{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.683","julian_year":2026.683,"time":"2026-09-07T08:46:06.141Z","years_from_j2000":26.683,"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":"hd-191939-d","name":"HD 191939 d","class":"neptune_like_planet","category":"exoplanet","object_type":"Neptune-like planet","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":174.84884637379125,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":302.0256247,"dec_deg":66.8503014,"epoch_ra_deg":302.069935,"epoch_dec_deg":66.927722,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"HD 191939","semi_major_axis_km":31894266.033239998,"periapsis_km":null,"mass_kg":1.6722070029815862e+25,"mass_msun":0.00000840977,"constellation":"Draco","discovered":"2020","featured":false,"url":"https://spacecatalog.org/object/hd-191939-d","radius_km":19102.4095,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"HD 191939","host_v_mag":8.97,"eccentricity":0.031,"uncertainties":{"mass_kg":[3.5833007206748275e+24,3.5833007206748275e+24],"radius_km":[446.46700000000004,446.46700000000004],"distance_ly":[0.23842031211093942,0.23907262486637293],"eccentricity":[0.012,0.018],"host_mass_solar":[0.04,0.04],"inclination_deg":[0.08,0.05],"host_radius_solar":[0.02,0.02],"host_temperature_k":[100,100],"semi_major_axis_km":[912547.01127,972386.1595499999],"orbital_period_days":[0.00006,0.00006],"argument_of_periastron_deg":[160,90]},"host_mass_solar":0.81,"inclination_deg":89.49,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":0.94,"planets_in_system":6,"discovery_facility":"Transiting Exoplanet Survey Satellite (TESS)","host_spectral_type":"G9 V","host_temperature_k":5348,"orbital_period_days":38.353037,"transit_midpoint_bjd":2459433.906,"equilibrium_temperature_k":540,"argument_of_periastron_deg":15},"designations":[{"catalog":"Exoplanet","designation":"HD 191939 d"}],"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."}