Royal Observatory of Belgium

Battle of the Scientists 2026

Flore Van Maldeghem — Mon, 02 Mar 2026 09:01:37 +0000

On February 6, six researchers, including two from the Royal Observatory of Belgium, shared their knowledge on solar storms and space weather with a special audience during the eleventh Battle of the Scientists. 2,700 enthusiastic primary school children, 500 of whom were in the auditorium and 2,200 via livestream, voted for the most insightful presentation. The Belgian Space Weather Centre (STCE) and The floor is yours joined forces to organise this edition.

The Battle of the Scientists is a competition in which scientists present their research so clearly that even children can understand it. Even more, the children have the final say. They present, keep track of time, form a children’s jury and vote for the clearest scientist. This year, this honor went to De Mozaïek primary school from Kessel-Lo.

After each presentation, the children’s jury gives critical feedback and the children from the audience can ask questions.

Speaker Cis Verbeeck from the Royal Observatory of Belgium.

The central theme was ‘space weather’. This concerns the eruptions and particle streams from the Sun, which affect the Earth and our technology. Think, for example, of solar storms (sudden bursts of energy on the Sun), solar wind (a stream of charged particles coming from the Sun), and gigantic clouds of charged particles that the Sun explosively ejects into space. In Belgium, we even have a space weather centre where scientists collect and analyse data and issue space weather reports. The STCE is located in Uccle and is known far beyond the country’s borders.

The consequences of space weather for us? Satellites failing, disrupted GPS systems and in extreme cases even damaged electricity networks on Earth.

Speaker Andreas Debrabandere from the Royal Observatory of Belgium.

Based on a short video, the pupils selected the speakers listed below (Dutch).

Cis Verbeeck(Royal Observatory of Belgium): “Hoe voorspel je een super-zonnestorm?” (presentation)
Esmee Tackx en Stefan De Raedemaeker(KU Leuven): “Marsrover Marcel en de wraak van de zon” (presentation)
Dries Van Baelen(Defence): “Hoe bel je een soldaat in het midden van de woestijn?” (presentation)
Myrthe Flossie(KU Leuven): “Help! Zonnedeeltjes vallen astronauten aan” (presentation)
Andreas Debrabandere(Royal Observatory of Belgium): “Een eclips bouwen om ruimteweer te zien” (presentation)

In the end, Myrthe Flossie (KU Leuven) was chosen as the winner with her presentation on how we can protect astronauts from dangerous plasma particles from a solar storm. Dries Van Baelen (Defence) came in second and talked about HF radio and how to ensure that soldiers can continue to communicate safely with each other, even during a solar storm.

You can also watch the entire show on YouTube!

The Battle of the Scientists 2026 is an organisation of The Floor is Yours in collaboration with the Solar-Terrestrial Centre of Excellence (STCE), with the support of Redwire, KU Leuven and the Research Foundation – Flanders (FWO).

From left to right: Cis, Stefan, Myrthe, Andreas, Esmee and Dries.

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Daunting image of a pair of stars and its surrounding nebula

Le Binh San Pham — Thu, 26 Feb 2026 15:35:23 +0000

Last Monday, the European Southern Observatory (ESO) released a new Picture of the Week. It is an image of a pair of stars and its surrounding nebula. The two stars constitute the binary system AFGL 4106, which was recently studied in a recent Astronomy and Astrophysics paper, of which René Oudmaijer of the Royal Observatory of Belgium is a co-author.

The binary system AFGL 4106 (black dots at the centre) and its surrounding nebula (in orange). Image taken with ESO’s Very Large Telescope (VLT). Credit: ESO/G. Tomassini et al.

The two stars, shown as a pair of black dots at the centre of the image, are an old stellar couple. As most stars are born in pairs, a big question for astronomers is: how does being in a couple impact a star’s death?

Before dying, stars expel huge amounts of gas and dust, ingredients for a growing nebula. The massive stars shown here are at close yet distinct late stages of their lifecycles, with one having blown off enough mass to produce a dusty surrounding envelope (shown in orange in the picture).

In a recent paper led by Gabriel Tomassini (Université Côte d’Azur, France) and of which René Oudmaijer is co-author, researchers have mapped this debris and precisely characterised the central stars.

