{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.673","julian_year":2026.673,"time":"2026-09-03T21:13:11.019Z","years_from_j2000":26.673,"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-4172","name":"NGC 4172","class":"spiral_galaxy_sab","category":"galaxy","object_type":"Spiral galaxy Sab","mag":14.26,"mag_band":"B","abs_mag":null,"abs_mag_band":null,"distance_ly":452378290.6510566,"distance_method":"redshift (CMB frame), flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":183.06204166666666,"dec_deg":56.17755555555555,"epoch_ra_deg":183.396982,"epoch_dec_deg":56.028166,"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":"Ursa Major","discovered":"1789","featured":false,"url":"https://spacecatalog.org/object/ngc-4172","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"b_mag":14.26,"h_mag":10.11,"j_mag":10.83,"k_mag":9.87,"redshift":0.03108,"hubble_type":"Sab","wikidata_id":"Q1109525","redshift_cmb":0.03163070195294915,"discovered_by":"William Herschel","ngc_type_code":"G","uncertainties":{"distance_ly":[23172289.529036414,23172289.529036414]},"major_axis_arcmin":1.23,"minor_axis_arcmin":1.16,"wikipedia_article":"NGC 4172","position_angle_deg":0,"surface_brightness":23.38,"radial_velocity_km_s":9173},"designations":[{"catalog":"2MASX","designation":"2MASX J12121490+5610386"},{"catalog":"LEDA","designation":"LEDA 38887"},{"catalog":"MCG","designation":"MCG +09-20-109"},{"catalog":"NGC","designation":"NGC 4172"},{"catalog":"PGC","designation":"PGC 38887"},{"catalog":"SDSS","designation":"SDSS J121214.88+561039.1"},{"catalog":"SDSS","designation":"SDSS J121214.89+561039.1"},{"catalog":"SDSS","designation":"SDSS J121214.89+561039.2"},{"catalog":"SDSS","designation":"SDSS J121214.89+561039.3"},{"catalog":"UGC","designation":"UGC 7205"}],"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."}