Pierre Celerer (AFP)

Paris, France ●
Sunday 12 December 2021


Science and Technology
astronomy, james webb space telescope, universe, big bang, science

Looking back at space billions of years ago, the James Webb Telescope promises the clearest picture ever of the cosmic dawn of the universe when the first galaxies began to form.

The largest and most powerful telescope ever launched into space, which will replace Hubble, “will directly observe a portion of space and time that has never been seen before,” says NASA.

This is the universe in its youth, only a few hundred million years after the Big Bang.

With “very noble scientific goals” in mind, Webb will look back 13.5 billion years later, when the first galaxies in the universe evolved, said Begonia Vela, instrument systems engineer at NASA’s Goddard Space Flight Center.

It aims to allow us to observe “how it changes and evolves to get to the type of galaxy we live in today,” she said. Evidence for life as we know it: water, carbon dioxide, and methane.

Looking far into space means looking far into the past because of the time it takes light to travel – for example, sunlight takes eight minutes to reach our eyes on Earth.

The Hubble telescope reached its maximum 13.4 billion years ago with the discovery of the oldest observed galaxy GN-z11.

Swiss astrophysicist Pascal Auch, who first reported GN-z11, said the ancient galaxy might have been a pure little speck, but it was also “a surprise, with an unexpected brightness at such a distance.”

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Launched in 1990, Hubble focuses primarily on visible light, but Webb, scheduled for launch on December 22, focuses on infrared.

According to NASA, the light emitted by the first incandescent objects was “redshifted” as a result of the gradual expansion of the universe, and today it amounts to infrared light.

Webb, who has a much greater sensitivity than Hubble, is expected to provide more detailed images which, according to Oesch, “will allow us to explore this era in great detail.”

She assumes that “many galaxies will then be discovered, but they will be less bright.”

Its infrared ability would also allow Webb to penetrate interstellar dust clouds that absorb starlight and hide it from Hubble’s observations.

This “allows you to see what’s in the clouds, the birth of stars and galaxies,” said David Elbaz, an astrophysicist at the French Atomic Energy Commission.

lights and work

Webb was developed jointly by NASA, the European Space Agency, and the Canadian Space Agency.

Ochs said the ambition was to help explain a pivotal stage in the evolution of the universe when “the lights came on when the first stars began to form.”

After the Big Bang, which caused the expansion of the universe, it entered the nearly lightless period, the cosmic medieval period, when it was thrown into a gas fog of hydrogen and helium, making it opaque.

This period lasted hundreds of millions of years until the first stars began to form.

They were thought to be giants – about 300 times the size of our sun – that only burned for a few million years before exploding as supernovae.

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How and when these first stars formed remains uncertain. One idea is that dark matter – a substance whose existence is still theoretical – may have played a role.

This was a key time in the evolution of the universe because the radiation of these massive stars was able to split hydrogen atoms back into electrons and protons – ionizing them.

As the universe became more transparent, it became more transparent as the universe eventually led to “obvious” conditions now appearing in most parts of the universe.

The study of this phenomenon is the study of the formation of galaxies.

Webb hopes to see “the first galaxies containing stars of the second generation, which might teach us something about the first,” says Nicole Nesvadba, an astronomer at the Lagrange Laboratory at the Riviera Observatory.

Experts hope this will eventually provide clues to our existence.

“If we really want to know where our atoms came from and how little Earth has been able to sustain life, we need to measure what happened in the beginning,” said John Mather, chief scientist at the Webb Telescope Project, in comments on the project. website. .