JWST Finds an Exoplanet Around a Pulsar Whose Atmosphere is All Carbon
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JWST Finds An Exoplanet Around A Pulsar Whose Atmosphere Is All Carbon:
Science advances through data that don't fit our current understanding. At least that was Thomas Kuhn's theory in his famous On the Structure of Scientific Revolutions. So scientists should welcome new data that challenges their understanding of how the universe works. A recent paper, available in pre-print on arXiv, using data from the James Webb Space Telescope (JWST) might just had found some data that can do that. It looked at an exoplanet around a millisecond pulsar and found its atmosphere is made up of almost entirely pure carbon.
This type of pulsar, PSR J2322-2650, is known as a "black widow" system, as it powers its high energy outbursts by stealing material from a neighboring star. In this case, that neighboring star has likely been degraded to a "hot Jupiter" companion planet that orbits its parent neutron star every 7.8 hours. A typical "black widow" formation process has two steps - one where the neutron star (which in this case is also a pulsar) steals the material, and a second step where it blasts its companion with high energy gamma radiation, ripping off most of the companion star's outer layers and resulting in a Jupiter-sized exoplanet composed mainly of helium.
The exoplanet around PSR J2322-2650, known as PSR J2322-2650b, does fit the description of a Jupiter-sized planet that seems to have the same density as what would be expected if it was made up primarily of helium. However, its atmosphere is unlike any other black widow companion ever seen. According to the spectrographic reports from JWST, its atmosphere is composed mainly of elemental carbon, taking the form of tricarbon (C3) or dicarbon (C2).
Usually those types of elements are found in the tails of comets, or in actual flames here on Earth. Their presence in a planet's atmosphere, especially in such abundant quantities, is new to science.
Another interesting thing about the planet's atmosphere is the difference between the day and night side. On the dayside, which is always facing the pulsar since the planet is tidally locked, temperatures can reach above 2000 and there are very clear chemical signatures. However, on the night side, there were almost no features at all, suggesting that side of the planet is covered in soot or something similar that doesn't have any distinct features.
To further prove how strange this planet's atmosphere is, the researchers calculated the ratios between carbon and oxygen as well as carbon and nitrogen. The C/O ratio was over 100, while the C/N ratio was over 10,000. In comparison, the Earth has a C/O ratio of .01 and a C/N ratio of 40. Obviously, there's a lot of carbon on this planet.
And that doesn't fit well with models of how scientists thought the planet should form. As part of the "black widow" process, the outer layers of the planet should have been either siphoned up by the companion star or burned away by that star's radiation. The fact that such a rich carbon atmosphere still exists remains a mystery. There are processes that can create such an atmosphere, such as a white-dwarf merger between [two?] "carbon stars", but even that falls short of explaining how the planet's C/O ratio got so high.
See also:
- A carbon-rich atmosphere on a windy pulsar planet
- JWST Examines Planet With Never Before Seen Carbon Atmosphere
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