Ponderings on the Possible Preponderance of Perpendicular Planets
Misalignments between planetary orbits and the equatorial planes of their host stars are clues about the formation and evolution of planetary systems. Earlier work found evidence for a peak near 90° in the distribution of stellar obliquities, based on frequentist tests. We performed hierarchical Bay...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2023-01-01
|
| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/acd62f |
| _version_ | 1797694766300790784 |
|---|---|
| author | Jared C. Siegel Joshua N. Winn Simon H. Albrecht |
| author_facet | Jared C. Siegel Joshua N. Winn Simon H. Albrecht |
| author_sort | Jared C. Siegel |
| collection | DOAJ |
| description | Misalignments between planetary orbits and the equatorial planes of their host stars are clues about the formation and evolution of planetary systems. Earlier work found evidence for a peak near 90° in the distribution of stellar obliquities, based on frequentist tests. We performed hierarchical Bayesian inference on a sample of 174 planets for which either the full three-dimensional stellar obliquity has been measured (72 planets) or for which only the sky-projected stellar obliquity has been measured (102 planets). We investigated whether the obliquities are best described by a Rayleigh distribution or by a mixture of a Rayleigh distribution representing well-aligned systems and a different distribution representing misaligned systems. The mixture models are strongly favored over the single-component distribution. For the misaligned component, we tried an isotropic distribution and a distribution peaked at 90° and found the evidence to be essentially the same for both models. Thus, our Bayesian inference engine did not find strong evidence favoring a “perpendicular peak,” unlike the frequentist tests. We also investigated selection biases that affect the inferred obliquity distribution, such as the bias of the gravity-darkening method against obliquities near 0° or 180°. Further progress in characterizing the obliquity distribution will probably require the construction of a more homogeneous and complete sample of measurements. |
| first_indexed | 2024-03-12T03:02:34Z |
| format | Article |
| id | doaj.art-de942b7ae9f94916934e87fcb883131a |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-12T03:02:34Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj.art-de942b7ae9f94916934e87fcb883131a2023-09-03T14:42:56ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019501L210.3847/2041-8213/acd62fPonderings on the Possible Preponderance of Perpendicular PlanetsJared C. Siegel0https://orcid.org/0000-0002-9337-0902Joshua N. Winn1https://orcid.org/0000-0002-4265-047XSimon H. Albrecht2https://orcid.org/0000-0003-1762-8235Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA ; siegeljc@princeton.eduDepartment of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA ; siegeljc@princeton.eduDepartment of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA ; siegeljc@princeton.edu; Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University , Ny Munkegade 120, DK-8000 Aarhus C, DenmarkMisalignments between planetary orbits and the equatorial planes of their host stars are clues about the formation and evolution of planetary systems. Earlier work found evidence for a peak near 90° in the distribution of stellar obliquities, based on frequentist tests. We performed hierarchical Bayesian inference on a sample of 174 planets for which either the full three-dimensional stellar obliquity has been measured (72 planets) or for which only the sky-projected stellar obliquity has been measured (102 planets). We investigated whether the obliquities are best described by a Rayleigh distribution or by a mixture of a Rayleigh distribution representing well-aligned systems and a different distribution representing misaligned systems. The mixture models are strongly favored over the single-component distribution. For the misaligned component, we tried an isotropic distribution and a distribution peaked at 90° and found the evidence to be essentially the same for both models. Thus, our Bayesian inference engine did not find strong evidence favoring a “perpendicular peak,” unlike the frequentist tests. We also investigated selection biases that affect the inferred obliquity distribution, such as the bias of the gravity-darkening method against obliquities near 0° or 180°. Further progress in characterizing the obliquity distribution will probably require the construction of a more homogeneous and complete sample of measurements.https://doi.org/10.3847/2041-8213/acd62fExoplanet astronomyAstrostatistics |
| spellingShingle | Jared C. Siegel Joshua N. Winn Simon H. Albrecht Ponderings on the Possible Preponderance of Perpendicular Planets The Astrophysical Journal Letters Exoplanet astronomy Astrostatistics |
| title | Ponderings on the Possible Preponderance of Perpendicular Planets |
| title_full | Ponderings on the Possible Preponderance of Perpendicular Planets |
| title_fullStr | Ponderings on the Possible Preponderance of Perpendicular Planets |
| title_full_unstemmed | Ponderings on the Possible Preponderance of Perpendicular Planets |
| title_short | Ponderings on the Possible Preponderance of Perpendicular Planets |
| title_sort | ponderings on the possible preponderance of perpendicular planets |
| topic | Exoplanet astronomy Astrostatistics |
| url | https://doi.org/10.3847/2041-8213/acd62f |
| work_keys_str_mv | AT jaredcsiegel ponderingsonthepossiblepreponderanceofperpendicularplanets AT joshuanwinn ponderingsonthepossiblepreponderanceofperpendicularplanets AT simonhalbrecht ponderingsonthepossiblepreponderanceofperpendicularplanets |