Is this star alone?
Laplace is a search engine for star catalogues that reads 1.8 billion sources in ESA's Gaia DR3 for the pull of unseen companions. 220,656 candidates remain after the selection cut.
The sky is not finished.
Gaia has measured the position and motion of more stars than anyone can study one by one. Somewhere in that catalogue are stars pulled off course by companions no telescope has seen.
Laplace asks two questions of every star, and the stars that fail both are the ones worth a telescope.
What it reads.
- ESA Gaia DR3
- 1,811,709,771 sources with positions, motions, parallaxes and photometry.
How it works.
- Pull
- A single star fits a single-star path. A companion drags it off that path, and the misfit shows up as RUWE: near 1.0 alone, past 1.4 likely tugged, up to 64.26 in the working sets.
- Surprise
- From motion and distance the engine predicts brightness and colour and measures the miss. Its significance is a robust z score, and bootstrap resampling records how often it survives.
- Keep both apart
- Over the 947 tier-1 cards the two scores correlate at minus 0.185. They are close to independent by measurement.
- Keep the evidence
- Every candidate carries the measured values it was ranked on, in the same ledger as every system on HGE.
The pilot field.
One contiguous patch of Gaia DR3 in Taurus, Perseus and Aries, rendered whole.
- Sky patch
- Right ascension 22.5 to 78.7 degrees, declination 0.0 to 41.8.
- Candidates
- 947 tier-1 cards, all inside the field, at 29.1 to 4,519.6 parsecs and G magnitude 6.33 to 20.26.
- All surprises
- The highest RUWE in the field is 1.382, below the cut, so every candidate here is a Surprise.
- No famous names
- Each star carries its Gaia DR3 source id and its measured values. The well-known full-sky candidates are not in this field.
In figures.
- 1.8 bn
- Gaia DR3 sources searched
- 220,656
- Candidate companions after the cut
- 947
- Tier-1 candidates in the pilot field
- 9,274
- Follow-up targets observable from ESO: RUWE above 2, G brighter than 13, declination below plus 25
- 600,000
- Stars in the pilot field, each with positive parallax and full photometry, no imputation
Every number carries its cut.
A candidate count means nothing without the selection behind it. 220,656 sources pass the cut: RUWE of 1.4 or more, parallax of at least 10 milliarcseconds with a signal to noise of 5 or more, within 100 parsecs. A further figure of 190,583 strong candidates is projected from a one percent sample of 8,680 sources and has not been confirmed one by one.
The working platform, with the sky survey, an observation planner, the NSS solutions browser, a spectroscopy queue and a publication tracker, is open by login.
Papers, code and data.
Who it serves.
Observatories and astronomers who want the follow-up list or a briefing on the selection can write to us.
Write to us- Observatories choosing follow-up targets.
- Astronomers studying binary stars and hidden companions.