Imaging astronomical objects close to stars poses a challenge due to the overpowering effect of a star’s brightness and, in fact, the stars themselves appear in black as their brightness saturated the detector of the instrument used to make this image.

Fortunately, the SPHERE instrument on the VLT is well equipped to deal with large contrasts in light levels, enabling a detailed study of both the high luminosity stars and the faint surrounding nebula for the first time. Moreover, it can correct the blur caused by atmospheric turbulence, delivering very sharp images.

The shape of the nebula reveals the significant impact the companion is having on the gas ejection of the dying star, introducing asymmetries and shifting the clouds of gas and dust away from a perfectly spherical shape. Further observations of star systems like this one allow scientists to better understand how the presence of companions affects the death of stars.

The ESO image release: https://www.eso.org/public/images/potw2608a/

The research paper

Tomassini et al., Characterising the post-red supergiant binary system AFGL 4106 and its complex nebula with SPHERE/VLT, Astronomy and Astrophysics, 706, A5, 13 pp., 2026. https://doi.org/10.1051/0004-6361/202557705

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ROB and Belnet launch first span of Belgium’s resilient optical timing network

Le Binh San Pham — Wed, 21 Jan 2026 17:03:08 +0000

The Royal Observatory of Belgium (ROB) and Belnet are delighted to announce that – as part of the BOOSTED project – the first span of the Belgian time and frequency network is operational since December 4, 2025.

BOOSTED aims to develop an optical network for time and frequency transfer (T&F) in Belgium and connect it to the European metrology network. As the BOOSTED network is relying on optical links, it is insensitive to GNSS threats (like jamming, spoofing, …), supporting the development of resilient infrastructure.

This initial step enables already the delivery of an accurate timing signal, generated by the atomic clocks operated at the ROB, to 2 Belnet points-of-presence and 1 commercial data centre in the Brussels region. More specifically, the first 2 optical timing links are achieving an accuracy at the sub nanosecond level, making it more accurate than the timing signals currently generated by PTP and GNSS.

In the coming months, we will implement the next spans and will continue to connect users who have already expressed their desire to benefit from this service. If your organisation is also interested in joining the T&F network, be sure to register for the second time & frequency workshop, which will take place on March 10, 2026. This workshop, organised by the ROB and Belnet, will outline the progress made within the BOOSTED project and the steps that have already been taken in developing a sustainable T&F infrastructure in Belgium. Registration for this workshop is available via the following link: https://events.spacepole.be/event/269/.

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Seismic Activity in/around Belgium in 2025

Le Binh San Pham — Mon, 05 Jan 2026 14:59:39 +0000

In 2025, 137 earthquakes were located by the Royal Observatory of Belgium in or near Belgium. On Belgian territory, no earthquake was large enough to have been felt.

In 2025, 137 natural earthquakes were measured by the Royal Observatory of Belgium in a zone between 1° and 8°E longitude and 49° and 52°N latitude (Figure 1). 37 natural earthquakes were located on Belgium territory, although none of these events were felt by the local population as either these earthquake’s magnitudes were too small, or their focal depths were too deep. The largest earthquake in Belgium occurred on 31 December 2025 in Heppenbach and had a local magnitude of M_L=1.7. The 2025 ROB catalogue is complete for natural earthquakes with a magnitude M_L larger than 1.0. Events with magnitudes lower than 1.0 were also routinely detected where the Belgian seismic network is denser on the Belgian property. Outside Belgium, only those events that were large enough to be detected by the Belgian seismic network were included in the 2025 seismic catalogue. Most earthquakes recorded in 2025 occurred in regions with documented historical seismic activity (Figure 2).

In 2025, the Royal Observatory of Belgium (ROB) also measured four induced events, 307 quarry blasts and 4 explosions offshore linked to controlled explosions of WW1 and WW2 bombs by the Belgian, Dutch or French Armies.

In comparison, last year in 2024, 141 earthquakes were detected in and around Belgium.

Figure 1: Events recorded in 2025 by the Belgian Seismic Network of the Royal Observatory of Belgium. 37 earthquakes occurred on Belgian territory.

