{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.816","julian_year":2026.816,"time":"2026-10-26T04:52:52.125Z","years_from_j2000":26.816,"frame":"date","applied":"Proper motion, then precession and nutation. The catalogued position is carried along the great circle the object's own published motion puts it on, at a constant velocity, from the epoch that position was measured at, 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. The motion runs from position_epoch_jyear where the upstream publishes one — a timed pulsar's position belongs to the year it was timed — and from J2000 where it does not. 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":"megrez","name":"Megrez","class":"a2vn_white_main_sequence_star","category":"star","object_type":"A2Vn white main-sequence star","mag":3.32,"mag_band":"V","abs_mag":1.358,"abs_mag_band":"V","distance_ly":80.51268030851126,"distance_method":"parallax","ra_deg":183.85629,"dec_deg":57.032617,"epoch_ra_deg":184.190417,"epoch_dec_deg":56.882745,"epoch_moved_arcsec":2.785,"pm_ra_mas_yr":103.56,"pm_dec_mas_yr":7.81,"position_epoch_jyear":null,"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/megrez","source":{"id":"hyg","name":"HYG Database v4.1","url":"https://github.com/astronexus/HYG-Database","license":"CC-BY-SA-4.0","attribution":"HYG Database v4.1, Astronexus (github.com/astronexus/HYG-Database). Fields derived from it stay under CC BY-SA 4.0.","commercial_use":"allowed"},"radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"wds_id":"12154+5702","companions":[{"measured":2011,"magnitude":18.4,"components":"AD","discoverer_code":"JNN 240","separation_arcsec":3.3,"position_angle_deg":113},{"measured":2011,"magnitude":19.3,"components":"AE","discoverer_code":"JNN 240","separation_arcsec":5.7,"position_angle_deg":169},{"measured":2020,"magnitude":11.62,"components":"AC","discoverer_code":"BUP 140","separation_arcsec":174.8,"position_angle_deg":130},{"measured":2020,"magnitude":10.21,"components":"AB","discoverer_code":"BLL  29","separation_arcsec":181.9,"position_angle_deg":75}],"wikidata_id":"Q850779","also_known_as":["Delta Ursae Majoris","The Celestial Balance","δ UMa","δ Ursae Majoris"],"spectral_type":"A2Vn","color_index_bv":0.077,"luminosity_solar":24.9344618809783,"wikipedia_article":"Megrez","radial_velocity_km_s":-13.4,"spectral_type_source":"SIMBAD (2003AJ....126.2048G, quality C)","surface_temperature_k":8670,"proper_motion_ra_mas_yr":103.56,"proper_motion_dec_mas_yr":7.81,"stellar_parameters_method":"Spectroscopic determinations compiled from the literature (PASTEL, Soubiran+ 2016)"},"designations":[{"catalog":"Bayer/Flamsteed","designation":"69 Delta UMa"},{"catalog":"Common name","designation":"Megrez"},{"catalog":"Gliese","designation":"GJ 459"},{"catalog":"Gliese","designation":"Gl 459"},{"catalog":"HD","designation":"HD 106591"},{"catalog":"HIP","designation":"HIP 59774"},{"catalog":"HR","designation":"HR 4660"},{"catalog":"IRAS","designation":"IRAS 12129+5718"}],"updated_at":"2026-10-01T09:42:28.932Z","citation":{"plain":"SpaceCatalog. Megrez [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/megrez","bibtex":"@misc{spacecatalog_megrez,\n  author       = {{SpaceCatalog}},\n  title        = {{Megrez}},\n  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},\n  year         = {2026},\n  url          = {https://spacecatalog.org/object/megrez},\n  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from HYG Database v4.1.}\n}","url":"https://spacecatalog.org/object/megrez","release":"DR1","doi":null},"references":[{"bibcode":"2003AJ....126.2048G","ads_url":"https://ui.adsabs.harvard.edu/abs/2003AJ....126.2048G/abstract","quantity":"properties.spectral_type_source"}],"attribution":"Data from SpaceCatalog.org. Each record names its upstream in `source`, with that producer's terms in `source.license`, the acknowledgement it asks for in `source.attribution`, and whether its terms allow commercial use in `source.commercial_use`; those terms govern the record, and citing SpaceCatalog does not discharge them."}