James Webb Reveals an Unusual Rugby Ball-Shaped Exoplanet with Diamond Rain

NASA’s James Webb Space Telescope (JWST) has made a remarkable discovery: an exoplanet so extraordinary that it challenges existing planetary science paradigms. Named PSR J2322-2650b, this planet circles a pulsar—the dense, collapsed core left behind after a massive star’s explosion—offering a rare opportunity to examine such a system in great detail.

Aside from its striking elongated lemon-like shape, the planet is enveloped in an atmosphere abundant in helium and molecular carbon, lacking any measurable oxygen or nitrogen. Light spectra indicate that carbon soot condenses into diamond particles in this atmosphere, creating the phenomenon of diamond rain—a process theorized for other large planets but now confirmed in this extreme environment.

“This discovery was completely unexpected,” stated Peter Gao, planetary scientist at the Carnegie Earth and Planets Laboratory and co-author of the study. “It defies our past expectations.” The findings were released by NASA and are prompting new discussions about planetary system evolution after stellar death.

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A Hostile Orbit Close to a Stellar Remnant

The exoplanet PSR J2322-2650b is situated roughly 2,300 light-years from Earth and completes an orbit in only 7.8 hours at a distance of approximately 1 million miles from its neutron star host, classified as a millisecond pulsar. These compact remnants spin rapidly, emitting intense radiation beams that sweep across space.

The close proximity to the pulsar distorts the planet into a pronounced ellipsoid shape, supported by thermal imaging and orbital data. Powerful tidal forces pull and stretch the planet, keeping it permanently deformed. This shape has been visualized in detailed models from the Space Telescope Science Institute, using Webb’s infrared observations.

An artistic illustration depicting the exoplanet PSR J2322-2650b (left) as it orbits its rapidly rotating neutron star called a pulsar (right). Gravitational forces from the massive pulsar elongate the Jupiter-sized planet into a unique lemon-like shape. Credit: NASA, ESA, CSA, Ralf Crawford (STScI)

This type of binary system, known as a black widow pulsar, is infamous for its destructive influence. Usually, the pulsar gradually strips mass from a small companion star through intense radiation. In this exceptional case, the companion is a gas giant comparable to Jupiter, one of the rare known planets to endure in such a hostile environment.

This discovery opens a unique window into an uncommon astrophysical category. Fewer than five pulsars have confirmed planetary companions, and NASA notes this is the sole known example of a hot Jupiter-like planet orbiting so close to a pulsar.

A Totally Unprecedented Atmosphere

Infrared spectral analysis by JWST unveiled the planet’s atmospheric composition, which defies expectations. The atmosphere is primarily composed of helium and molecular carbon species like C₂ and C₃—markedly different from the usual atmospheres of gas giants that often contain water, methane, or carbon dioxide (see related study).

“We’ve never seen an atmosphere like this before,” remarked Michael Zhang, principal investigator at the University of Chicago. In Space.com, Zhang highlighted that among over 150 well-studied exoplanet atmospheres, none exhibit this level of molecular carbon.

An illustration of a classical black widow pulsar system, showing a neutron star drawing material off its stellar companion. Credit: NASA’s Goddard Space Flight Center

Another atmospheric oddity is the clear absence of oxygen and nitrogen, even though these elements typically exist at the high temperatures recorded. Daytime temperatures reach up to 3,700°F (2,040°C), cooling to 1,200°F (650°C) on the dark side. Under such conditions, carbon usually bonds with other elements, but here it apparently persists on its own.

This leads to the formation of dense clouds rich in carbon high in the atmosphere. Due to immense pressure, those carbon-rich clouds are expected to crystallize into diamonds that rain down toward the planet’s core. Infrared JWST data backs this extraordinary weather system, revealing phenomena never encountered in our solar system.

Unanswered Questions About Its Origin

A critical mystery remains: the planet’s origin story. “This could not have formed as a typical planet given its unique composition,” explained Zhang. “Nor is it likely a product of typical stellar stripping like other black widow systems, since nuclear processes don’t produce pure carbon.”

One hypothesis involves internal crystallization: if the planet’s core holds a mixture of oxygen and carbon, cooling could cause pure carbon to ascend and escape into the helium-rich atmosphere. Yet this process doesn’t clarify why no oxygen or nitrogen is detected, elements expected if they were significantly present.

Roger Romani from Stanford University, a co-author, proposes that pulsar environments may uniquely affect how materials segregate during planetary cooling. “Something must prevent oxygen and nitrogen from appearing,” Romani explains. “This is the core of the puzzle.”

These theories remain unconfirmed until similar exoplanets are identified or until Webb conducts more extensive follow-up observations of PSR J2322-2650b.