It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Thursday, December 18, 2025
US Congress ends Assad-era Syria sanctions, opening door to investment The US Congress has voted to permanently repeal sweeping sanctions imposed on Syria under former leader Bashar al Assad, clearing the way for foreign investment and marking a significant shift in Washington’s policy towards the war-ravaged country following the rise of a new government.
The US Congress on Wednesday permanently ended sanctions imposed on Syria under ousted leader Bashar al Assad, paving the way for the return of investment to the war-ravaged nation.
US President Donald Trump had already twice suspended the implementation of the sanctions in response to pleas from Saudi Arabia and Turkey, allies of the new government headed by former jihadist Ahmed al Sharaa.
However, Sharaa had sought a permanent end to the measures, fearing that as long as they remained on the books they would deter businesses wary of legal risks in the world’s largest economy.
The Senate passed the repeal of the 2019 Caesar Act as part of a sweeping annual defence package, voting 77 to 20 in favour of the legislation. The bill had already been approved by the House of Representatives and is expected to be signed by Trump.
The repeal, broadly backed by lawmakers from both parties, “is a decisive step towards giving the Syrian people a real chance to rebuild after decades of unimaginable suffering,” said Senator Jeanne Shaheen, the top Democrat on the Senate Foreign Relations Committee.
The Caesar Act, named after an anonymous photographer who documented atrocities in Assad’s prisons, severely restricted investment and cut Syria off from the international banking system.
The law was intended to prevent an influx of foreign businesses rebuilding Syria at a time when it appeared Assad had prevailed after more than a decade of brutal civil war. The conflict triggered a massive flow of refugees towards Europe and helped fuel the rise of the Islamic State extremist movement.
Sharaa’s fighters seized Damascus a year ago in a lightning offensive.
Sharaa – now dressed in a business suit and seeking improved relations with the West – has impressed Trump, including during their first meeting on the US leader’s May trip to Riyadh.
(FRANCE 24 with AFP)
Trump slaps full travel ban on seven more countries, including Syria
US President Donald Trump on Tuesday added Burkina Faso, Laos, Mali, Niger, Sierra Leone, South Sudan, and Syria as well as Palestinian Authority passport holders to a full travel ban. The decision to include Syria, a country Trump has moved to rehabilitate internationally, came days after three US nationals were killed in an attack in the central town of Palmyra.
President Donald Trump on Tuesday expanded a US travel ban by barring nationals of seven more countries including Syria, as well as Palestinian Authority passport holders, from entering the United States.
Trump, who has long campaigned to restrict immigration and has spoken in increasingly strident terms, moved to ban foreigners who "intend to threaten" Americans, the White House said.
He also wants to prevent foreigners in the United States who would "undermine or destabilize its culture, government, institutions or founding principles," a White House proclamation said.
Trump's move comes days after two US troops and a civilian were killed in Syria, which Trump has moved to rehabilitate internationally since the fall of longtime ruler Bashar al-Assad.
Syrian authorities said the perpetrator was a member of the security forces who was due to be dismissed for "extremist Islamist ideas."
The Trump administration had already informally barred travel from Palestinian Authority passport holders as it acts in solidarity with Israel against the recognition of a Palestinian state by other leading Western countries including France and Britain.
In a series of new actions, the White House said that Trump was also imposing partial travel restrictions on citizens of other African countries including the most populous, Nigeria, as well as Black-majority Caribbean nations. Ramping up anti-immigrant tone
Trump in recent weeks has used increasingly loaded languages in denouncing African-origin immigrants.
At a rally last week he said that the United States was only taking people from "shithole countries" and instead should seek immigrants from Norway and Sweden.
He also recently described Somalis as "garbage" following a scandal in which Somali Americans allegedly bilked the government out of money for fictitious contracts in Minnesota.
Trump last month made the ban even more sweeping against Afghans, severing a program that helped bring in Afghans who had fought alongside the United States against the Taliban, after an Afghan veteran who appeared to have post-traumatic stress shot two National Guards troops deployed by Trump in Washington.
Angola, Senegal and Zambia have all been prominent US partners in Africa, with former president Joe Biden hailing the three for their commitment to democracy.
In the proclamation, the White House alleged high crime rates from some countries on the blacklist and problems with routine record-keeping for passports.
