{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.778","julian_year":2026.778,"time":"2026-10-12T00:35:06.740Z","years_from_j2000":26.778,"frame":"icrs","applied":"Proper motion only. 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. The frame is ICRS at both ends — this is a position epoch and not an equinox, and the grid is not turned. Ask for frame=date to have it turned as well.","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":"polaris","name":"Polaris","class":"f8ib_yellow_white_supergiant","category":"star","object_type":"F8Ib yellow-white supergiant","mag":1.97,"mag_band":"V","abs_mag":-3.643,"abs_mag_band":"V","distance_ly":432.56815751060816,"distance_method":"parallax","ra_deg":37.94625,"dec_deg":89.264109,"epoch_ra_deg":37.971857,"epoch_dec_deg":89.264022,"epoch_moved_arcsec":1.225,"pm_ra_mas_yr":44.22,"pm_dec_mas_yr":-11.74,"position_epoch_jyear":null,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Ursa Minor","discovered":"Antiquity","featured":true,"url":"https://spacecatalog.org/object/polaris","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":"The North Star, currently within a degree of the celestial pole. It is also a Cepheid variable, one of the yardsticks astronomers use to measure cosmic distances.","properties":{"wds_id":"02318+8916","companions":[{"measured":2023,"magnitude":4.3,"components":"Aa,Ab","discoverer_code":"WRH  39","separation_arcsec":0.1,"position_angle_deg":293},{"measured":2016,"magnitude":9.1,"components":"AB","discoverer_code":"STF  93","separation_arcsec":18.4,"position_angle_deg":236},{"measured":2016,"magnitude":13.8,"components":"AC","discoverer_code":"STF  93","separation_arcsec":39,"position_angle_deg":103},{"measured":2016,"magnitude":14.3,"components":"AD","discoverer_code":"STF  93","separation_arcsec":83.2,"position_angle_deg":194}],"wikidata_id":"Q12980","also_known_as":["* alf UMi","Alpha Ursae Minoris","North Star","North pole star","Northern Star","Pole star","Pole-star","Polestar","Stella Polaris","V* alf UMi","alf UMi","α UMi","α Ursae Minoris"],"spectral_type":"F8Ib","uncertainties":{"metallicity_fe_h":[0.025,0.025]},"color_index_bv":0.636,"luminosity_solar":2495.743794831569,"metallicity_fe_h":0.025,"variability_type":"DCEPS","variable_mag_max":1.953,"variable_mag_min":1.993,"variability_class":"Classical Cepheid (low amplitude)","wikipedia_article":"Polaris","variable_epoch_hjd":2431495.813,"radial_velocity_km_s":-17,"spectral_type_source":"SIMBAD (1993ASPC...45...59L, quality C)","variable_designation":"Alp UMi","variable_period_days":3.9696,"surface_gravity_log_g":1.95,"surface_temperature_k":5932,"metallicity_fe_h_source":"Median of 2 spectroscopic determinations in 2 papers, compiled from the literature (PASTEL, Soubiran+ 2016); the error bar is the scatter between them","proper_motion_ra_mas_yr":44.22,"proper_motion_dec_mas_yr":-11.74,"stellar_parameters_method":"Spectroscopic determinations compiled from the literature (PASTEL, Soubiran+ 2016)"},"designations":[{"catalog":"Bayer/Flamsteed","designation":"1 Alpha UMi"},{"catalog":"Common name","designation":"Polaris"},{"catalog":"HD","designation":"HD 8890"},{"catalog":"HIP","designation":"HIP 11767"},{"catalog":"HR","designation":"HR 424"},{"catalog":"IRAS","designation":"IRAS 01490+8901"}],"updated_at":"2026-10-01T09:42:28.932Z","variability":{"type":"DCEPS","class":"Classical Cepheid (low amplitude)","period_days":3.9696,"epoch_hjd":2431495.813,"epoch_marks":"maximum","mag_brightest":1.953,"mag_faintest":1.993,"phase":{"at":"2026-10-12T00:35:06.740Z","at_hjd":2461325.525174,"event":"maximum","value":0.5385,"uncertainty":0.0947,"uncertainty_days":0.375727,"cycles_since_epoch":7514.539,"next":["2026-10-13T20:32:50.614Z","2026-10-17T19:48:51.459Z"],"unavailable":null,"applied":"The whole cycles between the published epoch and the instant asked for, counted at the published period. Both are on the same heliocentric scale: the instant is corrected for where the Earth was in its orbit, which is worth up to 8.3 minutes and is the difference between an eclipse timed in January and one timed in July.","excluded":"Any change in the period since it was measured. The uncertainty here is the published precision of the period carried through the cycles since the epoch, plus that of the epoch itself; it is not an error bar the upstream catalogue published, and where that catalogue has flagged a period as doubtful the true figure is larger. Nothing at all is claimed for classes whose period is a mean cycle time — a dwarf nova, an irregular or a semiregular variable gets elements and no phase, and says so."}},"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."}