{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.686","julian_year":2026.686,"time":"2026-09-08T17:18:11.688Z","years_from_j2000":26.686,"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-3929-c","name":"GJ 3929 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":51.56369253512855,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":239.5775678,"dec_deg":35.4081141,"epoch_ra_deg":239.831007,"epoch_dec_deg":35.330646,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"GJ 3929","semi_major_axis_km":12117427.5267,"periapsis_km":null,"mass_kg":3.4101078525088776e+25,"mass_msun":0.0000171499,"constellation":"Corona Borealis","discovered":"2022","featured":false,"url":"https://spacecatalog.org/object/gj-3929-c","radius_km":14414.506,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"GJ 3929","host_v_mag":12.675,"eccentricity":0,"uncertainties":{"mass_kg":[5.613837795723896e+24,5.613837795723896e+24],"distance_ly":[0.030984855883090624,0.03131101226080737],"host_mass_solar":[0.022,0.027],"host_radius_solar":[0.01,0.01],"host_temperature_k":[88,88],"semi_major_axis_km":[299195.7414,299195.7414],"orbital_period_days":[0.03,0.03]},"host_mass_solar":0.313,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":0.32,"planets_in_system":2,"discovery_facility":"Multiple Observatories","host_spectral_type":"M3.5 V","host_temperature_k":3384,"orbital_period_days":15.04,"transit_midpoint_bjd":2459070.9,"equilibrium_temperature_k":317,"argument_of_periastron_deg":90},"designations":[{"catalog":"Exoplanet","designation":"GJ 3929 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."}