The White House acknowledged "significant progress" by one initially targeted country, Turkmenistan.
The Central Asian country's nations will once again be able to secure US visas, but only as non-immigrants.
(FRANCE 24 with AFP)
France marks International Migrants Day amid growing pressure on migrant workers
Issued on: 18/12/2025 - FRANCE24
On International Migrants Day, hundreds of groups across France are mobilizing to highlight migrants’ contributions and struggles as immigration rules tighten and expulsions rise. Migrant workers remain vital to sectors like restaurants and construction, even as many face years of insecurity, with expulsions up sharply in 2024.
The Badalona town hall had argued that the squat was a public safety hazard. In 2020, an old factory occupied by around 100 migrants in the Catalan city near Barcelona caught fire, killing four people.
Police in Spain carried out eviction orders on Wednesday to clear an abandoned school building where around 400 mostly undocumented migrants were living north of Barcelona.
Many sub-Saharan migrants, mainly from Senegal and Gambia, had moved into the empty school building in Badalona — a working-class city that borders Barcelona — since it was left abandoned in 2023.
Badalona Mayor Xavier GarcĂa Albiol announced the evictions in a post on X.
"As I had promised, the eviction of the 400 illegal squatters in the B9 school in Badalona begins," he wrote.
Albiol, of the conservative Popular Party (PP), has built his political career on an anti-immigration stance.
A migrant's belongings are packed before he leaves as police in the background prepares to carry out eviction orders at an abandoned school in Badalona, 17 December, 2025
AP Photo
Knowing that the eviction in the middle of winter was coming, most of the occupants had left the squat to try to find other shelter before police in riot gear from Catalonia's regional police Mossos d'Esquadraentered the school’s premises early in the morning under court orders.
Those who had waited left peacefully.
The judicial order made the Badalona town hall provide the evicted people with access to social services, but it did not oblige local authorities to find alternative housing for all the squatters.
Lawyer Marta Llonch, who represents the squatters, said that many people would likely end up without shelter in the cold.
"Many people are going to sleep on the street tonight," Llonch said. "Just because you evict these people it doesn’t mean they disappear. If you don’t give them an alternative place to live they will now be on the street, which will be a problem for them and the city."
Many of the squatters lived from selling scrap metal collected from the streets. Others had residency and work permits but were forced to live there because they could not afford housing during a cost-of-living crunch that is making it difficult even for working Spaniards to buy or rent homes.
That housing crisis has led to widespread social angst and public protests.
People gather during a demonstration to protest high housing costs in Barcelona, 5 April, 2025 AP Photo
The Badalona town hall had argued that the squat was a public safety hazard. In 2020, an old factory occupied by around 100 migrants in Badalona caught fire, killing four people.
Like other southern European countries, Spain has for more than a decade seen migrants come to the country after risking their lives crossing the Mediterranean or Atlantic in small boats.
While many developed countries have taken a hard-line position against migration, Spain’s left-wing government has said that legal migration has helped its economy grow.
Trial of NGO workers accused of assisting 'illegal' migration opens in Tunisia
Aid workers accused of assisting irregular migration to Tunisia went on trial on Monday, as Amnesty International criticised what it called "the relentless criminalisation of civil society" in the country.
Six staff members of the Tunisian branch of the France Terre d'Asile aid group, along with 17 municipal workers from the eastern city of Sousse, face charges of sheltering migrants and facilitating their "illegal entry and residence".
If convicted, they face up to 10 years in prison.
Migration is a sensitive issue in Tunisia, a key transit point for tens of thousands of people seeking to reach Europe each year.
A former head of Terre d'Asile Tunisie, Sherifa Riahi, is among the accused and has been detained for more than 19 months, according to her lawyer Abdellah Ben Meftah.
"The only thing I'm sure of is that Sherifa and the other members of the association did nothing wrong. I'm certain they'll be released sooner or later. Will it be this Monday or at another hearing? I don't know, it's 50-50," Ben Meftah told RFI.
He also told French news agency AFP that the accused had carried out their work as part of a project approved by the state and in "direct coordination" with the government.
Amnesty denounced what it described as a "bogus criminal trial" and called on Tunisian authorities to drop the charges.
