Amateurs in the archive

I.A dip every 3.18 days

On 7 October 2026, Pavel Rabtsevich posted on Reddit under the title "I think I found a planet nobody knew existed. I used Claude Code to find it."[1][1] Rabtsevich, P., as u/This_Cell_1829 (7 October 2026). I think I found a planet nobody knew existed. I used Claude Code to find it. r/ClaudeAI, Reddit. reddit.com A day later his thread on X had close to half a million views,[2][2] Rabtsevich, P. (7 October 2026). "I think I found a planet nobody knew existed." Thread on X; view count checked on 8 October 2026. x.com and the French technology site Les Numériques had covered the story.[3][3] Les Numériques (8 October 2026). "Je crois avoir trouvé une planète que personne ne connaissait": épaulé par Claude Code, il obtient une observation du télescope TESS de la NASA. lesnumeriques.com

The work behind the headline is careful. Rabtsevich, an independent researcher in Tarragona, Spain,[4][4] Rabtsevich, P. (2026). A Pre-registered TESS Sector 110 Test of Two Transit-like Signals in TIC 4206066. Zenodo, version 1.1, 6 October 2026. doi.org searched the light curves of 126,246 stars from Sector 98 of NASA's Transiting Exoplanet Survey Satellite (TESS). A light curve records how a star's brightness changes over time. One star, TIC 4206066, a K dwarf about 60 percent the Sun's size and 116 light-years away, dims by about 0.05 percent for just under two hours every 3.18 days. He found the same dips in TESS data from 2018 and 2020, 23 transits in all. If a planet crossing that star causes them, the planet is 1.4 times the width of Earth.[1, 5][5] Rabtsevich, P. (2026). Two Transit-like Signals in TESS Photometry of the Nearby K Dwarf TIC 4206066. Preprint, Zenodo, 25 September 2026. doi.org

He ran most of the analysis through Claude Code, Anthropic's AI coding agent. By his account the agent downloaded the data, wrote the search code, fitted the transits, looked for false positives and reran tests that failed. He chose the questions and decided what counted as a pass. Fresh agent sessions with read-only access and OpenAI's tools reviewed the work.[1, 5] In about two weeks the project grew to 74 analyses and more than 1,000 scripts. One test hid a year of data, predicted its transits from the other two years and checked only those times. The dips arrived on schedule in all three years. A review also caught a statistical claim that was stronger than the data allowed, and he removed it.[1]

His preprint, posted on Zenodo on 25 September, calls the signal a planet candidate and claims nothing more. The vetting tool TRICERATOPS puts the false-positive probability at 3 to 4 percent, above the 1.5 percent limit its authors set for a validated planet. The main alternative is a planet orbiting an unseen companion star, which would take sharper imaging and radial-velocity measurements to rule out.[5, 6][6] Giacalone, S. et al. (2021). Vetting of 384 TESS Objects of Interest with TRICERATOPS and Statistical Validation of 12 Planet Candidates. The Astronomical Journal 161, 24. doi.org The TESS team approved his request for two-minute observations of the star as Director's Discretionary Targets program 100.[7][7] TESS Science Office, MIT (accessed 8 October 2026). Director's Discretionary Targets, program 100. tess.mit.edu On 6 October, before any new data existed, he published the predicted transit times and fixed rules for judging them. TESS is scheduled to observe the star from 31 October to 26 November 2026.[4]

It is tempting to call this a renaissance of amateur astronomy. The word needs care, because people outside universities have made discoveries all along. What has changed is how much of a professional analysis one person can now run alone.

II.Volunteers in the archive

Galaxy Zoo asked the public to sort galaxies by shape, and more than 100,000 people classified almost 900,000 objects from the Sloan Digital Sky Survey.[8][8] Lintott, C. et al. (2009). Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo? Monthly Notices of the Royal Astronomical Society 399, 129. doi.org In 2007 one of them, Hanny van Arkel, a Dutch schoolteacher, noticed a glowing green cloud of gas about the size of the Milky Way next to a spiral galaxy.[9][9] ESA/Hubble (2011). Hubble zooms in on a space oddity. Release heic1102. esahubble.org The team that studied "Hanny's Voorwerp" argued it was a light echo, gas still lit by a quasar in the neighbouring galaxy IC 2497 that has since faded or become hidden.[8] In 2009 the "Green Peas", small and very green galaxies that volunteers had noticed, turned out to be compact galaxies forming stars at extreme rates.[10][10] Cardamone, C. N. et al. (2009). Galaxy Zoo Green Peas: discovery of a class of compact extremely star-forming galaxies. Monthly Notices of the Royal Astronomical Society 399, 1191. doi.org

