{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.810","julian_year":2026.81,"time":"2026-10-24T00:14:18.393Z","years_from_j2000":26.81,"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":"3c-345","name":"3C 345","class":"quasar","category":"black_hole","object_type":"Quasar","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":11278042103.511065,"distance_method":"luminosity distance from a published redshift, flat ΛCDM with H0 = 70 km/s/Mpc","ra_deg":250.74504,"dec_deg":39.81028,"epoch_ra_deg":250.973066,"epoch_dec_deg":39.758961,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"position_epoch_jyear":null,"orbits":null,"semi_major_axis_km":null,"periapsis_km":null,"mass_kg":null,"mass_msun":null,"constellation":"Hercules","discovered":null,"featured":false,"url":"https://spacecatalog.org/object/3c-345","source":{"id":"curated","name":"SpaceCatalog curated data","url":"https://spacecatalog.org/releases","license":"CC-BY-4.0","attribution":null,"commercial_use":"allowed"},"radius_km":null,"radius_kind":null,"data_quality":null,"description":"Knots in its radio jet appear to travel faster than light. They do not: the jet points close to our direction, so it nearly keeps pace with the light it emits and the arrival times of successive images are squeezed together.","properties":{"redshift":0.59280791,"accretion":"quasar"},"designations":[{"catalog":"Common name","designation":"3C 345"}],"updated_at":"2026-10-01T09:42:28.932Z","citation":{"plain":"SpaceCatalog. 3C 345 [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/3c-345","bibtex":"@misc{spacecatalog_3c-345,\n  author       = {{SpaceCatalog}},\n  title        = {{3C 345}},\n  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},\n  year         = {2026},\n  url          = {https://spacecatalog.org/object/3c-345},\n  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from SpaceCatalog curated data.}\n}","url":"https://spacecatalog.org/object/3c-345","release":"DR1","doi":null},"references":[],"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."}