"They are being prosecuted simply for their legitimate work providing vital assistance and protection to refugees, asylum seekers and migrants in precarious situations," Sara Hashash, Amnesty's deputy MENA (Middle East North Africa) chief, said in the statement.
The defendants were arrested in May 2024 along with about a dozen humanitarian workers, including anti-racism pioneer Saadia Mosbah, whose trial is set to start later this month.
In February 2023, President Kais Saied said "hordes of illegal migrants", many from sub-Saharan Africa, posed a demographic threat to the Arab-majority country.
His speech triggered a series of racially motivated attacks as thousands of sub-Saharan African migrants in Tunisia were pushed out of their homes and jobs.
Thousands were repatriated or attempted to cross the Mediterranean, while others were expelled to the desert borders with Algeria and Libya, where at least a hundred died that summer.
This came as the European Union boosted efforts to curb arrivals on its southern shores, including a 255-million-euro deal with Tunis.
Page 1. MULTITUDE. WAR AND DEMOCRACY. IN THE AGE OF EMPIRE. MICHAEL HARDT. ANTONIO NEGRI ... pdf. 33. Richard Haass, for example, the U.S. State Department ...
Empire / Michael Hardt and Antonio Negri. p. cm. Includes bibliographical ... 4.3 The Multitude against Empire. 393. Notes. 415. Index. 473. Page 11. PREFACE.
AI-generated reconstructions of ancient Rome turn out to be full of errors A number of videos and images created by artificial intelligence that claim to accurately depict ancient Rome have been circulating online. However, these images are far from historically accurate, says one historian.
"A Journey Through Time with Artificial Intelligence,” reads the caption on a video posted on YouTube on November 9, 2024. The video, called "Ancient Rome | AI generated video", promises viewers "a dive into the fascinating world of the Roman Empire". The author further claims that AI can help transform our understanding of the past by uncovering “incredible details about Roman society, architecture, warfare and daily life".
In recent months, there have been an increasing number of AI-generated videos and images posted online that purport to offer historically accurate glimpses into the past, especially of the Roman Empire. However, while they may appear spectacular, these reconstructions don’t correspond to historical reality.
Our team spoke to Sarah Kourdy, a professor in Art History and Archaeology at the University of Bordeaux Montaigne, who specialises in ancient Greek and Roman culture. She demonstrated to us just how inaccurate some of these images are. An ancient Roman landscape, complete with a 20th-century building
It turns out that the "Ancient Rome” video is far from an accurate reconstruction; it actually contains some major errors. At 0'47, for example, you can see a Roman soldier standing in front of what is meant to be a backdrop of ancient Rome.
However, one of the buildings in the image is from another era entirely.
"The building in the background looks a lot like the monument to Victor Emmanuel II, [Editor’s note: built in 1911 to honour the first king of a united Italy], which is clearly anachronous.”
The soldier is wearing what’s called a lorica segmentata, a jointed breastplate worn by Roman legionnaires. However, Kourdy says that there are also issues with this uniform:
"The metal bands are too thin and are arranged vertically. Usually, they are of a decreasing size and arranged parallel and horizontally to better protect the soldier.”
At left is a lorica segmentata, where you can see that the metal bands are horizontally placed. At right is the monument honouring Victor Emmanuel II, which was inaugurated in 1911. Corbridge Museum; Wikipedia / Alvesgaspar
The hippodrome with erroneous architecture
There is also a chariot race in the YouTube video: a scene firmly planted in our imaginings of the Roman Empire since the film Ben-Hur. The race, in this case, seems to take place in Circus Maximus, the biggest hippodrome in the eternal city.
However, once again, the architecture doesn’t correspond with the historical reality, Kourdy says:
"The tiers seem particularly high and weren’t topped with a double row of arches. While the image is undoubtedly based on Circus Maximus, the largest edifice of its kind in Rome, the architecture in the background looks like an aqueduct. Moreover, real Roman chariots had two wheels while, in this image, they have four.”
An image said to represent the Baths of Caracalla has garnered 592,000 views on X. It was also shared on a number of Facebook groups dedicated to ancient history. These baths, which were some of the most luxurious and grand in the history of the Roman Empire, were constructed by the Emperor Caracalla in 216 AD. The image shows what seems to be the natatio – or swimming pool – set beneath a decadently ornate ceiling of white marble and gold.
