{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.665","julian_year":2026.665,"time":"2026-08-31T22:01:08.930Z","years_from_j2000":26.665,"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-18-d","name":"Kepler-18 d","class":"gas_giant","category":"exoplanet","object_type":"Gas giant","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":1412.4104090110259,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":298.0794448,"dec_deg":44.746248,"epoch_ra_deg":298.291601,"epoch_dec_deg":44.814795,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"Kepler-18","semi_major_axis_km":17532870.446039997,"periapsis_km":null,"mass_kg":9.794355303177861e+25,"mass_msun":0.0000492572,"constellation":"Cygnus","discovered":"2011","featured":false,"url":"https://spacecatalog.org/object/kepler-18-d","radius_km":44519.138000000006,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"Kepler-18","host_v_mag":13.771,"eccentricity":0,"uncertainties":{"mass_kg":[8.361035014907931e+24,8.361035014907931e+24],"radius_km":[2104.773,2104.773],"distance_ly":[10.300018408294758,10.45005034204446],"host_mass_solar":[0.042,0.042],"inclination_deg":[0.1,0.1],"host_radius_solar":[0.051,0.051],"host_temperature_k":[100,100],"semi_major_axis_km":[254316.38018999997,254316.38018999997],"orbital_period_days":[0.00004,0.00004]},"host_mass_solar":0.972,"inclination_deg":88.07,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":1.108,"planets_in_system":3,"discovery_facility":"Kepler","host_temperature_k":5345,"orbital_period_days":14.85888,"transit_midpoint_bjd":2455169.1776,"equilibrium_temperature_k":720},"designations":[{"catalog":"Exoplanet","designation":"Kepler-18 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":"2026-08-30T09:56:50.739Z","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."}