Using Chile’s Atacama Large Millimeter/submillimeter Array (ALMA), a research team has detected water gas in the planet-forming disk around the star V883 Orionis.
This molecule carries a chemical signature that would explain the journey of water from star-forming gas clouds to planets, supporting the idea that Earth’s water is even older than our Sun.
The chemical signature of water detected in a planet-forming disk could explain its journey, supporting the idea that Earth’s water is even older than our Sun.
“Now we can trace the origins of water in our solar system before the formation of the Sun”, says John J. Tobin, astronomer at the National Radio Astronomy Observatory (USA) and lead author of the study published today in the journal Nature.
The discovery was made while studying the composition of the water present in V883 Orionis, a planet-forming disk located about 1,300 light-years from Earth. When a cloud of gas and dust collapses, it forms a star at its center. Around the star, cloud material also forms a disk.
Over a few million years, matter in the disk clumps together to form comets, asteroids, and eventually planets. Tobin and his team used the array of antennas SOULwhich the European Southern Observatory (ESO) is a partner, to measure the chemical signatures of water and its path from the star-forming cloud to the planets.
We can now trace the origins of our solar system’s water before the formation of the Sun.
John J. Tobin, lead author of the study
Normally, water consists of one oxygen atom and two hydrogen atoms. Tobin’s team studied a slightly heavier version of water, where one of the hydrogen atoms is replaced by deuterium, a isotope heavy hydrogen.
In the disk that surrounds the V883 Orionis, the distribution of water, dust and carbon monoxide can be observed. / SOUL
Since simple water and heavy water form under different conditions, their ratio can be used to track when and where the water formed. For example, this ratio, in some solar system comets, has been shown to be similar to that of water on Earth, suggesting that comets could have supplied Earth with water.
The proportion of water in some comets is similar to Earth’s
The journey of water from clouds to young stars, and then from comets to planets, has been observed before, but until now the link between young stars and comets has not existed. “In this case, the V883 Orionis represents the missing link,” says Tobin.
“The composition of the water in the disk is very similar to that of comets in our own solar system. This confirms that the water in planetary systems formed billions of years ago, before the Sun, in interstellar space, and was inherited by both comets and and by the Earth, with relatively few alterations”, adds the astronomer.
Water in planetary systems formed billions of years ago
John J Tobin
Observation was a difficult task. “Most of the water in planet-forming disks is frozen like ice, so it’s usually hidden,” says co-author Margot Leemker, a doctoral student at the Leiden Observatory in the Netherlands.
This diagram illustrates how a gas cloud collapses, forming a star with a disk around it. / THAT
In its gaseous form, it can be detected thanks to the radiation emitted by molecules as they rotate and vibrate, but when it is frozen, molecular movement is more restricted.
The dusty disk makes it difficult to detect gaseous water near the star
Water can be found in a gaseous state towards the central zone of the disks, close to the star, where the temperature is higher. However, these nearby regions are hidden by the dust disk itself and are too small to be seen by telescopes.
Happily, in a recent study The V883 Orionis disc was found to have an exceptionally high temperature. An impressive burst of energy from the star heats the disk “to a temperature where the water is no longer in the form of ice, but in the form of gas, which allows us to detect it,” says Tobin.
The disc contains 1,200 times more water than all of Earth’s oceans.
To observe the gaseous water from V883 Orionis, the team used ALMA, an array of radio telescopes located in northern Chile. Thanks to their sensitivity and ability to distinguish small details, they were able to detect water and determine its composition, in addition to mapping its distribution within the disk. From these observations, they discovered that this disk contains at least 1,200 times the amount of water present in all of Earth’s oceans.
In the future, they hope to use the next Extremely Large Telescope (ELT) and its first-generation instrument METIS. This mid-infrared instrument will be able to resolve the gas phase of water in this type of disk, providing more precise information about the path of water from star-forming clouds to solar systems. “This will give us a much more complete picture of ice and gas in planet-forming disks,” concludes Leemker.
Reference:
Tobin JJ et al. “Deuterium-enriched water links planet-forming disks to comets and protostars” Nature (2023).