An international team of astronomers, with participation from European and American institutions, has identified a exoplanet with an elongated, lemon-like silhouettewhich is forcing a review of some established ideas about how worlds outside the Solar System are born and evolve.
The object, cataloged as PSR J2322-2650b, was analyzed with the James Webb Space Telescope (JWST), developed by NASA in collaboration with the European Space Agency (ESA) and the Canadian Space Agency. The data reveal not only a shape highly distorted by gravity, but also a unusual atmosphere dominated by helium and carbon which baffles the scientific community.
A gas giant deformed into the shape of a lemon
PSR J2322-2650b has a mass comparable to that of JupiterBut its shape is far from spherical. Models derived from JWST observations indicate that its The equatorial diameter is approximately 38% larger than the polar diameter., which gives it that appearance of an American football or a stretched-out lemon.
The cause of this extreme geometry is its proximity to a pulsara tiny, very dense neutron star that rotates at high speed. The planet is located only 1,6 million kilometers from its stara minuscule distance compared to the approximately 150-160 million kilometers that separate the Earth from the Sun. Under these conditions, the gravitational tidal forces They pull on the planet until it is deformed.
This tight orbit makes its year extraordinarily short: PSR J2322-2650b takes about 7,8 hours to complete one orbit around the pulsarIn practice, it's as if the planet were permanently subjected to a brutal gravitational pull, which explains the elongated silhouette detected by the scientific team.
The researchers themselves admit that the detection caught them off guard. After downloading the first data from the JWST, the reaction in the group was literally a «What the hell is this?", after verifying that the object did not match, either in shape or composition, any exoplanet studied so far.
A "black widow" type system with a planet as the victim
The environment in which PSR J2322-2650b moves is also unique. The planet orbits a millisecond pulsarA neutron star with the mass of the Sun compressed into a body the size of a city. These objects rotate hundreds of times per second and They emit beams of electromagnetic radiation that sweep across space like the beam of a lighthouse.
These types of configurations are known as “black widow” systemsIn these cases, the pulsar gradually strips matter from its companion. Typically, this companion is a light star, whose gaseous envelope is torn away and evaporated by bombardment from gamma rays and high-energy particle winds. In this case, however, the object accompanying the pulsar is a exoplanet officially recognized as such by the International Astronomical Union, and not a star.
Of the more than 6.000 exoplanets Confirmed to date, PSR J2322-2650b stands out as the only hot gas giant detected in orbit around a pulsarFurthermore, only a very small number of pulsars are known to host planets, making the system a rare natural laboratory for studying extreme physics.
The pulsar emits mainly gamma rays and other very energetic particleswhich, paradoxically, turn out to be an observational advantage. These emissions are practically invisible to infrared instruments from the James Webb telescope, so that the telescope can cleanly record the thermal light coming from the planet without the usual glare from a bright main-sequence star.
An atmosphere dominated by helium and molecular carbon
While the lemon shape already makes the PSR J2322-2650b unique, what has truly perplexed specialists is its exotic atmosphereInstead of the usual molecules that have been seen on other worlds—like water vapor, methane, or carbon dioxide-, infrared observations from the JWST show a mixture dominated by helium and molecular carbon.
The analyzed spectra clearly show signatures of C₂ and C₃Two configurations of carbon molecules that had never been detected so clearly on an exoplanet. The authors of the study emphasize that, among the approximately 150 planetary atmospheres studied in detail inside and outside the Solar System, none resemble that of this object.
Temperatures on the planet are extremely high. On the side illuminated by the pulsar, they reach nearly 2.040 ºC, while on the shaded side, always directed in the opposite direction by tidal coupling, estimates are around 650 ºCIn this temperature range, if there were an abundance of other elements, carbon would tend to combine with them, forming more complex molecules instead of appearing as "free" molecular carbon.
However, the analysis indicates a almost total absence of oxygen and nitrogen in the atmosphere. This deficiency explains why carbon can dominate in the form of C₂ and C₃, but at the same time poses a puzzle about the planet's origin: no standard model of planetary formation predicts such an extreme composition, rich in carbon and so poor in other light elements.
The researchers even point to the possibility that there are clouds of soot and carbon particles floating in the upper layers, which in the depths could condense and give rise to diamond-like structures, according to studies on minerals and rocksAlthough this idea remains hypothetical for now, it fits with calculations of pressure and temperature inside the planet.
An origin that challenges planetary formation models
Understanding how a body with these characteristics could have formed has become one of the great mysteries of the study. The authors of the paper rule out that PSR J2322-2650b formed as a “conventional” planet in a protoplanetary diskbecause its chemical composition does not match what is observed in other gas giants close to their stars.
The hypothesis that it is the bare remains of an ancient companion star The pulsar would have been stripping away outer layers, as happens in typical black widows. The nuclear physics that governs the stellar interior does not favor the production of large quantities of almost pure carbon without significant support from other elements, so this scenario leaves the current atmosphere of the planet unexplained.
One of the alternative ideas being considered is that, as the object cooled, the internal mixture of carbon and oxygen will begin to crystallizeIn that process, the carbon crystals The purer elements would have tended to rise and mix with helium in the outer layers, leaving the oxygen more confined in the interior or trapped in solid phases. Despite this, astronomers acknowledge that It is unclear how oxygen and nitrogen have been so effectively removed from the atmosphere.
In the words of those responsible for the study, the system seems contradict all known formation mechanismsFor the scientific community, this type of finding represents a challenge, but also an opportunity to test current theories and, if necessary, reformulate them.
The key role of the James Webb Space Telescope
The discovery of PSR J2322-2650b has been made possible thanks to the capabilities of James Webb Space Telescope, the most powerful active space observatory, jointly managed by the NASA, European Space Agency (ESA) and the Canadian Space Agency. Located about 1,5 million kilometers from EarthThe Webb operates in the infrared and is protected from solar heat by a huge sunshade.
This heat shield keeps the instruments at very low temperatures, allowing them to record extremely faint signals. From European soil, even with large telescopes, it would be virtually impossible to observe such a thin atmosphere like that of this exoplanet: the Earth's own heat and that of the equipment contributes additional photon noise that masks the signal being measured.
In the specific case of PSR J2322-2650b, the fact that the pulsar shines dimly in infrared This has been a point in its favor. The JWST was able to track the planet throughout its entire orbit, measuring how the emitted radiation varied as it revolved around the neutron star. This has allowed scientists to obtain a particularly clean spectrum, without the typical glare of ordinary stars.
Thanks to this data quality, the team has been able not only to identify the presence of C₂ and C₃, but also of reconstruct the geometry of the planet and the temperature distribution between the day and night hemispheres. This information is key to understanding how the atmospheres of gas giants respond to such extreme radiation conditions.
Since its launch in 2021, the James Webb Space Telescope has yielded numerous results on distant galaxies, young stars, and exoplanets. Findings like this one They reinforce the role of space infrastructure in European and global astronomy., and they show the extent to which there are still surprises even in fields as well-studied as the physics of giant planets.
With PSR J2322-2650b, the list of strange worlds gains a new member: a giant hot gaseous, deformed into the shape of a lemonNestled around a millisecond pulsar, with an atmosphere dominated by helium and molecular carbon and the potential for diamond formation in its interior, this planet, far from fitting classical models, has become a puzzle that, with future observations from the James Webb Space Telescope and other observatories, could force us to adjust our understanding of how planets form and evolve in extreme environments.
