{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.681","julian_year":2026.681,"time":"2026-09-06T17:28:06.592Z","years_from_j2000":26.681,"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":"81-cet-b","name":"81 Cet b","class":"gas_giant","category":"exoplanet","object_type":"Gas giant","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":330.2659480759744,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":39.4243555,"dec_deg":-3.3963607,"epoch_ra_deg":39.763117,"epoch_dec_deg":-3.279648,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"81 Cet","semi_major_axis_km":314753919.9528,"periapsis_km":null,"mass_kg":6.277098051401448e+27,"mass_msun":0.00315684,"constellation":"Cetus","discovered":"2008","featured":false,"url":"https://spacecatalog.org/object/81-cet-b","radius_km":83553.11,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"81 Cet","host_v_mag":5.64307,"eccentricity":0.037,"uncertainties":{"mass_kg":[1.2717434818967246e+26,1.4805371880491288e+26],"distance_ly":[3.9856309356986044,3.9856309356986044],"eccentricity":[0.025,0.015],"host_mass_solar":[0.25,0.3],"host_radius_solar":[0.35,0.81],"semi_major_axis_km":[448793.61209999997,448793.61209999997],"orbital_period_days":[1.94,1.84],"argument_of_periastron_deg":[36,54.4]},"host_mass_solar":1.23,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":11.21,"planets_in_system":1,"discovery_facility":"Okayama Astrophysical Observatory","host_spectral_type":"G5 III","host_temperature_k":4734,"orbital_period_days":1005.57,"periastron_epoch_bjd":2453458.4,"equilibrium_temperature_k":526.92,"argument_of_periastron_deg":-166.7},"designations":[{"catalog":"Exoplanet","designation":"81 Cet b"},{"catalog":"Host star","designation":"81 Cet"}],"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."}