# Exoplanets and star systems (`data/exoplanets.csv`, `data/star_systems.csv`) — sources and licence Both files are generated by `tools/build_exoplanets.py` (Python 3 standard library; run it to rebuild them from the sources below, downloads cached in `tools/.exo_cache/`). Built 2026-09-27. Column meanings and the provenance rule (measured / inferred / hypothetical) are in `docs/STAR_SYSTEMS.md`. ## Licence The tables are keyed to the HYG v4.1 star catalogue (star ids, catalogue row indices, companion names), so the adapted tables are distributed like `data/stars.csv` under **Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)**. Rows for stars in `data/stars_extra.csv` (`hyg_id` above 10,000,000) carry only archive values and survey limits; that star file itself is CC BY-NC 3.0 IGO (Gaia DR3, see `data/STARS_EXTRA_LICENSE.md`). The three `star_systems.csv` rows whose `ref` says "Gaia DR3 astrophysical_parameters" also contain Gaia DR3 values (ESA/Gaia/DPAC, CC BY-NC 3.0 IGO; see `data/GAIA_LICENSE.md`). Measured values (facts) are not themselves copyrightable; the citations let every number be checked. `data/star_metallicity.csv` (each star's [Fe/H], for the exoplanet model, `docs/design/EXOPLANET_MODEL.md`) is built by `tools/build_metallicity.py`. Rows with `src` "host" are the archive's `st_met` for planet hosts (with each value's paper); rows with `src` "gaia" are Gaia DR3 GSP-Spec metallicities (Recio-Blanco et al. 2023, A&A 674, A29; calibrated by their Table 3), **ESA/Gaia/DPAC, CC BY-NC 3.0 IGO** (see `data/GAIA_LICENSE.md`). Without the file the game draws every star's metallicity from the solar neighbourhood's distribution instead. ## Planets — NASA Exoplanet Archive *This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.* * Table: Planetary Systems Composite Parameters (`pscomppars`), DOI [10.26133/NEA13](https://doi.org/10.26133/NEA13), queried through the TAP service https://exoplanetarchive.ipac.caltech.edu/TAP/sync on 2026-09-29 (6,372 confirmed planets round 4,779 hosts; 6,339 of them orbit a catalogue star: 1,165 a star in `data/stars.csv`, 5,174 one of the 3,952 hosts HYG lacks, added from Gaia DR3 and the archive in `data/stars_extra.csv` — see `data/STARS_EXTRA_LICENSE.md`. The other 33 have no host that can be placed: 18 hosts with no distance, 15 with no magnitude of any kind, see "Known gaps"). * Planets of hosts added after 2026-09-27 (beyond 100 pc) leave the `summary` column empty; the game writes the same sentence from the row's columns (`StarSystems.planet_summary()`, the port of the build tool's `planet_summary()`). * Each planet row's `ref` column names the paper(s) behind its orbit, mass and radius (author, year and ADS bibcode, taken from the archive's per-value reference links). * Values the archive computed itself ("Calculated Value") are marked `inferred`: radius from mass or mass from radius with the mass–radius relation of **Chen J. & Kipping D. 2017, ApJ 834, 17**; semi-major axis from Kepler's third law; equilibrium temperature T_eq = T★ √(R★ / 2a) (zero Bond albedo, full redistribution); insolation L★ / a². The same relations fill gaps here when the archive has none. * The archive does not endorse this game. ## Stellar parameters * Planet hosts: `pscomppars` stellar columns (T_eff, R★, M★, L★, age), each from the reference the archive cites. * α Centauri A and B: Kervella P. et al. 2017, A&A 597, A137 (radii, T_eff); Akeson R. et al. 2021, AJ 162, 14 (masses). * Debris-disc stars without planets: Pearce et al. 2022 (below). * Three remaining stars: Gaia DR3 FLAME / GSP-Phot astrophysical parameters, Creevey O. L. et al. 2023, A&A 674, A26 (ESA/Gaia/DPAC). ## Debris discs * **Pearce T. D., Launhardt R., Ostermann R. et al. 2022, A&A 659, A135** — "Planet populations inferred from debris discs", 178 systems, via VizieR J/A+A/659/A135 (*This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France*). Resolved discs (ALMA, Herschel, …) give the inner and outer edges (`disc_src = measured`); SED-only discs give a single corrected blackbody radius (`disc_src = inferred`, inner = outer). 