Water is essential for life as we know it – water makes up around 70% of the human body, covers about 70% of the planet Earth, has been found in the far reaches of our universe, and is at the centre of our search for habitable planets around other stars.

But how does this water find its way from interstellar space to the comets and planets it is found on? This was one of the questions that Professor Michel Fich from the Faculty of Science, and his international colleagues set out to research, using observations from the Herschel Space Observatory.

Measuring infrared light waves from its orbit around the Earth, this telescope had a unique eye on the stars, away from the water vapour in the Earth’s atmosphere. This let the telescope search the infrared wavelengths for signs of water in the far reaches of our universe.

Five years and over 100 academic papers later, this international group of researchers has published a summary and new analysis of their findings in the paper Water in star-forming regions: Physics and chemistry from clouds to disks as probed by Herschel spectroscopy.

Michel Fich“This paper paints the most complete picture ever done of how water is formed in space, and ultimately ends up in planets,” says Fich. “It’s very exciting to see the work of so many people around the world brought together in one place.”

Every molecule has a unique “fingerprint”, known as a spectrum, that can be studied and traced under different wavelengths of light. By identifying, isolating, and measuring the various spectra of water in its different molecular forms and at different temperatures, Fich and the other researchers were able to piece together the movement of water molecules in regions of space where stars and planets are still forming.

Most of these water molecules are formed in dense molecular clouds between the starry regions of space, also known as star-forming regions. Once these clouds get massive enough, they collapse from gravity and create dense balls of gas, forming stars.

During star formation, most of the hot water vapour is lost to space, due to an outward flow of gas coming from the forming star. This leaves the cool water molecules – liquid and ice still present in these regions. Most of the water molecules are ice, crystallized in layers around particles of dust. These icy dust crystals grow to be about the size of small pebbles, and are used as some of the building blocks as the leftover materials begin to gather together to create planets and solar systems around the newly formed stars.

Through this research, the international team has concluded that new planetary systems likely have enough water to become habitable – enough water to fill several thousand oceans!

Professor Fich, alongside his most recent graduate student Mollie Conrad (BSc ’16, MSc ’19), contributed to this international effort by studying the star forming region NGC 7129, located 3000 light years away from Earth.

“By studying this region, we were able to show that the high energy spectral lines of water that contained heavier-than typical atoms of oxygen have the highest potential for successfully probing the water in star forming regions like this one,” says Fich.

The overall findings of this international research are expected to be an important resource for astronomers in the decades to come, as scientists continue to study the origins of water on potentially habitable planets in distant solar systems.