5 things to know about the first image unveiled by NASA

SPACE – This Monday, July 11, the starry sky just went into high definition. US President Joe Biden unveiled the first scientific image from the James Webb Space Telescope. We see a tiny slice of our sky with incredible clarity, showing a distant galaxy 13 billion light-years away.

In the coming hours, NASA will unveil four more shots taken by James Webb. But this simple picture deserves attention. First, because it traces the journey since the launch of the Hubble Telescope in 1990. Because this particular region of our sky, centered on the galaxy cluster “SMACS 0723” (we’ll come back to it), already was. 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 make pretty pictures. Space telescopes will allow us to unravel some of the mysteries of the universe. And this first photo shows our premises. For better understanding, HuffPost Explains you every detail of this picture and their meaning.

A small patch of sky

First, let’s enjoy this great image one more time (to see it in very high resolution, here it is).

Space Telescope Science Institute/NASA, ESA, CSA, and STScI First image taken by the James Webb Space Telescope

Space Telescope Science Institute/NASA, ESA, CSA, and STScI

You need to start by defining what you are looking at. This square represents a very small part of the sky. To give you an idea, stretch your hand toward the sky and point your index finger, then imagine a grain of sand on it. It is shown in this first image taken by the James Webb Telescope.

Even with a superhero zoom, you can’t see it, because this space telescope operates at a different wavelength, infrared. This allows it to better see galaxies far away from Earth.

Stars “taint” the picture

Let’s keep looking at this picture. Very bright points, which have the shape of a star… precisely the stars of our galaxy. They are very “closer” to us than everything else.

All the rest are spots of different shapes and colors, more or less clear. They are galaxies. It has billions of stars. Around which probably several million exoplanets orbit.

A long time ago, in a galaxy far, far away

Some galaxies are not very distant, others are extremely distant. One of James Webb’s main objectives is 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 more than 13 billion light-years away from Earth.

Because by doing so, we will see the universe as it was just after the Big Bang. Why? Because even if nothing goes faster than light, its speed is limited. When we say that 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 Waring Zoom

To succeed in going back to the origin 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 mass (here, large galaxy clusters) can create a kind of magnifying glass effect. As a result, it is possible to observe many more distant galaxies, located behind the cluster, on a much larger scale.

The problem is that it distorts the view of the target galaxy (space-time warping is discussed in more detail in this article). This video helps to understand the concept better:

This is why when you look in detail, some galaxies have a strange, curved shape. They are distorted by the gravitational lensing caused by SMACS-0723, a cluster of galaxies less than 5 billion light-years from Earth. specific Astronomer Katie Mack. Very bright white dot in the center of this image. Conversely, the red marks are precisely distant and distorted galaxies. Obviously, the most extended galaxies are also the most distant.

The most impressive thing is the weather

Finally, one last thing essential to fully understand how incredible this picture is is not visible in the picture. The James Webb Telescope observed this small patch of sky for 12 hours to achieve such sharpness. Its predecessor, Hubble, needed more than 10 days of observations to produce similar, but much less clear, images. remember Astronomer Jonathan McDowell.

What if James Webb observed this same small piece of sky for 10 days? The resolution won’t change, the researcher specifies, but the image quality will, with increased accuracy and much less blur. Long live the sequel.

See also HuffPost: James Webb, Space Telescopes Mapping Our Universe

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