{"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":"2026-09-03T02:21:14.397Z","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":"55-cnc-c","name":"55 Cnc c","class":"gas_giant","category":"exoplanet","object_type":"Gas giant","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":41.04841091754074,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":133.1468373,"dec_deg":28.3298154,"epoch_ra_deg":133.550199,"epoch_dec_deg":28.228877,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"55 Cnc","semi_major_axis_km":36950674.0629,"periapsis_km":null,"mass_kg":3.25326677996494e+26,"mass_msun":0.000163611,"constellation":"Cancer","discovered":"2004","featured":false,"url":"https://spacecatalog.org/object/55-cnc-c","radius_km":54277.631,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"55 Cnc","host_v_mag":5.95084,"eccentricity":0.088,"uncertainties":{"mass_kg":[1.043934943289933e+25,1.043934943289933e+25],"distance_ly":[0.04011723445915944,0.04044339083687618],"eccentricity":[0.23,0.23],"host_mass_solar":[0.051,0.051],"inclination_deg":[24.54,24.49],"host_radius_solar":[0.016,0.016],"host_temperature_k":[31,31],"semi_major_axis_km":[598391.4828,598391.4828],"orbital_period_days":[0.0024,0.0024],"argument_of_periastron_deg":[14,14]},"host_mass_solar":1.015,"inclination_deg":89.73,"stars_in_system":2,"discovery_method":"Radial Velocity","host_radius_solar":0.98,"planets_in_system":7,"discovery_facility":"McDonald Observatory","host_spectral_type":"G8 V","host_temperature_k":5198,"orbital_period_days":44.3936,"periastron_epoch_bjd":2453028.63,"transit_midpoint_bjd":2455491.23,"equilibrium_temperature_k":499.27,"argument_of_periastron_deg":31},"designations":[{"catalog":"Exoplanet","designation":"55 Cnc c"}],"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."}