The Water in Our Solar System May Be Billions of Years Older Than the Sun

Scientists have learned a great deal about how our solar system was born, but there are some things you can’t discern from studying the sun and planets as they exist today. In those cases, astronomers can look for younger sun-like stars in the cosmos to test their hypotheses. That’s where the protostar V883 Orionis comes in. Data from the Atacama Large Millimeter/submillimeter Array (ALMA) shows that the water around this young star predates the star itself, suggesting it could be the same for our solar system.

V883 Orionis sits roughly 1,305 light-years away in the constellation Orion. It only formed about 500,000 years ago, so it’s still accumulating material from the parent molecular cloud. Like all young stars of this type, it has pulled that material into a protoplanetary disk ripe for investigation with radio astronomy.

Usually, studying water in protoplanetary disks is difficult because most of it is frozen. Lucky for us, V883 Orionis is just warm enough to start turning the ice in that disk into gas. The team used ALMA’s Band 5 (1.6mm) and Band 6 (1.3mm) receivers to collect data from this “snow line,” where the signature of water was significant enough to measure.

The team found that the water in V883 Orionis matches the water in the surrounding region. Specifically, it has the same ratio of hydrogen and deuterium (a rare isotope of hydrogen). Therefore, it’s reasonable to conclude that the water was incorporated into the protoplanetary disk as-is — it was not formed or heavily altered within the infant solar system.

The Milky Way, behind the ALMA radio telescopes

Crucially, the hydrogen-deuterium ratio also matches what we see in our solar system. V883 Orionis is relatively isolated, and we believe the sun formed in a dense cluster, but both coalesced from a molecular cloud. This research suggests a similar process happened with the water that today makes up 60% of your body. It existed in a molecular cloud before the sun formed and was then incorporated into the solar system. That means the water in our solar system could be billions of years older than the sun itself.

Understanding the origins of water before it becomes part of planets and comets is essential to accurately model the sun’s past, present, and future. V883 Orionis is just what we needed to move that research forward — the team describes it as a “missing link” in the chain of water development in our solar system.

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