Le télescope spatial Webb révèle les secrets “remués” d’une nébuleuse planétaire à couper le souffle

Les chercheurs ont reconstruit la scène, trouvant jusqu’à trois compagnons stellaires invisibles qui pourraient avoir façonné les couches de gaz et de poussière de la nébuleuse planétaire.

Attendez, combien de stars étaient à cette fête ? Il y en a probablement eu jusqu’à cinq, mais seuls deux apparaissent maintenant ! Une équipe de recherche a récemment commencé à creuser dans les images très détaillées de Webb de la nébuleuse de l’anneau sud pour reconstruire la scène. Il est possible que plus d’une étoile ait interagi avec le gradateur des deux étoiles centrales, qui apparaît en rouge sur cette image, avant de créer cette nébuleuse planétaire à couper le souffle. La première star qui a « dansé » avec l’hôte de la fête a créé un spectacle de lumière, envoyant des jets de matière dans des directions opposées. Avant de se retirer, il a donné à l’étoile sombre un manteau de poussière. Aujourd’hui beaucoup plus petit, le même danseur a peut-être fusionné avec l’étoile mourante – ou est maintenant caché dans son éclat.

Un spectateur tiers peut s’être approché plusieurs fois de l’étoile centrale. Cette étoile a suscité les jets éjectés par le premier compagnon, ce qui a contribué à créer les formes ondulées que nous voyons aujourd’hui aux confins du gaz et de la poussière. Pour ne pas être en reste, une quatrième étoile avec une orbite projetée beaucoup plus large, a également contribué à la célébration. Il a fait le tour de la scène, agitant davantage le gaz et la poussière, et générant l’énorme système d’anneaux observé à l’extérieur de la nébuleuse. La cinquième étoile est la plus connue – c’est l’étoile blanche-bleue brillante visible sur les images qui continue à orbiter de manière prévisible et calme.

La découverte finale est une mesure précise de la masse que l’étoile centrale avait avant d’éjecter ses couches de gaz et de poussière. Les chercheurs estiment que l’étoile avait environ trois fois la masse du Soleil avant de créer cette nébuleuse planétaire – et environ 60 % de la masse du Soleil après. Il n’en est qu’à ses débuts – il s’agit de l’une des premières recherches publiées sur certaines des premières images de Webb à être publiées, donc beaucoup plus de détails sont sûrs de venir.

Le télescope spatial Webb offre des vues radicalement différentes de la même scène ! Chaque image combine la lumière infrarouge proche et moyenne de trois filtres.
À gauche, l’image de Webb de la nébuleuse de l’anneau sud met en évidence le gaz très chaud qui entoure les étoiles centrales. Ce gaz chaud est entouré d’un anneau pointu de gaz plus froid, qui apparaît sur les deux images.
À droite, l’image de Webb retrace les sorties dispersées de l’étoile qui ont atteint plus loin dans le cosmos. La majeure partie du gaz moléculaire qui se trouve à l’extérieur de la bande de gaz plus froid est également froide. Il est également beaucoup plus aggloméré, composé de nœuds denses de gaz moléculaire qui forment un halo autour des étoiles centrales. “L’une des choses qui a attiré mon attention était la forte différence entre les images du gaz ionisé chaud et du gaz moléculaire froid”, a expliqué Isabel Aleman de l’Université fédérale d’Itajubá (UNIFEI), au Brésil. “Le gaz chaud est très lisse, mais le gaz froid montre ces mini touffes, pointes et arcs. Les images de Webb sont très, très riches en détails.
En tenant compte des températures et de la teneur en gaz dans les deux zones, à l’intérieur et à l’extérieur de la bande, et en combinant les données de Webb avec des mesures précises d’autres observatoires, elle et l’équipe de recherche ont pu créer des modèles beaucoup plus précis pour démontrer quand le gaz a été éjecté par l’étoile centrale (qui apparaît en rouge sur l’image de gauche).
Qu’en est-il de la troisième étoile visible sur le bord inférieur droit de la bande à l’intérieur de la nébuleuse ? Du point de vue de Webb, il apparaît dans la scène, mais ne fait pas partie de la nébuleuse elle-même. C’est simplement du “photobombing” ce parti.
Crédit : Science : NASA, ESA, CSA, STScI, Orsola De Marco (Université Macquarie), Traitement d’image : Joseph DePasquale (STScI)

Certaines des premières données de

” data-gt-translate-attributes=”[{” attribute=””>NASA’s James Webb Space Telescope has shown there were at least two, and possibly three, more unseen stars that crafted the oblong, curvy shapes of the Southern Ring Nebula. Plus, for the first time, by pairing Webb’s infrared images with existing data from ESA’s (European Space Agency’s) Gaia observatory, researchers were able to precisely pinpoint the mass of the central star before it created the nebula. A team of almost 70 researchers led by Orsola De Marco of Macquarie University in Sydney, Australia, analyzed Webb’s 10 highly detailed exposures of this dying star to produce these results.

