{"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":"2026-09-06T07:12:24.653Z","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":"gj-581-c","name":"GJ 581 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":20.541654824978217,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":229.8564725,"dec_deg":-7.7226935,"epoch_ra_deg":230.216111,"epoch_dec_deg":-7.820508,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"GJ 581","semi_major_axis_km":10741127.11626,"periapsis_km":null,"mass_kg":4.067046317965929e+25,"mass_msun":0.0000204538,"constellation":"Libra","discovered":"2007","featured":false,"url":"https://spacecatalog.org/object/gj-581-c","radius_km":15945.25,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"GJ 581","host_v_mag":10.57,"eccentricity":0.032,"uncertainties":{"mass_kg":[6.927714726638e+24,1.2541552522361896e+24],"distance_ly":[0.006832976113165775,0.006832976113165775],"eccentricity":[0.021,0.027],"host_mass_solar":[0.01,0.01],"inclination_deg":[89,15],"host_radius_solar":[0.005,0.005],"host_temperature_k":[26,26],"semi_major_axis_km":[134638.08362999998,119678.29656],"orbital_period_days":[0.0007,0.0008],"argument_of_periastron_deg":[89,61]},"host_mass_solar":0.295,"inclination_deg":47,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":0.302,"planets_in_system":3,"discovery_facility":"La Silla Observatory","host_spectral_type":"M3.0 V","host_temperature_k":3500,"orbital_period_days":12.9211,"periastron_epoch_bjd":2454759.2,"transit_midpoint_bjd":2455183.69,"equilibrium_temperature_k":346.13,"argument_of_periastron_deg":16},"designations":[{"catalog":"Exoplanet","designation":"GJ 581 c"},{"catalog":"Host star","designation":"GJ 581"}],"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."}