No astronomy training, just a coding AI and NASA's open data: people found planet candidates, and one candidate won telescope time

The star TIC 4206066, 116 light-years away, dims by about 0.05% for roughly two hours every 3.18 days. If a planet is passing in front of the star, that planet is about 1.4 times the radius of Earth. Rabtsevich checked 22 dimming events, and all 22 landed on the times predicted by a 3.18-day period. There is also a weaker signal that repeats every 11.13 days. Of that one, Rabtsevich wrote: "The evidence for that one is much weaker." X +1

Rabtsevich also ran a hold-out test: hide one year of data, then use the remaining years to predict when the star would dim in the hidden year. The test was run three times, hiding 2018, 2020, and 2025 in turn, and all three predictions hit. Rabtsevich checked 36 star catalogs and papers, plus 340,505 automated TESS detection alerts, to make sure the signal had not already been reported. That check covers published lists only. According to Scientific American, the signal passed a TESS detection filter once in 2020 but was dropped for lack of evidence. A search run with LEO-Vetter, a tool astronomer Michelle Kunimoto built to weed out false signals, also flagged this candidate in early 2026 but did not make it public. Over about two weeks, the work with Claude Code and Codex produced 74 analyses and more than 1,000 scripts. reddit +2

Claude Code (Opus 5.5 and Fable 5.1) downloaded the data, wrote the search code, fit the shape of the dips, checked nearby stars and false-signal scenarios, drew the plots, and reran failed tests. Rabtsevich wrote: "I chose what questions to ask, what tests mattered, and what counted as pass/fail." The results were reviewed separately by Codex and by a fresh agent session given read-only access. reddit

The preprint Rabtsevich posted to Zenodo on September 25 has logged 6,542 views and 900 downloads. On the TESS Director's Discretionary Time (DDT) list, Rabtsevich's proposal to observe this star at two-minute cadence is marked approved. The entry reads: "Pavel Rabtsevich | Two-minute cadence for TIC 4206066, a nearby K-dwarf with a 1.4R planet candidate," approved "yes." With that approval, TESS will record the star's brightness every two minutes during its next observing period. zenodo +1

TESS images the sky one patch at a time, and each of these observing periods is called a sector. Sector 110, which covers this star again, runs from October 31 to November 26. On October 6, Rabtsevich pre-registered the times the star should dim during Sector 110, based on both the 3.18-day and the 11.13-day signals. The forecast is nine dips from the 3.18-day signal and three from the 11.13-day signal, with a timing uncertainty of about four minutes. The three earlier hold-out tests, which hid 2018, 2020, and 2025, used data that already existed. This is the first time a pre-registered prediction will be checked against brand-new observations. At the end of the thread, Rabtsevich linked a 3D site, tic4206066.pages.dev, where you can fly out to the star. zenodo +1

After reading Rabtsevich's post, Thick_Ad_9875 used Opus 5.5 to take a second look at about 2,900 small stars within 200 light-years. The chosen stars had been imaged by TESS over several years, but only in its wide full-frame images, so no search program had ever analyzed all those years of data together. Before starting, Thick_Ad_9875 used the search setup to recover Rabtsevich's signal, to confirm the setup actually worked. reddit

Before downloading the 2026 data, Thick_Ad_9875 locked in a record of when each candidate star should dim and the criteria for judging it, so neither could be changed later. One candidate failed this prediction test. Two dimmed at the predicted times and survived. reddit

Of the two survivors, TIC 451641911 is 134 light-years away and dims by about 0.06% every 3.91 days. TIC 26432942 is 112 light-years away and dims by about 0.07% every 10.39 days. If they are planets, both are about 1.3 times the size of Earth. Neither appeared on any planet or candidate list Thick_Ad_9875 could find, or among roughly 312,000 automated TESS alerts. reddit

Both passed all 17 checks in the vetting tool LEO-Vetter. Another vetting tool, TRICERATOPS, put the probability of a planet orbiting the target star at 96.5% for TIC 26432942 and 76.7% for TIC 451641911. The vetting results and predicted times are public on Zenodo. reddit +1

After seeing Rabtsevich's Reddit post about finding a planet candidate with Claude Code, Chopra spent a morning combing through data on nearby stars that TESS had imaged only at long intervals, using an analysis program written with Claude Code. X

TIC 370612437, 158 light-years away in the direction of Cygnus, dims by 0.02% every 3.56 days. If it is a planet, it is almost exactly Earth's size. HIP 114417, 134 light-years away toward Andromeda, dims by 0.03% every 4.93 days and would be about 1.1 times Earth's size. Across four observing years between 2019 and 2024, the dips repeated 55 times and 21 times, respectively. X

In the hold-out test, where one year is hidden and the rest are used to predict when the star should dim that year, the predictions held in three of the four years. Codex and a newly launched Claude session reviewed the method and results separately. Chopra posted the results on X with a 50-second video and said the candidates would be reported to ExoFOP, NASA's site for sharing exoplanet candidates, as community candidates (CTOI). As of October 19, the ExoFOP page for TIC 370612437 still shows no community candidate entry. X +1

Krone had Codex and Claude coding agents analyze archival data from TESS and from ZTF, a separate sky survey. The analysis turned up a candidate outburst in LP 119-10, a cooling white dwarf whose surface pulsates, which suddenly brightened in December 2024. Its brightness rose about 6.5% in TESS data, which covers red to near-infrared light, and more than 31% in ZTF data taken through a green filter (g band). The two numbers are brightness measured in different colors of light. A pulsation with a 575.9-second period also showed up. Fewer than ten pulsating cooling white dwarfs are known to have had outbursts. zenodo

The preprint states that "a second AI system repeated the analysis independently from the raw archive files." zenodo