2023-05-10 ミシガン大学
U-M graduate student Isaac Malsky, a co-author of the study, ran three-dimensional models for the planet, testing models with and without clouds and hazes, to see how these aerosols shape the thermal structure of the planet and help interpret the data. Image credit: NASA/JPL-Caltech/R. Hurt (IPAC)
◆GJ 1214bは雲や霞で覆われているが、JWSTの赤外線技術によって、その雲や霞を透過することができた。GJ 1214bの大気中には水蒸気や重い分子が含まれていることが判明し、水を大量に含んでいる可能性もあるという。
◆GJ 1214bは生命に適さない温度であるが、今後、JWSTの観測によって類似の惑星の観測が進められる見通しとなった。
＜関連情報＞
- https://news.umich.edu/researchers-measure-the-light-emitted-by-a-sub-neptune-planets-atmosphere-for-the-first-time/
- https://www.nature.com/articles/s41586-023-06159-5
JWSTの位相曲線から、GJ 1214bの反射的で金属に富む大気がわかる A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve
Eliza M.-R. Kempton,Michael Zhang,Jacob L. Bean,Maria E. Steinrueck,Anjali A. A. Piette,Vivien Parmentier,Isaac Malsky,Michael T. Roman,Emily Rauscher,Peter Gao,Taylor J. Bell,Qiao Xue,Jake Taylor,Arjun B. Savel,Kenneth E. Arnold,Matthew C. Nixon,Kevin B. Stevenson,Megan Mansfield,Sarah Kendrew,Sebastian Zieba,Elsa Ducrot,Achrène Dyrek,Pierre-Olivier Lagage,Keivan G. Stassun,Gregory W. Henry,Travis Barman,Roxana Lupu,Matej Malik,Tiffany Kataria,Jegug Ih,Guangwei Fu,Luis Welbanks & Peter McGill
Nature Published:10 May 2023
DOI:https://doi.org/10.1038/s41586-023-06159-5
Abstract
There are no planets intermediate in size between Earth and Neptune in our Solar System, yet these objects are found around a substantial fraction of other stars [1]. Population statistics show that close-in planets in this size range bifurcate into two classes based on their radii [2, 3]. It is hypothesized that the group with larger radii (referred to as “sub-Neptunes”) is distinguished by having hydrogen-dominated atmospheres that are a few percent of the total mass of the planets [4]. GJ 1214b is an archetype sub-Neptune that has been observed extensively using transmission spectroscopy to test this hypothesis [5-14]. However, themeasured spectra are featureless, and thus inconclusive, due to the presence of high-altitude aerosols in the planet’s atmosphere. Here we report a spectroscopic thermal phase curve of GJ 1214b obtained with JWST in the mid-infrared. The dayside and nightside spectra (average brightness temperatures of 553 ± 9 and 437 ± 19 K, respectively) each show >3σ evidence of absorption features, with H2O as the most likely cause in both. The measured global thermal emission implies that GJ 1214b’s Bond albedo is 0.51 ± 0.06. Comparison between the spectroscopic phase curve data and three-dimensional models of GJ 1214b reveal a planet with a high metallicity atmosphere blanketed by a thick and highly reflective layer of clouds or haze.
