Sublimating exocomets in the PDS 70 system

Sublimating exocomets in the PDS 70 system | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Sublimating exocomets in the PDS 70 system Aline Novais, Jens Hoeijmakers, Bibiana Prinoth, Alexandra Murphy, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6925058/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Young star systems are used to study ongoing or recent planet formation processes, by observations of protoplanets, gas, and planetesimals in their disks. The young protostar PDS 70 hosts two gas giant planets and a disk containing gas and dust that is being cleared by the emerging star. Recent observations by the James Webb Space Telescope (JWST) have indicated the presence of water in the inner 0.05 AU from the star (Perotti et al. 2023), but the origin of this water remains unclear. Here we report the discovery of variable absorption lines of neutral sodium in archival High Accuracy Radial velocity Planet Searcher (HARPS) spectra of PDS 70. These absorption lines are strongly Doppler-shifted and partially cover the projected stellar disk, indicating that the absorbing clouds are fast-moving and spatially confined. We interpret these sodium lines as sublimation of planetesimals as they pass close to the star on highly elliptical orbits, reminiscent of the exocomet phenomenon that has presently been observed only in a handful of other young debris-disk hosting systems (Ferlet et al. 1987, Montgomery & Welsh 2012, Kiefer et al. 2014, Kiefer et al. 2014b, Rappaport et al. 2018, Strøm et al. 2020). These HARPS data therefore suggest that infalling, sublimating icy exocomets could be responsible for sourcing the previously observed water in the inner, terrestrial planet-forming region of the PDS 70 system. This is the first evidence of exocomet activity in PDS 70, placing the system as the youngest system in which exocomets have been detected, at a time when planet formation is still ongoing. In the Solar System, planetesimals from the giant planet region are proposed as having been a source of delivery of volatiles to the inner parts of the system (O’brien et al. 2006, Raymond et al. 2009, Walsh et al. 2011, O’brien et al. 2014, Raymond & Izidoro 2017, O’Brien et al. 2018, Mandt et al. 2024), and a similar phenomenon may be presently occurring in PDS 70. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Exoplanets Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Transient astrophysical phenomena Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6925058","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":478640862,"identity":"da9882bc-faf4-40b8-8ef1-a79e8cf4aec7","order_by":0,"name":"Aline 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The young protostar PDS 70 hosts two gas giant planets and a disk containing gas and dust that is being cleared by the emerging star. Recent observations by the James Webb Space Telescope (JWST) have indicated the presence of water in the inner 0.05 AU from the star (Perotti et al. 2023), but the origin of this water remains unclear. Here we report the discovery of variable absorption lines of neutral sodium in archival High Accuracy Radial velocity Planet Searcher (HARPS) spectra of PDS 70. These absorption lines are strongly Doppler-shifted and partially cover the projected stellar disk, indicating that the absorbing clouds are fast-moving and spatially confined. We interpret these sodium lines as sublimation of planetesimals as they pass close to the star on highly elliptical orbits, reminiscent of the exocomet phenomenon that has presently been observed only in a handful of other young debris-disk hosting systems (Ferlet et al. 1987, Montgomery \u0026 Welsh 2012, Kiefer et al. 2014, Kiefer et al. 2014b, Rappaport et al. 2018, Strøm et al. 2020). These HARPS data therefore suggest that infalling, sublimating icy exocomets could be responsible for sourcing the previously observed water in the inner, terrestrial planet-forming region of the PDS 70 system. This is the first evidence of exocomet activity in PDS 70, placing the system as the youngest system in which exocomets have been detected, at a time when planet formation is still ongoing. In the Solar System, planetesimals from the giant planet region are proposed as having been a source of delivery of volatiles to the inner parts of the system (O’brien et al. 2006, Raymond et al. 2009, Walsh et al. 2011, O’brien et al. 2014, Raymond \u0026 Izidoro 2017, O’Brien et al. 2018, Mandt et al. 2024), and a similar phenomenon may be presently occurring in PDS 70.","manuscriptTitle":"Sublimating exocomets in the PDS 70 system","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-28 03:06:22","doi":"10.21203/rs.3.rs-6925058/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"5b81ba98-f896-4e47-a719-1a2c9b58fffc","owner":[],"postedDate":"July 28th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":50821334,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Exoplanets"},{"id":50821335,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Transient astrophysical phenomena"}],"tags":[],"updatedAt":"2025-12-08T10:50:34+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-28 03:06:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6925058","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6925058","identity":"rs-6925058","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}