{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.674","julian_year":2026.674,"time":"2026-09-04T02:26:42.178Z","years_from_j2000":26.674,"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":"k2-54-b","name":"K2-54 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":570.6268906343284,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":338.0541631,"dec_deg":-17.5440636,"epoch_ra_deg":338.416363,"epoch_dec_deg":-17.406068,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"K2-54","semi_major_axis_km":11384397.960269999,"periapsis_km":null,"mass_kg":4.377599047091081e+25,"mass_msun":0.0000220156,"constellation":"Aquarius","discovered":"2016","featured":false,"url":"https://spacecatalog.org/object/k2-54-b","radius_km":16657.635934250004,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"K2-54","host_v_mag":14.542,"eccentricity":0.24,"uncertainties":{"radius_km":[1215.3639845270002,1358.347975203],"distance_ly":[3.3088564519363617,3.3088564519363617],"eccentricity":[0.18,0.4],"host_mass_solar":[0.031,0.031],"inclination_deg":[0.5,0.59],"host_radius_solar":[0.031,0.031],"host_temperature_k":[300,300],"semi_major_axis_km":[194477.23190999997,194477.23190999997],"orbital_period_days":[0.0012,0.0013],"argument_of_periastron_deg":[120,93]},"host_mass_solar":0.615,"inclination_deg":89.08,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":0.643,"planets_in_system":1,"discovery_facility":"K2","host_temperature_k":3990,"orbital_period_days":9.7833,"transit_midpoint_bjd":2457012.2875,"equilibrium_temperature_k":560,"argument_of_periastron_deg":-43},"designations":[{"catalog":"Exoplanet","designation":"K2-54 b"},{"catalog":"Host star","designation":"K2-54"}],"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."}