Fundamental Science: James Webb’s First Birthday

Fundamental Science: James Webb’s First Birthday

It has been quite a year for international astronomical research: on December 25, 2021, after a long period of dashed hopes, the James Webb Space Telescope was finally launched. More than 30 years after the advent of Hubble, there was a huge expectation regarding the images that the new device would be able to produce.

Twelve months later, we find that he has said what he came for. A huge relief, of course, and now we’re just waiting for the flood of new data and observations to come. As Ronaldinho Gaúcho once said, “they are letting us dream.”

To begin to understand its importance, we first need to know how it differs from its predecessors. First of all, it is the largest space telescope in history, with a diameter of 6.5 meters (against 2.4 meters for the Hubble, for example) and a mirror capable of capturing the faintest light signals from distant objects.

In addition, unlike Hubble, it sees in the infrared, radiation characteristic of colder stars, or gas clouds in space, and also the energy that reaches us from the most distant galaxies, after their light is modified by the expansion of the universe. over the billions of years of travel. The ability to capture infrared makes it a technically more advanced companion to its predecessor, which detects visible light: together, the two offer a more complete view of the physical phenomena at work in celestial bodies.

Fortunately, its launch and the so-called commissioning period — the operations phase to determine how well it works — were successful. There was fear of opening the mirror, which, being too large, traveled folded inside the rocket, which had never happened with such a delicate instrument.

Now, to say that everything happened in a blue sky would be an untrue. There was a huge concern about possible wear on the filter wheel mechanism in one of the cameras. Afraid of the friction that could damage its operation, James Webb suspended observations from that camera for a few weeks, until it was verified that everything was under control.

The most persistent problem was the calibration of the data, which, although not unexpected, caused a lot of headaches among administrators and users of the observatory.

To guarantee the quality of the images, an astronomical observatory devotes a great deal of time to obtaining auxiliary calibration data, which allow scientists to remove possible sources of noise, such as the background brightness of the sky or the electronics of the devices on board. Everyone was concerned, therefore, when the prediction of operation made on the ground was not verified, and the first measurements of brightness of the stars showed a deviation of up to 20%. But many corrections have already been made, and we are well on the way to a smooth operation.

One of the main objectives of this telescope has already been achieved: the detection of the most distant galaxies in the universe. As it allows us to observe light emitted more than 13 billion years ago, we can glimpse the universe in its infancy, when it was only 200 million years old. That is, it allows us to understand much better the formation of the first stars and galaxies.

Soon after the launch, we witnessed a flood of candidates for this condition of prime stars, let’s say. Too bad that most of these possible distant galaxies had a wrong distance estimate due to calibration errors. Recently, however, work led by Dr. Emma Curtis-Lake of the University of Hertfordshire in the UK confirmed the discovery of the most distant galaxy ever observed.

The James Webb also detected for the first time the presence of carbon dioxide in the atmosphere of a planet outside the solar system, about 600 light years away. The telescope took advantage of the moment when the planet placed itself in front of its host star, and, analyzing how the star’s light was modified by the planetary atmosphere, was able to determine the chemical composition of the gases around it. Research of this nature is fundamental to understanding the chemical evolution of planetary atmospheres and the possible conditions that may have given rise to life in the universe.

In the first few weeks, observations focused on ensuring the device was working. Once this step is completed, we can tackle more ambitious projects. Which are? What else is out there? That’s the best part: we still don’t know. With new infrared eyes peering into space, we can expect to observe hitherto unknown phenomena, and perhaps understand a little better the origin of this small planet of ours among so many in the universe.


Thiago Gonçalves is an astronomer at the Valongo Observatory/UFRJ and a science promoter.

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