Scientists trace the formation of water in a distant protostar

A team of astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to detect gaseous water in a colossal planet-forming disc surrounding the star V883 Orionis.

A chemical signature in that water explains the journey gaseous water undertakes from star-forming clouds to planets, as was the case with Earth. The new observations support the idea that water on Earth is even older than our Sun.

Tracing the origins of water in the cosmos

V883 Orionis is a protostar, meaning it is still gathering mass from its surrounding molecular cloud. This makes it a great candidate for studying the early evolution of solar systems.

The researchers made their discovery by analyzing the composition of water in V883 Orionis, a planet-forming disc that is located roughly 1,300 light-years from Earth.

"We can now trace the origins of water in our Solar System to before the formation of the Sun," John J. Tobin, an astronomer at the National Radio Astronomy Observatory, USA, and lead author of a new study on the topic, explained in a press statement.

Stars are formed when a cloud of dust and gas collapses. This process will also form a disc around the star, made from material around the cloud. The matter in this disc eventually clumps together over millions of years to form comets, asteroids, and planets.

For their research, published in a new paper in the journal Nature, the scientists used ALMA to measure the chemical signatures of the water and the path it takes from the star-forming cloud to the planets. During their observations, they found that the planet-forming disc surrounding V883 Orionis contains at least 1200 times the amount of water in all of Earth's oceans in ice form.

"V883 Orionis is the missing link"

The team searched for a heavier form of water, with one deuterium atom replacing one of the two hydrogen atoms that typically accompany an oxygen atom in water. Simple and heavy water forms under different conditions, meaning the water ratio can be used to trace where and when the water was formed. This method was previously used to show that comets may have transported water to Earth.

Now, the new research has helped to fill a gap in knowledge regarding the journey of water from young stars to comets.

"V883 Orionis is the missing link in this case," Tobin explained. "The composition of the water in the disc is very similar to that of comets in our own Solar System. This is confirmation of the idea that the water in planetary systems formed billions of years ago, before the Sun, in interstellar space, and has been inherited by both comets and Earth, relatively unchanged."

The team hopes to conduct follow-up observations of V883 Orionis in the future using the European Southern Observatory's (ESO's) Extremely Large Telescope. That observatory's mid-infrared METIS instrument will be able to image the gas phase of water in star-forming discs, allowing for much more detailed observations.