{"id":19178,"date":"2026-02-12T22:05:18","date_gmt":"2026-02-12T22:05:18","guid":{"rendered":"https:\/\/readtrends.com\/en\/lhs-1903-inside-out\/"},"modified":"2026-02-12T22:05:18","modified_gmt":"2026-02-12T22:05:18","slug":"lhs-1903-inside-out","status":"publish","type":"post","link":"https:\/\/readtrends.com\/en\/lhs-1903-inside-out\/","title":{"rendered":"Astronomers detect a solar system they say should not be possible &#8211; CNN"},"content":{"rendered":"<article>\n<p><strong>Lead:<\/strong> Astronomers announced on 12 February 2026 the discovery of an unusual four-planet system around the red dwarf LHS 1903, located about 116 light-years from Earth. Using data from NASA\u2019s TESS and ESA\u2019s Cheops plus ground-based follow-up, the team found an unexpected sequence: a small rocky world close in, two gas-rich planets at intermediate distances, and a distant outer planet that is rocky. The outer planet, LHS 1903 e, is a roughly 1.7 Earth-radius super-Earth \u2014 a configuration that conflicts with the standard model in which rocky planets form inside and gas giants form outside a star\u2019s snow line. Researchers report their interpretation in a paper published this week in the journal Science and say the system may require rethinking how planets form around the galaxy\u2019s most common stars.<\/p>\n<h2>Key takeaways<\/h2>\n<ul>\n<li>Distance and discovery: LHS 1903 lies about 116 light-years away; the system was identified with TESS and characterized with ESA\u2019s Cheops (NASA\/ESA missions, launched 2018 and 2019 respectively).<\/li>\n<li>Architecture: Four planets orbit the M-dwarf in an order of rocky\u2013gaseous\u2013gaseous\u2013rocky, with the outermost, LHS 1903 e, being a 1.7 R\u2295 super-Earth.<\/li>\n<li>Formation tension: This &#8220;inside-out&#8221; ordering contradicts the typical pattern tied to the protoplanetary disk\u2019s snow line and the rapid core growth that leads to gas giants beyond it.<\/li>\n<li>Ruling out collisions and stripping: Dynamical simulations by the discovery team indicate giant impacts or envelope loss are unlikely to produce the observed architecture.<\/li>\n<li>Proposed mechanism: The authors favor a gas-depleted, sequential formation scenario in which planets form from the inside out as the disk\u2019s gas supply dwindles.<\/li>\n<li>Implications for M-dwarfs: If confirmed, the system provides a counterexample that will force planet-formation models for low-mass stars to account for very different formation timelines.<\/li>\n<li>Follow-up prospects: LHS 1903 e may be within reach of detailed atmospheric study with observatories like the James Webb Space Telescope, offering a test of its composition and formation history.<\/li>\n<\/ul>\n<h2>Background<\/h2>\n<p>Planet-formation theory has long linked a star\u2019s temperature gradient and the disk\u2019s snow line to the distribution of planet types. Close to a young star, high temperatures vaporize volatile compounds, leaving refractory materials such as silicates and iron to coagulate into rocky cores; farther out, ices can condense and speed core growth, enabling rapid accumulation of hydrogen and helium when cores exceed roughly 10 Earth masses. That dichotomy explains why the Solar System\u2019s four small rocky planets sit inside and the gas giants lie outside.<\/p>\n<p>Red dwarf stars (M dwarfs) like LHS 1903 are the most abundant stellar type in the Galaxy and have long been known to host compact planetary systems. But relative to Sun-like stars, their lower luminosity pushes the snow line closer in, altering where ices and gas are available during planet formation. Observational surveys over the past decade have shown many compact M-dwarf systems with mixed planet sizes, but the clear reversal \u2014 a distant rocky world sitting beyond gas-rich neighbors \u2014 is novel enough to challenge standard expectations.<\/p>\n<h2>Main event<\/h2>\n<p>The system was first flagged by TESS, which detects transiting planets by measuring periodic dips in starlight. The candidate configuration was then followed up with ESA\u2019s Cheops to refine planet radii and transit timing, and by an international network of ground-based facilities to validate the signals. The combined dataset resolved four transiting planets around LHS 1903 and allowed precise determination that the outer planet is denser and smaller than its two inner gaseous neighbors.<\/p>\n<p>Lead author Thomas Wilson (University of Warwick) and colleagues performed dynamical simulations to test whether collisions, tidal stripping, or late-stage envelope loss could explain the outer planet\u2019s rockier nature. According to the team, those scenarios could not consistently reproduce the observed masses, separations and long-term system stability. The simulations included numerous configurations and impact histories but failed to recreate the system without invoking an unlikely fine tuning of events.