Planet Hunters applied the same idea to data from NASA's Kepler telescope. Two volunteers, Kian Jek and Robert Gagliano, spotted the transits of PH1b, announced in 2012, a planet that circles a pair of stars inside a system of four.[11][11] Schwamb, M. E. et al. (2013). Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System. The Astrophysical Journal 768, 127. Preprint arXiv:1210.3612, October 2012. doi.org Volunteers also called the light curve of the Kepler star KIC 8462852 "bizarre". Its brightness dropped irregularly, by up to about 20 percent. The 2016 paper on it, led by Tabetha Boyajian, favoured a swarm of comet fragments.[12][12] Boyajian, T. S. et al. (2016). Planet Hunters IX. KIC 8462852, where's the flux? Monthly Notices of the Royal Astronomical Society 457, 3988. doi.org

Planet Hunters TESS does the same with TESS data. In its first two years, more than 22,000 volunteers took part and the team presented 90 new planet candidates.[13][13] Eisner, N. L. et al. (2021). Planet Hunters TESS II: findings from the first two years of TESS. Monthly Notices of the Royal Astronomical Society 501, 4669. doi.org The project's first planet, TOI-813 b, is a Saturn-sized world on an 84-day orbit.[14][14] Eisner, N. L. et al. (2020). Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit. Monthly Notices of the Royal Astronomical Society 494, 750. doi.org In 2024 the team reported a mini-Neptune found by volunteers in the habitable zone of TOI 4633, a star with a stellar companion.[15][15] Eisner, N. L. et al. (2024). Planet Hunters TESS. V. A Planetary System Around a Binary Star, Including a Mini-Neptune in the Habitable Zone. The Astronomical Journal 167, 241. doi.org Volunteer flags also led to TESS's first planet around two stars. In 2019 Wolf Cukier, a high-school student interning at NASA Goddard, was reviewing systems that volunteers had marked as eclipsing binaries. About three days in, he saw a dip whose timing did not fit an eclipse. It was TOI-1338 b, a planet 6.9 times the size of Earth.[16, 17][16] Kazmierczak, J. (7 January 2020). NASA's TESS Mission Uncovers Its 1st World With Two Stars. NASA. nasa.gov[17] Kostov, V. B. et al. (2020). TOI-1338: TESS' First Transiting Circumbinary Planet. The Astronomical Journal 159, 253. doi.org

In Backyard Worlds: Planet 9, volunteers search animated infrared maps from NASA's WISE and NEOWISE missions for faint moving objects.[18][18] Kuchner, M. J. et al. (2017). The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project. The Astrophysical Journal Letters 841, L19. doi.org Dan Caselden wrote his own software to look for brown dwarfs, objects that lack the mass to burn like stars. While checking one candidate, he spotted a fainter object moving fast across the screen. Nicknamed "The Accident", it had slipped past standard searches because it looked like no known brown dwarf.[19][19] NASA Jet Propulsion Laboratory (31 August 2021). An Accidental Discovery Hints at a Hidden Population of Cosmic Objects. jpl.nasa.gov It is probably old and poor in heavy elements.[20][20] Kirkpatrick, J. D. et al. (2021). The Enigmatic Brown Dwarf WISEA J153429.75-104303.3 (a.k.a. "The Accident"). The Astrophysical Journal Letters 915, L6. doi.org

III.Telescopes in the backyard

On 20 September 2016, Víctor Buso, an amateur astronomer in Rosario, Argentina, was testing a new camera on his 40-centimetre telescope when a supernova appeared in the galaxy NGC 613. His images caught the explosion's first rise, at an unprecedented rate of about 40 magnitudes per day.[21][21] Bersten, M. C. et al. (2018). A surge of light at the birth of a supernova. Nature 554, 497. doi.org In 2019 Gennady Borisov, an amateur astronomer in Crimea, discovered the first confirmed interstellar comet.[22][22] NASA Science (accessed 8 October 2026). Comet 2I/Borisov. science.nasa.gov In 2021 three Australian amateurs saw a star blink before and after the dwarf planet Quaoar passed in front of it.[23][23] Astronomical Society of Australia (7 April 2026). Amateurs find 100 distant planets. And a giant ring that shouldn't be. Media release. asa.astronomy.org.au They co-authored the 2023 Nature paper on a dense ring around Quaoar outside its Roche limit, the distance inside which rings normally stay.[23, 24][24] Morgado, B. E. et al. (2023). A dense ring of the trans-Neptunian object Quaoar outside its Roche limit. Nature 614, 239. doi.org

