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Scientists using NASA\u2019s James Webb Space Telescope have observed an entirely new type of exoplanet whose atmospheric composition challenges our understanding of how this type of planet forms.<\/p>\n
This bizarre, lemon-shaped body, possibly containing diamonds at its core, blurs the line between planets and stars.<\/p>\n
\u201cThis is a new type of planet atmosphere that nobody has ever seen before.\u201d<\/p>\n
Officially named PSR J2322-2650b, this object has an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. It has a mass about the same as Jupiter, but soot clouds float through the air\u2014and deep within the planet, these carbon clouds can condense and form diamonds. It orbits a rapidly spinning neutron star.<\/p>\n
How the planet came to be is a mystery.<\/p>\n
\u201cThe planet orbits a star that\u2019s completely bizarre\u2014the mass of the Sun, but the size of a city,\u201d explains the University of Chicago\u2019s Michael Zhang, the principal investigator on this study, which is accepted for publication in The Astrophysical Journal Letters<\/a>. \u201cThis is a new type of planet atmosphere that nobody has ever seen before.\u201d<\/p>\n \u201cThis was an absolute surprise,\u201d says team member Peter Gao of the Carnegie Earth and Planets Laboratory in Washington, DC. \u201cI remember after we got the data down, our collective reaction was \u2018What the heck is this?’\u201d<\/p>\n Odd couple<\/p>\n The new planet, PSR J2322-2650b, is orbiting a rapidly spinning neutron star, also known as a pulsar.<\/p>\n This star emits beams of electromagnetic radiation from its magnetic poles at regular intervals just milliseconds apart. But the star is emitting mostly gamma rays and other high-energy particles, which are invisible to the Webb telescope\u2019s infrared vision.<\/p>\n This means scientists can study the planet in intricate detail across its whole orbit\u2014normally an extremely difficult task, because stars usually far outshine their planets.<\/p>\n \u201cThis system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all,\u201d explains Maya Beleznay, a graduate student at Stanford University who worked on modelling the shape of the planet and the geometry of its orbit.<\/p>\n \u201cSo we get a really pristine spectrum. And we can better study this system in more detail than normal exoplanets.\u201d<\/p>\n Taking stock of the planet, the team was surprised.<\/p>\n \u201cInstead of finding the normal molecules we expect to see on an exoplanet\u2014like water, methane, and carbon dioxide\u2014we saw molecular carbon, specifically C3 and C2,\u201d says Zhang.<\/p>\n At the core of the planet, subjected to intense pressure, it\u2019s possible this carbon could be squeezed into diamonds.<\/p>\n But to the scientists, the larger question is how such a planet could have formed at all.<\/p>\n \u201cIt\u2019s very hard to imagine how you get this extremely carbon-enriched composition,\u201d says Zhang. \u201cIt seems to rule out every known formation mechanism.\u201d<\/p>\n Puzzling planet<\/p>\n PSR J2322-2650b is extraordinary close to its star, just 1 million miles away. In contrast, the Earth\u2019s distance from the Sun is about 100 million miles.<\/p>\n Because of its extremely tight orbit, the exoplanet\u2019s entire year\u2014the time it takes to go around its star\u2014is just 7.8 hours.<\/p>\n Applying models to the planet\u2019s brightness variations over its orbit, the team finds that immense gravitational forces from the much heavier pulsar are pulling the Jupiter-mass planet into a lemon shape.<\/p>\n