{"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":"2026-09-07T13:13:29.661Z","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-168021","name":"HD 168021","class":"b0ib_blue_white_supergiant","category":"star","object_type":"B0Ib blue-white supergiant","mag":6.84,"mag_band":"V","abs_mag":null,"abs_mag_band":null,"distance_ly":null,"distance_method":null,"ra_deg":274.68041655,"dec_deg":-18.61944444,"epoch_ra_deg":275.075024,"epoch_dec_deg":-18.608982,"epoch_moved_arcsec":0.322,"pm_ra_mas_yr":11,"pm_dec_mas_yr":5,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Sagittarius","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/hd-168021","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"wds_id":"18187-1837","companions":[{"measured":2021,"magnitude":8.2,"components":"AB","discoverer_code":"BU  639","separation_arcsec":0.5,"position_angle_deg":138},{"measured":2023,"magnitude":7.63,"components":"AB,C","discoverer_code":"SHJ 264","separation_arcsec":17.5,"position_angle_deg":52},{"measured":2000,"magnitude":10.78,"components":"AB,E","discoverer_code":"FOX 225","separation_arcsec":145.6,"position_angle_deg":328}],"spectral_type":"B0Ib","radial_velocity_km_s":4,"proper_motion_ra_mas_yr":11,"proper_motion_dec_mas_yr":5},"designations":[{"catalog":"HD","designation":"HD 168021"},{"catalog":"HR","designation":"HR 6848"}],"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."}