PSR J2322-2650b, a captivating exoplanet with a mass akin to Jupiter, is in orbit around the millisecond pulsar PSR J2322-2650 and possesses an extraordinary atmosphere dominated by helium and carbon, a composition hitherto unobserved.
This artistic rendition illustrates the potential appearance of PSR J2322-2650b. Image attribution: NASA / ESA / CSA / Ralf Crawford, STScI.
“This finding was an utterly unexpected revelation,” stated Dr. Peter Gao, an esteemed astronomer affiliated with the Carnegie Earth and Planets Laboratory.
“Upon receiving the data, our collective initial reaction was one of profound astonishment, a sentiment of ‘What on earth is this? It diverges dramatically from our preconceptions.’”
“The unique characteristic of this celestial system lies in our capacity to observe the planet illuminated by its parent star without directly perceiving the star itself,” explained Maya Beleznay, a doctoral candidate at Stanford University.
“Consequently, we obtain an exceptionally pure spectrum, enabling a more detailed analysis of this system than is typically possible with conventional exoplanets.”
“The planet is in orbit around a star that is profoundly anomalous—possessing the mass of our Sun yet confined to the dimensions of a city,” remarked Dr. Michael Zhang, an astronomer at the University of Chicago.
“This represents a novel category of planetary atmosphere, one that has not been documented previously. Rather than encountering the standard molecules commonly found in exoplanetary atmospheres, such as water, methane, and carbon dioxide, we detected molecular carbon, specifically in the forms of C3 and C2.”
The prevalence of molecular carbon is highly unusual, given that at temperatures exceeding 2,000 degrees Celsius, carbon would typically form chemical bonds with any other available atomic species within the atmosphere.
Among the approximately 150 planets that astronomers have investigated, both within and beyond our Solar System, none have exhibited detectable amounts of molecular carbon.
“Did this celestial body form through standard planetary accretion processes? No, given its entirely dissimilar composition,” posited Dr. Zhang.
“Was its formation the result of stellar material stripping, akin to the genesis of ‘typical’ black widow systems? Unlikely, as nuclear physics does not yield pure carbon.”
“It is exceedingly challenging to conceptualize a mechanism that could lead to this exceptionally carbon-enriched composition, as it appears to invalidate all established planetary formation theories.”
The researchers have put forth a compelling hypothetical phenomenon that might account for the peculiar atmospheric conditions.
“As the companion star undergoes cooling, the internal blend of carbon and oxygen begins to crystallize,” elaborated Dr. Roger Romani, an astronomer at Stanford University and the Kavli Institute for Particle Astrophysics and Cosmology Institute.
“Crystals of pure carbon ascend to the surface and become integrated into the helium, which is what we are observing.”
“However, some process must be at play to exclude oxygen and nitrogen from this mix, and therein lies the enigma.”
“Yet, there is a certain satisfaction in encountering the unknown. I eagerly anticipate further elucidations regarding the peculiarities of this atmosphere; it presents an exciting scientific puzzle to unravel.”
This groundbreaking discovery is detailed in a publication in the Astrophysical Journal Letters.
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Michael Zhang et al. 2025. A Carbon-rich Atmosphere on a Windy Pulsar Planet. ApJL 995, L64; doi: 10.3847/2041-8213/ae157c
