The James Webb space telescope has discovered water in the region around a young star where planets can form. ‘Basic ingredients for life are more common than you think, if you look carefully.’
Life as we know it is not possible without water. But how this important ingredient ended up on Earth and whether it can also make other rocky planets habitable are still open questions. Maybe it came with meteorites hitting Earth. It is also possible that it was already present in the rock from which the Earth formed 4.5 billion years ago. Astronomers are trying to discover the origin of the ‘elixir of life’ by studying how planets form around other stars.
New measurements from the James Webb space telescope can contribute to this research. The space telescope has observed water vapor near the young star PDS 70, 370 light years from Earth.
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Earth-like planets
Around that star, which is slightly colder and less massive than the sun, is a disk of gas and dust that is probably clumping together to form planets. In the disk of PDS 70, two large gaseous planets have already formed in this way. These so-called gas giants have wiped part of the disk clean. As a result, there is a gap between the inner and outer part of the disc.
The James Webb has detected water vapor in the inner part of the disk with a temperature of about 300 degrees Celsius. ‘This discovery came as a surprise to me,’ says astronomer Inga Kamp of the University of Groningen. ‘It is the first time that we see water vapor in the area close to this star. That’s interesting, because we think rocky planets could form in that area.” So if Earth-like planets form at PDS 70, they form in an environment with a lot of water. Kamp and her colleagues published about the discovery in the journal last week Nature.
Beep
What makes the discovery even more exciting is that this planetary system-to-be is very similar to our own solar system, says Kamp. Two gas giants revolve around our sun: Jupiter and Saturn. And the inner portion of the disk is about as close to PDS 70 as the orbits of the rocky planets Mercury, Venus, Earth, and Mars are to the Sun.
PDS 70 is very young at 5 million years of life compared to our 4.6 billion year old sun. The PDS 70 system thus gives astronomers a glimpse into what could have happened billions of years ago in our solar system.
‘This is an important discovery, because it shows that one of the basic ingredients of life is probably much more common than previously thought: if you look carefully,’ says exoplanet researcher Gijs Mulders. He is affiliated with Adolfo Ibáñez University in Chile and was not involved in the discovery.
Unexpected
Mulders also calls the find unexpected, because it was assumed that the part of a planet-forming disc close to its star would have dried out. Close to the star, water has a very short life. In addition, the gas giants would hold back water-rich dust particles, preventing the particles from reaching this area. Jupiter would have played a similar role in our solar system.
Astronomers are therefore still looking for an explanation for the presence of the discovered water vapor. One scenario is that water is created locally by a chemical reaction of hydrogen with oxygen. Another possibility is that water-rich dust particles from the outer regions can still slip past the gas giants to the inner part. These can be dust particles with a layer of ice – it is cold enough at that distance from the star – or rock in which water is stored, as happens in clay.
In the trashcan?
If the Earth formed from water-containing rock, in a similar environment to what James Webb sees at PDS 70, that would explain why water was found tens of kilometers deep in the Earth’s mantle. That does not mean that the theory about water from impacting meteorites can be thrown into the trash. ‘It is quite possible that both processes contributed,’ says Kamp. ‘But we don’t know what percentage of the water each process is responsible for.’
To better understand this, the space telescope will image the disk of PDS 70 in more detail in the near future and will search for water vapor in other planetary systems in the making.
Water sightings
How do you detect water vapor near a star light years away? To do this, the light from the star that the James Webb Space Telescope detects is pulled apart into different wavelengths, just like a prism pulls sunlight apart into different wavelengths, each with a different color. That is the spectrum of light. Every molecule, from CO2 to water, leaves its own recognizable fingerprint of clear lines in that spectrum. For example, astronomers can see from the light spectrum which molecules are present around a star and even how many of them are and what temperature they have.
2023-08-03 07:59:26
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