Water has been discovered in a galaxy in the early universe!

Laura Faz Laura Faz Meteorized Chile 5 min
galaxy representation SPT0311-58
The molecular lines of carbon monoxide and water were the compounds detected in this distant galaxy. Credit: ALMA (ESO / NAOJ / NRAO) / S. Dagnello (NRAO).

A few days ago, the ALMA Observatory (Atacama Large Millimeter / Submillimeter Array) issued an important announcement: they had discovered signs of water (H2O) in the most massive galaxy in the early universe. The galaxy SPT0311-58 is located approximately 12.88 billion light-years from Earth. In its composition, they not only identified molecules of H2O, but also large amounts of carbon monoxide (CO).

This study, published by The Astrophysical Journal, includes the most comprehensive analysis of the molecular gas content of a galaxy in the early universe and shows the most distant detection of H2O in a stellar incubator.

Indeed, when scientists refer to SPT0311-58, they specify that it is a set of two galaxies. In 2017, ALMA took the first images demonstrating the existence of massive galaxies full of stars born when the universe was only 780 million years old, or 5% of its current age. Until then, it was thought that the first galaxies resembled the dwarf galaxies in the neighboring universe.

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The two galaxies in connection SPT0311-58 are so close that they could merge to form the largest galaxy never observed in astronomical history. This star incubator “contains more dust and gas than other galaxies in the early universe, which could give us many opportunities to observe a large number of molecules and better understand how these basic elements of life affected the development of the early universe “, explained the astronomer and lead researcher in the study, Sreevani Jarugula.

How could the water have been discovered at such a distance?

With ALMA, impressive observations are made: its reception of light in millimeters and submillimeter wavelengths from space used to discover cosmic origin. This radio telescope located in Chajnantor, in the Atacama Desert (Chile), captures the light coming from the large cold clouds in space and from some of the most distant and youngest galaxies. With this information, data are obtained on the physical and chemical composition present in these molecular clouds.

With high-resolution molecular gas observations of the galactic ensemble SPT0311-58, molecules of water and carbon monoxide could be detected in the larger of the two galaxies.

In previous studies, it has been shown that water is the third most abundant molecule in the universe, after hydrogen and CO. But … which detection method confirmed it? The authors of the study relied on the link between water and dust emissions in the far infrared range.

The study of dust and gas allows us to know the chemical properties of these galaxies, the number of stars formed there, and the interplay between them.

The dust, which absorbs the ultraviolet radiation from the galaxy’s stars, re-emits in the form of photons in the distant infrared. In this way, the water molecules are stimulated, causing them to emit, and this is how researchers get observations.

The lead author concludes with a question she raises in this study: “How could all this gas and dust combine to give rise to stars and galaxies so early in the history of the universe?” It remains a long astrophysical path to go to solve this great mystery.

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