Kourdy says that this image of the Baths of Caracalla is also historically inaccurate.
First, the AI-generated image depicts the Roman baths in a Baroque style. The baroque artistic movement didn’t begin until the 16th century.
Moreover, the baths weren’t made out of white marble but “out of bricks held together by a mortar similar to cement". The historian also added that the baths were, of course, “humid” spaces, and the gilding that appears abundantly in the illustration wouldn’t be compatible with this kind of atmosphere. Only salons and libraries – rooms dedicated to rest, reading or gatherings – would have been decorated this luxuriously.
Finally, the image simply doesn’t match the real dimensions of the baths:
"The archaeological digs at the Baths of Caracalla have revealed that the imperial baths did have imposing dimensions. But the image created by artificial intelligence goes beyond that: depicting an immense swimming pool filled with giant columns whose bases sit in the water, which just wasn’t the case."
US Senate confirms Jared Isaacman as NASA chief amid budget cuts and moon race
The US Senate has confirmed billionaire private astronaut Jared Isaacman as NASA administrator, installing a strong advocate of Mars missions to lead the space agency as it faces deep budget cuts and intensifying competition with China to return humans to the Moon.
The US Senate on Wednesday confirmed billionaire private astronaut Jared Isaacman to become President Donald Trump’s NASA administrator, making an advocate of Mars missions and a former associate of SpaceX chief executive Elon Musk the space agency’s 15th leader.
The vote on Isaacman, who Trump removed and then renamed as NASA administrator nominee this year, passed 67–30, two weeks after he told senators in his second hearing that NASA must pick up the pace in beating China back to the Moon this decade.
Isaacman will lead an agency of 14,000 employees as it invests billions of dollars into its most ambitious space exploration endeavour yet: returning humans to the Moon to seed a long-term presence on the surface before eventually sending astronauts to Mars.
NASA workforce cut in efficiency push
The White House, in its government efficiency push led by Musk, slashed NASA’s workforce by 20 percent and has sought to cut the agency’s 2026 budget by roughly 25 percent from its usual $25 billion, imperilling dozens of space science programmes that scientists and some officials regard as priorities.
Isaacman envisions a revamped focus on sending missions to Mars on top of the Artemis Moon effort, as well as a greater dependence on private companies such as SpaceX to save taxpayer money and stimulate private-sector competition.
Of the 67 votes in Isaacman’s favour, 16 were from Democrats, joining 51 from Republicans. All 30 votes against his confirmation were from Democrats.
Maria Cantwell, the ranking member of the Senate Commerce Committee that oversees NASA, has criticised the Trump administration’s efforts to cut NASA’s science unit. She supported Isaacman’s confirmation on Wednesday.
“During his nomination process, Mr Isaacman emphasised the importance of developing a pipeline of future scientists, engineers, researchers and astronauts to support the science and technology development and align with NASA’s objectives. I strongly agree,” Cantwell said.
Some Democratic senators said during Isaacman’s hearing on December 3 that they were concerned about his closeness to Musk, whose company holds about $15 billion in NASA contracts and could benefit from certain policies Isaacman has advocated.
Musk advocated for Isaacman’s nomination when Trump was elected in 2024. Musk had sought to realign the US space programme with a greater focus on Mars during his stint as a close adviser to Trump.
Senate Republicans and some Democrats, including Cantwell, have also stressed urgency in NASA’s Moon race with China, which is aiming to send its astronauts to the lunar surface by 2030. NASA faces a shaky target of 2028 using its Space Launch System rocket and SpaceX’s giant Starship rocket, under development, as the lander.
Acting NASA chief Sean Duffy, who also leads the US Transportation Department, congratulated Isaacman on X, wishing him “success as he begins his tenure and leads NASA as we go back to the Moon in 2028 and beat China”.
(FRANCE 24 with Reuters)
Possible "superkilonova" exploded not once but twice
Double explosion may have produced gravitational waves and light
This artist's concepts shows a hypothesized event known as a superkilonova. A massive star explodes in a supernova (left), which generates elements like carbon and iron. In the aftermath, two neutron stars are born (middle), at least one of which is believed to be less massive than our Sun. The neutron stars spiral together, sending gravitational waves rippling through the cosmos, before merging in a dramatic kilonova (right). Kilonovae seed the universe with the heaviest elements, such as gold at platinum, which glow with red light.
