Tracing the Story of Water in our Solar System

“Until now, the chain of water in the development of our Solar System was broken. V883 Ori is the missing link in this case, and we now have an unbroken chain in the lineage of water from comets and protostars to the interstellar medium.” – John Tobin, an astronomer at the National Science Foundation’s National Radio Astronomy Observatory (NRAO)

Scientists studying a nearby protostar have detected the presence of water in its circumstellar disk. The new observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) mark the first detection of water being inherited into a protoplanetary disk without significant changes to its composition. These results further suggest that the water in our Solar System formed billions of years before the Sun. 

V883 Ori is a unique protostar whose temperature is just hot enough that the water in its circumstellar disk has turned to gas, making it possible for radio astronomers to trace the water’s origins. New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) have provided the first confirmation that the water in our Solar System may come from the same place as the water in disks surrounding protostars elsewhere in the Universe: the interstellar medium. Image credit: ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF)

V883 Orionis is a protostar located roughly 1,305 light-years from Earth in the constellation Orion. The new observations of this protostar have helped scientists to find a probable link between the water in the interstellar medium and the water in our Solar System by confirming they have similar composition.

John Tobin, an astronomer at the National Science Foundation’s National Radio Astronomy Observatory (NRAO) explained:

“We can think of the path of water through the Universe as a trail. We know what the endpoints look like, which are water on planets and in comets, but we wanted to trace that trail back to the origins of water.

 “Before now, we could link the Earth to comets, and protostars to the interstellar medium, but we couldn’t link protostars to comets. V883 Ori has changed that, and proven the water molecules in that system and in our Solar System have a similar ratio of deuterium and hydrogen.”

Observing water in the circumstellar disks around protostars is difficult because in most systems water is present in the form of ice. When scientists observe protostars they’re looking for the water snow line or ice line, which is the place where water transitions from predominantly ice to gas, which radio astronomy can observe in detail. 

 “If the snow line is located too close to the star, there isn’t enough gaseous water to be easily detectable and the dusty disk may block out a lot of the water emission. But if the snow line is located further from the star, there is sufficient gaseous water to be detectable, and that’s the case with V883 Ori,” added Tobin

Clarifying the role of water in the development of comets and planetesimals is critical to building an understanding of how our own Solar System developed. Although the Sun is believed to have formed in a dense cluster of stars and V883 Ori is relatively isolated with no nearby stars, the two share one critical thing in common: they were both formed in giant molecular clouds. 

The Atacama Large Millimeter/submillimeter Array (ALMA) an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Click on this link to access the paper, “Deuterium-enriched water ties planet-forming disks to comets and protostars,” J. Tobin et al, 8 March 2023, published in Nature

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