{"id":17,"date":"2016-02-01T13:01:04","date_gmt":"2016-02-01T13:01:04","guid":{"rendered":"http:\/\/www.wilder.diskstation.me\/pascal-tremblin\/?p=17"},"modified":"2016-08-19T14:28:14","modified_gmt":"2016-08-19T14:28:14","slug":"cloudless-atmospheres-for-lt-dwarfs-and-extra-solar-giant-planets","status":"publish","type":"post","link":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/?p=17","title":{"rendered":"Cloudless atmospheres for L\/T dwarfs and extra-solar giant planets"},"content":{"rendered":"<p>The admitted, conventional scenario to explain the complex spectral evolution of brown dwarfs (BDs) since their first detection 20 years ago has always been the key role played by micron-size condensates, called \u201cdust\u201d or \u201cclouds,\u201d in their atmosphere. This scenario, however, faces major problems, in particular the J-band brightening and the resurgence of FeH absorption at the L to T transition, and a physical first-principle understanding of this transition is lacking.\u00a0<a href=\"http:\/\/iopscience.iop.org\/article\/10.3847\/2041-8205\/817\/2\/L19\/meta\" target=\"_blank\">In a Letter published in ApJL<\/a>, we propose a new, completely different explanation for BD and extrasolar giant planet (EGP) spectral evolution, without the need to invoke clouds. We show that, due to the slowness of the CO\/ CH4 and N2\/NH3 chemical reactions, brown dwarf (L and T, respectively) and EGP atmospheres are subject to a thermo-chemical instability similar in nature to the fingering or chemical convective instability present in Earth oceans and at the Earth core\/mantle boundary. The induced small-scale turbulent energy transport reduces the temperature gradient in the atmosphere, explaining the observed increase in near-infrared J\u2013H and J\u2013K colors of L dwarfs and hot EGPs, while a warming up of the deep atmosphere along the L to T transition, as the CO\/CH4 instability vanishes, naturally solves the two aforementioned puzzles, and provides a physical explanation of the L to T transition. This new picture leads to a drastic revision of our understanding of BD and EGP atmospheres and their evolution.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The admitted, conventional scenario to explain the complex spectral evolution of brown dwarfs (BDs) since their first detection 20 years ago has always been the key role played by micron-size condensates, called \u201cdust\u201d or \u201cclouds,\u201d in their atmosphere. This scenario,<span class=\"ellipsis\">&hellip;<\/span> <span class=\"read-more\"><a href=\"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/?p=17\">Read more &#8250;<\/a><\/span><\/p>\n","protected":false},"author":2,"featured_media":61,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-17","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-atmospheres"],"_links":{"self":[{"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/posts\/17","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=17"}],"version-history":[{"count":2,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/posts\/17\/revisions"}],"predecessor-version":[{"id":53,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/posts\/17\/revisions\/53"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=\/wp\/v2\/media\/61"}],"wp:attachment":[{"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wilder.diskstation.me\/pascal-tremblin\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}