Astronomers have made a groundbreaking discovery with the identification of a lemon-shaped planet, designated as PSR J2322-2650b, which challenges existing theories of planetary formation. This planet, approximately the size of Jupiter, orbits a pulsar—an ultra-dense remnant of a deceased star—every 7.8 hours. Its unique characteristics and extreme atmospheric composition raise questions about how such a celestial body could form in the universe.
The planet’s proximity to its host pulsar subjects it to intense high-energy radiation. Observations indicate that temperatures on the dayside reach about 3,700 degrees Fahrenheit, while the nightside cools to approximately 1,200 degrees Fahrenheit. The gravitational forces and heat distort the planet into an elongated shape reminiscent of a lemon, a phenomenon not previously observed in known gas giants.
Unusual Atmospheric Composition Revealed
Utilizing the James Webb Space Telescope, scientists conducted extensive studies of PSR J2322-2650b throughout its orbit. They aimed to analyze how light interacted with the planet’s atmosphere. The results were unexpected; rather than the typical mixture of hydrogen, oxygen, and nitrogen found in gas giants, the spectrum displayed a high concentration of carbon-based molecules, including the carbon chains C2 and C3. Notably, oxygen and nitrogen were either scarce or entirely absent.
Lead author Michael Zhang commented on the discovery, stating, “The planet orbits a star that’s completely bizarre—the mass of the Sun, but the size of a city. This is a new type of planet atmosphere that nobody has ever seen before.” The carbon-to-oxygen ratio for this planet exceeds 100 to 1, and the carbon-to-nitrogen ratio is more than 10,000 to 1. Such extreme ratios are unparalleled in known planetary systems around normal stars, and established theories about planet formation around pulsars do not account for these findings.
Exploring Theories Behind the Formation
Typically, systems containing pulsars, often referred to as “black widows,” undergo a process where the pulsar gradually strips material from a companion star. This process usually results in a diverse mix of elements, not an atmosphere overwhelmingly dominated by carbon. The research team considered multiple explanations for this unusual atmospheric composition, including the possibility of atypical stellar chemistry or the presence of carbon-rich dust. Nonetheless, none of these hypotheses fully explained the observations made by the James Webb Space Telescope.
Interestingly, the heating patterns of PSR J2322-2650b diverge from those of standard hot Jupiters. Gamma rays penetrate deeper into the atmosphere, creating wind patterns that distribute heat westward instead of directly away from the pulsar. As a result, the hottest region of the planet does not align with conventional models’ predictions.
At present, PSR J2322-2650b stands as a significant outlier in our understanding of planetary formation. While the James Webb Space Telescope has confirmed the presence of a unique atmospheric composition, the precise mechanisms that led to its formation remain unresolved. This discovery opens new avenues for research and highlights the complexities and mysteries of the universe.
