{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.675","julian_year":2026.675,"time":"2026-09-04T16:20:29.136Z","years_from_j2000":26.675,"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-17904","name":"20 Per","class":"f6v_yellow_white_main_sequence_star","category":"star","object_type":"F6V yellow-white main-sequence star","mag":5.34,"mag_band":"V","abs_mag":1.094,"abs_mag_band":"V","distance_ly":230.49927832171062,"distance_method":"parallax","ra_deg":43.42752,"dec_deg":38.337488,"epoch_ra_deg":43.852524,"epoch_dec_deg":38.446689,"epoch_moved_arcsec":2.449,"pm_ra_mas_yr":47.62,"pm_dec_mas_yr":-78.48,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Perseus","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/hd-17904","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"wds_id":"02537+3820","companions":[{"measured":2022,"magnitude":6.8,"components":"AB","discoverer_code":"BU  524","separation_arcsec":0.2,"position_angle_deg":291},{"measured":2021,"magnitude":9.68,"components":"AB,C","discoverer_code":"STF 318","separation_arcsec":13.8,"position_angle_deg":238},{"measured":2002,"magnitude":12.6,"components":"AB,D","discoverer_code":"STF 318","separation_arcsec":58.1,"position_angle_deg":40}],"spectral_type":"F6V","color_index_bv":0.423,"luminosity_solar":31.798014276915243,"radial_velocity_km_s":6,"spectral_type_source":"SIMBAD (2009ApJS..180..117A, quality C)","surface_temperature_k":6644,"proper_motion_ra_mas_yr":47.62,"proper_motion_dec_mas_yr":-78.48,"stellar_parameters_method":"Spectroscopic determinations compiled from the literature (PASTEL, Soubiran+ 2016)"},"designations":[{"catalog":"Bayer/Flamsteed","designation":"20 Per"},{"catalog":"HD","designation":"HD 17904"},{"catalog":"HIP","designation":"HIP 13490"},{"catalog":"HR","designation":"HR 855"}],"source":{"id":"hyg","name":"HYG Database v4.1","url":"https://github.com/astronexus/HYG-Database","license":"CC-BY-SA-4.0"},"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."}