James Webb delivers an unprecedented and breathtaking view of the early Universe

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The James Webb Space Telescope offers astronomers images of our universe of unparalleled quality. The researchers point it to areas already imaged by the Hubble telescope, but the details revealed by Webb are incredibly accurate. Recently, it made it possible to contemplate the galaxies closest to the Big Bang (the oldest) known to date. Studying these star clusters could reveal valuable clues about the formation of the early Universe and its evolution.

NASA’s James Webb Space Telescope was specially designed to detect faint infrared light from very distant galaxies and give astronomers a glimpse of the early universe. Indeed, the light emitted in the first ages of our universe, to reach us, must cross space and time.

However, as predicted by Einstein’s theory of relativity, the Universe is constantly expanding, causing celestial objects to move away from each other. The light which crosses the Universe undergoes a stretching, and its wavelengths which at the beginning are in the visible spectrum, become larger and larger and end up in the near infrared zone, even infrared (for the light of the galaxies the more distant).

It should be known that the nature of the galaxies during this first luminous period of the Universe is not well known nor understood. For scientists, after the Big Bang, the universe was like a hot soup of particles (i.e. protons, neutrons and electrons) and without any light.

Light from objects dating from 100 to 250 million years after the Big Bang is strongly red-shifted. © NASA/Aleš Tošovský

As the Universe began to cool, protons and neutrons began to combine into ionized atoms of hydrogen (and eventually helium). These ionized atoms of hydrogen and helium attracted electrons, turning them into neutral atoms — which allowed light to travel freely for the first time, since this light was no longer scattering free electrons. The universe was no longer opaque!

However, it would still take some time (a few hundred million years) before the first stars began to form. But astronomers don’t know how. The James Webb Telescope could provide the answer with this new snapshot of the early universe. It captured an image of a cluster of galaxies called MACS0647, as well as the distant galaxy MACS0647-JD.

A galaxy (known for 10 years) that hides another

Dan Coe, of AURA/STScI for the European Space Agency and Johns Hopkins University, in a NASA statement, explains that he discovered the MACS0647-JD galaxy 10 years ago with the Hubble Space Telescope. He specifies : ” Back then, with Hubble, it was just this faint red dot. We could tell it was really small, just a tiny galaxy in the first 400 million years of the Universe. Now we look with Webb, and we are able to see TWO objects! “.

Hubble Space Telescope images of MACS0647-JD from 2012. © NASA, ESA, CSA, STScI and Tiger Hsiao (Johns Hopkins University)/Alyssa Pagan (STScI)

During the press conference concerning this discovery, the second researcher, Tiger Hsiao of Johns Hopkins University, underlines the difference in colors between these two objects, one being more blue, the other drawing on red. He explains : ” Blue gas and red gas have different characteristics. The blue actually reveals very young star formation and almost no dust, but the small red object has more dust inside and is older. And their stellar masses are also probably different “.

Without the two authors being able to really conclude on the nature of this observation, they agree that it might be a fusion of galaxies in the very first moments of the universe.

A gravitational lens complementing James Webb

The capture of this image was made possible thanks to the presence of a particular structure in this zone of the Universe, a gravitational lens. It is a cluster of galaxies located in front of the area pointed by the telescope. Due to the very strong overall gravity of this cluster, it acts like a magnifying glass on the most distant objects located behind. The lens not only magnifies these objects, but also multiplies their image in different orientations. Dan Coe explains: Due to the gravitational lensing of the huge galaxy cluster MACS0647, it is split into three images: JD1, JD2, and JD3. They are amplified by factors of eight, five and two, respectively “.

The MACS0647 galaxy cluster deflects and amplifies light from the more distant MACS0647-JD galaxy. He also tripled the JD system, causing his image to appear in three separate locations. These images, which are highlighted with white boxes on the central image, are marked JD1, JD2 and JD3; magnified views are displayed in the panels to the right. © NASA, ESA, CSA, STScI and Tiger Hsiao (Johns Hopkins University)/Alyssa Pagan (STScI)

Studying these images will provide insight into how such galaxies formed and how they evolved through time into a galaxy like the Milky Way, according to team member Rebecca Larson of the University of Texas at Austin. .

For the trio of researchers, as for all NASA astronomers, the prowess of James Webb is astonishing, especially since these discoveries concern only the first image of the telescope. Rebecca Larson says: If you look in the background, there are all these little dots — and they’re all galaxies! Each of them. It’s amazing how much information we get that we just couldn’t see before. And it’s not a deep field. It’s not a long exposure. We didn’t even really try to use this telescope to observe a place for a long time. This is just the beginning ! “.

Finally, as mentioned CNN, the research team has written about the discovery of the potential fusion, but as with most of Webb’s early observations since science operations began in July, the findings have yet to go through the review process. peer review. The team is also planning a more detailed study of MACS0647-JD in January.

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