An artist's illustration of what exoplanet PSR J2322-2650b might look like. Because of its extremely tight orbit, the planet’s entire year—the time it takes to go around the pulsar—is just 7.8 hours. (Credit: NASA, ESA, CSA, Ralf Crawford (STScI))

Nothing about this planet makes sense. And that’s both confounding and exciting for astronomers. In A Nutshell

Astronomers discovered a Jupiter-sized planet with an atmosphere unlike anything seen before, dominated by carbon molecules in ratios that defy current planetary formation theories.

The planet orbits a pulsar (a dead star’s ultra-dense core) every 7.8 hours and is blasted with gamma rays, heating its atmosphere to nearly 3,000 degrees Fahrenheit while stretching it into a lemon shape.

The carbon-to-oxygen ratio exceeds 100 to 1, and carbon-to-nitrogen tops 10,000 to 1—numbers so extreme that no known planet orbiting a normal star comes close, leaving scientists without an explanation for how it formed.

The planet’s unusual heating from gamma rays creates powerful westward winds and dramatic temperature differences between its day and night sides, making it a unique laboratory for studying atmospheres under extreme conditions.

Astronomers have discovered what might be the strangest planet ever found: a lemon-shaped world where soot clouds drift through the air and diamonds may form deep underground. Its composition is so extreme that scientists are left searching for an explanation of how such an object could form.

The Jupiter-sized world dubbed “PSR J2322-2650b” circles a pulsar just 1 million miles away, closer than any planet in our solar system gets to the Sun. It completes one orbit in just 7.8 hours. The intense gravity from this dead star squeezes the planet into an oval shape like a lemon.

But the real mystery is what the planet is made of. Its atmosphere contains carbon in amounts that scientists can’t explain. No theory of how planets form can account for what they’re seeing.

Using the James Webb Space Telescope to observe the entire orbit, researchers explain that molecular carbon dominates the spectrum so completely that oxygen, nitrogen, and hydrogen (elements typically abundant in planetary atmospheres) appear strongly depleted or weren’t clearly detected.

“The planet orbits a star that’s completely bizarre — the mass of the Sun, but the size of a city,” explained lead author Michael Zhang, of the University of Chicago, in a statement. “This is a new type of planet atmosphere that nobody has ever seen before.”

This artist’s concept shows what the exoplanet called PSR J2322-2650b (left) may look like as it orbits a rapidly spinning neutron star called a pulsar (right). Gravitational forces from the much heavier pulsar are pulling the Jupiter-mass world into a bizarre lemon shape. (Credit: NASA, ESA, CSA, Ralf Crawford (STScI))

“This was an absolute surprise,” added co-author Peter Gao of the Carnegie Earth and Planets Laboratory in Washington, D.C. “I remember after we got the data down, our collective reaction was ‘What the heck is this?'”

An Atmosphere Built From Carbon Chains

When light passes through the planet’s atmosphere, different molecules absorb specific colors. By analyzing which colors are missing, astronomers can identify what molecules are present. In this case, the spectrum revealed molecules rarely seen in planetary atmospheres: C3 (three carbon atoms bonded together) and C2 (two carbon atoms).

These carbon chains absorbed light at specific wavelengths (particular colors in the infrared, invisible to human eyes). C3 showed up as a sudden drop at 3.014 microns, in the infrared beyond human vision. C2 created a sawtooth pattern between 2.45 and 2.85 microns. Additional absorption features suggested the presence of carbon-hydrogen bonds, though the exact molecules remain uncertain.

To understand how unusual this is, consider what should happen in a hot atmosphere. Carbon and oxygen atoms strongly prefer to bond together, forming carbon monoxide. The only way to have more molecular carbon than carbon monoxide is if carbon outnumbers oxygen by huge amounts, in this case, by more than 2,000 to one. Similarly, carbon and nitrogen should bond together unless carbon outnumbers nitrogen by more than 10,000 to one.

“The extreme carbon enrichment poses a severe challenge to the current understanding of ‘black-widow’ companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores,” the researchers wrote.

How Black Widows Form, And Why This One Breaks the Rules

The planet orbits what astronomers call a pulsar, or the collapsed core left behind when a massive star explodes. Pulsars spin incredibly fast and shoot out beams of radiation like cosmic lighthouses.

