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“There were tears of joy in the first pictures”

The James Webb Space Telescope (JWT) has recently been sending images of its location 1.5 million kilometers from Earth that are unsurpassed in sharpness and detail. In an interview, Ludmila Carone from the Institute for Space Research of the Austrian Academy of Sciences explains why the new telescope is a milestone for science and how Austrian space researchers use the data.

As an expert, what was your experience of the publication of James Webb’s first dates?

Ludmila Carone: Most colleagues followed the publication online at home. Parallel to the press conference, we exchanged information with other experts from all over the world on the Internet. Everyone saw the data for the first time and of course immediately started to carry out the first rough analyzes in real time. The JWT exceeded all expectations, the quality of the recordings is incredible. When we saw the first pictures, many people cried tears of joy. That was really overwhelming. The JWT is groundbreaking and will keep us busy with discoveries for decades to come.

What distinguishes the images shown at the press conference from the data the researchers receive?

Carone: The images presented to the public at the press conference are all already reduced representations of the data. We get the unfiltered raw data. This is particularly relevant for spectral analyses: the spectrum of the light that has passed through the atmosphere of exoplanet Wasp 96b is initially a smeared rainbow on a photocell. A layman couldn’t do anything with it, there are spectrography experts who process this data and present it in a nice diagram, where you can then see the chemical composition of the atmosphere.

Processing of the raw data

What needs to be filtered out?

Carone: There are many sources of interference, such as optical artifacts caused by the honeycomb shape of the JWT mirrors. This has to be factored out in order to get presentable images. The beauty is that different groups are working independently on the same raw data at the same time. This gives us a well-functioning quality control system.

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What do you do with the data in your research group?

Carone: We take the spectrum from the light that has passed through the exoplanet’s atmosphere and combine it with our models, which simulate physics, chemistry and cloud formation. Then we look at which parameters we need to change so that the model fits the observations. This can be the amount of heavy elements – in this context all except hydrogen and helium – the temperature or the cloud cover. Various other groups also do this in an international and interdisciplinary back and forth.

How is the JWT different from predecessors like Hubble?

Unlike Hubble, which operates in the visible and UV parts of the spectrum, the JWT sees light primarily in the infrared. This expands our view of the universe enormously. With Hubble, for example, no sign of clouds was seen in Wasp 96b’s atmosphere. However, the JWT has now found clues in the infrared range. Together we now get a lot of information about the universe with the two telescopes.

Gem clouds on exoplanets

How can clouds be detected on an exoplanet?

Carone: We’re looking at a tiny point in the distance, that’s just a pixel on the image sensor, because of course the exoplanets aren’t resolvable from that distance. But the starlight that reaches us through the planet’s atmosphere gives us information about the composition of the gases. Wasp 96b is a gas giant orbiting very close to its sun. Even so, the planet only occludes about 1 percent of the star as it passes in front of it from our perspective. And of this area, the atmosphere makes up only one percent. Nevertheless, we can clearly see a “water hump” in the spectrum of light.

Were there any surprises in the JWT’s first exoplanet spectrum?

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Carone: The water signal was not as strong as had been generally assumed. So something weakens the signal. Based on the data, that can only be clouds! Namely corundum and quartz, because these are the only materials that can still condense under the conditions on Wasp 96b. So there are practically clouds of gems there. A 2008 paper in the journal Nature, based on Hubble observations, concluded that there were no clouds on Wasp 96b. That now needs to be revised.

What can JWT spectrometers do better than their predecessors?

Carone: Water vapor and methane are quite transparent to ultraviolet and optical wavelengths. Infrared waves, on the other hand, are swallowed up by water vapour, methane and CO2 and the gas then appears more opaque. We can therefore also detect more complex molecules with infrared photons. Dust in the atmosphere also becomes visible. The JWT will teach us much about the formation of planets and galaxies and will allow us to look deeper into space and into the past than ever before and examine the composition of very old stars and galaxies.

Will there also be spectral analyzes of the atmospheres of Earth-like planets?

Carone: We probably won’t be able to probe an Earth-like planet’s atmosphere, but in principle, JWT could tell if a rocky exoplanet has an atmosphere. We now know that there are countless rocky planets. That’s a huge step forward because it wasn’t until 1995 that we confirmed that exoplanets exist at all. Since then we have also discovered many exotic types of planets not found in our solar system, such as mini Neptunes. Of course, watching one and seeing an atmosphere would be fantastic too.

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Where could we look for rocky exoplanets with atmosphere?

Carone: The Trappist 1 system orbits a red dwarf that regularly exhibits strong bursts of radiation. As a result, an atmosphere can also be blown away quickly. But if there were a Venus-like planet in the Trappist 1 system, we should be able to see the atmosphere with JWT. This is at the limit of what is possible. The Trappist 1 data will start pouring in within the next year. If we see an atmosphere, we have confirmed for the first time that there are rocky, gaseous planets outside our solar system.

look in the past

How far into the past can we see with the JWT?

Carone: We see back to about 300 million years after the Big Bang. At that time the first galaxies were formed, in which the first generation of stars was formed. These giants only had hydrogen, helium and a little bit of lithium as building material because all other elements were first bred in stars. The formation of iron, for example, took two stellar generations.

As a layman, I found the deep-field recording very impressive. Is this also interesting for experts?

Carone: The DeepField recording is of course something very special, also from a scientific point of view. Just a few days ago, two new galaxies were published on this basis, with redshifts of 12 and more. This is a very deep look into the universe, the two galaxies are candidates for the oldest known objects in the universe. We’ve never been able to see that far into the past, it’s all new territory.

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