When the most massive stars reach the ends of their lives, they blow up in spectacular supernova explosions, which seed the universe with heavy elements such as carbon and iron. Another type of explosion—the kilonova—occurs when a pair of dense dead stars, called neutron stars, smash together, forging even heavier elements such as gold and uranium. Such heavy elements are among the basic building blocks of stars and planets.
So far, only one kilonova has been unambiguously confirmed to date, a historic event known as GW170817, which took place in 2017. In that case, two neutron stars smashed together, sending ripples in space-time, known as gravitational waves, as well as light waves across the cosmos. The cosmic blast was detected in gravitational waves by the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO) and its European partner, the Virgo gravitational-wave detector, and in light waves by dozens of ground-based and space telescopes around the world.
Now, astronomers are reporting evidence for a possible second kilonova event, but the case is not closed. In fact, this situation is much more complex because the candidate kilonova, namedAT2025ulz, is thought to have stemmed from a supernova blast that went off hours before, ultimately obscuring astronomers' view.
"At first, for about three days, the eruption looked just like the first kilonova in 2017," says Caltech's Mansi Kasliwal (PhD '11), professor of astronomy and director of Caltech's Palomar Observatory near San Diego. "Everybody was intensely trying to observe and analyze it, but then it started to look more like a supernova, and some astronomers lost interest. Not us."
Kasliwal is lead author of a new study describing the findings in The Astrophysical Journal Letters. In the report, she and her colleagues describe evidence that this oddball event may be a first-of-its-kind superkilonova, or a kilonova spurred by a supernova. Such an event has been hypothesized but never seen.
Evidence for the possible rarity first came on August 18, 2025, when the twin detectors of LIGO in Louisiana and Washington, as well as Virgo in Italy, picked up a new gravitational-wave signal. Within minutes, the team that operates the gravitational-wave detectors (an international collaboration that also includes the organization that runs the KAGRA detector in Japan) sent an alert to the astronomical community letting them know that gravitational waves had been registered from what appeared to be a merger between two objects, with at least one of them being unusually tiny. The alert included a rough map of the source's location.
"While not as highly confident as some of our alerts, this quickly got our attention as a potentially very intriguing event candidate," says David Reitze, the executive director of LIGO and a research professor at Caltech. "We are continuing to analyze the data, and it's clear that at least one of the colliding objects is less massive than a typical neutron star."
A few hours later, the Zwicky Transient Facility (ZTF), a survey camera at Palomar Observatory, was the first to pinpoint a rapidly fading red object 1.3 billion light-years away, which is thought to have originated in the same location as the source of gravitational waves. The event, initially called ZTF 25abjmnps, was later renamed AT2025ulz by the International Astronomical Union Transient Name Server.
About a dozen other telescopes set their sights on the target to learn more, including the W. M. Keck Observatory in Hawaiʻi, the Fraunhofer telescope at the Wendelstein Observatory in Germany, and a suite of telescopes around the world that were previously part of the GROWTH (Global Relay of Observatories Watching Transients Happen) program, led by Kasliwal.
The observations confirmed that the eruption of light had faded fast and glowed at red wavelengths—just as GW170817 had done eight years earlier. In the case of the GW170817 kilonova, the red colors came from heavy elements like gold; these atoms have more electron energy levels than lighter elements, so they block blue light but let red light pass through.
Then, days after the blast,AT2025ulz started to brighten again, turn blue, and show hydrogen in its spectra—all signs of a supernova not a kilonova (specifically a "stripped-envelope core-collapse" supernova). Supernovae from distant galaxies are generally not expected to generate enough gravitational waves to be detectable by LIGO and Virgo, whereas kilonovae are. This led some astronomers to conclude that AT2025ulz was triggered by a typical ho-hum supernova and not, in fact, related to the gravitational-wave signal.
What Might Be Going On?
Kasliwal says that several clues tipped her off that something unusual had taken place. Though AT2025ulz did not resemble the classic kilonova GW170817, it also did not look like an average supernova. Additionally, the LIGO–Virgo gravitational-wave data had revealed that at least one of the neutron stars in the merger was less massive than our Sun, a hint that one or two small neutron stars might have merged to produce a kilonova.