Figure 2: Earthquakes recorded in 2025 by the Belgian Seismic Network of the Royal Observatory of Belgium. The full Belgian seismic catalogue is shown in white. Earthquakes measured in 2025 occurred in regions with documented historical seismic activity.

Website: https://seismologie.be/en

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Proba-3 is 1 year in space

Le Binh San Pham — Tue, 09 Dec 2025 16:36:34 +0000

December 5, 2024 – 1 year ago, the duo satellite Proba-3 left Earth to head to space. The telescope ASPIICS, whose task is to make perfect total solar eclipses from space, was onboard. The launch went flawless.

December 5, 2025 – exactly 1 year later, ASPIICS has already delivered a wealth of amazing pictures of the solar atmosphere close to its surface, a treasure box for solar scientists.

A peek in the treasure box

The picture below is a white-light image of the solar corona taken by ASPIICS on September 9, 2025. The corona has a shape typical for a maximum in the solar activity cycle, with streamers visible all around the solar limb. A Coronal Mass Ejection is seen propagating towards the west (right in the image).

Credit: ESA/Proba-3/ASPIICS

The next image/video shows the Sun and the solar atmosphere on July 16, 2025. The green images are more detailed compared to the red images. A Coronal Mass Ejection is seen propagating towards the west (right in the image). The middle EUV image is taken by SDO/AIA. The green white-light image is taken by ASPIICS, the red white-light image is from SOHO/LASCO.

Click on the image to get the movie. Credit: ESA/Proba-3/ASPIICS.

Reactions from a few people of the Belgian ASPIICS team

Laurent Dolla, Science Planner – one can never get bored

ASPIICS is really a cutting-edge instrument, for which I plan the observations. Our images are ‘clean’ and of exceptional good quality. It was a surprise that the instrument achieves this even with “normal” exposure times. We can now see features that were never seen before because they clearly stand out from the background. For us, solar scientists, this is very exciting. When I wake up in the middle of the night, it’s not uncommon that I start working. With ASPIICS, one can never get bored.

Andrei Zhukov, Principal Investigator – being on the forefront of solar physics

I joined the Proba-3 team already in 2009. Now, after launch and commissioning, I can finally do what I love to do: science. We make total solar eclipses, almost as on an assembly line, which feels for me as being a kid on a science playground toying with unprecedented images. In June 2025, I witnessed the first huge prominence eruption with ASPIICS. We could already see it in our images before they were even cleaned! I’m looking forward to presenting the science results at the annual meeting of the American Geophysical Union in December 2025.

Zoe Zontou, Instrument Operator – this is the coolest job ever

It is so cool that we make total solar eclipses from space and I’m an operator of this instrument! I come from a totally different background than solar physics, so I was thrilled when I joined the team in May 2025. The day that we showed the first official science image to the public was really exciting. I already learned so many things about the solar atmosphere. ASPIICS showed me that I will never stop asking questions and never stop learning. I love it and look forward to meeting even more interesting people and discovering more on solar physics and our Sun!

Andreas, Instrument Operator – bitten by the heliophysics bug

I plan and write commands for the telescope, but I also do surveillance of the newly arrived data. This means that I’m one of the first taking a glimpse at the images! I’m really on the front line to see things which were never seen before. The commanding of ASPIICS can in theory be done a bit beforehand, but in the early phases of the mission I was sometimes at the Mission Operations Center in Redu where I had to take immediate action and call to remote ground stations. Together we had to command the satellites and ASPIICS in real-time. Since my PhD, I have had big dreams. Now, it is amazing to be part of this passionate researchers community and figure out important open questions on the Sun.

Late growth spurt of young stars allows giant planets to form after all

Le Binh San Pham — Wed, 03 Dec 2025 16:49:32 +0000

Brussels, 3 December 2025 – By measuring the rate at which young stars grow, astronomers discovered that contrary to earlier expectations, young stars appear to grow much faster in the later stages of their formation than at the onset. So, much like humans, intermediate mass stars undergo a growth spurt and have a voracious appetite during their adolescence. This finding, reported by an international team led by Sean Brittain of Clemson University USA, and including René Oudmaijer of the Royal Observatory of Belgium, solves a long-standing problem with giant planets that are routinely detected around stars of intermediate mass, but should not exist.

