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Researchers reveal a new class of molten planet
Artistic conception of the James Webb Space Telescope. Credit: NASA GSFC/CIL/Adriana Manrique Gutierre.
The exoplanet (a planet that orbits a star outside the Solar System), known as L 98-59 d, orbits a small red star about 35 light-years from Earth. Recent observations from the James Webb Space Telescope (JWST) and ground-based observatories suggested something unusual: the planet has an especially low density, given its size (which is about 1.6 times that of the Earth) and contains significant amounts of hydrogen sulfide in its atmosphere.
Until now, astronomers would have placed a planet like this into one of two familiar categories, either a rocky ‘gas-dwarf’ with an atmosphere of hydrogen, or a water-rich world made of deep oceans and ice. But these new findings reveal that L 98-59 d fits neither description – instead, it appears to belong to an entirely different class of planet containing heavy sulphur molecules.
A planet with an ocean of magma
This discovery suggests that the categories astronomers currently use to describe small planets may be too simple. … We may then ask: what other types of planet are waiting to be uncovered?
Lead author Dr Harrison Nicholls (Department of Physics, University of Oxford)
Using advanced computer simulations, a team of researchers from the University of Oxford, the University of Groningen, the University of Leeds and ETH Zurich, reconstructed the planet’s history from shortly after its birth to the present day – a span of nearly five billion years. By directly linking telescope observations to these detailed physical models of planetary interiors and atmospheres, they were able to determine what must be happening deep inside the planet.
Their results reveal that the mantle of L 98-59 d is likely molten silicate (similar to lava on Earth), with a global magma ocean extending thousands of kilometres beneath. This vast molten reservoir allows the planet to store extremely large amounts of sulphur deep inside its interior, over geologic timescales. The magma ocean also helps L 98-59 d to retain a thick hydrogen-rich atmosphere containing sulphur-bearing gases such as hydrogen sulphide (H2S). Normally, this would be lost to space over time, due to X-ray radiation produced by the host star.
Over billions of years, chemical exchanges between its molten interior and atmosphere have shaped what telescopes observe on L 98-59 d today. The researchers suggest that L 98-59 d may be the first recognised member of a broader population of gas-rich sulphurous planets sustaining long lived magma oceans. If so, the diversity of worlds in our galaxy may be even greater than previously imagined.
Lead author Dr Harrison Nicholls (Department of Physics, University of Oxford) said: ‘This discovery suggests that the categories astronomers currently use to describe small planets may be too simple. While this molten planet is unlikely to support life, it reflects the wide diversity of the worlds which exist beyond the Solar System. We may then ask: what other types of planet are waiting to be uncovered?’
How sulphur shapes the planet
What’s exciting is that we can use computer models to uncover the hidden interior of a planet we will never visit… this research shows that it is possible to reconstruct the deep past of these alien worlds – and discover types of planets with no equivalent in our own Solar System.
Co-author Professor Raymond Pierrehumbert (Department of Physics, University of Oxford)
JWST observations from 2024 pointed to the presence of sulphur dioxide, among other sulphur gases, high in L 98-59 d’s upper atmosphere. The team’s new models show that these gases can be created when ultraviolet light from the host star, the red dwarf L 98-59, triggers chemical reactions. At the same time, the magma ocean below acts as a massive reservoir for buffering these volatile gases, storing and releasing them over billions of years after the planet formed. This combination of deep volatile storage within its interior and ultraviolet-driven atmospheric chemistry explains the planet’s notable properties.
According to the simulations, L 98-59 d likely formed with a very large amount of volatile material and may once have looked more like a larger sub-Neptune planet. Over billions of years, it gradually shrank as it cooled and lost some of its atmosphere. Importantly, magma oceans represent the universal initial states of all rocky planets (including the Earth and Mars), so new insights into magma ocean physics can inform us about our own world and its primordial history.
Co-author Professor Raymond Pierrehumbert (Department of Physics, University of Oxford) said: ‘What’s exciting is that we can use computer models to uncover the hidden interior of a planet we will never visit. Although astronomers can only measure a planet’s size, mass and atmospheric composition from afar, this research shows that it is possible to reconstruct the deep past of these alien worlds – and discover types of planets with no equivalent in our own Solar System.’
A wealth of new data are being delivered by JWST, with more to come from the upcoming Ariel and PLATO missions. The research team intend to apply their simulations to these new measurements, using machine learning methods, to map the diversity of worlds beyond the Solar System, and make connections with their early histories. In doing so, we will learn about how planets form, how they evolve, and thereby set expectations for which might be habitable (or not).
Dr Richard Chatterjee, (University of Leeds/ University of Oxford) said: ‘Our computer models simulate various planetary processes, effectively enabling us to turn back the clock and understand how this unusual rocky exoplanet, L 98-59 d, evolved. Hydrogen sulphide gas, responsible for the smell of rotten eggs, appears to play a starring role there. But, as always, more observations are needed to understand this planet and others like it. Further investigation may yet show that rather pungent planets are surprisingly common.’
