Figure showing a the plausible orbits for Eps Eri b, and a panel showing the scale of the orbits relative to the outer debris disk model of Booth et al.

A three panel figure showing the statistical distribution of inclination versus mass for the planet, broken down by seven different combinations of data. The scatter points follow an m*sin(i) curve, except for a series that does not include any RV data. A small black concentrated region shows the full model, with 1 and 3 sigma contours. The planet's mass is quoted at 0.98 +- 0.09 Mjup, and inclination as 41 +- 7 degrees.

Time for the promised thread on ε Eridani b!

I should emphasize this manuscript is a submitted draft—comments from the community are very welcome.

Bottom line: ε Eri b is likely a 1.0 Jupiter-mass planet, only 3.2pc away, on a 3.55 AU near-circular orbit, ~aligned with its debris disk. 🔭🪐🧪 [1/7]

Requirements for Joint Orbital Characterization of Cold Giants and Habitable Worlds with Habitable Worlds Observatory We determine optimal requirements for the joint detection of habitable-zone planets and cold giant planets with the Habitable Worlds Observatory (HWO). Analysis of 164 nearby stars shows that a corona...

A timely paper for #HWO25: is it enough to find Earth-like planets around other nearby stars? No! We need their planetary system contexts. Does life on Earth depend on Jupiter?

@sabinastro.bsky.social led this nice analysis of HWO requirements to detect Earths + Jupiters.

arxiv.org/abs/2507.21443

Congrats

The counter explanation against a water-world explanation for TOI-270d from Benneke+ is on my mind here. Not apparent to me that the intepretation from Wogan+ remains a strong fit with the current abudance measurements? Keen to get your thoughts 3/n

The arguments for abiotic origins for organosulfuric compounds is compelling. I wonder if there is a compelling alternate explanation to the water worlds hypothesis based on current abudance estimates for CH4 and CO2 and non-detections of H2O, NH3, or CO + potential abiotic organic compounds. 2/n

I think its unlikely the new evidence + interpretation for a water world will get as much discussion (newer data from Greaves, Seager, Bain+ for PH3 on Venus is an example that comes to mind) and a lot of the early impressions of the data being a flat line may prove difficult to change. 1/n

A water-rich interior in the temperate sub-Neptune K2-18 b revealed by JWST Temperate sub-Neptunes are compelling targets for detecting liquid-water oceans beyond the Solar System. If water-rich and lacking massive hydrogen-helium envelopes, these planets could sustain liquid...

Keen to get you and @luiswel.bsky.social thoughts on this expanded re-analysis from Hu et al. with additional NIRSpec data that still seem consistent with a water world arxiv.org/abs/2507.12622

Congrats 👏

Nice 👍

Congrats to Nora, she has done really well. How was the food?

Wonderful, good to know there is short to medium term follow up options for these exciting candidates

Congrats

Congrats John, great paper. Will repeat observations help here or is a far-IR scope the only way to break the degeneracy and confirm these planets?

Is there room for Vera Rubin Obs + DES survey transits to fit in? 😀

This is a photo of an exoplanet from JWST.

A photo.

Of a planet orbiting a star 60 lightyears away.

A real world, 568 trillion kilometres away.

Thank you for sharing this paper.....really useful to this discussion and it definitely flew under the radar even though i was actively looking for other papers on K2-18b. I'll give it a read soon

Maybe my bias but i am seeing a lot of "can't/is not" statements rather than "unlikely" statements when the hypothesis (not the claimed biosignature detections) is being discussed. This is why i brought up the under-discussed TOI-270d interpretation papers as a counter-example. 3/n

In this context, i am referencing broad dismissal of the validity of the water world hypothesis because the speaker/writer (blogs, articles not papers) favours alternate explanations despite current data (as i am aware) still allowing for this hypothesis (lifeless or not). 2/n

No worries on my end, happy to try and clarify my thoughts

Original hypothesis i am referencing is the water world concept (lifeless or not). For discourse, I am mostly referring to those online mostly from scicomms, amateur enthusiasts and other professional astronomers. 1/n

Why is an interpretation of say just the two-sided posterior yields on CO2 from SPARTA and JExoRES retrieval alone to constrain both lower and higher limits not valid e.g. Fig. 2? Thanks for engaging as its helpful for me to contextualize the discussions as a non-expert

Luque+ show median CO2 is slightly higher by 0.1 dex compared to Madhu2023 implying consistency. The pipelines don't show a flat or one-sided posteriors that would indicate non-detection. Posterior structure variation seem to me to be due to some sensitivity to modeling assumptions

I would re-phrase my earlier comment on robust detection for CO2 as my comment could be interpreted to mean stronger replication which is not the case and Mahdu23+ only reported CO2 to 3σ. Upon re-read of Luque, a rejection of the moderate CO2 detection is not apparent

original hypothesis even if the speaker/writer favours the intepretation by Wogan et al. Hopefully you agree these acknowledgments become important for accessing other parallel interpretations e.g. discussions on TOI-270d. 2/n

Thank you, this answer here directly addresses part of my poorly phrased question and my broad thoughts on online discussions of alternate hypothesis e.g. scaled down mini-Neptune intepretation by Wogan et al. with no follow-on acknowledgement of the limitations of current data to rule out the 1/n

Won't most detections from model-constrained parameters be hard to constrain if similar or better fits is likely from "broader hypothesis space"? How will this paradigm allow for two inconsistent but valid parallel solutions/interpretations as highlighted in Seager&Welbanks+?

My question then would be how to validate or test "constrained atmospheric models" e.g. Gasman et al. including the three hydrocarbons into their base model based on previous modelling of a likely atmosphere if a "broader/full hypothesis space" may provide a better fit based on real data.

The degree of sample context available for terrestrial samples is mostly missing for extrasolar atmospheres so I would agree with the assessment in your paper arguing for consideration of broader hypothesis space in searches and retrieval.

Thanks for pointing this out, big misread on my part. I went back to re-read some of the other examples i hinted at yesterday e.g. Chubb et al. 2020 (arxiv.org/abs/2004.13679) but they are mostly HST data which has its own issues so not sure what to make of it.

Thanks for breaking this down. I only read off each model with one hydrocarbon being tested for significance and I missed that each retrievals included all three hydrocarbon compounds.

Based on Schmidt et al. several commentators and critics have even cast doubt on CO2 at K2-18b when its detection appears to be robust and reproducible based on Luque et al. Any insights into why there is this discrepancy for independent reductions of the same data?