How Cosmic Atlas represents the sky
This page separates measured, inferred, projected, sampled, and unavailable information. Source catalogs remain authoritative for quantitative analysis.
What the map position means
Cosmic Atlas is a top-down physical map. It displays the heliocentric ecliptic x/y plane; z is retained in source records but is not a visibility cut. The ruler therefore measures projected x/y separation, not full 3D separation.
Top-down x/y projection; source z is retained but is not used as a visibility cut. The map ruler measures projected x/y separation, not full three-dimensional separation
Sources
Epochs and moving sources
A catalog release date, a catalog reference epoch, and the date shown by the atlas are different things. Cosmic Atlas names the applicable epoch and does not silently treat every source as current-day.
Gaia DR3 astrometry has reference epoch J2016.0. Atlas rows with complete proper motion may be propagated to J2026.0. Solar-system state and osculating-element records use their declared epochs.
Sources
Distances and cosmology
Nearby-star distance can come from parallax; nearby-galaxy distance can come from published literature; distant-survey positions can use redshift converted to comoving distance. These are not interchangeable measurements.
DESI spectroscopic and Quaia inferred-redshift projections use the checked-in flat LambdaCDM parameters H0=67.66 km/s/Mpc, Omega_m=0.30966, and Omega_lambda=0.69034. A comoving distance is not converted back into a precise measured redshift or lookback time in the UI.
Sources
Selection and survey footprints
A blank or dense patch may describe the observing survey, its quality cuts, or its footprint rather than the universe itself.
Gaia T2 uses positive-parallax and signal-to-noise tiers. DESI includes successful spectra inside its footprint and target/class cuts. Quaia G<20 is an almost-all-sky quasar-candidate catalog with inferred redshifts. HEASARC NEARGALCAT is a literature compilation, not a uniform volume-limited survey.
Sources
Tiles, sampling, and level of detail
The atlas may display a deterministic sample when a layer is too dense for a browser. Zooming changes the level of detail; it does not create synthetic objects.
SMP3 layers record source counts, retained point counts, raw point counts, and deterministic sample buckets per level. Sampling is uniform within a level and immutable releases make the visible density reproducible.