Their calculations show the central star was nearly three times the mass of the Sun before it ejected its layers of gas and dust. After those ejections, it now measures about 60 percent of the mass of the Sun. Knowing the initial mass is a critical piece of evidence that helped the team reconstruct the scene and project how the shapes in this nebula may have been created.

Examine the straight, brightly-lit lines that pierce through the rings of gas and dust around the edges of the Southern Ring Nebula in the Webb Space Telescope’s image. These “spokes” appear to emanate from one or both of the central stars, marking where light streams through holes in the nebula. The holes are evidence of where the dimmer star that created this scene shot out material, creating open pathways for light to flow through.
Some of the star’s ejections followed thin, straight lines (second box) through the gas and dust. Other ejections (first box) look bent, curvy, and thicker. Why? A team of researchers, led by Orsola De Marco of Macquarie University in Sydney, Australia, modeled how these complex structures might have formed. Studies of planetary nebulae have shown that even when dying stars eject their gas and dust at all angles simultaneously, the outflowing gas may not stay symmetrical for long. In the Southern Ring Nebula, the team projects that the straight lines may have been shot out hundreds of years earlier and at greater speeds than those that appear thicker and curvy. It’s possible the second set is a mix of material that slowed, creating less linear shapes.
By carefully comparing the appearance and timing of these ejections in the data and simulations, De Marco and her team propose that this is more evidence of the presence of a star with a slightly wider orbit that “stirred the pot” of ejections.
This image combines near- and mid-infrared light. The dimmer star that created the planetary nebula appears as a faint red star next to the central blue star.
Credit: Science: NASA, ESA, CSA, STScI, Orsola De Marco (Macquarie University), Image Processing: Joseph DePasquale (STScI)

Let’s start with the top-tier celebrity of this particular “party,” the star that sloughed off its layers of gas and dust over thousands of years. It appears red in the image on the left because it is surrounded by an orbiting, dusty disk similar in size to our solar system’s Kuiper Belt. While some stars expel their layers as solo acts “on stage,” researchers propose that there were a few companions with front-row seats – and at least one that may have joined the central star before it began to create the Southern Ring Nebula. “With Webb, it’s like we were handed a microscope to examine the universe,” De Marco said. “There is so much detail in its images. We approached our analysis much like forensic scientists to rebuild the scene.”

It’s common for small groups of stars, spanning a range of masses, to form together and continue to orbit one another as they age. The team used this principle to step back in time, by thousands of years, to determine what might explain the shapes of the colorful clouds of gas and dust.

This image of the Southern Ring Nebula (NGC 3132) was captured by Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). Credit: Science: NASA, ESA, CSA, STScI, Orsola De Marco (Macquarie University), Image Processing: Joseph DePasquale (STScI)

First, they focused on the aging star that cast off its layers and is still surrounded by a dusty red “cloak” of dust. Extensive research about these types of aging stars shows that dusty cloaks like these must take the form of dusty disks that orbit the star. A quick dive into the data revealed the disk. “This star is now smaller and hotter, but is surrounded by cool dust,” said Joel Kastner, another team member, from the Rochester Institute of Technology in New York. “We think all that gas and dust we see thrown all over the place must have come from that one star, but it was tossed in very specific directions by the companion stars.”

Before the dying star shed its layers, the team proposes that it interacted with one or even two smaller companion stars. During this intimate “dance,” the interacting stars may have launched two-sided jets, which appeared later as roughly paired projections that are now observed at the edges of the nebula. “This is much more hypothetical, but if two companions were interacting with the dying star, they would launch toppling jets that could explain these opposing bumps,” De Marco explained. The dusty cloak around the dying star points to these interactions.

Where are those companions now? They are either dim enough to hide, camouflaged by the bright lights of the two central stars, or have merged with the dying star.

