{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.664","julian_year":2026.664,"time":"2026-08-31T14:57:19.354Z","years_from_j2000":26.664,"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":"castor-b","name":"Castor B","class":"a_m_white_star","category":"star","object_type":"A m white star","mag":2.85,"mag_band":"V","abs_mag":1.856,"abs_mag_band":"V","distance_ly":51.54999396726445,"distance_method":"parallax","ra_deg":113.652405,"dec_deg":31.89052,"epoch_ra_deg":114.080482,"epoch_dec_deg":31.831449,"epoch_moved_arcsec":5.066,"pm_ra_mas_yr":-162.69,"pm_dec_mas_yr":-98.14,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Gemini","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/castor-b","radius_km":null,"radius_kind":null,"data_quality":null,"description":null,"properties":{"wikidata_id":"Q12069681","also_known_as":["Alpha Geminorum B","α Gem","α Geminorum B","α¹ Gem"],"spectral_type":"A m","luminosity_solar":15.761589049638374,"radial_velocity_km_s":-1.2,"proper_motion_ra_mas_yr":-162.69,"proper_motion_dec_mas_yr":-98.14},"designations":[{"catalog":"Common name","designation":"Castor B"},{"catalog":"Gliese","designation":"GJ 278 B"},{"catalog":"Gliese","designation":"Gl 278B"},{"catalog":"HD","designation":"HD 60178"},{"catalog":"HR","designation":"HR 2890"}],"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."}