The Webb telescope took off on December 25, 2021 to its observation post, 1.5 million kilometers from Earth. A real Christmas tale since since its launch, the operations to bring it back to its observation point and deploy it have been going wonderfully. A first image has been unveiled. A small step point is therefore necessary.
The Webb telescope, resulting from an international partnership between NASA, ESA and the Canadian Space Agency (CSA), is often presented as the successor to the NASA Hubble telescope.
It is in fact its scientific complement. Despite its 30 years of age, Hubble still observes the universe in visible, ultraviolet and near infrared wavelengths. But despite its historic advances, it has reached its limits. Clouds of dust and gas, present in the interstellar medium, for example in planetary nebulae (where stars are born), are opaque to it. Webb, he will see “through” these clouds, because he observes in infrared, near and medium. It will also see “better”, and therefore further, thanks to its 6.5 meter mirror, compared to 2.5 meters for Hubble.
NASA/ESA, CC BY
France has largely participated in the realization of this titanic project. On the one hand via its major position within ESA, which supplied the Ariane 5 launcher and is involved in the supply of two of the four scientific instruments of the Webb: the MIRI spectro-imager in the mid-infrared and the NIRSpec spectrograph in the near infrared.
But also via the CNES, which directly contributed, with its national partners from the CEA and the CNRS, to the design and production of the imager of the MIRI instrument. As a result, French scientists benefit from privileged observation times, reserved for those who have financed, designed and manufactured the instruments. These programs will allow our researchers to be on the front line for the publication of the first results.
Unfold an origami in space
But deploying such a cathedral of technology in space is not easy. Webb was folded up like an origami in Ariadne’s headdress, specially modified for the occasion.
NASA/ESA, CC BY
And as Christmas tales always go well, the launch was perfect: the injection precision even made it possible to preserve 20 years of fuel reserve instead of the planned 10 years! Indeed, when the telescope approaches its final observation post, it must be maneuvered with precision. It consumes a lot of propellants. But the trajectory given to it by Ariane 5 was so precise that very few were used. So much more left for the mission!
To be able to observe in the infrared, Ariane propelled Webb 1.5 million kilometers from Earth, unlike Hubble, which revolves around it at an altitude of 570 km. Its destination is called Lagrange point L2. It reached it on January 24, 2022. It therefore now revolves around the Sun at the same speed as the Earth and the Moon, but it turns its back on them and protects itself from their radiation thanks to a huge shield which has been deployed. 10 days after firing.
Five layers of Mylar (a heavy-duty polyester that can withstand extreme temperatures) the size of a tennis court. Thanks to them, it now reigns, on the Sun side, between 14 and 51 ° C, while on the telescope side, protected by the shield, it reigns from -235 to -241 ° C.
A cold close to absolute zero
But if these very low temperatures are suitable for the operation of the three instruments which must work in the near infrared, they are not cold enough for our MIRI instrument, which looks at it in the middle infrared. In fact, the mid-infrared makes it possible to better probe, for example, the close vicinity of stars to detect the presence of planets. As the detectors working at these wavelengths require an even colder temperature, NASA therefore added a “cold machine” (“cryo-cooler”), which was started 87 days after the launch. A feat and a technological first hailed by NASA, which announced that it had reached the extremely cold temperature of 7 degrees Kelvin, or approximately -267 ° C, on April 6. MIRI has reached its operating temperature.
Before that, NASA had also deployed the 6.5-meter mirror, and carried out the fine alignment of the 10 segments of the mirror, so that each one observes well in the continuity of its six neighbors. Final alignment to correct any remaining small positioning errors was completed in early May. The first image taken with the imager of the MIRI instrument was made public by NASA at the end of April.
The next step is now to verify that all the functionalities of all the scientific instruments are operational. The first full resolution images will be released this summer.
Webb, fully operational, will help solve the mysteries of our solar system, look beyond distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.
But Webb is much more than that. Webb alone symbolizes all the interest that Astrophysics holds for humanity. Certainly science and knowledge are the first beneficiaries of the discoveries that the analysis of Webb’s images will make possible for all scientists on the planet. But the technological mastery of all the industrial fabric called upon to meet the unique challenges that Webb demanded has greatly benefited from it.
And that’s not all: Astrophysics, which has always fascinated humans for centuries, finds with Webb a leading philosophical tool. By observing the most distant universe, therefore the oldest, it will inform us about the life of the first stars and the structure of the first galaxies. By observing exoplanets orbiting other stars, it will be able to detect the presence of an atmosphere and analyze its composition. By also observing our outer solar system, the icy moons of our giants Neptune or Uranus, it will teach us about its formation and therefore about our Earth.
So Webb questions us about our origins and our place in the universe. Where do we come from ? How did our galaxy, our Sun, our Earth appear? Did life appear elsewhere? Are we alone? Have other civilizations followed a path similar to ours? Will Webb be able to help us continue the reflection around thedrake equation which attempts to quantify the number of intelligent and technologically advanced civilizations in the Universe, or to explain the fermi paradox who is surprised that none of them (if they exist) have ever manifested themselves to us?
Asking where we come from forces us to ask ourselves where we are going. The discussions that Webb’s observations and results will generate will not only appeal to researchers and scientists. All societies, from their leaders to the very general public, will thus be sent back to the fragility and complexity of our world. It is extremely salutary for the spirits in these times of war, of pandemic, of critical deterioration of the environment and of the living by those very people, the human beings, who live there.
Astrophysicist David Elbaz raises the philosophical power of such images accessible to everyone, but also artistic through the emotions they arouse, like the paintings of grandiose landscapes at the end of the 19th century.e century “Confronted with such images, the reason of the observer is pushed to rise […] they lead reason to surpass itself”.
As for scientific knowledge and the knowledge that is enriched by it astrophysicist Hélène Courtois emphasizes “Scientific knowledge is an integral part of culture. Through their work, researchers contribute to education, standing up against violence and obscurantism”.
Strongly, then, the first images of Webb, in these times which call for a supplement of light, even infrared!
This article is part of the series “The great stories of science in open access”, published with the support of the Ministry of Higher Education, Research and Innovation. To find out more, please visit the page Ouvrirlascience.fr.