMA NAOJ/NRAO)/S. Dagnello (NRAO/ESO

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