Amateurs also do the follow-up that turns candidates into planets. In April 2026 the Astronomical Society of Australia gave its Page Medal to Chris Stockdale, who checks TESS candidates from a dome in his backyard and has co-authored more than 100 planet discovery papers.[23] NASA's Exoplanet Watch lets anyone time transits with their own telescope or with data from robotic telescopes, using free software.[25][25] NASA Science (accessed 8 October 2026). Exoplanet Watch. science.nasa.gov Exoplanet Watch and Unistellar observers helped confirm TIC 393818343 b, a warm Jupiter on a very eccentric orbit that TESS had seen transit only once.[26][26] Sgro, L. A. et al. (2024). Confirmation and Characterization of the Eccentric, Warm Jupiter TIC 393818343 b with a Network of Citizen Scientists. The Astronomical Journal 168, 26. doi.org Kilonova Seekers volunteers, who sort live detections from the GOTO telescopes, made 20 discoveries in the project's first months.[27][27] Killestein, T. L. et al. (2024). Kilonova Seekers: the GOTO project for real-time citizen science in time-domain astrophysics. Monthly Notices of the Royal Astronomical Society 533, 2113. doi.org In 2024 they caught a dwarf nova, an outbursting binary star, as it brightened by 8.5 magnitudes.[28][28] Killestein, T. L. et al. (2025). GOTO065054+593624: An 8.5 mag amplitude dwarf nova identified in real time via Kilonova Seekers. Astronomy & Astrophysics 699, A8. doi.org

IV.Machine learning enters the search

Professional teams brought machine learning into the same archives. In December 2017 NASA announced Kepler-90i, an eighth planet around the star Kepler-90, found by a neural network that Christopher Shallue of Google and astronomer Andrew Vanderburg trained on Kepler signals.[29, 30][29] NASA (14 December 2017). Artificial Intelligence, NASA Data Used to Discover Eighth Planet Circling Distant Star. Release 17-098. nasa.gov[30] Shallue, C. J. & Vanderburg, A. (2018). Identifying Exoplanets with Deep Learning: A Five-planet Resonant Chain around Kepler-80 and an Eighth Planet around Kepler-90. The Astronomical Journal 155, 94. doi.org NASA's ExoMiner classifier validated 301 Kepler planets in 2021 and 69 more in 2023.[31, 32][31] Valizadegan, H. et al. (2022). ExoMiner: A Highly Accurate and Explainable Deep Learning Classifier That Validates 301 New Exoplanets. The Astrophysical Journal 926, 120. Preprint arXiv:2111.10009, November 2021. doi.org[32] Valizadegan, H. et al. (2023). Multiplicity Boost of Transit Signal Classifiers: Validation of 69 New Exoplanets using the Multiplicity Boost of ExoMiner. The Astronomical Journal 166, 28. doi.org Its successor, ExoMiner++, flagged 7,000 TESS planet candidates on its first run and is free to download.[33][33] Leese, L. (22 January 2026). NASA AI Model That Found 370 Exoplanets Now Digs Into TESS Data. NASA Science. science.nasa.gov

The same methods reached students. Matteo Paz, a Pasadena high-school student, joined Caltech's Planet Finder Academy in 2022 and later worked with IPAC astronomer Davy Kirkpatrick on data from NEOWISE.[34][34] Motrunich, A. (11 April 2025). Exploring Space with AI. Caltech News. caltech.edu His single-author paper in The Astronomical Journal describes VARnet, a model built to find variable objects among NEOWISE's nearly 200 billion detections.[35][35] Paz, M. (2024). A Submillisecond Fourier and Wavelet-based Model to Extract Variable Candidates from the NEOWISE Single-exposure Database. The Astronomical Journal 168, 241. doi.org The finished VarWISE catalogue, published in 2026, lists 457,080 high-confidence variable objects, about half of them new.[36][36] Paz, M. et al. (2026). VarWISE: Infrared Variability via NEOWISE Single-exposure Photometry. The Astrophysical Journal Supplement Series 284, 41. doi.org

