Scientists using NASA’s James Webb Space Telescope have observed a rare type of exoplanet, or planet outside our solar system, whose atmospheric composition challenges our understanding of how it formed.
Officially named PSR J2322-2650b, this Jupiter-mass object appears to have an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. Soot clouds likely float through the air, and deep within the planet, these carbon clouds can condense and form diamonds. How the planet came to be is a mystery. The paper appears Tuesday in The Astrophysical Journal Letters.
“This was an absolute surprise,” said study co-author Peter Gao of the Carnegie Earth and Planets Laboratory in Washington. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’ It's extremely different from what we expected.”
Image A: Exoplanet PSR J2322-2650b and Pulsar (Artist's Concept)
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. Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)
This planet-mass object was known to orbit a pulsar, a rapidly spinning neutron star. A pulsar emits beams of electromagnetic radiation at regular intervals typically ranging from milliseconds to seconds. These pulsing beams can only be seen when they are pointing directly toward Earth, much like beams from a lighthouse.
This millisecond pulsar is expected to be emitting mostly gamma rays and other high energy particles, which are invisible to Webb’s infrared vision. Without a bright star in the way, scientists can study the planet in intricate detail across its whole orbit.
“This system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all,” said Maya Beleznay, a third-year PhD candidate at Stanford University in California who worked on modeling the shape of the planet and the geometry of its orbit. “So we get a really pristine spectrum. And we can study this system in more detail than normal exoplanets.”
“The planet orbits a star that's completely bizarre — the mass of the Sun, but the size of a city,” said the University of Chicago’s Michael Zhang, the principal investigator on this study. “This 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 — like water, methane, and carbon dioxide — we saw molecular carbon, specifically C 3 and C 2. ”
Molecular carbon is very unusual because at these temperatures, if there are any other types of atoms in the atmosphere, carbon will bind to them. (Temperatures on the planet range from 1,200 degrees Fahrenheit at the coldest points of the night side to 3,700 degrees Fahrenheit at the hottest points of the day side.) Molecular carbon is only dominant if there's almost no oxygen or nitrogen. Out of the approximately 150 planets that astronomers have studied inside and outside the solar system, no others have any detectable molecular carbon.
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