{"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":"2026-09-05T17:12:57.737Z","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-3557","name":"NGC 3557","class":"elliptical_galaxy_e","category":"galaxy","object_type":"Elliptical galaxy E","mag":10.42,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":157815749.37617278,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":167.49016666666665,"dec_deg":-37.53916666666667,"epoch_ra_deg":167.807965,"epoch_dec_deg":-37.684756,"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":"Centaurus","discovered":"1835","featured":false,"url":"https://spacecatalog.org/object/ngc-3557","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":11.41,"h_mag":7.5,"j_mag":8.16,"k_mag":7.2,"v_mag":10.42,"redshift":0.01013,"hubble_type":"E","wikidata_id":"Q1105346","redshift_cmb":0.01120258192518131,"discovered_by":"John Frederick William Herschel","ngc_type_code":"G","uncertainties":{"distance_ly":[15464526.046175908,15464526.046175908]},"major_axis_arcmin":4.36,"minor_axis_arcmin":3.43,"wikipedia_article":"NGC 3557","position_angle_deg":32,"surface_brightness":23.46,"radial_velocity_km_s":3023},"designations":[{"catalog":"2MASX","designation":"2MASX J11095583-3732345"},{"catalog":"2MASX","designation":"2MASX J11095765-3732210"},{"catalog":"2MASX","designation":"2MASX J11095773-3732216"},{"catalog":"ESO","designation":"ESO 377-016"},{"catalog":"ESO","designation":"ESO 377-16"},{"catalog":"ESO-LV","designation":"ESO-LV 337-0160"},{"catalog":"ESO-LV","designation":"ESO-LV 377-0160"},{"catalog":"LEDA","designation":"LEDA 33871"},{"catalog":"MCG","designation":"MCG -06-25-005"},{"catalog":"NGC","designation":"NGC 3557"},{"catalog":"PGC","designation":"PGC 33871"}],"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."}