{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.677","julian_year":2026.677,"time":"2026-09-05T04:59:51.275Z","years_from_j2000":26.677,"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":"k2-291-b","name":"K2-291 b","class":"super_earth","category":"exoplanet","object_type":"Super-Earth","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":293.7240398293459,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":76.44594,"dec_deg":21.548199,"epoch_ra_deg":76.847371,"epoch_dec_deg":21.58496,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"K2-291","semi_major_axis_km":4878386.563526999,"periapsis_km":null,"mass_kg":3.875936946196605e+25,"mass_msun":0.0000194926,"constellation":"Taurus","discovered":"2019","featured":false,"url":"https://spacecatalog.org/object/k2-291-b","radius_km":10134.8009,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"K2-291","host_v_mag":10.014,"eccentricity":0,"uncertainties":{"mass_kg":[6.927714726638e+24,6.927714726638e+24],"radius_km":[459.2232,605.9195000000001],"distance_ly":[1.5981662508120427,1.6154525388310301],"host_mass_solar":[0.038,0.038],"inclination_deg":[0.2,0.23],"host_radius_solar":[0.033,0.035],"host_temperature_k":[60,60],"semi_major_axis_km":[65823.063108,65823.063108],"orbital_period_days":[0.000068,0.000066]},"host_mass_solar":0.934,"inclination_deg":85.26,"stars_in_system":1,"discovery_method":"Transit","host_radius_solar":0.899,"planets_in_system":1,"discovery_facility":"K2","host_temperature_k":5520,"orbital_period_days":2.225177,"transit_midpoint_bjd":2457830.06163,"equilibrium_temperature_k":1278,"argument_of_periastron_deg":0},"designations":[{"catalog":"Exoplanet","designation":"K2-291 b"},{"catalog":"Host star","designation":"K2-291"}],"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."}