The Orion Nebula is one of the best-known objects in the world. astronomersastronomers. A star nursery located at ” only “ 1,500 light years from Earth. So close and active that it is visible to the naked eye when our sky is dark enough. The Orion Nebula – or M42, Messier 42 – is undoubtedly the most photographed in the world. But today, the James Webb Space Telescope (JWST) offers us to discover images of the region of incredible clarity. A zoom, in particular, on the famous “Orion Bar”. Breathtaking images, but also rich in lessons for scientists.
“These images are so detailed that it will likely take us years to fully analyze themsays Els Peeters, astrophysicist, in a press release from Western University (Canada). They will serve as a reference for astrophysics research for decades.” Thanks to the diving they allow into the often chaotic environments that accompany star formation.
Spotlight on a region where stars form
In a series of studies published in the journal Astronomy & Astrophysicsthe researchers today present the first analyzes of the processes physicalphysical and chemicals that play out in the heart of the Orion Bar. Several discoveries “surprising and major”.
The Orion Nebula in the eyes of the James Webb telescope for the first time
Before going into detail, let us remember that stars form when too dense regions in gigantic cloudsclouds of gasgas and dust collapse under their own gravitygravity. It then appears a protostarprotostar enveloped in gas and dust. These budding stars continue to gather mattermatter until they become massive enough to trigger nuclear fusion. It seems simple. But in reality, said overly dense regions do not all have the same size or the same massmass. They also don’t all collapse at the same time. As a result, star nurseries end up with stars of varying masses at different stages of their development in a chaotic cloud of gas and dust.
To understand how stars form, astronomers must better understand the physics and chemistrychemistry so-called photodissociation regions. They call them PDR regions. And what is at stake is essentially determined by the way in which the radiation ultravioletultraviolet young stars interact with surrounding gas and dust. Interactions that give rise to structures like the Orion Bar.
The Orion Nebula at its best
The Orion Bar is therefore a ridge-shaped feature that runs diagonally across the nebula. It is made up of the remains of gas and dust from which stars were formed. It corresponds to the edge of a large bubble hollowed out by some of the massive stars that feed the Orion Nebula. The transition between the hot ionized gas near the Trapezium stars and the cold molecular cloud on the other side.
In images from the James Webb Space Telescope, breathtaking details appear in the Orion Bar seen in its best profile. Details that reveal eyeseyes astronomers a structure more complex than they had imagined. Gases and dust both in the foreground and in the background and which the quality of the images, explain the researchers, makes it possible to separate to reveal a sort of immense wallwall.
The data returned by the JWST in the domain ofinfraredinfrared close reveal, in turn, the way in which the chemical composition — but also the temperature, density and intensity of radiation — of the Orion bar can vary. Spectroscopic analyses, in fact, show numerous fairly clear peaks like so manyfingerprintsfingerprints of various chemical compounds present in the region. No less than 600!
Astronomers have used them to significantly improve existing models of PDRs. And specify how changes in the physical environment affect local chemistry and vice versa.
JWST and artificial intelligence to unravel the mysteries of the Orion Nebula
The researchers also used the data returned by the James-Webb space telescope to try to understand the hitherto unexplained strong variations in the broadcastsbroadcasts of dust in the Orion bar. And the data provided their answer. They clearly point to the attenuation of radiation by dust and the effective destruction of smaller dust particles as the underlying cause of these variations.
Other studies published in the journal Astronomy & Astrophysics are interested in big shows moleculesmolecules carbonaceous, aromatic hydrocarbonsaromatic hydrocarbons polycyclics (PAH). The latter constitute one of the largest reservoirs of carbonaceous materials in our UniverseUniverse. Hence their importance in the very history of our humanity. And more broadly, in our understanding of the existence of life on planets that form around young stars. What astronomers are showing today, thanks to JWST data and with the support of machine learning, is that ultraviolet radiation breaks down molecules of carboncarbon smaller. The emissions of larger molecules, for their part, are modified. Which marks a very clear change in the structure of said molecules. Another lesson from artificial intelligence. As if there was a principle of survival of the fittest at the molecular level in the harshest environments of space.
