SPACE – This Monday, July 11, the starry sky has just gone into high definition. US President Joe Biden unveiled the first scientific image from the space telescope James Webb. We see a small piece of our sky with incredible clarity, showing distant galaxies of 13 billion light-years.
In the coming hours, NASA will unveil four other shots taken by James Webb. But this simple photo deserves attention. Firstly, because it shows the path traveled since the launch of the Hubble telescope in 1990. Because this very particular zone of our sky, centered on the cluster of galaxies “SMACS 0723” (we will come back to this), had already been photographed by Hubble. And the difference is stark, as you can see in the video above.
By moving the space to HD, James Webb isn’t just going to produce beautiful images. The space telescope will allow us to pierce certain mysteries of the universe. And this first photo shows us the premises. To understand it well, Le HuffPost explains to you every detail of this photo and their meaning.
A tiny patch of sky
First, let’s enjoy this wonderful image once more (to see it in very high resolution, it’s this way).
Space Telescope Science Institut/NASA, ESA, CSA, and STScI
You have to start by defining what you see. This square represents a very small portion of the sky. To give you an idea, extend your arm to the sky and point your index finger, then imagine a grain of sand resting on it. This is shown in this first image taken by the James Webb Telescope.
Even with a superhero zoom, you wouldn’t see this, because this space telescope operates on a different wavelength, infrared. This allows it to better see galaxies located very far from Earth.
The stars “pollute” the image
Let’s keep watching this photo. The very luminous points, which have a star shape… are precisely stars of our galaxy. They are very “close” to us compared to everything else.
All the rest are these spots of various shapes and colors, more or less clear. They are galaxies. Which have hundreds of millions of stars. Around which probably hundreds of millions of exoplanets orbit.
A long time ago, in a galaxy far, far away
Some galaxies are not far away, others extremely distant. One of James Webb’s main objectives is precisely to bring to life the famous phrase from Star Wars: “A long time ago, in a galaxy far, far away”. What astronomers want is to be able to observe galaxies located more than 13 billion light-years from Earth.
Because by doing that, we can see the universe as it was just after the Big Bang. Why? Because if nothing goes faster than light, its speed is still limited. When we say that a galaxy is 13 billion light-years away, it means that the photo taken by James Webb shows us the light that left this galaxy… 13 billion years ago.
By photographing distant galaxies, telescopes make it possible to go back in time to understand how stars behaved when the universe was very young, just a few hundred million years after the Big Bang.
Einstein’s warping zoom
To succeed in going back to the origins of the universe, the James Webb telescope “cheats”. It uses a “gravitational lens”. This concept was predicted by Albert Einstein and first observed in 1979.
Simply put, sufficient masses (here, a cluster of large galaxies) can create a kind of magnifying glass-like effect. Consequently, it is possible to observe a much more distant galaxy, located behind the cluster, in much larger.
The problem is that this distorts the view we have of the target galaxy (a matter of space-time warping discussed in more detail in this article). This video helps to better understand the concept:
That’s why when you look in detail, some galaxies have a weird, curved shape. They have been distorted by gravitational lensing caused by SMACS-0723, a cluster of galaxies located less than 5 billion light-years from Earth, precise astronomer Katie Mack. These are the very bright white dots in the center of the image. Conversely, the red traces are precisely the distant and deformed galaxies. Clearly, the most stretched galaxies are also the most distant.
The most impressive thing is the weather
Finally, one last essential point to fully understand how incredible this photo is is not visible in the image. The James Webb Telescope observed this small patch of sky for 12 hours to achieve such sharpness. Its predecessor Hubble, to produce the same image, but much less clear, needed more than 10 days of observations, remember astronomer Jonathan McDowell.
What if James Webb observed this same little piece of sky for 10 days? The resolution would not change, specifies the researcher, but the quality of the image yes, with increased precision and much less blurring. Long live the sequel.
See also on Le HuffPost: James Webb, the space telescope mapping our universe