The study ‘Volatile-rich evolution of molten super-Earth L 98-59 d’ has been published in Nature Astronomy.
For more information about this story or republishing this content, please contact [email protected]
An artist’s impression of L 98-59 d in orbit around its host star, the red dwarf L 98-59. Credit: Mark A. Garlick / markgarlick.com
The coffee dispenser at the Headington Waitrose is out of order and not for the first time according to reports, leaving customers disappointed they can no longer access their free cappuccino or flat white using their Waitrose card.
The Headington News said: “The Headington Waitrose free coffee machine is out of order again today (Saturday 29 August).”
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The notice on the machine at the store in Old High Street says: “The coffee machine is currently out of order. Apologies for the inconvenience.”
The issue is not a universal problem – coffee machines at other Waitrose stores are working well.
The Waitrose chain, owned by the John Lewis Partnership, restored its free coffee offer in January 2025.
Following outrage over the withdrawal of the offer during the pandemic, the company told the nine million members on its My Waitrose loyalty scheme they would again be entitled to a complementary americano, cappuccino, latte or tea once a day regardless of whether they bought anything – as long as they have their own reusable cup.
In a statement, Waitrose said at the time: “Some of our My Waitrose members like to have the free coffee before they shop or during the shop, rather than afterwards, so we are just offering a bit of flexibility in response to customer feedback.”
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There were queues at coffee stations and complaints from customers that the offer was attracting the “wrong type of shopper” when Waitrose introduced the perk in 2013.
In 2017, it cracked down on ‘freeloaders’ by forcing members to buy something before pouring themselves a free hot drink.
The scheme was scrapped during the Covid crisis, but reintroduced in November 2022 – again for customers making a purchases. This is no longer a requirement.
Thames Valley Police has launched an investigation after a pigeon was killed in a wildlife crime incident in Plover Drive, Oxford, at around 6.50pm on August 24.
The force said that two teenage boys used a catapult to knock a pigeon from a tree before the bird was attacked by three smaller terrier-type dogs that were with them.
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Descriptions of the two boys have been released with the first described as wearing a black sleeveless vest, dark-coloured bottoms, black trainers with white soles.
In addition he had a black-and-white flat-peaked cap worn backwards and was believed to have been carrying a catapult.
The second was reportedly wearing a light-coloured T-shirt and blue jeans, with brown, medium-length hair.
He was also seen carrying an unidentified item.
A spokesperson for the police said: “We are keen to hear from anyone who witnessed this incident or who may recognise those involved from the descriptions above.
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“We would also like to hear from anyone with dashcam footage from the Plover Drive area between 6.30pm and 7pm on 24 August that may assist our investigation.
“Wildlife crime has a real impact on our communities, and we take reports of offences against wild animals and birds seriously.
” If you have any information, please contact the force on 101 or report online, quoting reference 43260448136.”
Following the incident in North Way, Barton on Monday, August 17, Thames Valley Police said it wanted the public’s help to locate Oxford local Arthur McDonagh.
The force warned the public not to approach the 33-year-old, but instead to call the police if they see him.
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On Tuesday, August 18, a spokesperson said: “Thames Valley Police is appealing for the public’s help to locate Arthur McDonagh, aged 33, from Oxford.
“He is wanted in connection with a serious assault that happened in North Way, Barton, yesterday (August 17).
“Arthur is known to frequent the Garsington area.
“If you have any information about his whereabouts call 101 or make a report online, quoting reference 43260426989.
“If you see him, do not approach him, but instead call 999.”
Well over a week on, the police has revealed that Mr McDonagh remains at large.
The spokesperson said today (Saturday, August 29): “Arthur McDonagh remains outstanding; our enquiries are ongoing to locate him.”
During the incident emergency services were called to Barton Village Road at about 11.10am.
The force closed North Way to the junction with Edgecombe Road while officers carried out their enquiries.
A damaged white pickup truck was left in the middle of the street, surrounded by broken glass and with what appeared to be blood splattered on the rear right-hand side.
The white pickup truck could be seen behind the police cordon.
There were multiple reports of different weapons being used during the assault, but Thames Valley Police confirmed that they do not believe an axe, bat or machete were used in the attack.
But police declined to say what weapon they do believe was used in the assault.
The force confirmed a man was taken to hospital for treatment, and that he was in a stable condition, and they thanked the local community for their support.
Following the incident, Mike Rowley, Labour councillor for Barton and Sandhills, said his thoughts were with the victim and praised local officers for their response.
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He said: “My thoughts are with the victim as the incident sounds horrible.
“I am in touch with the police, but I’m not expecting any updates yet as their priority is finding the offender and making sure there aren’t any further offences.”
Appeals for public help in finding individuals by the police can relate to suspects, witnesses or others who may have vital information in relation to the incident.
They do not mean the person is to blame nor do they imply guilt.
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