{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.653","julian_year":2026.653,"time":"2026-08-27T16:19:12.207Z","years_from_j2000":26.653,"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":"m101","name":"M101","class":"intermediate_spiral_galaxy_sabc","category":"galaxy","object_type":"Intermediate spiral galaxy SABc","mag":7.9,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":20900000,"distance_method":"literature value (curated)","ra_deg":210.80225000000002,"dec_deg":54.34894444444445,"epoch_ra_deg":211.04214,"epoch_dec_deg":54.219554,"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":"1781","featured":true,"url":"https://spacecatalog.org/object/m101","radius_km":null,"radius_kind":null,"data_quality":null,"description":"A face-on spiral with lopsided, asymmetric arms, presented to us at exactly the angle that shows off its structure.","properties":{"b_mag":8.36,"h_mag":5.81,"j_mag":6.52,"k_mag":5.51,"v_mag":7.9,"redshift":0.000811,"hubble_type":"SABc","wikidata_id":"Q14371","redshift_cmb":0.0012132987166677545,"discovered_by":"Pierre Méchain","ngc_type_code":"G","major_axis_arcmin":23.99,"minor_axis_arcmin":23.07,"wikipedia_article":"Pinwheel Galaxy","position_angle_deg":28,"surface_brightness":23.97,"radial_velocity_km_s":243},"designations":[{"catalog":"IRAS","designation":"IRAS 14013+5435"},{"catalog":"IRAS","designation":"IRAS F14012+5434"},{"catalog":"LEDA","designation":"LEDA 50063"},{"catalog":"MCG","designation":"MCG +09-23-028"},{"catalog":"Messier","designation":"M 101"},{"catalog":"NGC","designation":"NGC 5457"},{"catalog":"PGC","designation":"PGC 50063"},{"catalog":"SDSS","designation":"SDSS J140312.52+542056.2"},{"catalog":"UGC","designation":"UGC 8981"}],"source":{"id":"openngc","name":"OpenNGC","url":"https://github.com/mattiaverga/OpenNGC","license":"CC-BY-SA-4.0"},"updated_at":"2026-08-27T16:03:54.983Z","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."}