Kepler-90i came from a Google engineer working with an astronomer, and Paz had Caltech mentors. Rabtsevich's preprint has a single author, and an AI agent wrote its code under his direction.[5]

V.Why one person can do this now

The data are public. NASA keeps all Kepler and TESS data in open archives.[33] As of 8 October 2026, Kepler data had produced 2,787 confirmed planets and TESS 1,008, and the TESS team had flagged 8,148 objects of interest.[37][37] NASA Exoplanet Archive (accessed 8 October 2026). Exoplanet and Candidate Statistics. exoplanetarchive.ipac.caltech.edu ESA's Gaia mission released measurements of about 1.8 billion sources in 2022, and its next release, due on 2 December 2026, will hold roughly 400 terabytes, most of it individual observations.[38, 39][38] ESA Gaia (accessed 8 October 2026). Gaia Data Release 3. cosmos.esa.int[39] ESA Gaia (accessed 8 October 2026). Gaia DR4 content, last updated 14 September 2026, and Gaia Data Release 4 announcement page. cosmos.esa.int and cosmos.esa.int The Zwicky Transient Facility publishes a public stream of alerts about objects that change or move.[40][40] Bellm, E. C. et al. (2019). The Zwicky Transient Facility: System Overview, Performance, and First Results. Publications of the Astronomical Society of the Pacific 131, 018002. doi.org The Vera C. Rubin Observatory sent its first world-public alerts on 24 February 2026, readable by anyone through community brokers, and will eventually send up to seven million a night.[41][41] NSF NOIRLab (25 February 2026). NSF-DOE Rubin Observatory Celebrates First Public Alerts. Announcement sci26008. noirlab.edu It began its ten-year Legacy Survey of Space and Time on 30 June.[42][42] Rubin Observatory (30 June 2026). Action! NSF-DOE Vera C. Rubin Observatory Begins Capturing the Greatest Cosmic Movie Ever Made. rubinobservatory.org A winter storm in July forced staff off the mountain, and on 2 October the telescope was still off sky, with a return expected within weeks.[43, 44][43] Rubin Observatory (15 and 20 July 2026). Winter Storm in Chile. Rubin Community Forum, posts by user rblum5. rubin.community[44] Rubin Observatory (2 October 2026). Summit technical progress (week ending 2026-10-02). Rubin Community Forum. rubin.community JWST data join the public MAST archive when a program's exclusive access period ends, and some programs have none.[45][45] STScI (accessed 8 October 2026). Exclusive Access Period. JWST User Documentation. jwst-docs.stsci.edu

The software is free. Astropy, a community-built Python package, is the foundation that many specialised astronomy packages build on,[46][46] Astropy Collaboration, Price-Whelan, A. M. et al. (2022). The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package. The Astrophysical Journal 935, 167. doi.org and Lightkurve calls itself "a friendly Python package for making discoveries with Kepler & TESS".[47][47] Lightkurve Collaboration (accessed 8 October 2026). Lightkurve documentation. lightkurve.github.io STScI's free TIKE service gives anyone with an account a cloud notebook about as powerful as a modern laptop, with TESS, Kepler, Hubble and JWST data attached.[48][48] STScI (accessed 8 October 2026). Timeseries Integrated Knowledge Engine (TIKE). timeseries.science.stsci.edu

The newest piece is the AI coding agent, which takes instructions in plain language, then writes, runs and fixes the code, as Rabtsevich's account shows.[1] On 1 October 2026 the NASA Exoplanet Archive let assistants such as Claude Code and Codex connect to its own AI service and, through it, query NASA archives.[49][49] NASA Exoplanet Archive (1 October 2026). Have Your Assistant Talk to Our Assistant. Archive news. exoplanetarchive.ipac.caltech.edu That changes who can attempt a search. The standard of evidence stays where it was.

