JAMES WEBB. The space telescope's final target is 27 million light-years from Earth. This is the Tourbillon galaxy and its superb spiral structure, photographed by James Webb.
Drawn then photographed many times since its discovery in 1773, the Tourbillon galaxy is actually a pair of galaxies forming a spiral structure near the Big Dipper. Thanks to its NIRCam and MIRI cameras, the James Webb telescope offers us an unprecedented view of this hypnotic celestial structure. To obtain this result, it was necessary to combine two shots taken independently by the two cameras sensitive to infrared radiation.
In the center of the photo unveiled on August 21, 2023 by the European Space Agency, the bulge of the galaxy which contains a large density of stars appears bluish white. Around this core, spiral arms are made up of filaments of interstellar dust. The yellow and orange structures correspond to regions of gas very strongly heated by clusters of young stars.
Month after month, the collection of photos from the space telescope is advancing rapidly. Since the first shot in July 2022, the images published by NASA have been more spectacular than each other. Using his state-of-the-art instruments, James Webb opens a window to the wonders of the cosmos in unparalleled quality:
In June 2023, an article published by a research team in the scientific journal Nature revealed the space telescope's latest discovery: the presence of the methyl cation in the Orion Nebula. If this molecule is not known to the general public, it is a kind of holy grail for astronomers who have been looking for it for 50 years. Although this molecule has been theorized since the 1970s, it has the particularity of being very discreet and difficult to detect. This time, it was the heat emitted by young stars nearby that betrayed it, making it vibrate and radiate in the infrared, which allowed James Webb's MIRI instrument to spot it.
The methyl cation is a fundamental building block in understanding interstellar chemistry since it allows the formation of complex organic molecules from carbon, nitrogen and oxygen. It is therefore a major discovery made by the James Webb telescope, which confirms theories put forward for several decades.
What is James Webb's orbit?
After its launch aboard an Ariane 5 rocket, the James Webb telescope reached its final location after a month in space. It is now in orbit around the Lagrange 2 point. It therefore revolves around this location, but also around the Sun following the movement of the Earth. It is from this position that he makes his observations.
After take-off followed by a month-long journey, the James Webb telescope placed itself in orbit around a point in the solar system known as the "Lagrange L2 point". This point is located in the alignment of the Sun and the Earth and allows the telescope to remain fixed with respect to these two objects. This point was chosen for its stability, whereby the telescope does not need to expend a lot of energy to maintain its position.
This location is also a way to keep the telescope instruments cool since it is located behind the Earth in relation to the Sun. However, this position is not enough to keep all of its tools at a sufficiently low temperature. That's why the telescope also has a huge sunshade to keep its instruments away from the heat.
The James Webb Telescope must fulfill various objectives during its mission, which has an initial duration of 5 years, but which could be extended to 10 years. First, James Webb observes the first galaxies, which appeared just after the Big Bang. He will therefore go back in time to understand the formation of these structures and their diversity. The telescope also studies exoplanets and is more specifically interested in their atmosphere, in search of biosignatures, that is to say, signs of potential traces of life within the compounds of the atmospheres of the planets. Finally, he keeps an eye on an object much closer to us, the Sagittarius A* black hole, located at the center of our galaxy, the Milky Way. It should thus collect data which will supplement those of the network of telescopes which had produced the first image of this black hole in May 2022.
A true jewel of technology, the James Webb telescope is equipped with a huge mirror 6.5 meters in diameter which concentrates the light it receives. Four different instruments then capture this light ray and analyze it. These instruments are cameras and spectrometers, tools capable of detecting and analyzing infrared light, invisible to our eyes. It is thanks to this technology that the telescope can notably study distant galaxies formed shortly after the Big Bang.
These tools, however, require an extremely low ambient temperature to operate without the heat of its instruments or the environment distorting the results. The James Webb telescope was therefore equipped accordingly. A sun visor the size of a tennis court has been designed to protect all of the measuring tools.
The unprecedented size of this telescope was a real headache to accommodate it in the fairing of the Ariane 5 rocket on board which it left Earth. The mirror is therefore made up of 18 foldable segments that unfold once in space with remarkable precision.
The James Webb Telescope studies light in wavelengths ranging from 0.6 to 28 micrometers, i.e. in the mid and near infrared. It is a part of the light that the human eye does not perceive but which makes it possible to detect very distant and cold objects like the first galaxies which formed just after the Big Bang.
James Webb is orbiting Lagrange Point 2, 1.5 million kilometers from Earth. It moves around this point at a speed of about 1 kilometer per second. He thus goes around the Lagrange point in 6 months. At the same time, the telescope accompanies the Earth as it moves around the Sun. It therefore completes one tour of the Sun in 365 days, like our planet.
Hubble is an extremely powerful space telescope which has made it possible to discover a very large number of galaxies and to obtain completely new images of numerous nebulae and other celestial objects. Although it was only supposed to last around ten years, Hubble continues, 30 years later, to send us spectacular images and improve our knowledge of the Universe. “One of Hubble's most enduring achievements is bringing the wonders of the universe to the general public,” said Kenneth Sembach, director of the Space Telescope Science Institute, in National Geographic magazine.
Since the 90s, technologies have greatly evolved and the modern design of James Webb makes it an instrument with even greater ambitions than those of its predecessor. While Hubble is in orbit around the Earth, James Webb was positioned 1.5 million kilometers from our planet. Thanks to this positioning and its state-of-the-art instruments, it gains in precision and can observe even older objects. It can also provide details on structures discovered by Hubble, such as the Carina Nebula photographed by Hubble and then by the James Webb Telescope.
From a technical point of view, the two space telescopes are without common measure. The James Webb Telescope is equipped with the largest mirror ever sent into space. With 6.5 meters in diameter, the latter is 3 times larger than that of Hubble. Its sun visor is also of unparalleled size, measuring 22 meters by 12, or 4 times the area of Hubble's.
The James Webb Telescope was manufactured by two American manufacturers: Northrop Grumman and Ball between 2009 and 2021. It was designed by three space agencies partners on the project: NASA (the American space agency), ESA (the European Space Agency) as well as the CSA (the Canadian Space Agency). Each agency equipped the telescope with one or more instruments of its design. This is how France developed MIRI, one of the four instruments that will detect distant galaxies.
The final cost of the James Webb telescope is commensurate with the excessive ambitions of its mission. Estimated at the start of the project at around 500 million dollars, it ultimately cost 10 billion US dollars, which is equivalent to 9 billion euros. This colossal budget was partially covered by the Canadian agency and the European Space Agency.
The name of the telescope was chosen to pay tribute to a NASA administrator, James Edwin Webb. He held office between 1961 and 1968 during the Apollo program of the American agency, which aimed to land a man on the Moon. His responsibility for the success of the program is widely accepted within NASA.