<\/p>\n<p>After excluding those pathways, the authors propose a gas-depleted, sequential formation model: the inner planets formed first when disk gas was abundant; the middle two accreted more gas and became mini-Neptunes, while the outermost formed later, when the disk had already lost much of its gas. In that late stage there was insufficient gas to form a hydrogen-helium envelope, leaving a rocky super-Earth at a larger orbital distance \u2014 effectively an &#8220;inside-out&#8221; formation order.<\/p>\n<h2>Analysis &#038; implications<\/h2>\n<p>If the authors\u2019 interpretation holds, LHS 1903 demonstrates that planet formation is more temporally variable than models that assume concurrent core formation predict. Disk lifetimes, local solid surface density, pebble drift and migration rates can all differ from system to system; a late-forming outer core in a gas-depleted environment offers one clear route to produce the observed architecture. Modelers will need to incorporate time-dependent disk depletion and stochastic growth histories to see how common such outcomes might be.<\/p>\n<p>The result is particularly important for M-dwarfs because their lower luminosity and closer-in snow lines change the radial structure where volatile-rich solids and gas are available. If sequential, inside-out growth is efficient around many low-mass stars, population-level predictions for planet radii and atmospheric retention around M-dwarfs will shift \u2014 with consequences for habitability estimates and target prioritization for atmospheric characterization.<\/p>\n<p>Observationally, LHS 1903 e presents a high-value target. A confirmed rocky composition and a measurable atmosphere (or lack thereof) would discriminate between formation scenarios: a secondary, thin atmosphere would support late, gas-poor formation; a retained thick hydrogen envelope would contradict the gas-depleted hypothesis. JWST and next-generation ground-based spectrographs could constrain atmospheric scale height and composition if transit spectroscopy is feasible given the system&#8217;s brightness and transit geometry.<\/p>\n<h2>Comparison &#038; data<\/h2>\n<figure>\n<table>\n<thead>\n<tr>\n<th>System<\/th>\n<th>Typical inner\/outer type<\/th>\n<th>Notable numbers<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Solar System<\/td>\n<td>Inner rocky, outer gas giants<\/td>\n<td>Inner planets small; gas giants >10 M\u2295 formed early<\/td>\n<\/tr>\n<tr>\n<td>LHS 1903<\/td>\n<td>Rocky, gas-rich, gas-rich, rocky (outer)<\/td>\n<td>Distance \u2248116 ly; LHS 1903 e \u22481.7 R\u2295<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>The table highlights the contrast between the canonical Solar System ordering and LHS 1903\u2019s unusual sequence. While the Solar System\u2019s giants reached runaway gas accretion early, LHS 1903\u2019s architecture suggests a staggered timeline with varying local gas availability. The core mass threshold of ~10 Earth masses for runaway gas accretion remains a key benchmark in these comparisons.<\/p>\n<h2>Reactions &#038; quotes<\/h2>\n<p>Wilson, the study\u2019s first author, framed the system as a direct challenge to prevailing formation intuition. He emphasized that the outer rocky planet is hard to reconcile with standard models without invoking a late, gas-poor formation epoch.<\/p>\n<blockquote>\n<p>&#8220;This is the first time we see a rocky planet so far out after gas-rich neighbors \u2014 it shouldn\u2019t happen under the standard picture,&#8221;<\/p>\n<p><cite>Thomas Wilson, University of Warwick (study lead)<\/cite><\/p><\/blockquote>\n<p>Coauthor Sara Seager described the result as an intriguing but still-debatable interpretation that will drive further work. Independent experts welcomed the data point while urging caution until atmospheric measurements or mass determinations tighten the constraints.<\/p>\n<blockquote>\n<p>&#8220;New discoveries remind us how much we still must learn about building planetary systems,&#8221;<\/p>\n<p><cite>Sara Seager, MIT (coauthor)<\/cite><\/p><\/blockquote>\n<p>External commentators stressed the system\u2019s value as a laboratory. Heather Knutson (Caltech), who was not part of the team, highlighted LHS 1903 e as an excellent JWST target to probe atmospheres and test formation scenarios observationally.