{"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":"2026-09-04T13:26:04.341Z","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-170904","name":"HD 170904","class":"b8ii_blue_white_bright_giant","category":"star","object_type":"B8II blue-white bright giant","mag":8.32,"mag_band":"V","abs_mag":0.676,"abs_mag_band":"V","distance_ly":1101.8795310379362,"distance_method":"parallax","ra_deg":278.113755,"dec_deg":-15.932036,"epoch_ra_deg":278.500128,"epoch_dec_deg":-15.912757,"epoch_moved_arcsec":0.225,"pm_ra_mas_yr":-3.64,"pm_dec_mas_yr":-7.59,"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-170904","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"mass_solar":4.197,"radius_solar":7.956,"spectral_type":"B8II","color_index_bv":0.131,"luminosity_solar":46.730453963151,"radial_velocity_km_s":0,"spectral_type_source":"SIMBAD (1988MSS...C04....0H, quality C)","surface_gravity_log_g":2.941,"surface_temperature_k":7474,"proper_motion_ra_mas_yr":-3.64,"proper_motion_dec_mas_yr":-7.59,"stellar_parameters_method":"Gaia DR3 model fit (GSP-Phot, FLAME; RUWE ≤ 1.4)","bolometric_luminosity_solar":526.9517},"designations":[{"catalog":"HD","designation":"HD 170904"},{"catalog":"HIP","designation":"HIP 90897"}],"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."}