{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.678","julian_year":2026.678,"time":"2026-09-05T13:13:52.888Z","years_from_j2000":26.678,"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":"gj-3998-c","name":"GJ 3998 c","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":59.184010144102544,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":259.0020507,"dec_deg":11.0561751,"epoch_ra_deg":259.317632,"epoch_dec_deg":11.025804,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"GJ 3998","semi_major_axis_km":13463808.362999998,"periapsis_km":null,"mass_kg":4.07301848583372e+25,"mass_msun":0.0000204838,"constellation":"Ophiuchus","discovered":"2016","featured":false,"url":"https://spacecatalog.org/object/gj-3998-c","radius_km":15945.25,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"GJ 3998","host_v_mag":10.844,"eccentricity":0,"uncertainties":{"mass_kg":[4.4791259008435344e+24,4.658290936877276e+24],"distance_ly":[0.05381580232326267,0.05381580232326267],"host_mass_solar":[0.05,0.05],"host_radius_solar":[0.05,0.05],"host_temperature_k":[68,68],"semi_major_axis_km":[448793.61209999997,448793.61209999997],"orbital_period_days":[0.004,0.003]},"host_mass_solar":0.52,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":0.5,"planets_in_system":3,"discovery_facility":"Roque de los Muchachos Observatory","host_spectral_type":"M1","host_temperature_k":3726,"orbital_period_days":13.727,"transit_midpoint_bjd":2460196.96,"equilibrium_temperature_k":423.49},"designations":[{"catalog":"Exoplanet","designation":"GJ 3998 c"}],"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."}