{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.663","julian_year":2026.663,"time":"2026-08-31T07:48:14.671Z","years_from_j2000":26.663,"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":"alcor","name":"Alcor","class":"a5v_m3_4v_white_main_sequence_star","category":"star","object_type":"A5V+M3-4V white main-sequence star","mag":3.99,"mag_band":"V","abs_mag":1.995,"abs_mag_band":"V","distance_ly":81.72304662621809,"distance_method":"parallax","ra_deg":201.306195,"dec_deg":54.987958,"epoch_ra_deg":201.577006,"epoch_dec_deg":54.847873,"epoch_moved_arcsec":3.241,"pm_ra_mas_yr":120.35,"pm_dec_mas_yr":-16.94,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Ursa Major","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/alcor","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"wds_id":"13239+5456","companions":[{"measured":2009,"magnitude":8,"components":"Ca,Cb","discoverer_code":"PSF   1","separation_arcsec":1,"position_angle_deg":207}],"spectral_type":"A5V+M3-4V","color_index_bv":0.169,"luminosity_solar":13.867558288718882,"radial_velocity_km_s":-8.9,"spectral_type_source":"SIMBAD (2010AJ....139..919M, quality C)","surface_temperature_k":8008,"proper_motion_ra_mas_yr":120.35,"proper_motion_dec_mas_yr":-16.94,"stellar_parameters_method":"Spectroscopic determinations compiled from the literature (PASTEL, Soubiran+ 2016)"},"designations":[{"catalog":"Bayer/Flamsteed","designation":"80 UMa"},{"catalog":"Common name","designation":"Alcor"},{"catalog":"Gliese","designation":"GJ 3785"},{"catalog":"HD","designation":"HD 116842"},{"catalog":"HIP","designation":"HIP 65477"},{"catalog":"HR","designation":"HR 5062"}],"source":{"id":"hyg","name":"HYG Database v4.1","url":"https://github.com/astronexus/HYG-Database","license":"CC-BY-SA-4.0"},"updated_at":"2026-08-30T09:56:50.739Z","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."}