Saved in:
| Main Authors: | , , , , , , , , , , , , |
|---|---|
| Format: | Preprint |
| Published: |
2025
|
| Subjects: | |
| Online Access: | https://arxiv.org/abs/2509.17231 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866914188705660928 |
|---|---|
| author | Teske, Johanna K. Wallack, Nicole L. Piette, Anjali A. A. Dang, Lisa Lichtenberg, Tim Plotnykov, Mykhaylo Pierrehumbert, Raymond T. Postolec, Emma Boucher, Samuel McGinty, Alex Peng, Bo Valencia, Diana Hammond, Mark |
| author_facet | Teske, Johanna K. Wallack, Nicole L. Piette, Anjali A. A. Dang, Lisa Lichtenberg, Tim Plotnykov, Mykhaylo Pierrehumbert, Raymond T. Postolec, Emma Boucher, Samuel McGinty, Alex Peng, Bo Valencia, Diana Hammond, Mark |
| contents | Ultrashort-period (USP) exoplanets -- with $R_p \leq 2~$R$_{\oplus}$ and periods $\leq$1 day -- are expected to be stripped of volatile atmospheres by intense host star irradiation, which is corroborated by their nominal bulk densities and previous eclipse observations consistent with bare rock surfaces. However, a few USP planets appear anomalously under-dense relative to an Earth-like composition, suggesting an exotic interior structure (e.g., core-less) or a volatile-rich secondary atmosphere increasing their apparent radius. Here we present the first dayside emission spectrum of the low-density (4.3$\pm$0.4 g~cm$^{-3}$) USP planet TOI-561 b, which orbits an iron-poor, alpha-rich, $\sim$10 Gyr old thick disk star. Our 3-5 $μ$m JWST/NIRSpec observations demonstrate the dayside of TOI-561 b is inconsistent with a bare-rock surface at high statistical significance, suggesting instead a thick volatile envelope that is cooling the dayside to well below the $\sim$3000 K expected in the bare-rock or thin-atmosphere case. These results reject the popular hypothesis of complete atmospheric desiccation for highly irradiated exoplanets and support predictions that planetary-scale magma oceans can retain substantial reservoirs of volatiles, opening the geophysical study of ultrahot super-Earths through the lenses of their atmospheres. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_17231 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A Thick Volatile Atmosphere on the Ultrahot Super-Earth TOI-561 b Teske, Johanna K. Wallack, Nicole L. Piette, Anjali A. A. Dang, Lisa Lichtenberg, Tim Plotnykov, Mykhaylo Pierrehumbert, Raymond T. Postolec, Emma Boucher, Samuel McGinty, Alex Peng, Bo Valencia, Diana Hammond, Mark Earth and Planetary Astrophysics Ultrashort-period (USP) exoplanets -- with $R_p \leq 2~$R$_{\oplus}$ and periods $\leq$1 day -- are expected to be stripped of volatile atmospheres by intense host star irradiation, which is corroborated by their nominal bulk densities and previous eclipse observations consistent with bare rock surfaces. However, a few USP planets appear anomalously under-dense relative to an Earth-like composition, suggesting an exotic interior structure (e.g., core-less) or a volatile-rich secondary atmosphere increasing their apparent radius. Here we present the first dayside emission spectrum of the low-density (4.3$\pm$0.4 g~cm$^{-3}$) USP planet TOI-561 b, which orbits an iron-poor, alpha-rich, $\sim$10 Gyr old thick disk star. Our 3-5 $μ$m JWST/NIRSpec observations demonstrate the dayside of TOI-561 b is inconsistent with a bare-rock surface at high statistical significance, suggesting instead a thick volatile envelope that is cooling the dayside to well below the $\sim$3000 K expected in the bare-rock or thin-atmosphere case. These results reject the popular hypothesis of complete atmospheric desiccation for highly irradiated exoplanets and support predictions that planetary-scale magma oceans can retain substantial reservoirs of volatiles, opening the geophysical study of ultrahot super-Earths through the lenses of their atmospheres. |
| title | A Thick Volatile Atmosphere on the Ultrahot Super-Earth TOI-561 b |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2509.17231 |