SPACETRC / RESEARCH CONTEXT
SPACETRC / GAIA DR3 · 2MASS · ICRS
The sky has an epoch.
The same candidate source can appear at different positions in two catalogues. Examine observation epoch and search radius together using real Gaia–2MASS records.
The dated 20-star selection has not been opened. No dataset or external service is requested on page load.
Published neighbourhood candidates
The list contains only published Gaia-archive good neighbours for this selection; it is not a new cone search of all 2MASS. A nearest candidate or record within the radius does not establish physical identity.
| 2MASS candidate | Observation epoch | Separation from2016 position | Epoch-propagated | Radius condition |
|---|
Colour–magnitude view of the selection
M_G = G + 5log₁₀(parallax[mas]) − 10. Extinction and parallax zero point are not corrected. Twenty selected high-proper-motion sources do not represent the stellar population; colour alone is not an age measurement.
Carry the calculation with its sources
Exports preserve the actual selected source identifier, dataset SHA-256, epoch, assumptions and method. No account or personal data is included.
SPACETRC / WORKED REPEAT ON ARCHIVED DATA
Changing the epoch changes the comparison.
In this fixed selection, 19 sources have published 2MASS candidates and one has none. Median nearest-candidate separation is 6.6339″ using 2016 positions and 0.0857″ after propagation to each candidate’s epoch. The number of sources with a candidate within 1″ changes from 0 to 19.
The selection depends on already published neighbour candidates; it is not an independent completeness/accuracy benchmark or a new discovery. No independent specialist review or real participant campaign is claimed.
Model scope
Uniform rectilinear barycentric 3D velocity over 1990–2040 uses parallax, two proper-motion components and measured radial velocity when available. Missing radial velocity is conditionally assumed 0 km/s; this is not a measured zero velocity or zero uncertainty.
Gaia’s five-parameter covariance is propagated through a numerical Jacobian. Reported radial-velocity error is assumed independent of astrometry. Annual parallax, observer location, light time, Galactic forces and binary motion are not modelled. The formal ellipse does not include all these model errors.
2MASS Julian date is converted to approximate Julian year; seconds between time scales and approximately ±30 seconds of date uncertainty are neglected in this educational calculation. A J2000 coordinate reference does not mean the observation occurred in 2000.
Dataset identity and sources
SHA-256 623ac0d0e3d1a9a545d23a532aee9b8d3ca4e555bcc11899042258b76634db4f
- Gaia DR3 data and reference epoch ↗
- Gaia DR3 astrometric transformations and covariance ↗
- Gaia DR3 data credit and citation ↗
- Gaia Archive crossmatch query tutorial ↗
- 2MASS all-sky PSC positions, errors and epochs ↗
- 2MASS acknowledgements ↗
ESA/Gaia/DPAC · Gaia Collaboration et al. (2023). 2MASS · University of Massachusetts / IPAC-Caltech · NASA / NSF · Skrutskie et al. (2006).
Source links do not imply institutional partnership or endorsement.