VI.Most dips are not planets

TESS's automated pipelines produce hundreds of thousands of possible transit signals.[33] The TESS team screens out signals from eclipsing binary stars, variable stars and instrument systematics, and only 8,148 have become TESS Objects of Interest.[37, 50][50] Guerrero, N. M. et al. (2021). The TESS Objects of Interest Catalog from the TESS Prime Mission. The Astrophysical Journal Supplement Series 254, 39. doi.org Even then, follow-up often fails. Of the 2,836 objects of interest whose status the follow-up working group has settled, 1,415 turned out to be false positives or false alarms, according to the ExoFOP table on 8 October 2026.[51][51] ExoFOP-TESS (accessed 8 October 2026). TESS Objects of Interest table, TFOPWG disposition column: 8,148 TOIs, of which 815 confirmed planets, 606 known planets, 1,315 false positives, 100 false alarms, 4,820 planet candidates and 490 ambiguous candidates. exofop.ipac.caltech.edu Blended light is a common cause. Each TESS pixel is 21 arcseconds across, so a faint eclipsing binary next to the target can produce a dip that looks like a small planet.[50]

AI agents add failure modes of their own. A study of 16 code-writing language models found that, on average, at least 5.2 percent of the software packages that commercial models recommended did not exist, and at least 21.7 percent for open-source models.[52][52] Spracklen, J. et al. (2025). We Have a Package for You! A Comprehensive Analysis of Package Hallucinations by Code Generating LLMs. USENIX Security Symposium 2025. arxiv.org In a 2023 test, GPT-4 fabricated 18 percent of the references it cited in short literature reviews.[53][53] Walters, W. H. & Wilder, E. I. (2023). Fabrication and errors in the bibliographic citations generated by ChatGPT. Scientific Reports 13, 14045. doi.org Analysis code can also run cleanly and answer the wrong question. Rabtsevich asked other users how they audit agent-written analysis "when a result can look completely convincing and still be wrong".[1]

The TESS Follow-up Observing Program confirms candidates in steps. Ground-based photometry catches nearby eclipsing binaries, spectroscopy spots binary host stars, high-resolution imaging finds close companions, and precise radial velocities measure the planet's mass.[54][54] TESS Science Office, MIT (accessed 8 October 2026). TESS Follow-up Observing Program (TFOP). tess.mit.edu When a mass is out of reach, a team can validate the planet statistically by showing that all false-positive scenarios together are very unlikely. With TRICERATOPS, that means a false-positive probability below 1.5 percent and less than a 0.1 percent chance that a nearby star is the source.[6]

Reporting matters as much as finding. New supernova candidates go to the Transient Name Server, the official IAU channel since 2016.[55][55] Transient Name Server (accessed 8 October 2026). wis-tns.org ExoFOP, the shared follow-up database for TESS, used to let users upload planet candidates directly. It paused uploads on 31 March 2026 and reopened them on 19 August, citing the quality and usefulness of candidates. Candidates must now appear in a peer-reviewed journal first, and uploaders need approval.[56][56] ExoFOP (accessed 8 October 2026). ExoFOP News, entries of 31 March 2026 and 19 August 2026. exofop.ipac.caltech.edu A Research Note of the American Astronomical Society also counts, but only if it cites a peer-reviewed paper that describes the detection and vetting method.[57][57] ExoFOP (accessed 8 October 2026). Guidelines for Submitting Published Planet Candidates. exofop.ipac.caltech.edu As of 8 October, ExoFOP listed no TESS or community candidate for TIC 4206066.[58][58] ExoFOP (accessed 8 October 2026). TIC 4206066 target overview. exofop.ipac.caltech.edu

Rabtsevich's work is easy to check, which is its strongest feature. He deposited the code, the per-transit measurements, the false-positive runs and a list of every input file with its checksum.[59][59] Rabtsevich, P. (2026). Supporting data and code for "Two Transit-like Signals in TESS Photometry of the Nearby K Dwarf TIC 4206066". Zenodo, version 1.0.0. doi.org His preregistration fixes the predictions, the frozen code and four possible outcomes in advance, so the rules of the November test cannot shift once the data arrive. The protocol also says that recovering the signal would not prove a planet.[4]

VII.What an open community could do

A community of amateurs with AI agents will produce many candidates, and most will be wrong. That is workable if the wrong ones are caught early and in public. Four habits would help.

• Publish the code, the input files and their checksums with every claim, so anyone can rerun it.
• Before announcing a candidate, give it to someone with a different pipeline and ask them to break it.
• Write predictions down before new data arrive, as Rabtsevich did for Sector 110.
• Credit negative results. A short report showing that a promising dip came from a neighbouring star spares others the same dead end and deserves its author's name as much as a discovery does. ExoFOP's candidate form already lets submitters label a candidate a false positive.[57]

The first test of these habits is on the calendar. TESS is due back on TIC 4206066 on 31 October, and the predicted transit times have been public since 6 October.[4]