Young stars begin their life surrounded by a disk of gas and dust. Over the past 40 years, astronomers have established that the material in this disk gradually falls onto the young star as it grows and matures. The disk is ionized by radiation from the star, which causes it to spread, like a mound of clay on a potter’s wheel. Some of this material falls onto the star, some is blown away, and some of it forms into planets. As the disk dissipates, the rate at which material falls onto the star decreases as well. Ultimately the star reaches its final mass and further planet formation comes to a halt.

This image combines data from Webb’s near- and mid-infrared observations of the Pillars of Creation, including thousands of stars that show up in near-infrared light, and all the dust that pops out in mid-infrared light.
NASA, ESA, CSA, STScI; Image Processing: Joseph DePasquale (STScI), Alyssa Pagan (STScI), Anton Koekemoer (STScI). Source: https://science.nasa.gov/asset/webb/pillars-of-creation-nircam-and-miri-composite-image/

This theory does a very good job at explaining the formation of stars similar to the Sun, but it has been challenged by the observations of young stars that are slightly more massive. These stars were found to be gaining mass at much higher rates than expected.

How can astronomers measure the growth rate of stars? As Professor Sean Brittain explains, ‘When material falls onto a star, a lot of energy is released, just like when you drop a chair it will make a noise or even break. In the case of material being accreted, the energy released is much greater. We can see this as extra radiation coming from the system, and this allows us to determine the rate at which the stars grow in mass.’

The team studied young stars, also referred to as Herbig stars that are hotter and more massive than our Sun. Their accretion rates were already well studied and – as expected – observed to decrease with age as the stars reach their full maturity. However, it also meant that in their earlier phases, the stars must accrete at even higher rates than observed now.

Team member Dr René Oudmaijer, from the Royal Observatory of Belgium, says, ‘This implied that the disks surrounding these stars must start out to be very massive indeed. This would pose a problem because such massive disks would be unstable and break up before planets even have the chance to be formed.’

Recent surveys identified stars that would evolve into Herbig stars which prompted the team to study how the accretion rates of these younger objects would differ from those of the Herbig stars. What they found was unexpected as team member Dr Gwendolyn Meeus of the Universidad Autónoma de Madrid in Spain comments: ‘Instead of higher accretion rates, we found values that were up to 30 times lower than those of the Herbig stars. In a way this would solve the mass problem, as the disk does not need to be so massive to begin with.’ But this posed yet another problem as Brittain continues: ‘Theory would predict that the stars accrete less material over time, not more. This new finding needs an explanation based on well-grounded physics if we are to change our current thinking.’

The team found that there was one key ingredient missing in the models so far. The so-called Herbig stars have high temperatures, but their precursors start out much cooler. It is precisely the stellar temperatures that affect the disks and determine how quickly they lose their material to the star. A star that gets hotter will gradually emit much more ultraviolet radiation. This in turn ionizes the gas in the circumstellar disks, which then results in an increasingly larger accretion onto the star.

The long-standing mystery that gas giant planets around intermediate mass stars were observed, but not predicted to exist, appears to be solved with this work. ‘Indeed,’ as team member Josh Kern of Clemson University concludes, ‘this unexpected late growth spurt opens up the possibility for giant planets to be formed in the earlier stages, when the stars are still much cooler, after all.’

The findings are published in the Astronomical Journal.

The article:
Brittain et al., ‘Evolution of the Accretion Rate of Young Intermediate Mass Stars: Implications for Disk Evolution and Planet Formation’ The Astronomical Journal, DOI: 10.3847/1538-3881/ae1a42, published online.

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Northern Lights Over Belgium

Le Binh San Pham — Wed, 12 Nov 2025 15:38:48 +0000

November 12, 2025, very early in the morning. Colleagues from the STCE, the Belgian Space Weather Centre, admired the northern lights from their terrace in Brussels and are amazed by the show of colours. After all, it is quite exceptional to be able to observe this phenomenon in Belgium (let alone in the middle of a city with a lot of light pollution), even if our Sun is now in the most active phase of its cycle.

Image credits: Nancy Narang (Royal Observatory of Belgium).

Indeed, the Sun is the cause of these northern lights. In recent days, our Earth has been in the sights of a very active solar region. This region produced several solar flares of the highest category (X). These were accompanied by eruptions of solar plasma and protons, which are very fast particles. The successive plasma clouds were directed toward Earth and were launched with increasingly higher speeds.

