{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.654","julian_year":2026.654,"time":"2026-08-27T18:02:00.460Z","years_from_j2000":26.654,"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":"gj-251-b","name":"GJ 251 b","class":"super_earth","category":"exoplanet","object_type":"Super-Earth","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":18.201384967947266,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":103.7002499,"dec_deg":33.2664632,"epoch_ra_deg":104.139659,"epoch_dec_deg":33.232756,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"GJ 251","semi_major_axis_km":12087507.952559998,"periapsis_km":null,"mass_kg":2.299284629099681e+25,"mass_msun":0.0000115634,"constellation":"Gemini","discovered":"2020","featured":false,"url":"https://spacecatalog.org/object/gj-251-b","radius_km":11416.799,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"GJ 251","host_v_mag":9.89,"eccentricity":0,"uncertainties":{"mass_kg":[1.9708153963711551e+24,2.0902587537269827e+24],"distance_ly":[0.00645789627879152,0.00645789627879152],"host_mass_solar":[0.04,0.05],"host_radius_solar":[0.01,0.01],"host_temperature_k":[24,24],"semi_major_axis_km":[628311.0569399999,628311.0569399999],"orbital_period_days":[0.0015,0.0015]},"host_mass_solar":0.35,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":0.36,"planets_in_system":2,"discovery_facility":"W. M. Keck Observatory","host_spectral_type":"M3.0 V","host_temperature_k":3342,"orbital_period_days":14.237,"transit_midpoint_bjd":2458626.81,"equilibrium_temperature_k":336,"argument_of_periastron_deg":0},"designations":[{"catalog":"Exoplanet","designation":"GJ 251 b"}],"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":"2026-08-27T16:03:54.983Z","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."}