Matt Nixon
@nixonmatthew.bsky.social
51 Pegasi b Fellow at Arizona State University and jazz enthusiast
The gas that came closest to explaining the observations out of everything we tested was propyne (C3H4), a hydrocarbon found on Neptune that hadn’t been tested before for K2-18 b. But it still fell far short of what we would consider a detection.
May 2, 2025 at 1:29 AM
The gas that came closest to explaining the observations out of everything we tested was propyne (C3H4), a hydrocarbon found on Neptune that hadn’t been tested before for K2-18 b. But it still fell far short of what we would consider a detection.
In fact, by those same Bayesian metrics mentioned earlier, we found that we could “detect” a whole range of gases, as long as you only compared them against a model with most other gases excluded. But if you test all of them together, those supposed detections vanish, even for DMS and DMDS.
May 2, 2025 at 1:29 AM
In fact, by those same Bayesian metrics mentioned earlier, we found that we could “detect” a whole range of gases, as long as you only compared them against a model with most other gases excluded. But if you test all of them together, those supposed detections vanish, even for DMS and DMDS.
We found that, due to the small signal size and high measurement uncertainty, anything from a collection of gases to random noise can explain the data. There just isn’t enough information in the spectrum to reach strong conclusions. But that only becomes clear if you test a large set of models.
May 2, 2025 at 1:29 AM
We found that, due to the small signal size and high measurement uncertainty, anything from a collection of gases to random noise can explain the data. There just isn’t enough information in the spectrum to reach strong conclusions. But that only becomes clear if you test a large set of models.
However, that initial analysis only considered a small set of chemical species in their atmospheric model. So we tried a range of alternative models, and considered dozens of chemical species that weren’t explored in previous work, some of which we might expect to see on this planet, others less so.
May 2, 2025 at 1:29 AM
However, that initial analysis only considered a small set of chemical species in their atmospheric model. So we tried a range of alternative models, and considered dozens of chemical species that weren’t explored in previous work, some of which we might expect to see on this planet, others less so.
As a case study, we investigate recent claims of a potential biosignature detection on K2-18 b. For K2-18 b, previous work found that a model including DMS and DMDS – gases proposed as potential biosignatures - outperformed a model without those chemicals, according to a Bayesian model comparison.
May 2, 2025 at 1:29 AM
As a case study, we investigate recent claims of a potential biosignature detection on K2-18 b. For K2-18 b, previous work found that a model including DMS and DMDS – gases proposed as potential biosignatures - outperformed a model without those chemicals, according to a Bayesian model comparison.
In exoplanet atmospheres, we often use Bayesian statistics to figure out if we have detected a gas. This is a powerful tool, but it comes with caveats. We can use it to compare the performance of two models, but just because one outperforms the other, doesn’t mean that either is necessarily “right”.
May 2, 2025 at 1:29 AM
In exoplanet atmospheres, we often use Bayesian statistics to figure out if we have detected a gas. This is a powerful tool, but it comes with caveats. We can use it to compare the performance of two models, but just because one outperforms the other, doesn’t mean that either is necessarily “right”.
To start, it’s important to recognise the amazing observations of exoplanet atmospheres we’re getting from JWST. This has allowed us to find strong evidence of several chemical species that were really hard to detect in the past, like methane and carbon dioxide.
May 2, 2025 at 1:29 AM
To start, it’s important to recognise the amazing observations of exoplanet atmospheres we’re getting from JWST. This has allowed us to find strong evidence of several chemical species that were really hard to detect in the past, like methane and carbon dioxide.
Just shared a new paper on the arXiv, led my @luiswel.bsky.social and me, on the challenges associated with detecting gases in exoplanet atmospheres. As the field pushes towards new and exciting opportunities, we thought it was time to talk about what it really means to “detect” something!
May 2, 2025 at 1:29 AM
Just shared a new paper on the arXiv, led my @luiswel.bsky.social and me, on the challenges associated with detecting gases in exoplanet atmospheres. As the field pushes towards new and exciting opportunities, we thought it was time to talk about what it really means to “detect” something!