Stormy Nights

Last night, the first of these solar clouds arrived at Earth. They caused very strong disturbances in our magnetic field. This is measured using ground-based instruments called magnetometers, which, for Belgium, we have installed in Dourbes and Manhay. Based on these measurements, a local K-index is compiled that reflects the disturbance of the magnetic field in our region. A local K > 8 indicates the possibility of visible northern lights. The graph below clearly shows that this condition was met last night.

Magnetic Activity Indices for Belgium (source)

Should we be concerned?

The northern lights are primarily a beautiful spectacle to be enjoyed to the fullest, but a geomagnetic storm can affect our technology. In addition to the geomagnetic field, they also disrupt the ionosphere, a layer in our atmosphere that is crucial for communication. Last night, warnings were sent to the aviation industry to alert them to disruptions in their radio communications. GPS positioning may also be slightly less accurate during a storm. In countries closer to the poles, disruptions can occur in the electricity grid. Network operators and the Defence forces in our country were therefore also notified. The STCE is monitoring the situation closely.

What can we expect next?

Yesterday, on November 11, this active region launched the most recent solar flare and plasma cloud. This cloud left the sun at a speed of more than 1500 km per second and is now racing through space toward Earth. We estimate it will reach us tonight. We can therefore expect additional disruption to our magnetic field. Space weather will thus remain stormy for a few more days.

In addition, the sun is still very active and the area causing all the disturbances is still facing Earth. New solar flares and plasma clouds cannot be ruled out. The STCE forecasters are facing a busy week. And if we are lucky, we may also see the northern lights tonight, as long as the clouds do not spoil the show: look north!

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Scientists of the Bepicolombo mission met at the Royal Observatory of Belgium

Le Binh San Pham — Mon, 13 Oct 2025 11:18:31 +0000

Tuesday, September 30, 2025, marked the beginning of a 3-day workshop gathering international members from the BELA and MORE experiments onboard the BepiColombo mission to Mercury.

The joint ESA and JAXA mission was launched in 2018 and is about to reach the end of its long voyage to Mercury where it is slated to insert into orbit at the end of 2026. Scientists are now actively perfecting all the necessary tools and techniques to make the most of the forthcoming measurements and scientific data, which will offer an unprecedented window into the elusive interior of the planet.

The Mercury Orbiter Radio-science Experiment (MORE) onboard BepiColombo will measure Mercury’s gravity field, including small temporal variations, for example due to tides. The BepiColombo Laser Altimeter (BELA) will map the surface of the planet with groundbreaking accuracy and will determine subtle motions caused by tides and rotation. The data from both these experiments will allow scientists, among which several from the Royal Observatory of Belgium (ROB), to infer properties of the planet’s deep interior.

Scientists from the ROB also participated in another meeting on BepiColombo at the Paris Observatory on Thursday and Friday of the same week. Members of the SIMBIO-SYS team, the spectrometer and camera of BepiColombo, discussed the latest advances in the preparation of the data analysis. By precisely measuring the rotation of Mercury, SIMBIO-SYS will complement data from MORE and BELA to probe the deep interior of Mercury.

Van Hoolst is Co-I of MORE, Co-I of SIMBIO-SYS, team member and WG lead of BELA
Rivoldini is Co-I and WG lead of BELA
Yseboodt, R.-M. Baland, and J. Rekier are team members of BELA

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WiseNight 2025 Festival at the Planetarium

Le Binh San Pham — Fri, 19 Sep 2025 17:01:18 +0000

On 26 September 2025, come to the free WiseNight festival at the Planetarium of the Royal Observatory of Belgium.

WiseNight is a fun and inclusive event that aims to bring science and scientists in interactive contact with the public.

WiseNight is part of the European Researchers’ Night, taking place everywhere in Europe simultaneously. The aim is to show that science is about passion, teamwork and for anyone with an insatiable curiosity to discover and change the world.

In 2025, the WiseNight Festival will take place at two different places:

On 26 September 2025 at the Planetarium of Brussels
On 27 September 2025 at the Museum of Natural Sciences of Belgium

On the programme at the Planetarium: workshops and demonstrations for children and young people, interaction and exchanges with researchers, a splendid photo exhibition featuring today’s inspiring scientists and 360° movies.

