{"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":"2026-09-04T07:19:04.255Z","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":"k2-128-b","name":"K2-128 b","class":"super_earth","category":"exoplanet","object_type":"Super-Earth","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":373.8958867231432,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":204.4376666,"dec_deg":-8.5970858,"epoch_ra_deg":204.790928,"epoch_dec_deg":-8.733961,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"K2-128","semi_major_axis_km":8377480.759199999,"periapsis_km":null,"mass_kg":1.5527636456257586e+25,"mass_msun":0.00000780907,"constellation":"Virgo","discovered":"2017","featured":false,"url":"https://spacecatalog.org/object/k2-128-b","radius_km":9056.902,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"K2-128","host_v_mag":12.58,"eccentricity":0.23,"uncertainties":{"radius_km":[829.153,1020.4960000000001],"distance_ly":[2.9843308561082025,3.033254312765714],"eccentricity":[0.19371,0.220222],"host_mass_solar":[0.071125,0.071125],"inclination_deg":[0.66,1.08],"host_radius_solar":[0.060808,0.076202],"host_temperature_k":[145.15,171.97],"semi_major_axis_km":[299195.7414,299195.7414],"orbital_period_days":[0.000414,0.000411],"argument_of_periastron_deg":[113.7218,71.2834]},"host_mass_solar":0.711248,"inclination_deg":87.4,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":0.777569,"planets_in_system":1,"discovery_facility":"K2","host_temperature_k":4469.51,"orbital_period_days":5.675819,"transit_midpoint_bjd":2457255.503,"equilibrium_temperature_k":803.1,"argument_of_periastron_deg":62.55},"designations":[{"catalog":"Exoplanet","designation":"K2-128 b"},{"catalog":"Host star","designation":"K2-128"}],"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."}