{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.678","julian_year":2026.678,"time":"2026-09-05T15:35:03.733Z","years_from_j2000":26.678,"frame":"date","applied":"Proper motion, then precession and nutation. The catalogued J2000 position is carried along the great circle the object's own published motion puts it on, at a constant velocity, and the result is referred to the true equator and equinox of this instant. Those are separate things: the motion moves the object, and the rotation turns the grid under it by about fifty arcseconds a year, with nutation adding up to another seventeen.","excluded":"Parallax, the radial-velocity perspective term, aberration and refraction; each is below the accuracy of the catalogued positions themselves. An object with no published proper motion comes back where the catalogue has it rather than at a fabricated zero, and says so with a null pm_ra_mas_yr. A body with no fixed position is not propagated at all — its place comes from an ephemeris, which is what /api/v1/visible answers with."},"slug":"ngc-2931","name":"NGC 2931","class":"spiral_galaxy_sb","category":"galaxy","object_type":"Spiral galaxy Sb","mag":14.84,"mag_band":"B","abs_mag":null,"abs_mag_band":null,"distance_ly":370277566.15462816,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":144.406875,"dec_deg":23.240750000000002,"epoch_ra_deg":144.788929,"epoch_dec_deg":23.120186,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Leo","discovered":"1863","featured":false,"url":"https://spacecatalog.org/object/ngc-2931","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":14.84,"h_mag":11.33,"j_mag":12.07,"k_mag":11.06,"redshift":0.025,"hubble_type":"Sb","wikidata_id":"Q1101939","redshift_cmb":0.02599704206609199,"discovered_by":"Heinrich Louis d'Arrest","ngc_type_code":"G","uncertainties":{"distance_ly":[20631521.486531597,20631521.486531597]},"major_axis_arcmin":0.75,"minor_axis_arcmin":0.54,"position_angle_deg":68,"surface_brightness":22.76,"radial_velocity_km_s":7401},"designations":[{"catalog":"2MASX","designation":"2MASX J09373771+2314270"},{"catalog":"IRAS","designation":"IRAS F09347+2328"},{"catalog":"LEDA","designation":"LEDA 27415"},{"catalog":"MCG","designation":"MCG +04-23-019"},{"catalog":"NGC","designation":"NGC 2931"},{"catalog":"PGC","designation":"PGC 27415"},{"catalog":"SDSS","designation":"SDSS J093737.65+231426.6"},{"catalog":"SDSS","designation":"SDSS J093737.65+231426.7"},{"catalog":"SDSS","designation":"SDSS J093737.65+231426.8"}],"source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0"},"updated_at":"2026-09-02T19:50:56.720Z","attribution":"Data from SpaceCatalog.org. Individual records carry their source and license in `source`; attribution is required for CC-BY and CC-BY-SA rows."}