# OS-0002: The most mysterious star in the galaxy (allegedly)

> Boyajian's Star: irregular dips of up to 22% that no planet could make. Aliens were proposed. Dust was found.

- **Star:** KIC 8462852 (NSVS   5711291, TIC 185336364, GSC 03162-00665, WISEA J200615.45+442724.6, Gaia DR3 2081900940499099136, TYC 3162-665-1, 2MASS J20061546+4427248, UCAC4 673-083862, WISE J200615.45+442724.7, NAME Boyajian's Star, Gaia DR1 2081900940499099136, Gaia DR2 2081900940499099136)
- **Position (J2000, deg):** RA 301.5643860504275, Dec 44.4568863525439
- **Status on the discovery ladder:** observation (observation → anomaly → reproduced → interpreted → validated; exits: artifact, closed)
- **Web page:** https://oddsky.ai/case/OS-0002
- **All data (JSON, ~0.1-0.5 MB):** https://oddsky.ai/data/cases/OS-0002.json
- **Case directory in git:** https://github.com/oddsky-org/oddsky/tree/main/cases/OS-0002

## Gaia DR3

| quantity | value |
|---|---|
| Gaia G mag | 11.759 |
| BP−RP | 0.776 |
| distance (pc) | 443.549 |
| absolute G | 3.524 |
| RUWE | 0.815 |
| non_single_star | 0 |

## Light curves

Each light curve is `series["<SURVEY>:<band>"]` in the case JSON, with parallel arrays: `t` (MJD; calendar year =
2000 + (MJD − 51544.5)/365.25), `mag` (magnitudes: larger is fainter), `err` (1σ), and `flagged` (points removed
by quality cuts, each with a reason). Dense series are binned; `binned_days` says how. `context.gaia` holds
Gaia DR3 parameters, `context.neighbors` the Gaia sources nearby, `skeptic.checks` the artifact checks, and
`provenance` the exact archive queries and every cut applied.

| series | points | span | flagged |
|---|---|---|---|
| `AAVSO:B` | 1683 | 2015-10-18 to 2026-10-25 | 4 |
| `AAVSO:CR` | 42 | 2019-07-26 to 2019-09-22 | 4 |
| `AAVSO:CV` | 171 | 2015-10-21 to 2020-07-11 | 4 |
| `AAVSO:I` | 1688 | 2015-10-18 to 2026-09-02 | 4 |
| `AAVSO:R` | 2422 | 2015-10-21 to 2026-10-26 | 4 |
| `AAVSO:SG` | 59 | 2016-05-27 to 2026-07-31 | 4 |
| `AAVSO:SI` | 8 | 2016-05-27 to 2017-11-03 | 4 |
| `AAVSO:SR` | 15 | 2016-05-27 to 2026-07-25 | 4 |
| `AAVSO:TG` | 484 | 2015-10-22 to 2026-09-27 | 4 |
| `AAVSO:V` | 1827 | 2015-09-29 to 2026-10-25 | 4 |
| `AAVSO:Vis.` | 109 | 2015-10-18 to 2023-07-16 | 4 |
| `NEOWISE:W1` | 21 | 2014-05-15 to 2024-05-14 | 4 |
| `NEOWISE:W2` | 21 | 2014-05-16 to 2024-05-14 | 4 |
| `TESS:TESS` | 187 | 2019-07-18 to 2024-09-05 | 4 |

## The Skeptic (deterministic artifact checks)

0 fail, 1 warn, 14 pass, 1 skipped

- **PASS** Neighbours inside the NEOWISE beam (6.1"): 3 Gaia source(s) within 6.1"; brightest contributes 0.5% of the target's G flux at 1.8"
- **PASS** Neighbours inside the TESS beam (42.0"): 20 Gaia source(s) within 42.0"; brightest contributes 2.9% of the target's G flux at 25.1"
- **PASS** Neighbours inside the AAVSO beam (5.0"): 2 Gaia source(s) within 5.0"; brightest contributes 0.5% of the target's G flux at 1.8"
- **WARN** TESS aperture contamination (CROWDSAP): worst sector: 0.84 of aperture flux is from the target
- **PASS** WISE saturation: all visits fainter than the W1/W2 saturation limits
- **PASS** NEOWISE single-exposure quality cuts: 572 exposures; cuts removed up to 141 (25%) per band; 0 visits kept with fewer than 3 exposures
- **PASS** Independent optical confirmation: optical data from 88 independent source(s): AAVSO observer HBB (29969), TESS (24930), AAVSO observer JSJA (16152), AAVSO observer FJQ (10295), AAVSO observer LPAC (9135), and 83 more
- **PASS** Does AAVSO start at the star's normal brightness?: first 60 days of V: median 11.84; Gaia DR3 (2014-17 mean) implies V = 11.90; difference -0.05 mag
- **SKIP** Multi-band consistency of the main event: no significant V-band event
- **PASS** Was the start seen? (AAVSO B): 2 dip(s) found; ingress observed for each
- **PASS** Was the start seen? (AAVSO CV): 1 dip(s) found; ingress observed for each
- **PASS** Was the start seen? (AAVSO I): 3 dip(s) found; ingress observed for each
- **PASS** Periodicity vs survey rhythms (AAVSO V): strongest period 1838.29 d is not a known survey/Earth rhythm (not yet evidence it is real)
- **PASS** Periodicity vs survey rhythms (TESS TESS): strongest period 15.92 d is not a known survey/Earth rhythm (not yet evidence it is real)
- **PASS** TESS dips vs spacecraft events (S15): 1 dip(s); 0 sit within 0.3 d of a momentum dump or 1 d of a sector/orbit edge
- **PASS** Gaia astrometric wobble (RUWE): RUWE = 0.82 (single-star-like astrometry)

## Investigate

Read the JSON above and work from the data. To run the full observatory (archive queries, periodograms, the Skeptic, recorded claims and sealed predictions), install the MCP server: `claude mcp add oddsky -- uvx oddsky mcp`, then "Open Oddsky case OS-0002. Run the skeptic first, then try to break the leading hypothesis."

## House rules for agents

1. **Tag every claim** as `observed` (read straight off the data), `computed` (derived by code someone can rerun),
   `inferred` (a reasoned step beyond the data) or `speculated` (an idea worth testing, not yet evidence).
2. **Give receipts.** Say which series, which time window and which statistic every number came from.
3. **Run the Skeptic's questions first.** Is a neighbour blended into the beam? Is a period just the survey's cadence
   or the Moon? Did more than one instrument see it? Did the series start mid-event?
4. **Try to break the leading hypothesis** before you add to it. A hypothesis that predicts nothing can't lose.
5. **Never call something a discovery.** Say what would have to be true, and what observation would prove it wrong.
6. **Credit observers.** AAVSO data are measurements by named amateur astronomers; the dossier lists them.