This particular system is what’s called a “black widow,” named after the creepy, venomous spiders that eat their mates. In space, the pulsar slowly destroys its companion star through radiation and gravity, stealing away its outer layers bit by bit.

Scientists thought they understood how these systems form. This process should produce an object made mostly of helium if the stripping happens early enough, before the star begins converting helium into carbon in its core through nuclear fusion. The remnant should contain whatever elements existed in the star’s core at that moment, typically a mix of helium, carbon, nitrogen, and oxygen in moderate ratios.

This planet doesn’t fit that pattern at all.

“Did this thing form like a normal planet? No, because the composition is entirely different,” said Zhang. “Did it form by stripping the outside of a star, like normal black widow systems? Probably not, because nuclear physics doesn’t make pure carbon.”

Some rare stars show elevated carbon levels, with carbon-to-oxygen ratios reaching 12 to 81. While higher than typical stars, these values still fall far short of what this planet displays.

Other aging stars convert helium into carbon through a nuclear process, creating what astronomers call “carbon stars.” These reach carbon-to-oxygen ratios of only several. They produce carbon-rich dust in their outflows, offering another potential carbon source. However, the mechanism for concentrating that dust into a Jupiter-mass planet with such extreme ratios remains unclear.

In one illustrative model, the planet consists mostly of helium with roughly 1% carbon by mass in its interior. A planet made entirely of carbon would be much smaller and denser than observations indicate, about one-third Jupiter’s radius rather than roughly matching it. But if the planet is mostly helium inside, what process concentrated so much carbon in the atmosphere we can see?

VIDEO: This animation shows an exotic exoplanet orbiting a distant pulsar, or rapidly rotating neutron star with radio pulses. The planet, which orbits about 1 million miles away from the pulsar, is stretched into a lemon shape by the pulsar’s strong gravitational tides. (Credit: NASA, ESA, CSA, Ralf Crawford (STScI))

Gamma-Ray Heat and Westward Winds

The planet’s heating differs from anything seen on worlds orbiting normal stars. Gamma rays likely penetrate deep into the atmosphere instead of warming just the surface layers the way visible sunlight does on Earth.

In the models, these high-energy photons deposit their energy at a depth where the pressure reaches about 10 bars, roughly 10 times the air pressure at sea level on Earth. This deep heating drives the planet’s wind patterns differently than on normal hot Jupiters (giant planets orbiting close to their stars).

The researchers tracked how the planet’s light shifted to bluer or redder wavelengths as it moved toward or away from Earth in its orbit. From these measurements, they determined the planet orbits at a tilt of 31 degrees (imagine tilting a hula hoop from flat by about one-third of a right angle) and has a mass between 1.4 and 2.4 times Jupiter’s mass.

The temperature structure shows dramatic day-night contrasts. The nightside maintains a relatively uniform 900 Kelvin (about 1,160 degrees Fahrenheit) with a smooth spectrum, suggesting either consistent temperature throughout that side or a thick cloud deck blocking our view. The dayside reaches 2,300 Kelvin (about 3,680 degrees Fahrenheit) at its hottest points.

Surprisingly, the hottest spot doesn’t line up with the point facing the pulsar. Instead, the temperature peak appears shifted westward by about 12 degrees, indicating powerful winds blowing opposite to the planet’s rotation direction.

Computer models of rapidly rotating planets predict exactly this behavior. Most hot Jupiters orbiting normal stars have winds flowing eastward around their equators, like a jet stream. But when a planet spins faster than once every 10 hours or so, the pattern flips. Westward winds dominate away from the equator. PSR J2322-2650b offers strong evidence consistent with this predicted pattern.

Diamonds and Soot

Here’s where it gets even wilder. At the planet’s surface, carbon exists as simple molecules and floating soot particles. But deep inside, the pressure is so intense that carbon atoms might be getting squeezed into diamond crystals.

Roger Romani of Stanford University, who is also one of the world’s top experts on black widow systems, has a theory: “As the companion cools down, the mixture of carbon and oxygen in the interior starts to crystallize. Pure carbon crystals float to the top and get mixed into the helium, and that’s what we see.”