Neutron stars are the leftover remains of massive stars that explode as supernovae. They are thought to be around the size of San Francisco (about 25 kilometers across) with masses that range from 1.2 to about three times that of our Sun. Some theorists have proposed ways in which neutron stars might be even smaller, with masses less than the Sun's, but none have been observed so far. The theorists invoke two scenarios to explain how a neutron could be that small. In one, a rapidly spinning massive star goes supernova, then splits into two tiny, sub-solar neutron stars in a process called fission.
In the second scenario, called fragmentation, the rapidly spinning star again goes supernova, but, this time, a disk of material forms around the collapsing star. The lumpy disk material coalesces into a tiny neutron in a manner similar to how planets form.
With LIGO and Virgo having detected at least one sub-solar neutron star, it is possible, according to theories proposed by co-author Brian Metzger of Columbia University, that two newly formed neutron stars could have spiraled together and crashed, erupting as a kilonova that sent gravitational waves rippling through the cosmos. As the kilonova churned out heavy metals, it would have initially glowed in red light as ZTF and other telescopes observed. The expanding debris from the initial supernova blast would have obscured the astronomers’ view of the kilonova.
In other words, a supernova may have birthed twin baby neutron stars that then merged to make a kilonova.
"The only way theorists have come up with to birth sub-solar neutron stars is during the collapse of a very rapidly spinning star," Metzger says. "If these 'forbidden' stars pair up and merge by emitting gravitational waves, it is possible that such an event would be accompanied by a supernova rather than be seen as a bare kilonova."
But while this theory is tantalizing and interesting to consider, the research team stresses that there is not enough evidence to make firm claims.
The only way to test the superkilonovae theory is to find more. "Future kilonovae events may not look like GW170817 and may be mistaken for supernovae," Kasliwal says. "We can look for new possibilities in data like this from ZTF as well as the Vera Rubin Observatory, and upcoming projects such as NASA's Nancy Roman Space Telescope, NASA's UVEX [led by Caltech's Fiona Harrison], Caltech's Deep Synoptic Array-2000, and Caltech’s Cryoscope in the Antarctic. We do not know with certainty that we found a superkilonova, but the event nevertheless is eye opening."
The paper, titled "ZTF25abjmnps (AT2025ulz) and S250818k: A Candidate Superkilonova from a Sub-threshold Sub-Solar Gravitational Wave Trigger," was funded by the Gordon and Betty Moore Foundation, the Knut and Alice Wallenberg Foundation, the National Science Foundation (NSF), the Simons Foundation, the US Department of Energy, a McWilliams Postdoctoral Fellowship, and the University of Ferrara in Italy. Other Caltech authors include Tomás Ahumada (now at NOIRLab, Chile), Viraj Karambelkar (now at Columbia University), Christoffer Fremling, Sam Rose, Kaustav Das, Tracy Chen, Nicholas Earley, Matthew Graham, George Helou, and Ashish Mahabal.
Caltech's ZTF is funded by the NSF and an international collaboration of partners. Additional support comes from the Heising-Simons Foundation and from Caltech. ZTF data are processed and archived by IPAC, an astronomy center at Caltech.
Journal
The Astrophysical Journal Letters
NASA’s Webb telescope finds bizarre atmosphere on a lemon-shaped exoplanet
This artist’s concept shows what the exoplanet called PSR J2322-2650b (left) may look like as it orbits a rapidly spinning neutron star called a pulsar (right). Gravitational forces from the much heavier pulsar are pulling the Jupiter-mass world into a bizarre lemon shape.
Scientists using NASA’s James Webb Space Telescope have observed an entirely new type of exoplanet whose atmospheric composition challenges our understanding of how this type of planet forms.
This bizarre, lemon-shaped body, possibly containing diamonds at its core, blurs the line between planets and stars.
Officially named PSR J2322-2650b, this object has an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. It has a mass about the same as Jupiter, but soot clouds float through the air—and deep within the planet, these carbon clouds can condense and form diamonds. It orbits a rapidly spinning neutron star.
How the planet came to be is a mystery.
