{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.832","julian_year":2026.832,"time":"2026-10-31T19:21:42.807Z","years_from_j2000":26.832,"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":"hd-4391","name":"HD 4391","class":"g3v_yellow_main_sequence_star","category":"star","object_type":"G3V yellow main-sequence star","mag":5.8,"mag_band":"V","abs_mag":4.897,"abs_mag_band":"V","distance_ly":49.44008835981484,"distance_method":"parallax","ra_deg":11.43975,"dec_deg":-47.551985,"epoch_ra_deg":11.756952,"epoch_dec_deg":-47.40377,"epoch_moved_arcsec":5.365,"pm_ra_mas_yr":183.96,"pm_dec_mas_yr":78.36,"position_epoch_jyear":null,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Phoenix","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/hd-4391","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":"00458-4733","age_years":6179384700,"companions":[{"measured":2015,"magnitude":13.5,"components":"AB","discoverer_code":"HDO 183","separation_arcsec":16.4,"position_angle_deg":311},{"measured":2015,"magnitude":14,"components":"AC","discoverer_code":"RAG   4","separation_arcsec":47.1,"position_angle_deg":240}],"mass_solar":0.969,"radius_solar":0.998,"spectral_type":"G3V","uncertainties":{"metallicity_fe_h":[0.044,0.044]},"color_index_bv":0.635,"luminosity_solar":0.9576349769692682,"metallicity_fe_h":-0.055,"radial_velocity_km_s":-11.4,"spectral_type_source":"SIMBAD (2006A&A...460..695T, quality C)","surface_gravity_log_g":4.406,"surface_temperature_k":5694,"metallicity_fe_h_source":"Median of 4 spectroscopic determinations in 5 papers, compiled from the literature (PASTEL, Soubiran+ 2016); the error bar is the scatter between them","proper_motion_ra_mas_yr":183.96,"proper_motion_dec_mas_yr":78.36,"stellar_parameters_method":"Gaia DR3 model fit (GSP-Phot, FLAME; RUWE ≤ 1.4)","bolometric_luminosity_solar":0.9353},"designations":[{"catalog":"Gliese","designation":"GJ 1021"},{"catalog":"HD","designation":"HD 4391"},{"catalog":"HIP","designation":"HIP 3583"},{"catalog":"HR","designation":"HR 209"}],"updated_at":"2026-10-01T09:42:28.932Z","citation":{"plain":"SpaceCatalog. HD 4391 [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-4391","bibtex":"@misc{spacecatalog_hd-4391,\n  author       = {{SpaceCatalog}},\n  title        = {{HD 4391}},\n  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},\n  year         = {2026},\n  url          = {https://spacecatalog.org/object/hd-4391},\n  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from HYG Database v4.1.}\n}","url":"https://spacecatalog.org/object/hd-4391","release":"DR1","doi":null},"references":[{"bibcode":"2006A&A...460..695T","ads_url":"https://ui.adsabs.harvard.edu/abs/2006A%26A...460..695T/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."}