{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.671","julian_year":2026.671,"time":"2026-09-02T22:08:49.279Z","years_from_j2000":26.671,"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":"kepler-557-b","name":"Kepler-557 b","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":6839.8906283733695,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":293.7084179,"dec_deg":41.6151084,"epoch_ra_deg":293.930018,"epoch_dec_deg":41.673371,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"Kepler-557","semi_major_axis_km":7016140.135829999,"periapsis_km":null,"mass_kg":4.5448197473892395e+25,"mass_msun":0.0000228566,"constellation":"Cygnus","discovered":"2016","featured":false,"url":"https://spacecatalog.org/object/kepler-557-b","radius_km":17029.527000000002,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"Kepler-557","host_v_mag":14.723,"eccentricity":0,"uncertainties":{"radius_km":[2423.6780000000003,5102.4800000000005],"distance_ly":[388.5011693172989,388.5011693172989],"host_mass_solar":[0.092,0.125],"host_radius_solar":[0.162,0.348],"host_temperature_k":[199.33,151.79],"orbital_period_days":[0.000004867,0.000004867]},"host_mass_solar":1.11,"inclination_deg":82.05,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":1.16,"planets_in_system":1,"discovery_facility":"Kepler","host_temperature_k":6068,"orbital_period_days":3.705989551,"transit_midpoint_bjd":2455002.94342,"equilibrium_temperature_k":1281},"designations":[{"catalog":"Exoplanet","designation":"Kepler-557 b"},{"catalog":"Host star","designation":"Kepler-557"}],"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."}