RUM – This Monday, July 11, the starry sky has just gone into high definition. US President Joe Biden unveiled the first scientific image from the James Webb Space Telescope. We see a small slice of our sky with incredible clarity, showing distant galaxies 13 billion light years away.
In the coming hours, NASA will reveal four other images taken by James Webb. But this simple picture deserves attention. First, because it shows the way since the launch of the Hubble telescope in 1990. Because this very special area of our sky, centered on the galaxy cluster “SMACS 0723” (we will return to this), had already been photographed by Hubble. And the difference is significant, as you can see in the video above.
By moving space to HD, James Webb will not only produce beautiful images. The space telescope will allow us to unravel certain mysteries of the universe. And this first picture shows us the premises. To understand it well, HuffPost explains to you all the details of this image and their meaning.
A little piece of heaven
First, let’s enjoy this magnificent image again (to see it in very high resolution, here it is).
Space Telescope Science Institute/NASA, ESA, CSA and STScI
You need to start by defining what you see. This square represents a very small part of the sky. To give you an idea, stretch your arm toward 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 enables it to better see galaxies located very far from Earth.
The stars “contaminate” the image
Let’s keep seeing this picture. The very bright points, which have a star shape… are precisely stars in our galaxy. They are very “close” to us compared to everything else.
All the others are these spots of different shapes and colors, more or less clear. They are galaxies. Which has several hundred million 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 aims is to bring the famous phrase from Star Wars to life: “A long time ago, in a galaxy far, far away”. What astronomers want is to be able to observe galaxies that are more than 13 billion light years from Earth.
Because by doing so, 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 a galaxy is 13 billion light years away, it means that the image 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 twisting zoom
To succeed in going back to the origin of the universe, the James Webb telescope “cheats”. It uses a “gravity lens”. This concept was predicted by Albert Einstein and was first observed in 1979.
Simply put, sufficient masses (here a cluster of large galaxies) can create a kind of magnifying glass-like effect. As a result, it is possible to observe a much more distant galaxy that lies behind the cluster in much larger.
The problem is that this distorts the view one has of the target galaxy (an issue of space-time distortion discussed in more detail in this article). This video helps to understand the concept better:
This is why, when viewed in detail, some galaxies have a strange, 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, exactly astronomer Katie Mack. These are the very bright white dots in the center of the image. Conversely, the red tracks are precisely the distant and deformed galaxies. It is clear that the most extended galaxies are also the most distant.
The most impressive thing is the weather
Finally, one last essential point to fully appreciate how incredible this photo is is not visible in the image. The James Webb telescope observed this small part of the sky for 12 hours to achieve such sharpness. Its predecessor Hubble needed more than 10 days of observations to produce the same image, but much less clear, Remember astronomer Jonathan McDowell.
What if James Webb observed the same small patch of sky for 10 days? The resolution would not change, the researcher specifies, but the quality of the image yes, with increased precision and much less blur. Long live the sequel.
Also look at HuffPost: James Webb, the space telescope mapping our universe