“The planet orbits a star that's completely bizarre — the mass of the Sun, but the size of a city,” explained the University of Chicago’s Michael Zhang, the principal investigator on this study, which is accepted for publication in The Astrophysical Journal Letters. “This is a new type of planet atmosphere that nobody has ever seen before.”
“This was an absolute surprise,” said team member Peter Gao of the Carnegie Earth and Planets Laboratory in Washington, D.C. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’”
A bizarre pair
The new planet, PSR J2322-2650b, is orbiting a rapidly spinning neutron star, also known as a pulsar.
This star emits beams of electromagnetic radiation from its magnetic poles at regular intervals just milliseconds apart. But the star is emitting mostly gamma rays and other high-energy particles, which are invisible to the Webb telescope’s infrared vision.
This means scientists can study the planet in intricate detail across its whole orbit—normally an extremely difficult task, because stars usually far outshine their planets.
“This system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all,” explained Maya Beleznay, a graduate student at Stanford University who worked on modelling the shape of the planet and the geometry of its orbit. “So we get a really pristine spectrum. And we can better study this system in more detail than normal exoplanets.”
Taking stock of the planet, the team was surprised.
“Instead of finding the normal molecules we expect to see on an exoplanet—like water, methane and carbon dioxide—we saw molecular carbon, specifically C3 and C2,” said Zhang.
At the core of the planet, subjected to intense pressure, it’s possible this carbon could be squeezed into diamonds.
But to the scientists, the larger question is how such a planet could have formed at all.
“It's very hard to imagine how you get this extremely carbon-enriched composition,” said Zhang. “It seems to rule out every known formation mechanism.”
‘A puzzle to go after’
PSR J2322-2650b is extraordinary close to its star, just 1 million miles away. In contrast, the Earth’s distance from the Sun is about 100 million miles.
Because of its extremely tight orbit, the exoplanet’s entire year—the time it takes to go around its star—is just 7.8 hours.
Applying models to the planet’s brightness variations over its orbit, the team finds that immense gravitational forces from the much heavier pulsar are pulling the Jupiter-mass planet into a lemon shape.
Together, the star and exoplanet may be considered a “black widow” system. Black widows are a rare type of system where a rapidly spinning pulsar is paired with a small, low-mass companion. In the past, material from the companion would have streamed onto the pulsar, causing it to spin faster over time, which powers a strong wind. That wind and radiation then bombard and evaporate the smaller and less massive star.
Like the spider for which it is named, the pulsar slowly consumes its unfortunate partner.
But in this case, the tiny companion is officially considered an exoplanet by the International Astronomical Union, not a star.
“Did this thing form like a normal planet? No, because the composition is entirely different,” said Zhang. “Did it form by stripping the outside of a star, like ‘normal’ black widow systems are formed? Probably not, because nuclear physics does not make pure carbon.”
Team member Roger Romani, of Stanford and the Kavli Institute for Particle Astrophysics and Cosmology Institute, is one of the world’s preeminent experts on black widow systems. He proposes one evocative phenomenon that could occur in the unique atmosphere.
“As the companion cools down, the mixture of carbon and oxygen in the interior starts to crystallize,” Romani theorized. “Pure carbon crystals float to the top and get mixed into the helium, and that's what we see. But then something has to happen to keep the oxygen and nitrogen away. And that's where there's controversy.”
“But it's nice to not know everything,” said Romani. “I'm looking forward to learning more about the weirdness of this atmosphere. It's great to have a puzzle to go after.”
With its infrared vision and exquisite sensitivity, this is a discovery only the Webb telescope could make. Its perch a million miles from Earth and its huge sunshield keeps the instruments very cold, which is necessary for conducting these observations.
“On the Earth, lots of things are hot, and that heat really interferes with the observations because it's another source of photons that you have to deal with,” explained Zhang. “It's absolutely not feasible from the ground.”
Other UChicago scientists on the study included Prof. Jacob Bean, graduate student Brandon Park Coy and Rafael Luque, who was then a postdoctoral researcher at UChicago and is now with the Instituto de AstrofĂsica de AndalucĂa in Spain.
This animation shows an exotic exoplanet orbiting a distant pulsar, or rapidly rotating neutron star with radio pulses. The planet, which orbits about 1 million miles away from the pulsar, is stretched into a lemon shape by the pulsar’s strong gravitational tides.
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