A planet worth watching K2-18b sits at a distance from its star where liquid water<\/a> could pool on a surface. That position, combined with the atmospheric readings, made it a leading candidate for a Hycean world \u2013 a planet wrapped in a thick hydrogen atmosphere above a global ocean.<\/p>\n Nobody has confirmed that picture yet. Still, the possibility was enough to put the planet on every shortlist<\/a> for potential life beyond Earth.<\/p>\n The search for such life has a name. SETI \u2013 the search for extraterrestrial intelligence \u2013 looks for signals that no natural process should produce. <\/p>\n A narrow, focused radio transmission<\/a> is one of the cleanest signatures of technology, and that is what the team went looking for.<\/p>\n Two telescopes, one target<\/p>\n Dr. C.D. Tremblay, a project scientist at the SETI Institute<\/a>, led the effort. The search paired the Karl G. Jansky Very Large Array in New Mexico with the MeerKAT array in South Africa.<\/p>\n Coordinating two instruments on opposite sides of the world is unusual. The arrangement handed the team coverage no single site could provide. Together, the telescopes listened from 544 megahertz up to nearly 10 gigahertz.<\/p>\n Observing sessions were timed to span at least one full trip of the planet around its star. Any repeating alien signal from K2-18b would therefore have had its chance to appear.<\/p>\n Pointing two telescopes at a star is the easy part. Radio dishes pick up an avalanche of signals, and most come from human activity here on Earth. <\/p>\n Pulling a faint whisper out of that racket falls to software \u2013 and to the people deciding what the software should discard.<\/p>\n Cutting through the noise<\/p>\n The team built a filtering system with five separate checks, each aimed at something that could fool a search. <\/p>\n Whole frequency bands known to be jammed with earthly interference went first. It was the radio version of muting channels where humans never stop talking.<\/p>\n Another check leaned on the Doppler effect \u2013 the same shift that makes a siren change pitch as an ambulance races past. <\/p>\n A signal traveling between planets should drift in frequency. Anything sitting perfectly still almost certainly came from Earth.<\/p>\n A separate filter dropped signals that were either too faint or suspiciously strong. That cleared most false alarms. By the team\u2019s own admission, though, it might have swept away a weak real signal too.<\/p>\n The sharpest trick used the telescopes to form separate \u201cbeams\u201d<\/a> aimed at different patches of sky. A signal from the planet should land only in the beam pointed at it. Earthly interference, by contrast, bleeds into every beam at once.<\/p>\n Results from K2-18b<\/p>\n Across every band and every session, millions of candidate signals came through. Every one of them was rejected. None had the focused, narrow profile that would point to technology rather than nature.<\/p>\n A blank result still carries weight. Because the sweep was so thorough, the team could set a firm ceiling on the strength of any transmitter in that system. <\/p>\n The limit lands near the output once produced by the Arecibo radar system in Puerto Rico.<\/p>\n Put simply, anyone broadcasting from there is not using anything louder than humanity\u2019s own strongest beacons. <\/p>\n It is the first time such a limit has been drawn for a planet of this type using telescopes working in tandem.<\/p>\n Why the silence counts<\/p>\n The real prize is not the absence of a signal. Until this study, nobody had run a coordinated, two-telescope sweep of this kind on such a world. No one had shown that automated filtering could handle the incoming flood of data, either.<\/p>\n That proof of concept arrives at a useful moment. Sorting millions of signals by hand would be hopeless, and instruments like the planned Square Kilometre Array<\/a> will soon produce data volumes that dwarf anything available now. <\/p>\n A framework already tested on K2-18b hands those future surveys a running start instead of a blank page.<\/p>\n For now, the planet is quiet. The work done here means that if it ever does start talking, the listening tools will be sharp enough to notice \u2013 and to tell a real voice apart from the noise we make ourselves.<\/p>\n The study is published in the journal The Astronomical Journal<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates. <\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Astronomers have completed the first coordinated radio hunt for alien signals from K2-18b \u2013 a possible ocean world…\n","protected":false},"author":2,"featured_media":463546,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[111,139,69,147,392],"class_list":["post-463545","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-new-zealand","tag-newzealand","tag-nz","tag-science","tag-space"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/463545","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=463545"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/463545\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/463546"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=463545"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=463545"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=463545"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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