The festival is free of charge, but registration is required for practical purpose. For more information, visit the site www.wisenight.eu.

The WiseNight is organised by BeWiSe (Belgian Women in Science) with the participation of the Planetarium of the Royal Observatory of Belgium, Soapbox Science Brussels, the Museum of Natural Sciences of Belgium, the Vrije Universiteit Brussel, the Von Karman Institute and the associations Ekoli and GoodPlanet Belgium. This project received funding from the European Union.

Full programme for the WiseNight festival at the Planetarium: https://planetarium.be/storage/files/wise-night-2025-full-program.pdf

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Webb reveals new details of the Butterfly Nebula

Le Binh San Pham — Wed, 10 Sep 2025 18:08:02 +0000

The NASA/ESA/CSA James Webb Space Telescope has revealed new details in the core of the Butterfly Nebula, NGC 6302. From the dense, dusty torus that surrounds the star hidden at the centre of the nebula to its outflowing jets, the Webb observations reveal many new discoveries that paint a never-before-seen portrait of a dynamic and structured planetary nebula. Those new discoveries are published in a Monthly Notices of the Royal Astronomical Society science paper, to which Peter van Hoof from the Royal Observatory of Belgium and Joris Blommaert from the Vrije Universiteit Brussel (VUB) contributed.

Three views of the Butterfly Nebula, also called NGC 6302. The left and middle images shown here highlight the bipolar nature of the Butterfly Nebula in optical and near-infrared light captured by the NASA/ESA Hubble Space Telescope. The new Webb + ALMA image on the right zooms in on the centre of the Butterfly Nebula and its dusty torus, providing an unprecedented view of its complex structure. Credit: ESA/Webb, NASA& CSA, M. Matsuura, J. Kastner, K. Noll, ALMA (ESO/NAOJ/NRAO), M. Zamani (ESA/Webb). Source: https://esawebb.org/images/weic2517a.

The Butterfly Nebula, a bipolar planetary nebula

The Butterfly Nebula, located about 3400 light-years away in the constellation Scorpius, is one of the best-studied planetary nebulae in our galaxy. This stunning nebula was previously imaged by the NASA/ESA Hubble Space Telescope.

Planetary nebulae are among the most beautiful and most elusive creatures in the cosmic zoo. These nebulae form when stars with masses between about 0.8 and 8 times the mass of the Sun shed most of their mass at the end of their lives. The planetary nebula phase is fleeting, lasting only about 20 000 years.

Contrary to the name, planetary nebulae have nothing to do with planets: the naming confusion began several hundred years ago, when astronomers reported that these nebulae appeared round, like planets. The name stuck, even though many planetary nebulae aren’t round at all and the Butterfly Nebula is a prime example of the fantastic shapes that these nebulae can take.

The Butterfly Nebula is a bipolar nebula, meaning that it has two lobes that spread in opposite directions, forming the ‘wings’ of the butterfly. A dark band of dusty gas poses as the butterfly’s ‘body’. This band is actually a doughnut-shaped torus that’s being viewed from the side, hiding the nebula’s central star — the ancient core of a Sun-like star that energises the nebula and causes it to glow. The dusty doughnut may be responsible for the nebula’s insectoid shape by preventing gas from flowing outward from the star equally in all directions.

Picture of the Butterfly Nebula, NGC 6302, taken by the NASA/ESA Hubble Space Telescope. Credit: ESA/Webb, NASA & CSA, K. Noll, M. Zamani (ESA/Webb). Source: https://esawebb.org/images/weic2517d/.

New structures revealed by an international research team

This new Webb image zooms in on the centre of the Butterfly Nebula and its dusty torus, providing an unprecedented view of its complex structure. The image uses data from Webb’s Mid-InfraRed Instrument (MIRI) working in integral field unit mode. This mode combines a camera and a spectrograph to take images at many different wavelengths simultaneously, revealing how an object’s appearance changes with wavelength. The research team supplemented the Webb observations with data from the Atacama Large Millimetre/submillimetre Array (ALMA), a powerful network of radio dishes.

