Why is the James Webb eye revolutionizing astrophysics?
M-57, called the Ring Nebula seen by the James Webb NIRCam. A host of never-before-seen details appear in this image. © NASA / ESA
It sails 1.5 million kilometers from Earth, cool around the shadow of our planet, and points its mirror in the shape of a flower corolla towards the depths of the cosmos. The James Webb Space Telescope (JWST) is the most powerful ever put into orbit. It has often been presented as the successor to Hubble, to which it is rather complementary in reality. Indeed, the latter scans the universe mainly in visible light, a little in infrared and ultraviolet, while the JWST only has eyes for infrared, electromagnetic radiation of a wavelength invisible to being. human.
Comparison between Hubble and James-Webb. © ESA
From his first observations, James-Webb showed the enormous extent of his possibilities. Her first deep field was quickly forgotten those, yet already exceptional, of Hubble. Astronomers and astrophysicists would learn much more thanks to this incredible machine.
There are mainly three areas in which this optical and technological gem is taking us forward: observing the first galaxies in the Universe, the formation of stars and planets, as well as exoplanets capable of supporting life. Let us remember here, to see far into the Universe is also to see far into its past, the speed of light being finite (around 300,000 km/s in a vacuum).
At the end of 2023, James-Webb detects the oldest known supermassive black hole!
GN Z 11 seen by the GOODS Northfield survey. © NASA / ESA (James-Webb)
GN Z 11, this galaxy from the very earliest times of the Universe, was known thanks to Hubble, but we had little information about it. James-Webb made it possible to highlight the presence of a black hole of approximately 1.6 million solar masses, only 440 million years after the Big Bang, which is very early. The mass of this galaxy is certainly 100 times lower than that of our Milky Way, but it is already too massive according to our theoretical models…
Close-up of the supermassive black hole in the GN-Z 11 galaxy. © NASA/ESA (James-Webb)
Shortly after, the record for the oldest galaxy – or younger if we scroll back in time to ours – was broken: only 285 million years after the Big Bang. It is about JADES-GZ-14-0. From then on, it became absolutely clear that this new telescope does much more than keep its promises, it takes us where we have never looked before! Cosmology would advance like never before and our knowledge of the formation and evolution of galaxies would reach the limit of the Big Bang.
The formation of stars before our eyes, without veil
Protostars are magnificent, but surrounded by dust that is difficult for our human eyes to pass through. Precisely, the infrared light captured by James-Webb easily ignores this dark dust. The image of L1527, a star only 100,000 years old, still stabilizing, took the breath away from scientists and the general public.
L1527, a protostar in formation. We see the polar jets that the young star emits. © NASA / ESA (James-Webb, NIRCam)
Here is an object Herbig-Haroalso a star in the early stages of formation. Splendid, isn't it?
HH4647, a star in formation, called the Herbig-Haro object. © NASA / ESA (James-Webb)
The JWST even makes it possible to “search” in nebulae to detect molecules, the formation of protoplanetary disks (i.e. young solar systems) and the role of stars with their radiation. Here, the JWST made it possible to spot the methyl cation (CH3+), a molecule considered essential for the formation of extraterrestrial carbon life.
Disc of planets in the process of formation highlighted using James-Webb cameras. © ESA / Webb, Nasa, CSA, M. Zamani (ESA / Webb), The PDRs4All ERS Team
Atmospheres, atmospheres?
And that's not all. James-Webb also studies exoplanets not too far from us, looking for a potential place for life, something for which this space telescope was not even really initially intended. To do this, its instruments use starlight filtered by the atmosphere of planets located light years from Earth. This is called an absorption spectrum, which allows us to detail the molecules and atoms present in an atmosphere (the sky) of an exoplanet, therefore to determine if something living could breathe there. Here is an example of a spectrum on the atmosphere of a gaseous planet, the James-Webb detects water there for example (H2O).
Absorption spectrum of the planet Wasp 39b where we see in particular water H2O and carbon monoxide CO. © NASA / ESA (James-Webb, NIRIS)
The most remarkable results of JWST in this area are perhaps those expected around exoplanets Trappist and those of the atmosphere of LHS-1140b, a ocean exoplanet which is likely to have an atmosphere containing nitrogen, like the Earth.
LHS-1140b could host an ocean of liquid water and a nitrogen atmosphere (artist's illustration). © B.Gougeon, University of Montreal
In summary, the James-Webb telescope takes us forward in almost all areas of astronomy and astrophysics. Professional astronomers wait months before obtaining a few precious slots to use them and marvel at their discoveries. The JWST epic is therefore far from over.
A few little visual gems from James-Webb to finish.
Family portrait of the gaseous planets of the Solar System:
Jupiter, Saturn, Uranus and Neptune seen by the JWST. © NASA / ESA (James-Webb)
An incredible star formation zone named Rho Ophiucci (Serpentarius constellation):
Rho Ophiucci. © NASA / ESA (James-Webb)
And finally, the Crab Nebula formed by a type 2 supernova (a massive star explosion). The central, bluish torus is due to the presence of a very rapidly pulsing neutron star (a pulsar). This star exploded in 1054.
Crab Nebula in the constellation Taurus. © NASA / ESA (James-Webb)
