{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.679","julian_year":2026.679,"time":"2026-09-05T20:59:15.961Z","years_from_j2000":26.679,"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-4581","name":"NGC 4581","class":"elliptical_galaxy_e","category":"galaxy","object_type":"Elliptical galaxy E","mag":12.38,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":102557336.48673211,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":189.52154166666668,"dec_deg":1.4777500000000001,"epoch_ra_deg":189.865153,"epoch_dec_deg":1.329956,"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":"Virgo","discovered":"1882","featured":false,"url":"https://spacecatalog.org/object/ngc-4581","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":13.22,"h_mag":9.86,"j_mag":10.56,"k_mag":9.61,"v_mag":12.38,"redshift":0.00616,"hubble_type":"E","wikidata_id":"Q1112629","redshift_cmb":0.00730146969429013,"discovered_by":"Edward S. Holden","ngc_type_code":"G","uncertainties":{"distance_ly":[14650491.314618051,14650491.314618051]},"major_axis_arcmin":1.62,"minor_axis_arcmin":1.06,"position_angle_deg":172,"surface_brightness":23.12,"radial_velocity_km_s":1841},"designations":[{"catalog":"2MASX","designation":"2MASX J12380513+0128404"},{"catalog":"IRAS","designation":"IRAS F12355+0145"},{"catalog":"LEDA","designation":"LEDA 42199"},{"catalog":"MCG","designation":"MCG +00-32-028"},{"catalog":"NGC","designation":"NGC 4581"},{"catalog":"PGC","designation":"PGC 42199"},{"catalog":"SDSS","designation":"SDSS J123805.17+012839.8"},{"catalog":"SDSS","designation":"SDSS J123805.17+012839.9"},{"catalog":"UGC","designation":"UGC 7801"}],"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."}