{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.683","julian_year":2026.683,"time":"2026-09-07T09:46:14.424Z","years_from_j2000":26.683,"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":"hd-128311-b","name":"HD 128311 b","class":"gas_giant","category":"exoplanet","object_type":"Gas giant","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":53.25872723012247,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":219.0032292,"dec_deg":9.7454368,"epoch_ra_deg":219.331659,"epoch_dec_deg":9.628016,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"HD 128311","semi_major_axis_km":162164091.8388,"periapsis_km":null,"mass_kg":3.357799246640217e+27,"mass_msun":0.00168869,"constellation":"Boötes","discovered":"2002","featured":false,"url":"https://spacecatalog.org/object/hd-128311-b","radius_km":86104.35,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"HD 128311","host_v_mag":7.48,"eccentricity":0.303,"uncertainties":{"mass_kg":[4.365708460866308e+25,4.365708460866308e+25],"distance_ly":[0.0645789627879152,0.06490511916563195],"eccentricity":[0.011,0.011],"host_mass_solar":[0.012,0.008],"host_radius_solar":[0.02,0.02],"host_temperature_k":[44,44],"semi_major_axis_km":[897587.2241999999,897587.2241999999],"orbital_period_days":[0.404,0.404],"argument_of_periastron_deg":[3.258,3.258]},"host_mass_solar":0.828,"inclination_deg":30,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":0.76,"planets_in_system":2,"discovery_facility":"W. M. Keck Observatory","host_spectral_type":"K0","host_temperature_k":4965,"orbital_period_days":453.019,"periastron_epoch_bjd":2450198.691,"transit_midpoint_bjd":2455211.3,"equilibrium_temperature_k":200.47,"argument_of_periastron_deg":57.864},"designations":[{"catalog":"Exoplanet","designation":"HD 128311 b"},{"catalog":"Host star","designation":"HD 128311"}],"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."}