SPACE – This Monday, July 11, the starry sky has just entered high definition. US President Joe Biden has unveiled the first scientific image of the James Webb Space Telescope. We see a small piece of our sky with incredible clarity, showing galaxies 13 billion light years away.

In the next few hours, NASA will unveil four more shots taken by James Webb. But this simple photo deserves attention. First of all, because it shows the path traveled since the launch of the Hubble telescope in 1990. Because this very particular area of ​​our sky, centered on the cluster of galaxies “SMACS 0723” (we’ll 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 in HD, James Webb will not only produce beautiful images. The space telescope will allow us to unravel some mysteries of the universe. And this first photo shows us the premises. To understand it well, The HuffPost explains every detail of this photo and their meaning.

A tiny piece of heaven

First, let’s enjoy this magnificent image once again (to see it in very high resolution, it’s here).

You need to start by defining what you see. This square represents a very small portion of the sky. To give you an idea, reach out 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 it, because this space telescope operates on a different wavelength, infrared. This allows him to better see galaxies located very far from the Earth.

The stars “pollute” the image

Let’s keep looking at this photo. The very bright points, which have the shape of a star … are really 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 sharp. 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 goals is precisely to bring back 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 so, we can see the universe as it was right after the Big Bang. How come? 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 allow you to go back in time to understand how stars behaved when the universe was very young, a few hundred million years after the Big Bang.

Einstein’s deforming zoom

To be able to trace 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, enough masses (here, a cluster of large galaxies) can create some sort of magnifying glass-like effect. As a result, it is possible to observe a much more distant galaxy, located behind the cluster, in a much larger area.

The problem is that this distorts the view 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 strange curved shape. They were distorted by the gravitational lensing caused by SMACS-0723, a cluster of galaxies located less than 5 billion light-years from Earth, accurate astronomer Katie Mack. These are the very bright white spots in the center of the image. On the contrary, the red traces are precisely the distant and deformed galaxies. Clearly, the largest galaxies are also the furthest away.

The most impressive thing is the time

Finally, one last essential point to fully understand how amazing this photo is is not visible in the image. The James Webb telescope observed this small portion of the sky for 12 hours to achieve such sharpness. Its predecessor Hubble, to produce the same, but much less sharp image, required more than 10 days of observations. to remember astronomer Jonathan McDowell.

What if James Webb observed this same little piece of sky for 10 days? The resolution would not change, the researcher specifies, but the image quality would, with greater precision and much less blur. Long live the sequel.

See also on The HuffPost: James Webb, the space telescope that maps our universe

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