Researchers analysing these Webb data, including Peter van Hoof from the Royal Observatory of Belgium and Joris Blommaert from the VUB, identified nearly 200 spectral lines, each of which holds information about the atoms and molecules in the nebula. These lines reveal nested and interconnected structures traced by different chemical species.

The research team has pinpointed the location of the Butterfly Nebula’s central star, which heats a previously undetected dust cloud around it, making the latter shine brightly at the mid-infrared wavelengths that MIRI is sensitive to. The location of the nebula’s central star had remained elusive until now, because this enshrouding dust renders it invisible at optical wavelengths. Previous searches for the star lacked the combination of infrared sensitivity and resolution necessary to spot its obscuring warm dust cloud. With a temperature of 220 000 Kelvin, this is one of the hottest known central stars of a planetary nebula in our galaxy.

Image of the Butterfly Nebula, NGC 6302, which combined infrared data from the NASA/ESA/CSA James Webb Space Telescope with submillimetre observations from the Atacama Large Millimetre/submillimetre Array (ALMA). Credit: ESA/Webb, NASA & CSA, M. Matsuura, ALMA (ESO/NAOJ/NRAO), M. Zamani (ESA/Webb). Source: https://esawebb.org/images/weic2517b/.

This blazing stellar engine is responsible for the nebula’s gorgeous glow, but its full power is constrained by the dense band of dusty gas that surrounds it: the torus. The new Webb data show that the torus is composed of crystalline silicates like quartz as well as irregularly shaped dust grains. The dust grains have sizes on the order of a millionth of a metre — large, as far as cosmic dust is considered — indicating that they have been growing for a long time.

Outside the torus, the emission from different atoms and molecules takes on a multilayered structure. The ions that require the largest amount of energy to form are concentrated close to the centre, while those that require less energy are found farther from the central star. Iron and nickel are particularly interesting, tracing a pair of jets that blast outward from the star in opposite directions.

Intriguingly, the team also spotted light emitted by carbon-based molecules known as polycyclic aromatic hydrocarbons, or PAHs. They form flat, ring-like structures, much like the honeycomb shapes found in beehives. On Earth, we often find PAHs in smoke from campfires, car exhaust, or burnt toast. Given the location of the PAHs, the research team suspects that these molecules form when a ‘bubble’ of wind from the central star bursts into the gas that surrounds it. This may be the first-ever evidence of PAHs forming in a planetary nebula, providing an important glimpse into the details of how these molecules form.

The results have been published in Monthly Notices of the Royal Astronomical Society.

The complicated structure at the centre of the Butterfly Nebula, NGC 6302. There is a bright source at the centre of the image, labeled ‘dying star’. This is surrounded by greenish nebulosity and several looping lines in cream, orange and pink. One of these lines appears to form a ring oriented vertically and nearly edge-on around the bright source at the centre. This ring is labeled in several different places to indicate the near and far sides of a structure called the torus, a dust lane running along the torus and an area where the torus is ionised. Other lines trace out a figure eight shape. These lines are labeled to indicate the inner bubble as well as where the bubble intersects with the torus. Moving outward from these complex lines and green nebulosity, there is a section of red light on either side of the object, labeled ‘outer bubble’. The upper-right and lower-left corners of this image show a purple streak pointing out of the image. These purple streaks are labeled ‘jet’. Credit: ESA/Webb, NASA & CSA, M. Matsuura, ALMA (ESO/NAOJ/NRAO), M. Zamani (ESA/Webb). Source: https://esawebb.org/images/weic2517c/.

More information

Webb is the largest, most powerful telescope ever launched into space. This telescope is an international partnership between NASA, ESA and the Canadian Space Agency (CSA). Scientists of the Royal Observatory of Belgium are involved in several research projects using the Webb. See for example this news published on August 2023.
The science paper: Matsuura et al., The JWST/MIRI view of the planetary nebula NGC 6302 – I. A UV-irradiated torus and a hot bubble triggering PAH formation. Monthly Notices of the Royal Astronomical Society, Volume 542, Issue 2, September 2025, Pages 1287–1307, https://doi.org/10.1093/mnras/staf1194

This publication is adapted from an ESA press release. Other images of this news can be found on the ESA press release.

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