![\"This](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14429e-PSR-J2322-2650b.jpg\")
<\/a><\/p>\nThis artist\u2019s concept shows what PSR J2322-2650b may look like. Image credit: NASA \/ ESA \/ CSA \/ Ralf Crawford, STScI.<\/p>\n
\u201cThis was an absolute surprise,\u201d said Dr. Peter Gao, an astronomer at the Carnegie Earth and Planets Laboratory.<\/p>\n
\u201cI remember after we got the data down, our collective reaction was \u2018What the heck is this?\u2019 It\u2019s extremely different from what we expected.\u201d<\/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 said Maya Beleznay, a Ph.D. candidate at Stanford University.<\/p>\n
\u201cSo we get a really pristine spectrum. And we can study this system in more detail than normal exoplanets.\u201d<\/p>\n
\u201cThe planet orbits a star that\u2019s completely bizarre \u2014 the mass of the Sun, but the size of a city,\u201d said Dr. Michael Zhang, an astronomer at the University of Chicago.<\/p>\n
\u201cThis is a new type of planet atmosphere that nobody has ever seen before. Instead of finding the normal molecules we expect to see on an exoplanet \u2014 like water, methane, and carbon dioxide \u2014 we saw molecular carbon, specifically C3 and C2.\u201d<\/p>\n
Molecular carbon is very unusual because at these temperatures (over 2,000 degrees Celsius), if there are any other types of atoms in the atmosphere, carbon will bind to them.<\/p>\n
Out of the approximately 150 planets that astronomers have studied inside and outside the Solar System, no others have any detectable molecular carbon.<\/p>\n
\u201cDid this thing form like a normal planet? No, because the composition is entirely different,\u201d Dr. Zhang said.<\/p>\n
\u201cDid it form by stripping the outside of a star, like \u2018normal\u2019 black widow systems are formed? Probably not, because nuclear physics does not make pure carbon.\u201d<\/p>\n
\u201cIt\u2019s very hard to imagine how you get this extremely carbon-enriched composition. It seems to rule out every known formation mechanism.\u201d<\/p>\n
The authors propose one evocative phenomenon that could occur in the unique atmosphere.<\/p>\n
\u201cAs the companion cools down, the mixture of carbon and oxygen in the interior starts to crystallize,\u201d said Dr. Roger Romani, an astronomer at Stanford University and the Kavli Institute for Particle Astrophysics and Cosmology Institute.<\/p>\n
\u201cPure carbon crystals float to the top and get mixed into the helium, and that\u2019s what we see.\u201d<\/p>\n
\u201cBut then something has to happen to keep the oxygen and nitrogen away. And that\u2019s where the mystery come in.\u201d<\/p>\n
\u201cBut it\u2019s nice to not know everything. I\u2019m looking forward to learning more about the weirdness of this atmosphere. It\u2019s great to have a puzzle to go after.\u201d<\/p>\n