The Way of the Water

The water that fills the earth’s oceans, lakes and rivers has come a long way. It is initially formed in molecular clouds, which consist of 90 percent molecular hydrogen. When individual regions in these clouds condense into stars, it plays an important role in the formation of the protoplanetary disk. In the process, it is often transported as ice to their outer regions, from where it is later carried by comets to the inner planets. Cosmologists have already been able to document the first and the last section of this path well, but they have had measurement problems with the distribution within the accretion disk.

This is because it is often frozen. Gaseous water can be detected thanks to the radiation emitted by the molecules as they spin and oscillate, but with frozen water it is more complicated because the motion of the molecules is more hindered. Gaseous water is found near the star, in the center of the disks, where it is warmer. However, these nearby regions are obscured by the dust disk itself and are also too small to be detected by our telescopes.

So it came in handy for astronomers that the star V883 Orionis is very temperamental and has heated up its planet-forming disk by eruptions to a temperature where the water is no longer in the form of ice but as a gas, allowing researchers to detect it. To do this, a team of scientists used ALMA, an array of radio telescopes in northern Chile. Thanks to its sensitivity and ability to detect small details, they were able to detect the water and determine its composition as well as map its distribution within the disk. The observations revealed that this disk contains at least 1200 times as much water as all of Earth’s oceans. “We can now trace the origins of water in our solar system back to before the Sun was formed,” says John J. Tobin, an astronomer at the National Radio Astronomy Observatory, USA, and lead author of the study published in Nature.

ALMA images of the disk around the star V883 Orionis, showing the spatial distribution of water (left, orange), dust (center, green) and carbon monoxide (blue, right). (Image: ALMA (ESO/NAOJ/NRAO), J. Tobin, B. Saxton (NRAO/AUI/NSF))
This diagram illustrates how a cloud of gas collapses to form a star with a disc around it, out of which a planetary system will eventually form. (Image: ESO / L. Calçada)

One Comment

  • Then would it not be true that the presence of hydrogen in a atmosphere around a planet could be detected? When investigating a new planet this part the process to determine the presence of an atmosphere.

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  • BrandonQMorris
  • Brandon Q. Morris is a physicist and space specialist. He has long been concerned with space issues, both professionally and privately and while he wanted to become an astronaut, he had to stay on Earth for a variety of reasons. He is particularly fascinated by the “what if” and through his books he aims to share compelling hard science fiction stories that could actually happen, and someday may happen. Morris is the author of several best-selling science fiction novels, including The Enceladus Series.

    Brandon is a proud member of the Science Fiction and Fantasy Writers of America and of the Mars Society.