If he’s right, this planet could have a helium ocean with diamond icebergs floating in it.

“But then something has to happen to keep the oxygen and nitrogen away,” Romani added. “And that’s where there’s controversy.”

Blasted by Gamma Rays

The planet gets heated in a way nothing in our solar system experiences. Instead of visible sunlight warming just the surface, gamma rays from the pulsar penetrate deep into the atmosphere.

Computer models show this creates temperature extremes. The night side stays around 1,160°F, hot enough to melt lead. The day side reaches 3,680°F, nearly hot enough to vaporize iron.

Artist’s illustration of a gamma-ray burst resulting from a collapsing stars, ejecting particles and radiation in a narrow jet. (Credit: Soheb Mandhai)

The heating pattern also creates powerful winds. On most planets that orbit close to their stars, winds blow eastward, circling the equator like Earth’s jet streams. But this planet spins so fast, one full rotation every 7.8 hours, that the pattern flips. Westward winds dominate instead.

The hottest spot on the planet sits about 12 degrees west of the point facing directly at the pulsar, proving those westward winds exist.

What Comes Next

This system gave astronomers a unique opportunity. Normally when you study a planet, the star it orbits is much brighter and drowns out the planet’s light. But this pulsar emits mostly gamma rays and high-energy particles that are invisible to Webb’s infrared cameras.

The discovery establishes PSR J2322-2650b as a laboratory for studying planetary atmospheres under extreme conditions never before observed. It combines ultrahigh carbon ratios with ultrafast rotation and external gamma-ray heating.

The planet’s existence raises questions about other ultralight black-widow companions. Do they share similar compositions, or is PSR J2322-2650b uniquely weird?

The researchers encourage observations of PSR J1719-1438, another pulsar companion with similar mass but much higher density of 21 grams per cubic centimeter (about twice the density of lead). That object might be an ultralow-mass carbon white dwarf (the dense core of a dead star) rather than a gas giant, offering a comparison case.

Better atmospheric models will require improved laboratory data for larger carbon molecules, including C4, C5, C3H, and C2H. These molecules likely exist in the atmosphere but can’t yet be identified without better measurements of their unique light-absorption fingerprints.

The formation mystery remains unsolved. The extreme carbon enrichment sits far outside any established scenario for producing planetary-mass objects around pulsars.

“It’s nice to not know everything,” said Romani. “I’m looking forward to learning more about the weirdness of this atmosphere. It’s great to have a puzzle to go after.”

Paper Summary Limitations

The study acknowledges several limitations. Many potentially important carbon molecules lack published spectral data, preventing their inclusion in atmospheric models. The 1D atmosphere models don’t account for temperature and composition variations across the planet’s disk. The heating mechanism remains uncertain, though gamma rays likely dominate. The exact energy deposition profile is unknown.

Funding and Disclosures

This work was funded by JWST General Observer program #5263. M.Z. acknowledges support from the 51 Pegasi b Fellowship funded by the Heising-Simons Foundation. The MeerKAT telescope observations were conducted by the South African Radio Astronomy Observatory. Part of this work was supported by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (project CE230100016). R.L. received support through NASA Hubble Fellowship grant HST-HF2-51559.001-A awarded by the Space Telescope Science Institute.

Publication Details

Publication Information: Zhang, M., Beleznay, M., Brandt, T.D., Romani, R.W., Gao, P., Beltz, H., Bailes, M., Nixon, M.C., Bean, J.L., Komacek, T.D., Coy, B.P., Fu, G., Luque, R., Reardon, D.J., Carli, E., Shannon, R.M., Fortney, J.J., Piette, A.A.A., Miller, M.C., and Desert, J-M. (2025). “A Carbon-rich Atmosphere on a Windy Pulsar Planet.” The Astrophysical Journal Letters, 995:L64. DOI: 10.3847/2041-8213/ae157c. University affiliations: University of Chicago, Stanford University (KIPAC), Space Telescope Science Institute, Carnegie Science, University of Maryland, Swinburne University of Technology, Arizona State University, University of Oxford, Johns Hopkins University, UC Santa Cruz, University of Birmingham, and University of Amsterdam.