Marking a groundbreaking discovery, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile has detected signs of water molecules in a distant galaxy. Named SPT0311-58, the galaxy is located 12.8 billion light-years from the Earth and is the most massive galaxy in the early universe. Although the galaxy, which is a combination of two galaxies, was first spotted in 2017, experts say that the detection of two water molecules today suggest that the molecular Universe was going strong shortly after the elements were forged in early stars. 

Talking about the discovery, the lead author of the study and astronomer at the University of Illinois, Sreevani Jargula said in an official press release,

“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. 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”.

Studying the biggest galaxy ever

Published in The Astrophysical Journal, the new research comprises the most detailed study of molecular gas content of a galaxy in the early universe to date along with the most distant detection of water in a regular star-forming galaxy. According to the astronomers, the two galaxies merged into one when the Universe was just 780 million years old which is roughly 5-percent of its current age, and the first stars and galaxies were being born. Besides, they believe that the two galaxies may be merging, and that their rapid star formation is not only using up their gas, or star-forming fuel, but that it may eventually evolve the pair into massive elliptical galaxies.

Jarugula says that this galaxy, which is the most massive one ever, contains more gas and dust compared to other galaxies in the early Universe, giving them plenty of potential opportunities to observe abundant molecules. He says that it would also help to better understand how these life-creating elements impacted the development of the early Universe. Interestingly, it is this huge amount of dust that made it easier for scientists to detect water. 

“The dust absorbs the ultraviolet radiation from the stars in the galaxy and re-emits it as far-infrared photons. This further excites the water molecules, giving rise to the water emission that scientists are able to observe. In this case, it helped us to detect water emissions 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”, Jarugula explained. 

Why is the discovery significant?

What makes this discovery significant is the window that it opens into the past of our universe. Scientists say that studying the very first galaxies in the universe will offer a better understanding of the birth, growth, and evolution of the Universe, and everything in it, including our Solar System and our planet. “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”, said Jarugula. He further added that apart from answering where, and how far away, water can exist in the Universe, but also has given rise to a big question that how has so much gas and dust assembled to form stars and galaxies so early in the Universe?

Image: ALMA Observatory