{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.680","julian_year":2026.68,"time":"2026-09-06T07:13:08.484Z","years_from_j2000":26.68,"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":"wasp-121-b","name":"WASP-121 b","class":"gas_giant","category":"exoplanet","object_type":"Gas giant","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":880.2895403299362,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":107.6002312,"dec_deg":-39.0972705,"epoch_ra_deg":107.828006,"epoch_dec_deg":-39.140592,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"WASP-121","semi_major_axis_km":3846161.255697,"periapsis_km":null,"mass_kg":2.2208057817153632e+27,"mass_msun":0.00111688,"constellation":"Puppis","discovered":"2016","featured":false,"url":"https://spacecatalog.org/object/wasp-121-b","radius_km":124539.063660078,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"WASP-121","host_v_mag":10.514,"eccentricity":0.0085,"uncertainties":{"mass_kg":[8.161935778356682e+25,8.161935778356682e+25],"radius_km":[428.95197202800006,428.95197202800006],"distance_ly":[5.094562619935532,5.153270767924546],"eccentricity":[0.0012,0.0013],"host_mass_solar":[0.019,0.019],"inclination_deg":[0.16,0.16],"host_radius_solar":[0.005,0.005],"host_temperature_k":[66,66],"semi_major_axis_km":[14959.78707,14959.78707],"orbital_period_days":[1.5e-7,1.5e-7],"argument_of_periastron_deg":[1.05,1.05]},"host_mass_solar":1.33,"inclination_deg":88.49,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":1.461,"planets_in_system":1,"discovery_facility":"SuperWASP","host_spectral_type":"F6 V","host_temperature_k":6628,"orbital_period_days":1.27492504,"transit_midpoint_bjd":2460245.02038,"equilibrium_temperature_k":2409,"argument_of_periastron_deg":88.95},"designations":[{"catalog":"Exoplanet","designation":"WASP-121 b"},{"catalog":"Host star","designation":"WASP-121"}],"source":{"id":"exoplanet_archive","name":"NASA Exoplanet Archive (Planetary Systems Composite Parameters)","url":"https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PSCompPars","license":"Public domain (NASA)"},"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."}