{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.677","julian_year":2026.677,"time":"2026-09-05T09:28:25.108Z","years_from_j2000":26.677,"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-4559","name":"NGC 4559","class":"spiral_galaxy_sc","category":"galaxy","object_type":"Spiral galaxy Sc","mag":9.92,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":51282180.503774375,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":188.99020833333333,"dec_deg":27.96,"epoch_ra_deg":189.322958,"epoch_dec_deg":27.812009,"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":"Coma Berenices","discovered":"1785","featured":false,"url":"https://spacecatalog.org/object/ngc-4559","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":10.28,"h_mag":7.83,"j_mag":8.41,"k_mag":7.58,"v_mag":9.92,"redshift":0.002719,"hubble_type":"Sc","wikidata_id":"Q176208","redshift_cmb":0.0036610637169975924,"discovered_by":"William Herschel","ngc_type_code":"G","uncertainties":{"distance_ly":[14168578.729886327,14168578.729886327]},"major_axis_arcmin":10.57,"minor_axis_arcmin":4.82,"wikipedia_article":"NGC 4559","position_angle_deg":148,"surface_brightness":23.48,"radial_velocity_km_s":814},"designations":[{"catalog":"2MASX","designation":"2MASX J12355768+2757351"},{"catalog":"Caldwell","designation":"C 36"},{"catalog":"IRAS","designation":"IRAS 12334+2814"},{"catalog":"IRAS","designation":"IRAS F12334+2814"},{"catalog":"LEDA","designation":"LEDA 42002"},{"catalog":"MCG","designation":"MCG +05-30-030"},{"catalog":"NGC","designation":"NGC 4559"},{"catalog":"PGC","designation":"PGC 42002"},{"catalog":"SDSS","designation":"SDSS J123557.64+275735.9"},{"catalog":"UGC","designation":"UGC 7766"}],"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."}