Water moves. On earth, it moves in the form of rivers, rain or ocean swellings. In space, its movements are more subtle, but no less important, and so far we understand very little about this process. Fortunately, we had a tool to try to understand better – the Hershel Space Observatory. Despite being out of service for over 8 years, a team of scientists has now compiled all the overviews of all the work, using Hershel data to trace water from its birth in interstellar clouds to its eventual resting place on planets. There are still some loopholes, but it is a worthy step towards better understanding.
Hershel, which was introduced in 2009, had a special instrument called the Heterodyne Instrument for Far-Infrared (HIFI). One of the main goals of the HIFI, designed by Dutch scientists, was the search for water in space.
Artist’s impression of the HIFI instrument that was used as the basis for the review paper.
Photo credit: Caltech / NASA / ESA
It is not easy to track down one of the most common molecules in the universe, also because it can be found almost everywhere. From shock waves caused by star formation to feathers in front of Saturn’s moon Enceladus, water is abundant throughout the cosmos. However, it is more difficult to figure out how it moves in these different stages of cosmic evolution.
Hershel dates were a good place to try to understand, and there were plenty of them. A team led by Dr. Ewine van Dishoeck of the University of Leiden has published over dozen of articles in the past few years, collecting as much data as possible and discovering several new tidbits in the process.
ESA video describing some of Herschel’s achievements.
Photo credit: ESA
The first of these is how quickly water ice becomes bound with dust particles in early solar systems. These combinations of water and dust then form the building blocks of the planets that surround young stars. Much more water is available in these gaseous disks than expected. Enough water surrounds a typical young star to fill thousands of oceans. However, it doesn’t look like oceans when you start – the formation of these ice / dust shards was another result of this research. The team found that ice forms in layers on top of dust particles and collects the most readily available type of water (e.g. normal H2O or “heavy” water).
Completion of this research effort likely means that scientists have learned as much as possible about water migration from the Hershel data. Unfortunately, Herschel’s successor with similar capabilities won’t hit the market until 2040. The authors of the paper presented this review paper in order to preserve the collective memory during the drought of new data for the next 20 years.
Artist’s impression of the Herschel Space Telescope.
Photo credit: ESA / AOES Medialab / NASA / ESA / STScI
All hope for new data is not lost, however – there are some tools that could help advance our understanding of the waterway. The first is the James Webb Space Telescope with an instrument called the Mid-Infrared Instrument (MIRI). MIRI could potentially collect some additional data, but will largely focus on JWST’s larger mission objectives that are not just about understanding water. In addition, ALMA has the ability to peer through the water in the earth’s atmosphere to try to track it down in space. The interpretation of his data is still in its infancy, though an understanding of Hershel’s data will help there too.
Sometimes reviews are really one of the best tools in science as they help us maintain knowledge through the scientific generations. The one who suspects the years of data that Herschel collected is a fitting tribute to this space observatory.
Learn:
Astronomy NL – The long-awaited review shows the travel of water from interstellar clouds to habitable worlds
arXiv – Water in Star-Forming Regions (WISH): Physics and chemistry from clouds to disks as studied by Herschel spectroscopy
NASA – Herschel finds oceans of water in the disk of the nearby star
UT – Speedy Science: Here are four years of Herschel telescope work in a short video
Mission statement:
Artist’s impression of Herschel and the water he was looking for.
Photo credit: ESA / ALMA / NASA / LE Kristensen
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