{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.680","julian_year":2026.68,"time":"2026-09-06T05:49:00.752Z","years_from_j2000":26.68,"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-209458-b","name":"HD 209458 b","class":"gas_giant","category":"exoplanet","object_type":"Gas giant","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":157.53874893923054,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":330.7950219,"dec_deg":18.8842419,"epoch_ra_deg":331.113598,"epoch_dec_deg":19.013873,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"HD 209458","semi_major_axis_km":7041571.773848999,"periapsis_km":null,"mass_kg":1.385637902796698e+27,"mass_msun":0.000696857,"constellation":"Pegasus","discovered":"1999","featured":true,"url":"https://spacecatalog.org/object/hd-209458-b","radius_km":99374.050831,"radius_kind":null,"data_quality":null,"description":"The first exoplanet seen to transit its star, the first with a detected atmosphere, and the first observed to be evaporating — a gas giant so hot it trails a comet-like tail of hydrogen.","properties":{"host_star":"HD 209458","host_v_mag":7.65,"eccentricity":0,"uncertainties":{"mass_kg":[7.592536453680536e+25,7.592536453680536e+25],"radius_km":[1429.842458,1429.842458],"distance_ly":[0.40247697010246136,0.4044339083687618],"host_mass_solar":[0.09,0.09],"inclination_deg":[0.05,0.05],"host_radius_solar":[0.02,0.02],"host_temperature_k":[10,10],"semi_major_axis_km":[70310.999229,67319.04181499999],"orbital_period_days":[3.8e-7,3.8e-7]},"host_mass_solar":1.23,"inclination_deg":86.71,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":1.19,"planets_in_system":1,"discovery_facility":"W. M. Keck Observatory","host_spectral_type":"G0 V","host_temperature_k":6091,"orbital_period_days":3.52474859,"periastron_epoch_bjd":2451412.3085,"transit_midpoint_bjd":2451659.93742,"equilibrium_temperature_k":1459,"argument_of_periastron_deg":0},"designations":[{"catalog":"Exoplanet","designation":"HD 209458 b"},{"catalog":"Host star","designation":"HD 209458"}],"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."}