JAMES WEBB. The James Webb Telescope has given us a fascinating picture of Saturn and its rings. Captured in infrared, this unprecedented shot provides some information on the gaseous planet.
At the end of June, the James Webb Space Telescope turned its instruments towards a planet in the solar system, specifically the giant Saturn. The gaseous planet, famous for its spectacular rings, was photographed in infrared by MIRI, one of the cameras fitted to James Webb. The shot is exceptional and reveals the star dark and devoid of its usual stripes. On the left of the image are also three of its many moons: Dione, Enceladus, and Tethys.
The unusual appearance of the planet is linked to the fact that the MIRI device is sensitive to infrared radiation. Indeed at this wavelength, the methane which makes up the upper atmosphere of Saturn absorbs light, giving this dark tint to the planet. Rings, on the other hand, are devoid of this gas and are particularly bright. The dark spot present at the North Pole remains quite mysterious for scientists who have not yet advanced a unanimous explanation.
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 was theorized in the 1970s, it has the particularity of being very discreet and difficult to detect. This time, it was the heat emitted by nearby young stars that betrayed it, causing it to vibrate and radiate infrared, allowing James Webb’s MIRI instrument to spot it.
The methyl cation is a fundamental brick in the understanding of interstellar chemistry since it makes it possible to form complex organic molecules from carbon, nitrogen and oxygen. It is therefore a major discovery made possible by the James Webb telescope, which thus confirms the theories put forward for several decades.
What is James Webb’s orbit?
After its launch aboard an Ariane 5 rocket, the James Webb telescope has 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 tennis court sized sun shield has been designed to protect all 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 in orbit around 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 completes the tour of the Lagrange point in 6 months. At the same time, the telescope accompanies the Earth in its movement around the Sun. It therefore completes one revolution 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 shots of many nebulae and other celestial objects. While it was only supposed to last 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,” Kenneth Sembach, director of the Space Telescope Science Institute, told 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 up to the disproportionate 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 supported 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.