<\/p>\n<blockquote>\n<p>&#8220;Planet e could host several kinds of atmospheres and may be cool enough for condensates \u2014 a compelling JWST target,&#8221;<\/p>\n<p><cite>Heather Knutson, Caltech (external scientist)<\/cite><\/p><\/blockquote>\n<aside>\n<details>\n<summary>Explainer: protoplanetary disks and the snow line<\/summary>\n<p>Planets form in disks of gas and dust around young stars. The disk\u2019s temperature decreases with distance from the star; close in, only refractory solids survive, while beyond the snow line volatiles like water freeze into ices. Ices increase solid mass available for core growth, enabling faster formation of massive cores that can accrete hydrogen-helium atmospheres. Disk gas disperses over a few million years, so timing of core growth relative to gas dispersal strongly affects whether a world becomes rocky or gas-rich.<\/p>\n<\/details>\n<\/aside>\n<h2>Unconfirmed<\/h2>\n<ul>\n<li>Atmospheric composition of LHS 1903 e is not yet measured; the presence of water or secondary volatiles remains speculative.<\/li>\n<li>While the gas-depleted, inside-out formation scenario fits current data, alternative pathways (e.g., atypical migration histories) have not been exhaustively excluded.<\/li>\n<\/ul>\n<h2>Bottom line<\/h2>\n<p>LHS 1903 offers a rare and robust data point that challenges conventional expectations about where rocky and gaseous planets should form. The discovery team\u2019s gas-depleted, sequential-formation hypothesis is plausible and grounded in dynamical tests, but it rests on interpretations that future mass and atmospheric measurements must confirm.<\/p>\n<p>For planet-formation theory and exoplanet surveys, this system underscores the need for models that include time-dependent disk evolution and stochastic growth. Observational follow-up \u2014 particularly precise mass determinations and transit spectroscopy with facilities like JWST \u2014 will be decisive in determining whether LHS 1903 is an outlier or the first-known example of a common, previously overlooked formation pathway.<\/p>\n<h2>Sources<\/h2>\n<ul>\n<li><a href=\"https:\/\/www.cnn.com\/2026\/02\/12\/science\/solar-system-inside-out-planets\" target=\"_blank\" rel=\"noopener\">CNN<\/a> \u2014 news report on the discovery (news).<\/li>\n<li><a href=\"https:\/\/www.science.org\" target=\"_blank\" rel=\"noopener\">Science (AAAS)<\/a> \u2014 peer-reviewed journal hosting the study (peer-reviewed).<\/li>\n<li><a href=\"https:\/\/tess.mit.edu\/\" target=\"_blank\" rel=\"noopener\">TESS (MIT\/NASA)<\/a> \u2014 mission overview and instrument documentation (official mission page).<\/li>\n<li><a href=\"https:\/\/www.esa.int\/Science_Exploration\/Space_Science\/CHEOPS\" target=\"_blank\" rel=\"noopener\">CHEOPS (ESA)<\/a> \u2014 mission overview and instrument documentation (official mission page).<\/li>\n<\/ul>\n<\/article>\n","protected":false},"excerpt":{"rendered":"<p>Lead: Astronomers announced on 12 February 2026 the discovery of an unusual four-planet system around the red dwarf LHS 1903, located about 116 light-years from Earth. Using data from NASA\u2019s TESS and ESA\u2019s Cheops plus ground-based follow-up, the team found an unexpected sequence: a small rocky world close in, two gas-rich planets at intermediate distances, &#8230; <a title=\"Astronomers detect a solar system they say should not be possible &#8211; CNN\" class=\"read-more\" href=\"https:\/\/readtrends.com\/en\/lhs-1903-inside-out\/\" aria-label=\"Read more about Astronomers detect a solar system they say should not be possible &#8211; CNN\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":19172,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"rank_math_title":"Inside-out planetary system discovered \u2014 AstroBrief","rank_math_description":"A four-planet system 116 light-years away (LHS 1903) hosts an outer 1.7 R\u2295 rocky world beyond two gas-rich planets, challenging standard planet-formation models.","rank_math_focus_keyword":"LHS 1903, exoplanets, planet formation, super-Earth, inside-out","footnotes":""},"categories":[2],"tags":[],"class_list":["post-19178","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-top-stories"],"_links":{"self":[{"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/posts\/19178","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/comments?post=19178"}],"version-history":[{"count":0,"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/posts\/19178\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/media\/19172"}],"wp:attachment":[{"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/media?parent=19178"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/categories?post=19178"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/readtrends.com\/en\/wp-json\/wp\/v2\/tags?post=19178"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}