How did all the “partygoers” – up to five stars – create the Southern Ring Nebula? Let’s hit “rewind” and replay the interactions that might have created the scene!
First, it’s important to know that none of these illustrations are properly scaled, and three or as many as four of the stars would be too small and dim to appear in Webb’s image. Second, star 1 and star 2 are the only stars we see in the sixth and final panel above. The remaining “guests” will be known as stars 3, 4, and 5. They are all much less massive – in other words far smaller and dimmer – than stars 1 and 2.
The first illustration shows a wider field. Star 1, the most massive of this group of five stars, is the fastest to age and is responsible for creating the planetary nebula. Star 2 very slowly orbits star 1, which is easier to see in the last panel. All is relatively quiet at this stage as they orbit one another, though there is another star on the scene, number 5. It orbits star 1 far more tightly than star 2 does.
Cue the action! The second panel zooms way in on the scene – and two other companions appear in view. Star 1 has begun to swell as it ages rapidly, swallowing star 3. Through gravity, star 3 starts to draw in material from star 1 and launches jets in both directions. Star 4 is close by, but not yet interacting.
The third panel shows how much star 1 has expanded as it ages. Two companions also enter the mix. Stars 3 and 4 have sent off a series of bipolar jets. As these two stars interact, the jets they sent out are tumbled, which leads to the irregular, wavy edges of the gas and dust ejected by aging star 1. Both companions 3 and 4 are interacting within the gas and dust star 1 has ejected.
In panel 4, we zoom out to see more of the scene. Ultraviolet light and a fast, spherical wind from the newly exposed ultra-hot core of star 1 is helping to carve out its previously ejected gas and dust, creating a bubble-like cavity. There is also a leftover disk of material from the previous interactions with star 3. Star 3 is no longer visible, but star 5 is now in view. It has a wider orbit and is drawing “lines” through the ejected gas and dust from star 1 as it orbits, like a knife through a bowl of icing.
Now, it’s time to zoom out even wider! At this stage, we’re getting closer to a view of the planetary nebula we see today. The fifth panel shows the same trio – stars 1 and 2 with star 5. Now, to mix it up again: As it orbits, star 5 continues to interact with the ejected gas and dust that slowly travels farther and farther from star 1 into the surrounding space, generating the system of large rings seen in the outer nebula.
The sixth panel portrays the scene as we observe it today – by zooming all the way out, we see only stars 1 and 2 in the Southern Ring Nebula.
Now that you’re oriented, read the full recap of the potential events.
Credit: NASA, ESA, CSA, STScI, Elizabeth Wheatley (STScI)

The complex shapes of the Southern Ring Nebula are more evidence of additional unseen companions – its ejections are thinner in some areas and thicker in others. A third closely interacting star may have agitated the jets, skewing the evenly balanced ejections like spin art. In addition, a fourth star with a slightly wider orbit might have also “stirred the pot” of ejections, like a spatula running through batter in the same direction each time, generating the enormous set of rings in the outer reaches of the nebula.

What about the very bright blue-white star in Webb’s images? Think of the fifth star as the most responsible party guest that continues to orbit the dying star slowly, predictably, and calmly.

The two images shown here each combine near-infrared and mid-infrared data to isolate different components of the nebula. The image at left highlights the very hot gas that surrounds the central stars. The image at right traces the star’s scattered molecular outflows that have reached farther into the cosmos.

The team’s paper, entitled ” The messy death of a multiple star system and the resulting planetary nebula as observed by JWST,” was published in Nature Astronomy on December 8.

Reference: “The messy death of a multiple star system and the resulting planetary nebula as observed by JWST” by Orsola De Marco, Muhammad Akashi, Stavros Akras, Javier Alcolea, Isabel Aleman, Philippe Amram, Bruce Balick, Elvire De Beck, Eric G. Blackman, Henri M. J. Boffin, Panos Boumis, Jesse Bublitz, Beatrice Bucciarelli, Valentin Bujarrabal, Jan Cami, Nicholas Chornay, You-Hua Chu, Romano L. M. Corradi, Adam Frank, D. A. García-Hernández, Jorge García-Rojas, Guillermo García-Segura, Veronica Gómez-Llanos, Denise R. Gonçalves, Martín A. Guerrero, David Jones, Amanda I. Karakas, Joel H. Kastner, Sun Kwok, Foteini Lykou, Arturo Manchado, Mikako Matsuura, Iain McDonald, Brent Miszalski, Shazrene S. Mohamed, Ana Monreal-Ibero, Hektor Monteiro, Rodolfo Montez Jr, Paula Moraga Baez, Christophe Morisset, Jason Nordhaus, Claudia Mendes de Oliveira, Zara Osborn, Masaaki Otsuka, Quentin A. Parker, Els Peeters, Bruno C. Quint, Guillermo Quintana-Lacaci, Matt Redman, Ashley J. Ruiter, Laurence Sabin, Raghvendra Sahai, Carmen Sánchez Contreras, Miguel Santander-García, Ivo Seitenzahl, Noam Soker, Angela K. Speck, Letizia Stanghellini, Wolfgang Steffen, Jesús A. Toalá, Toshiya Ueta, Griet Van de Steene, Hans Van Winckel, Paolo Ventura, Eva Villaver, Wouter Vlemmings, Jeremy R. Walsh, Roger Wesson and Albert A. Zijlstra, 8 December 2022, Nature Astronomy.
DOI: 10.1038/s41550-022-01845-2

The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).