There’s been a big claim of a marker of life, known as a biosignature, found using JWST in the atmosphere of an exoplanet known as K2-18b. The data also confirmed this planet was a “Hycean” world, a planet with a liquid water ocean surrounded by a hydrogen dominated atmosphere. The biosignature that’s claimed to have been found is dimethyl sulphide, a molecule that on Earth is mostly produced by phytoplankton in the ocean. But how strong actually is the evidence for this claimed detection of dimethyl sulphide?

Madhusudhan et al (2023; JWST observations of K2-18b) - [ Ссылка ]
Bell et al. (2023; JWST methane detection in the atmosphere of WASP-80b) - [ Ссылка ]
Benneke et al. (2019; HST observations of K2-18b and detection of water) - [ Ссылка ]
Hu et al. (2021; prediction of the molecules present in a hycean world atmosphere) - [ Ссылка ]
Greaves et al. (2021; phosphine detected in Venus’ atmosphere) - [ Ссылка ]
Constantinou et al. (2023; the different JWST reduction pipelines for exoplanet data) - [ Ссылка ]
Seager et al. (2013; biosignatures in exoplanet atmospheres) - [ Ссылка ]

JWST proposal 2722 - [ Ссылка ]
JWST proposal 2372 - [ Ссылка ]

Dr Jake Taylor on Twitter: [ Ссылка ]
Dr Jake Taylor on TikTok: [ Ссылка ]
Dr Ryan MacDonald on Twitter: [ Ссылка ]
Prof Jayne Birkby on Twitter: [ Ссылка ]

00:00 Introduction
01:24 What do we already know about K2-18b?
04:01 How we use JWST to study exoplanet atmospheres
06:00 What has JWST found in the atmosphere of K2-18b
12:17 The caveats to these results (especially the DMS claim)
14:08 What’s next? How can we confirm or deny this claim of DMS?
15:52 Bloopers

Correction: 02:38 K2-18b is LESS dense than Earth, not more dense. Verbal typo.




Video filmed on a Sony ⍺7 IV

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👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars.


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