{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.671","julian_year":2026.671,"time":"2026-09-03T01:52:25.125Z","years_from_j2000":26.671,"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-17820","name":"HD 17820","class":"g5_yellow_star","category":"star","object_type":"G5 yellow star","mag":8.38,"mag_band":"V","abs_mag":4.453,"abs_mag_band":"V","distance_ly":198.9971384235612,"distance_method":"parallax","ra_deg":42.99315,"dec_deg":11.369978,"epoch_ra_deg":43.35779,"epoch_dec_deg":11.477268,"epoch_moved_arcsec":11.903,"pm_ra_mas_yr":37.33,"pm_dec_mas_yr":-444.71,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Aries","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/hd-17820","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"age_years":7354783000,"mass_solar":1.023,"radius_solar":1.184,"spectral_type":"G5","uncertainties":{"metallicity_fe_h":[0.057,0.057]},"color_index_bv":0.564,"luminosity_solar":1.44145138575821,"metallicity_fe_h":-0.685,"radial_velocity_km_s":4.5,"spectral_type_source":"SIMBAD (2000A&A...353..722N, quality D)","surface_gravity_log_g":4.283,"surface_temperature_k":5862,"metallicity_fe_h_source":"Median of 12 spectroscopic determinations in 14 papers, compiled from the literature (PASTEL, Soubiran+ 2016); the error bar is the scatter between them","proper_motion_ra_mas_yr":37.33,"proper_motion_dec_mas_yr":-444.71,"stellar_parameters_method":"Gaia DR3 model fit (GSP-Phot, FLAME; RUWE ≤ 1.4)","bolometric_luminosity_solar":1.5007},"designations":[{"catalog":"HD","designation":"HD 17820"},{"catalog":"HIP","designation":"HIP 13366"}],"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."}