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The NASA
Webb contains new technologies that have never been transported into space before
If it starts as planned in 2021, it will be 14 years late. Finally, the NASA James Webb Space Telescope promises an astronomical revolution.
The US space agency boasts of "literally going back in time to see the very first galaxies that formed in the first universe".
As if these claims were not bold enough, scientists have now assumed that the eventual successor to the world-famous Hubble Space Telescope could – thanks to its 6.5-meter golden mirror and his extremely sensitive cameras – have another extraordinary talent.
The JWST, as it is called, may be able to look for signs of extraterrestrial life – by detecting whether or not the atmospheres of planets orbiting nearby stars are modified by this life.
Despite this, the construction project survived cancellation by the US government in 2011. This is largely due to its astronomical cost (perhaps appropriately), estimated at $ 10 billion instead of $ 1 billion. dollars originally planned.
Back on Earth, however, astronomers – including the University of Washington team who proposed "life detection" observations using the telescope – are thrilled at the prospect of its launch.
How do you detect life on distant planets?
Joshua Krissansen-Totton, astronomer of the University of Washington, and his team investigated whether the telescope could detect signs of what they call "biosignatures" in the atmosphere of planets in orbits around a nearby star.
"We could do these life-detection observations in the next few years," said Krissansen-Totton.
The basis of this research could be that the JWST is so sensitive to light that it could capture what is called the "atmospheric chemical imbalance".
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Himawari / JMA / @ simon_sat
The atmosphere of the Earth would change if all life was abruptly removed
It may not be a catchy term, but it's an idea inherited from a long heritage, promoted by famous scientists James Lovelock and Carl Sagan.
The reasoning is this: If all life on Earth were to disappear tomorrow, the many gases that make up our atmosphere would undergo natural chemical reactions and the atmosphere would slowly become a different chemical mixture.
It is continually kept out of this state by the organisms on our planet that expel waste gases when they live.
Because of this, looking for signs of oxygen (or its chemical cousin, ozone) has long been considered a good way to find life. But this is based on the assumption that extraterrestrial life is governed by the same biological rules as ours.
This might not be the case. Therefore, the assessment of atmospheric chemical imbalance – looking for other gases and determining the extent of a planet's "normal" atmosphere – may be the key to finding any foreign life.
The chemical composition of the atmosphere of a planet gravitating around another star can be measured in light by carefully measuring the tiny immersion in the starlight as the planet passes between us and the planet. star on the orbit of the planet. The gases present in the planet 's atmosphere make the reduction in light vary with the wavelength – or color – of the light, revealing information about the amount of each chemical present.
Where is the best place to look?
Mr. Krissansen-Totton simulated the data that would be obtained if JWST were to examine planets orbiting a small Jupiter-sized star called TRAPPIST-1, about 39.6 light-years from our Sun. This star made a splash in 2017 when it was discovered to host seven Earth-sized planets, many of which could have liquid water, and so could be a good bet to accommodate life.
The Washington researcher predicts that James Webb could measure the amounts of methane and carbon dioxide in the atmosphere of the fourth planet, TRAPPIST-1e, from the troughs of light to the wavelengths affected by these gas.
It would be a difficult step of an unimaginably tiny signal, but Professor Jonathan Lunine, Cornell University astronomer, who did not participate in this study, is excited by this prediction, saying: "
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Once the measurement is done, says Krissansen-Totton, "we can then ask ourselves the question: do we know of non-biological processes that could produce this effect?"
Planetary atmospheres, including ours, he points out, can also be altered by non-biological processes, such as volcanic activity. Thus, if the TRAPPIST-1e atmosphere is found to be abnormal, researchers should then exclude any non-biological effects before declaring the existence of extraterrestrial life.
Mr. Krissansen-Totton stated that "this type of confirmation will require multiple observations to form a solid argument".
"But if we detect something for which we have no other explanation, I think it would be an incredibly exciting discovery."
Who else will do it?
For now, the golden mirror of the telescope remains locked in a laboratory in California, and astronomers must continue to wait for these possibilities to be explored.
JWST will join a host of new installations that will subject the planets around other stars to serious scrutiny over the next few decades.
Extensive ground-based telescopes in Hawaii and Chile are also planned, and the European Space Agency-led Ariel mission in the UK, designed to probe the atmosphere of planets around other stars, will fly towards the end of the 2020s.
Prof. Lunine says: "I think we are in a remarkable period to understand our universe and explore the cosmos, and James Webb will go one step further in this direction.
"It's really going to be worth it."
Professor Gillian Wright, senior scientist of the Mid InfraRed instrument led by the telescope in the UK, agrees. "We have never had access to something as big in space," she says.
"To say that a telescope will open new windows on the Universe seems a little cliche, but with James Webb, that's really true."
JWST is run by NASA but is a joint venture with European and Canadian space agencies. Dr. Jonathan Nichols is a global scientist from the University of Leicester and a media member of the British Science Association in 2018.
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