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Cosmic Water

May 1, 2023

Water is sometimes called the universal solvent, since so many substances can be dissolved in it. That's because the water molecule can both donate or accept a proton and thereby act as either an acid (proton donor) or base (proton acceptor). This property is called amphoterism, and it's described by the classic Brønsted–Lowry acid–base theory that has its hundredth anniversary this year. This theory was independently developed in 1923 by Danish physical chemist, Johannes Nicolaus Brønsted (1879-1947), and English physical chemist, Thomas Lowry (1874-1936).

Water is a good solvent for ionic materials, but its action is definitely not universal, as attempts to remove pizza sauce from polyester fabric with plain water will attest. One joke from my childhood told of the inventor of a true universal solvent and the reason he wasn't able to sell it as a product - No container could hold it. Of course, today's chemists would simply sell it as a two-part compound, just like epoxy glue. The idea of a universal solvent goes back to the 16th century, and it was a popular topic in the 17th and 18th centuries as alchemy flourished. The fundamental problem of its containment was also understood at that time.

Alchymya, an allegorical representation of the art of Alchemy, Wellcome image L0011583

Alchymya, an allegorical representation of alchemy.

While modern chemists evolved from alchemists, physicists were always physicists. There's a continuum of physicists from Thales of Miletus (c.624/623-c.548/545 BC), through Galileo Galilei (1564-1642) and Isaac Newton (1642-1727), to the present day.

(Portion of a Wikimedia Commons image, Photo no. L0011583 of Wellcome Images, a website operated by the Wellcome Trust. Click for larger image.)

The universal solvent of alchemy was called Alkahest. It was expected to dissolve all substances, including gold, without alteration of their components. Alkahest was called "immortal," since it would not be altered by any solute, as acids are are modified by reaction with what they dissolve. Interestingly, one motivation for the discovery of this universal solvent was the dissolution of kidney stones. American alchemist, George Starkey (1628-1665), who often wrote under the name, Philalethes, supposed that a vessel of any pure element would not be dissolved by a universal solvent, since the solvent's action would be to dissolve composite materials into their constituent elements, so it would not dissolve a pure element.

The solvent property of water was likely the most essential process for the genesis of life on Earth, and it's the reason why planetary scientists and astronomers are always searching for extraterrestrial water. Radio observations of the accretion disk around the protostar, V883 Orionis, suggests that the water in our solar system was present billions of years before the Sun.[1-2]

Location of the the protostar, V883 Orionis in the constellation of Orion.

Location of the the protostar, V883 Orionis in the constellation of Orion.

Orion is likely the most familiar constellation after the portion of Ursa Major known as the Big Dipper. Orion is home to the unusual star, Betelgeuse (α Orionis) about which I wrote in an recent article (Boisterous Betelgeuse, October 31, 2022).

(Modified Wikimedia Commons image by ESO/IAU and Sky & Telescope. Click for larger image.)

These observations are published in a recent paper in Nature by a research team with members from the National Radio Astronomy Observatory (Charlottesville, Virginia), the University of Michigan (Ann Arbor, Michigan), Leiden University (Leiden, The Netherlands), the European Southern Observatory (Garching, Germany), the National Astronomical Observatory of Japan (Mitaka, Japan), the National Tsing Hua University (Hsinchu, Taiwan), Chalmers University of Technology (Onsala, Sweden), Northwestern University (Evanston, Illinois), and the Universidad Diego Portales (Santiago, Chile). The observations were performed using the Atacama Large Millimeter Array (ALMA), a collaboration of the European Southern Observatory, the National Science Foundation, National Institutes of Natural Sciences (Japan), the National Research Council (Canada), and others, in cooperation with the Republic of Chile.[1]

The Atacama Large Millimeter Array (ALMA)

The Atacama Large Millimeter Array (ALMA). (Cropped Wikimedia Commons image by Gantz.pro.)

Water is an important part of planet formation, since it aids the growth of the solid material that eventually form planetesimals within stellar accretion disk.[1] As the study authors write, the water-snow radius and water (H2O):semiheavy water (HDO) ratio in protoplanetary disks have not been well characterized.[1] This is because the water-snow radii are less than 10 astronomical units (AU), and most water is frozen out onto dust grains.[1] How water affects the development of comets and planetesimals will give us an understanding of how our own Solar System developed from a giant molecular cloud. [2] Observations of V883 Orionis with ALMA mark the first detection of water being accumulated into a protoplanetary disk without significant compositional changes.[2]

V883 Orionis is located about 1,305 light-years from Earth, and it has a mass of 1.3 solar masses.[1] V883 Orionis is presently in a state in which it is accreting matter, and this has increased its luminosity to about 200 times that of the Sun.[1] The disk of V883 Orionis is massive, and previous observations suggested that its water-snow radius is in the range of 40-120 AU.[1-2] The large water region makes it a good candidate for radio observation.[2]

The research team used ALMA's highly sensitive 1.6 millimeter and 1.3 millimeter wavelength receivers to observe water in V883 Orionis, and they found that it was relatively unchanged between each stage of solar system formation, from protostar, to protoplanetary disk, to comets.[2] Says Merel van 't 'Hoff, an astronomer at the University of Michigan and a co-author of the Nature paper, "This means that the water in our Solar System was formed long before the Sun, planets, and comets formed. We already knew that there is plenty of water ice in the interstellar medium. Our results show that this water got directly incorporated into the Solar System during its formation."[2]

The snow-water radius was found to be approximately 80 AU, a radius comparable to that of our solar system's Kuiper Belt, and water was detected out to a radius of about 160 AU.[1] The HDO:H2O ratio of the V883 Orionis accretion disk was found to be (2.26 ± 0.63) x 10-3, which is comparable to that of protostellar envelopes and comets, and it exceeds that of Earth's oceans by 3.1σ.[1] The research team concludes that accretion disks directly incorporate water from the star-forming cloud and this water is likewise incorporated into large icy bodies, such as comets, without substantial chemical alteration.[1]

An artist's impression of the water-snow line around the young star V883 Orionis

An artist's impression of the water-snow line around the protostar, V883 Orionis.

(Wikimedia Commons image by A. Angelich (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO) via the European Southern Observatory. Click for larger image.)

Says John Tobin, an astronomer at the National Science Foundation's National Radio Astronomy Observatory and the lead author of the Nature paper,
"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."[2]

The acknowledgments section of the paper was interesting, since it mentioned quite a number of Python software packages used in the study. These were APLpy, an open source plotting package, Astropy, a community-developed Python package for astronomy, the Python package spectral-cube, and matplotlib color maps from cmocean.[1]


  1. John J. Tobin, Merel L. R. van 't Hoff, Margot Leemker, Ewine F. van Dishoeck, Teresa Paneque-Carreño, Kenji Furuya, Daniel Harsono, Magnus V. Persson, L. Ilsedore Cleeves, Patrick D. Sheehan, and Lucas Cieza, "Deuterium-enriched water ties planet-forming disks to comets and protostars," Nature, vol. 615 (March 8, 2023), pp. 227-230, https://doi.org/10.1038/s41586-022-05676-z.
  2. ALMA traces history of water in planet formation back to the interstellar medium, National Radio Astronomy Observatory Press Release, March 8,2023.

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