{"id":111,"date":"2016-02-01T10:06:31","date_gmt":"2016-02-01T10:06:31","guid":{"rendered":"http:\/\/www.wilder.diskstation.me\/erc-atmo\/?p=111"},"modified":"2016-02-01T10:06:31","modified_gmt":"2016-02-01T10:06:31","slug":"p2","status":"publish","type":"post","link":"https:\/\/www.erc-atmo.eu\/?p=111","title":{"rendered":"Pre-ERC result: Cloudless atmospheres for L\/T dwarfs and extra-solar giant planets"},"content":{"rendered":"<p style=\"text-align: justify;\">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\" rel=\"noopener\">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, however, faces major problems, in particular the J-band brightening and the resurgence of FeH absorption &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/www.erc-atmo.eu\/?p=111\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Pre-ERC result: Cloudless atmospheres for L\/T dwarfs and extra-solar giant planets&#8221;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":112,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[2],"tags":[],"_links":{"self":[{"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=\/wp\/v2\/posts\/111"}],"collection":[{"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=111"}],"version-history":[{"count":0,"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=\/wp\/v2\/posts\/111\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=\/wp\/v2\/media\/112"}],"wp:attachment":[{"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=111"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=111"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.erc-atmo.eu\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}