141 of its discs are around catalogue stars. * Added by hand, not in Pearce et al. 2022: * Vega — Su K. Y. L. et al. 2024, ApJ 977, 277 (JWST/MIRI; broad belt 80–170 au coinciding with the ALMA planetesimal belt). * Fomalhaut — MacGregor M. A. et al. 2017, ApJ 842, 8 (ALMA ring, a = 136.3 au, width 13.5 au; stored as 129.5–143.1 au). * β Pictoris — Matrà L. et al. 2019, AJ 157, 117 (ALMA planetesimal belt ≈ 50–150 au). * ε Eridani — cold ring 63.8–75 au from Pearce et al. 2022 (ALMA; Booth M. et al. 2017, MNRAS 469, 3200), plus the warm inner belt near 3 au from the Spitzer SED model of Backman D. et al. 2009, ApJ 690, 1522 (`inferred`). ## Survey limits (`survey_limits`) What published searches rule out, for the hypothetical-system generator. Values marked "approx." in `survey_ref` are read off the papers' stated limits or detection-limit figures and rounded towards larger masses (i.e. they rule out less than the paper does); they are game inputs, not measurements to quote. | Star | Limits | Source | |------|--------|--------| | Proxima Centauri | rv:1m_sini@0.1au; rv:10m_sini@1au | approx., Faria J. P. et al. 2022, A&A 658, A115; Suárez Mascareño A. et al. 2025, A&A 700, A11 | | α Centauri A | rv:53m_sini@2au; stable:3au | Zhao L. et al. 2018, AJ 155, 24; stability approx., Quarles B. & Lissauer J. J. 2016, AJ 151, 111 | | α Centauri B | rv:8.4m_sini@1.2au; stable:3au | Zhao L. et al. 2018, AJ 155, 24; Quarles & Lissauer 2016 | | Barnard's Star | rv:0.57m_sini@0.1au; rv:10m_sini@1au | Basant R. et al. 2025, ApJL 982, L1 (> 0.57 M⊕ excluded in the habitable zone); outer limit approx. | | ε Eridani | rv:20m_sini@1au; imaging:1mjup@10au | approx., Mawet D. et al. 2019, AJ 157, 33; Llop-Sayson J. et al. 2021, AJ 162, 181 | | τ Ceti | rv:5m_sini@1au | approx., Feng F. et al. 2017, AJ 154, 135 | | Lalande 21185 | rv:10m_sini@1au | approx., Hurt S. A. et al. 2022, AJ 163, 218 | | GJ 1061 | rv:3m_sini@0.1au | approx., Dreizler S. et al. 2020, MNRAS 493, 536; 2025, A&A 698, A114 | | Wolf 359 (Gl 406) | rv:5m_sini@0.1au | approx., CARMENES survey, Ribas I. et al. 2023, A&A 670, A139 | | 40 Eridani A | rv:5m_sini@0.3au | approx., Burrows A. et al. 2024, AJ 167, 243 | | 61 Cygni A, B | rv:1mjup_sini@5au | approx., Cumming A. et al. 2008, PASP 120, 531; Walker G. A. H. et al. 1995, Icarus 116, 359 | | ε Indi A | rv:10m_sini@1au; imaging:3mjup@5au | approx., Feng F. et al. 2019, MNRAS 490, 5002; Matthews E. C. et al. 2024, Nature 633, 789 | | TRAPPIST-1 | astrometry:4.6mjup@0.45au; astrometry:1.6mjup@1.3au | Boss A. P. et al. 2017, AJ 154, 103 (CAPSCam: no planet above ~4.6 M_J at P = 1 yr or ~1.6 M_J at 5 yr; a from P and M★ = 0.09 M☉) | | Teegarden's Star | rv:2m_sini@0.1au | approx., Dreizler S. et al. 2024, A&A 684, A117 (a 0.5 m/s signal is at their detection limit) | ## Companions (`companions`) Other `data/stars.csv` stars bound to a system star: the same HYG multiple-system id (`base`, from the Gliese catalogue) or within 1 ly with a common proper motion (to 15 %). Separations are projected (catalogue angle × mean distance), not orbital semi-major axes — α Cen A–B shows 25 au against a true a = 23.3 au. ## Known gaps * 33 planets have no system: their hosts cannot be placed. * No distance in the archive and no Gaia parallax measured to 20 % (18 hosts, 18 planets): Kepler-1676, -1737, -1760, -1813, -1910, -1945, -1964, -1984, -1985, CD-35 2722 B, CFHTWIR-Oph 98 A, Luhman 16 A, M62H, MXB 1658-298, OGLE-2016-BLG-1227L, OGLE-2017-BLG-1140L, PSR B1620-26, WISE J033605.05-014350.4. * No magnitude at all — no Gaia source, no archive V, and a T_eff / mass below the last dwarf-sequence row with an M_V (15 hosts): three nearby T / Y brown dwarfs (WISEP J121756.91+162640.2 A, CFBDSIR J145829+101343, CWISEP J193518.59-154620.3) and twelve microlensing brown-dwarf lenses (KMT-2016-BLG-1820L, -2142L, -2605L, KMT-2024-BLG-1005L, -1044L, -2242L, MOA-2013-BLG-605L, MOA-2015-BLG-337L, OGLE-2012-BLG-0358L, OGLE-2016-BLG-0261L, -1266L, OGLE-2017-BLG-1522L). * (TOI-2267 B shares TOI-2267 A's Gaia source: its planet is drawn at that point, so it is not among the 33.) * Microlensing hosts mostly have no optical magnitude: their V is estimated from T_eff or mass along the dwarf sequence (259 hosts, no extinction), so their brightness on the map is an upper limit. * Planets of a close companion that HYG merges with its primary (HD 41004 B, HD 133131 B) are listed at the pair's catalogue point; their summaries say so. * Planets the archive flags as controversial (27) are kept, and their summaries say the existence is disputed. ## Exomoon candidates (`data/exomoons.csv`) No exomoon has been confirmed. The two strongest candidates are drawn as moons of their planets (`parent` = the planet's letter), flagged `controv = 1` and `status = candidate, disputed`; the Target panel says "candidate, not confirmed" and lists the disputes. * **Kepler-1625 b I** — Teachey A. & Kipping D. M. 2018, *Science Advances* 4, eaav1784 (Kepler + Hubble photodynamics: a_SP ≈ 40 R_P with R_P = 11.4 R⊕, i.e. ≈ 0.0194 AU; R_S ≈ 4 R⊕; log₁₀ M_S/M⊕ = 1.2 ± 0.3 with a mass–radius prior, so the mass is tagged `inferred`; P_S ≈ 22 d; orbit tilted ≈ 42°); first flagged in Teachey A., Kipping D. M. & Schmitt A. R. 2018, AJ 155, 36. Disputed by Kreidberg L., Luger R. & Bedell M. 2019, ApJL 877, L15; Heller R., Rodenbeck K. & Bruno G. 2019, A&A 624, A95; Heller R. & Hippke M. 2024, *Nature Astronomy* 8, 193. Defended in Teachey A. et al. 2020, AJ 159, 142 and Kipping D., Teachey A. & Yahalomi D. A. 2024, arXiv:2401.10333 (reply to Heller & Hippke). * **Kepler-1708 b I** — Kipping D. et al. 2022, *Nature Astronomy* 6, 367 (a_SP = 11.7 R_P with R_P = 9.96 R⊕, i.e. ≈ 0.00496 AU; R_S = 2.61 R⊕; M_S < 37 M⊕ at 2σ, so the drawn mass, 7.3 M⊕, is `inferred` from the radius with Chen & Kipping 2017; P_S = 4.6 d; near-coplanar). Questioned by Heller R. & Hippke M. 2024, *Nature Astronomy* 8, 193; defended in Kipping, Teachey & Yahalomi 2024 (above). Weaker claims are listed only, with no body in the game: a volcanic "exo-Io" round WASP-49 b from transient sodium (Oza A. V. et al. 2019, ApJ 885, 168; Oza A. V. et al. 2024, ApJL 973, L53) and the same idea for other hot Jupiters in Oza et al. 2019; the microlensing event MOA-2011-BLG-262, which fits a free-floating planet with a moon as well as a star with a planet (Bennett D. P. et al. 2014, ApJ 785, 155 — the game shows the star-plus-planet reading the archive lists); transit-timing moon candidates round several Kepler planets (Fox C. & Wiegert P. 2021, MNRAS 501, 2378), contested by Kipping D. 2020, ApJL 900, L44.