“What the heck is this?”was the typical reaction of astronomers, and this is how scientists reacted when they received their first set of data from the James Webb Space Telescope (JWST) of PSR J2322-2650b, a Jupiter-like planet that revolves around a pulsar. The atmosphere is unlike any other, and instead of being made up of hydrogen and helium like gas giant planets, this one is mostly made up of helium and carbon, with molecules like C₂ and C₃ floating around in ‘sooty clouds that can potentially coagulate into diamonds due to intense pressure.
The planet’s parent body, PSR J2322-2650, is a millisecond pulsar. This is a neutron star that has the same mass as the Sun condensed into a ball about a kilometer in radius. It makes a complete revolution in 3.46 milliseconds. But instead of light, a pulsar gives off bursts of gamma radiation from their magnetic poles. In this case, however, the main source of gamma radiation can’t be detected by JWST’s infrared cameras anyway. First of all, there would be no point in observing a bright object in the background when a pulsar shines so much brighter.
PSR J2322-2650b is tidally locked in this extreme orbital tidality, with the planet orbiting only 1 million miles (1.6 million kilometers) away from the pulsar; that is one one-hundredth the distance between the Earth and the Sun. It has only a 7.8-hour year. The powerful tides generated by the pulsar also cause the extreme gravitational force that stretches the planet lemon-like. The infrared spectroscopy data collected by the JWST discovered that the planet has no presence of expected molecules like water, methane, carbon Dioxide. Yet the carbon in the atmosphere is not bound to the oxygen or nitrogen in its atmosphere. In other words, there is an almost complete absence of oxygen and nitrogen in the atmosphere – something that planetary theorists cannot yet adequately explain.
Surface temperatures vary between 1,200 °F and 3,700 °F, with atmospheric wind blowing westward at incredible velocities against the planet’s rotation. Given such intense heating, carbon should readily combine with other atoms. Hence, the prevalence of carbon in a molecular form seems even more inexplicable. There are a number of theories, such as that given by astrophysicist Roger Romani, which propose that when the object cooled down, carbon and oxygen inside started to crystallize. This carbon can rise and dissolve into the helium atmosphere in forms of pure carbon crystals, possibly diamonds, while some invisible force holds oxygen and nitrogen in a separate compartment.
The formation mechanisms of the planet are also shrouded in mystery. In a normal “black widow” pulsar binary, a secondary small star revolves around a companion pulsar and ultimately disappears into it after shedding a huge amount of radiation and particles, thereby forming a dead remnant. In a comment, co-leading author Michael Zhang states that the final composition of the stripped remnant is not a pure carbon-rich material, making it less likely for carbon-rich planets to form via such a mechanism. The existence of PSR J2322-2650 b could be that it initially began as a helium-rich star before being reduced to a planetary mass through extensive evaporation.
From an engineering point of view, JWST’s ability to detect the characteristics of this dim, exotic object is a testament to the strength of its mid-infrared detectors. Cameras like MIRI have the ability to spatially separate planetary emissions from stellar activity, making it feasible to detect atmospheric content, thermal properties, and clouds on planetary bodies even in challenging regions around pulsars.
The high-quality spectrum recorded in this observation is feasible thanks to the fact the pulsar’s emission flux is not recorded in the infrared spectrum. PSR J2322-2650b is the only known gas giant planet orbiting a pulsar and one of only a very few pulsar planets in existence. Its helium-carbon atmosphere, soot and diamond clouds, highly eccentric orbit, and mysterious origin defy current theories of planetary science. According to Romani, “It’s nice to not know everything… It’s great to have a puzzle to go after.”
